diff --git a/src/finiteArea/faMesh/faMeshTools/faMeshTools.cxx b/src/finiteArea/faMesh/faMeshTools/faMeshTools.cxx
index 42dc91ce10..33360518ff 100644
--- a/src/finiteArea/faMesh/faMeshTools/faMeshTools.cxx
+++ b/src/finiteArea/faMesh/faMeshTools/faMeshTools.cxx
@@ -32,7 +32,6 @@ License
 #include "edgeFields.H"
 #include "fileOperation.H"
 #include "BitOps.H"
-#include "ListOps.H"
 #include "polyMesh.H"
 #include "processorFaPatch.H"
 
@@ -432,12 +431,12 @@ Foam::faMeshTools::loadOrCreateMesh_impl
     }
     else if (readHandlerPtr && haveLocalMesh)
     {
-        const label numProcs = UPstream::nProcs(UPstream::worldComm);
+        const label numWorldProcs = UPstream::nProcs(UPstream::worldComm);
+        const label realWorldComm = UPstream::worldComm;
 
         const labelList meshProcIds(BitOps::sortedToc(haveMesh));
 
         UPstream::communicator newCommunicator;
-        const label oldWorldComm = UPstream::commWorld();
 
         auto& readHandler = *readHandlerPtr;
         auto oldHandler = fileOperation::fileHandler(readHandler);
@@ -447,13 +446,13 @@ Foam::faMeshTools::loadOrCreateMesh_impl
         // Instead allocate a new communicator for everyone with a mesh
 
         // Comparing global ranks in the communicator.
-
-        if (ListOps::equal(meshProcIds, UPstream::procID(fileHandler().comm())))
+        if (UPstream::sameProcs(fileHandler().comm(), meshProcIds))
         {
+            const_cast<fileOperation&>(fileHandler()).nProcs(numWorldProcs);
             // Can use the handler communicator as is.
             UPstream::commWorld(fileHandler().comm());
         }
-        else if (UPstream::nProcs(fileHandler().comm()) != numProcs)
+        else if (UPstream::nProcs(fileHandler().comm()) != numWorldProcs)
         {
             // Need a new communicator for the fileHandler.
 
@@ -468,10 +467,10 @@ Foam::faMeshTools::loadOrCreateMesh_impl
         meshPtr = autoPtr<faMesh>::New(areaName, pMesh, false);
 
         readHandler = fileOperation::fileHandler(oldHandler);
-        UPstream::commWorld(oldWorldComm);
+        UPstream::commWorld(realWorldComm);
 
         // Reset mesh communicator to the real world comm
-        meshPtr().comm() = UPstream::commWorld();
+        meshPtr().comm() = realWorldComm;
     }
 
 
diff --git a/src/finiteArea/fields/faPatchFields/faPatchField/faPatchFieldMapperPatchRef.H b/src/finiteArea/fields/faPatchFields/faPatchField/faPatchFieldMapperPatchRef.H
deleted file mode 100644
index ba6e52aa05..0000000000
--- a/src/finiteArea/fields/faPatchFields/faPatchField/faPatchFieldMapperPatchRef.H
+++ /dev/null
@@ -1,100 +0,0 @@
-/*---------------------------------------------------------------------------*\
-  =========                 |
-  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
-   \\    /   O peration     |
-    \\  /    A nd           | www.openfoam.com
-     \\/     M anipulation  |
--------------------------------------------------------------------------------
-    Copyright (C) 2016-2017 Wikki Ltd
--------------------------------------------------------------------------------
-License
-    This file is part of OpenFOAM.
-
-    OpenFOAM is free software: you can redistribute it and/or modify it
-    under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
-    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
-    for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
-
-Class
-    Foam::faPatchFieldMapperPatchRef
-
-Description
-
-\*---------------------------------------------------------------------------*/
-
-#ifndef faPatchFieldMapperPatchRef_H
-#define faPatchFieldMapperPatchRef_H
-
-#include "faPatchFieldMapper.H"
-
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-namespace Foam
-{
-
-/*---------------------------------------------------------------------------*\
-                   Class faPatchFieldMapperPatchRef Declaration
-\*---------------------------------------------------------------------------*/
-
-class faPatchFieldMapperPatchRef
-:
-    public faPatchFieldMapper
-{
-    // Private Data
-
-        const faPatch& sourcePatch_;
-        const faPatch& targetPatch_;
-
-
-    // Private Member Functions
-
-        //- No copy construct
-        faPatchFieldMapperPatchRef(const faPatchFieldMapperPatchRef&) = delete;
-
-        //- No copy assignment
-        void operator=(const faPatchFieldMapperPatchRef&) = delete;
-
-
-public:
-
-    // Constructors
-
-        //- Construct from components
-        faPatchFieldMapperPatchRef(const faPatch& source, const faPatch& target)
-        :
-            sourcePatch_(source),
-            targetPatch_(target)
-        {}
-
-
-    // Member functions
-
-        const faPatch& sourcePatch() const
-        {
-            return sourcePatch_;
-        }
-
-        const faPatch& targetPatch() const
-        {
-            return targetPatch_;
-        }
-};
-
-
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-} // End namespace Foam
-
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-#endif
-
-// ************************************************************************* //
diff --git a/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.C b/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.C
index aa794581a8..b20e9faddf 100644
--- a/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.C
+++ b/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2012-2016 OpenFOAM Foundation
-    Copyright (C) 2015-2023 OpenCFD Ltd.
+    Copyright (C) 2015-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -390,7 +390,7 @@ Foam::labelList Foam::fvMeshTools::removeEmptyPatches
             if (keepPatches.found(pp.name()))
             {
                 newToOld[newI] = patchI;
-                oldToNew[patchI] = newI++;                
+                oldToNew[patchI] = newI++;
             }
             else
             {
@@ -777,7 +777,7 @@ Foam::fvMeshTools::loadOrCreateMeshImpl
 
     // Patch types
     // ~~~~~~~~~~~
-    // Read and scatter master patches (without reading master mesh!)
+    // Read and broadcast master patches (without reading master mesh!)
 
     PtrList<entry> patchEntries;
     if (UPstream::master())
@@ -951,10 +951,12 @@ Foam::fvMeshTools::loadOrCreateMeshImpl
     }
     else if (readHandlerPtr && haveLocalMesh)
     {
+        const label numWorldProcs = UPstream::nProcs(UPstream::worldComm);
+        const label realWorldComm = UPstream::worldComm;
+
         const labelList meshProcIds(BitOps::sortedToc(haveMesh));
 
         UPstream::communicator newCommunicator;
-        const label oldWorldComm = UPstream::commWorld();
 
         auto& readHandler = *readHandlerPtr;
         auto oldHandler = fileOperation::fileHandler(readHandler);
@@ -963,31 +965,14 @@ Foam::fvMeshTools::loadOrCreateMeshImpl
         // only include the ranks for the current IO rank.
         // Instead allocate a new communicator for everyone with a mesh
 
-        const auto& handlerProcIds = UPstream::procID(fileHandler().comm());
-
         // Comparing global ranks in the communicator.
-        // Use std::equal for the List<label> vs List<int> comparison
-
-        if
-        (
-            meshProcIds.size() == handlerProcIds.size()
-         && std::equal
-            (
-                meshProcIds.cbegin(),
-                meshProcIds.cend(),
-                handlerProcIds.cbegin()
-            )
-        )
+        if (UPstream::sameProcs(fileHandler().comm(), meshProcIds))
         {
-            const_cast<fileOperation&>(fileHandler()).nProcs(UPstream::nProcs(oldWorldComm));
+            const_cast<fileOperation&>(fileHandler()).nProcs(numWorldProcs);
             // Can use the handler communicator as is.
             UPstream::commWorld(fileHandler().comm());
         }
-        else if
-        (
-            UPstream::nProcs(fileHandler().comm())
-         != UPstream::nProcs(UPstream::worldComm)
-        )
+        else if (UPstream::nProcs(fileHandler().comm()) != numWorldProcs)
         {
             // Need a new communicator for the fileHandler.
 
@@ -1002,10 +987,10 @@ Foam::fvMeshTools::loadOrCreateMeshImpl
         meshPtr = autoPtr<fvMesh>::New(io, false);
 
         readHandler = fileOperation::fileHandler(oldHandler);
-        UPstream::commWorld(oldWorldComm);
+        UPstream::commWorld(realWorldComm);
 
         // Reset mesh communicator to the real world comm
-        meshPtr().polyMesh::comm() = UPstream::commWorld();
+        meshPtr().polyMesh::comm() = realWorldComm;
     }
 
 
diff --git a/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.H b/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.H
index 347e7f212b..39456d01ca 100644
--- a/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.H
+++ b/src/finiteVolume/fvMesh/fvMeshTools/fvMeshTools.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2012-2016 OpenFOAM Foundation
-    Copyright (C) 2015-2023 OpenCFD Ltd.
+    Copyright (C) 2015-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -218,7 +218,7 @@ public:
     static autoPtr<mapDistributePolyMesh> readProcAddressing
     (
         const fvMesh& procMesh,
-        const autoPtr<fvMesh>& baseMeshPtr
+        const fvMesh* baseMeshPtr
     );
 
     //- Write addressing if decomposing (1 to many) or reconstructing
@@ -227,10 +227,23 @@ public:
     (
         const fvMesh& procMesh,
         const mapDistributePolyMesh& map,
+        //! running in decompose vs reconstruct mode
         const bool decompose,
-        const fileName& writeHandlerInstance,
+        //! the instance for maps
+        const fileName& writeInstance,
+        //! The output file handler
         refPtr<fileOperation>& writeHandler
     );
+
+
+    // Housekeeping
+
+        //- Read procAddressing components (reconstructing)
+        static autoPtr<mapDistributePolyMesh> readProcAddressing
+        (
+            const fvMesh& procMesh,
+            const autoPtr<fvMesh>& baseMeshPtr
+        );
 };
 
 
diff --git a/src/finiteVolume/fvMesh/fvMeshTools/fvMeshToolsProcAddr.C b/src/finiteVolume/fvMesh/fvMeshTools/fvMeshToolsProcAddr.C
index 18fea740cc..e22e0219d1 100644
--- a/src/finiteVolume/fvMesh/fvMeshTools/fvMeshToolsProcAddr.C
+++ b/src/finiteVolume/fvMesh/fvMeshTools/fvMeshToolsProcAddr.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2015-2023 OpenCFD Ltd.
+    Copyright (C) 2015-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -45,7 +45,7 @@ namespace Foam
 static autoPtr<mapDistributePolyMesh> createReconstructMap
 (
     const fvMesh& mesh,
-    const autoPtr<fvMesh>& baseMeshPtr,
+    const fvMesh* baseMeshPtr,
     const labelList& cellProcAddressing,
     const labelList& faceProcAddressing,
     const labelList& pointProcAddressing,
@@ -109,7 +109,7 @@ static autoPtr<mapDistributePolyMesh> createReconstructMap
 
 
     // NB: can only have a reconstruct on master!
-    if (Pstream::master() && baseMeshPtr && baseMeshPtr->nCells())
+    if (UPstream::master() && baseMeshPtr && baseMeshPtr->nCells())
     {
         const fvMesh& baseMesh = *baseMeshPtr;
 
@@ -219,7 +219,7 @@ Foam::autoPtr<Foam::mapDistributePolyMesh>
 Foam::fvMeshTools::readProcAddressing
 (
     const fvMesh& mesh,
-    const autoPtr<fvMesh>& baseMeshPtr
+    const fvMesh* baseMeshPtr
 )
 {
     // Processor-local reading
@@ -303,7 +303,7 @@ void Foam::fvMeshTools::writeProcAddressing
     const fvMesh& mesh,
     const mapDistributePolyMesh& map,
     const bool decompose,
-    const fileName& writeHandlerInstance,
+    const fileName& writeInstance,
     refPtr<fileOperation>& writeHandler
 )
 {
@@ -431,21 +431,22 @@ void Foam::fvMeshTools::writeProcAddressing
     // as instance so instead of e.g. 'celllMap.write()' directly call
     // the chosen file-handler.
 
+    if (!writeInstance.empty())
+    {
+        cellMap.instance() = writeInstance;
+        faceMap.instance() = writeInstance;
+        pointMap.instance() = writeInstance;
+        patchMap.instance() = writeInstance;
+    }
+
     const auto& tm = cellMap.time();
-    const IOstreamOption opt(tm.writeFormat(), tm.writeCompression());
+    const IOstreamOption opt(tm.writeStreamOption());
     {
         auto oldHandler = fileOperation::fileHandler(writeHandler);
 
-        cellMap.instance() = writeHandlerInstance;
         const bool cellOk = fileHandler().writeObject(cellMap, opt, true);
-
-        faceMap.instance() = writeHandlerInstance;
         const bool faceOk = fileHandler().writeObject(faceMap, opt, true);
-
-        pointMap.instance() = writeHandlerInstance;
         const bool pointOk = fileHandler().writeObject(pointMap, opt, true);
-
-        patchMap.instance() = writeHandlerInstance;
         const bool patchOk = fileHandler().writeObject(patchMap, opt, true);
 
         writeHandler = fileOperation::fileHandler(oldHandler);
@@ -463,4 +464,17 @@ void Foam::fvMeshTools::writeProcAddressing
 }
 
 
+// * * * * * * * * * * * * * * * Housekeeping  * * * * * * * * * * * * * * * //
+
+Foam::autoPtr<Foam::mapDistributePolyMesh>
+Foam::fvMeshTools::readProcAddressing
+(
+    const fvMesh& procMesh,
+    const autoPtr<fvMesh>& baseMeshPtr
+)
+{
+    return readProcAddressing(procMesh, baseMeshPtr.get());
+}
+
+
 // ************************************************************************* //
diff --git a/src/parallel/decompose/faDecompose/Make/files b/src/parallel/decompose/faDecompose/Make/files
index 965581e625..e7e33914bc 100644
--- a/src/parallel/decompose/faDecompose/Make/files
+++ b/src/parallel/decompose/faDecompose/Make/files
@@ -1,6 +1,6 @@
-faFieldDecomposer.C
-faFieldDecomposerCache.C
+faFieldDecomposer.cxx
+faFieldDecomposerCache.cxx
 
-faMeshDecomposition.C
+faMeshDecomposition.cxx
 
 LIB = $(FOAM_LIBBIN)/libfaDecompose
diff --git a/src/parallel/decompose/faDecompose/faFieldDecomposer.H b/src/parallel/decompose/faDecompose/faFieldDecomposer.H
index 442a7f62b4..dd164b4f93 100644
--- a/src/parallel/decompose/faDecompose/faFieldDecomposer.H
+++ b/src/parallel/decompose/faDecompose/faFieldDecomposer.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 Wikki Ltd
-    Copyright (C) 2021-2022 OpenCFD Ltd.
+    Copyright (C) 2021-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -35,9 +35,9 @@ Author
     Hrvoje Jasak, Wikki Ltd.
 
 SourceFiles
-    faFieldDecomposer.C
-    fvFieldDecomposerCache.C
-    faFieldDecomposerTemplates.C
+    faFieldDecomposer.cxx
+    faFieldDecomposer.txx
+    fvFieldDecomposerCache.cxx
 
 \*---------------------------------------------------------------------------*/
 
@@ -90,9 +90,9 @@ public:
                 );
 
 
-            // Member functions
+            // Member Functions
 
-                label size() const
+                label size() const noexcept
                 {
                     return directAddressing_.size();
                 }
@@ -102,7 +102,7 @@ public:
                     return sizeBeforeMapping_;
                 }
 
-                bool direct() const
+                bool direct() const noexcept
                 {
                     return true;
                 }
@@ -112,7 +112,7 @@ public:
                     return false;
                 }
 
-                const labelUList& directAddressing() const
+                const labelUList& directAddressing() const noexcept
                 {
                     return directAddressing_;
                 }
@@ -144,7 +144,7 @@ public:
 
             // Member Functions
 
-                label size() const
+                label size() const noexcept
                 {
                     return directAddressing_.size();
                 }
@@ -154,7 +154,7 @@ public:
                     return sizeBeforeMapping_;
                 }
 
-                bool direct() const
+                bool direct() const noexcept
                 {
                     return true;
                 }
@@ -164,7 +164,7 @@ public:
                     return false;
                 }
 
-                const labelUList& directAddressing() const
+                const labelUList& directAddressing() const noexcept
                 {
                     return directAddressing_;
                 }
@@ -192,7 +192,7 @@ public:
 
             // Member Functions
 
-                label size() const
+                label size() const noexcept
                 {
                     return addressing_.size();
                 }
@@ -202,7 +202,7 @@ public:
                     return sizeBeforeMapping_;
                 }
 
-                bool direct() const
+                bool direct() const noexcept
                 {
                     return false;
                 }
@@ -212,12 +212,12 @@ public:
                     return false;
                 }
 
-                const labelListList& addressing() const
+                const labelListList& addressing() const noexcept
                 {
                     return addressing_;
                 }
 
-                const scalarListList& weights() const
+                const scalarListList& weights() const noexcept
                 {
                     return weights_;
                 }
@@ -232,13 +232,13 @@ private:
         const faMesh& procMesh_;
 
         //- Reference to edge addressing
-        const labelList& edgeAddressing_;
+        const labelUList& edgeAddressing_;
 
         //- Reference to face addressing
-        const labelList& faceAddressing_;
+        const labelUList& faceAddressing_;
 
         //- Reference to boundary addressing
-        const labelList& boundaryAddressing_;
+        const labelUList& boundaryAddressing_;
 
         //- List of patch field decomposers
         PtrList<patchFieldDecomposer> patchFieldDecomposerPtrs_;
@@ -270,11 +270,11 @@ public:
         //- Construct without mappers, added later with reset()
         faFieldDecomposer
         (
-            const Foam::zero,
+            Foam::zero,
             const faMesh& procMesh,             // Target mesh
-            const labelList& edgeAddressing,
-            const labelList& faceAddressing,
-            const labelList& boundaryAddressing
+            const labelUList& edgeAddressing,
+            const labelUList& faceAddressing,
+            const labelUList& boundaryAddressing
         );
 
         //- Construct from components using information from the complete mesh
@@ -282,9 +282,9 @@ public:
         (
             const faMesh& completeMesh,         // Source mesh
             const faMesh& procMesh,             // Target mesh
-            const labelList& edgeAddressing,
-            const labelList& faceAddressing,
-            const labelList& boundaryAddressing
+            const labelUList& edgeAddressing,
+            const labelUList& faceAddressing,
+            const labelUList& boundaryAddressing
         );
 
         //- Construct from components without the complete mesh
@@ -292,15 +292,15 @@ public:
         (
             // Information about the complete mesh
             const label nTotalFaces,
-            const List<labelRange>& boundaryRanges,
+            const UList<labelRange>& boundaryRanges,
             const labelUList& edgeOwner,
             const labelUList& edgeNeigbour,
 
             // Addressing for processor mesh
             const faMesh& procMesh,             // Target mesh
-            const labelList& edgeAddressing,
-            const labelList& faceAddressing,
-            const labelList& boundaryAddressing
+            const labelUList& edgeAddressing,
+            const labelUList& faceAddressing,
+            const labelUList& boundaryAddressing
         );
 
 
@@ -311,7 +311,7 @@ public:
     // Member Functions
 
         //- True if no mappers have been allocated
-        bool empty() const;
+        bool empty() const noexcept;
 
         //- Remove all mappers
         void clear();
@@ -323,7 +323,7 @@ public:
         void reset
         (
             const label nTotalFaces,
-            const List<labelRange>& boundaryRanges,
+            const UList<labelRange>& boundaryRanges,
             const labelUList& edgeOwner,
             const labelUList& edgeNeigbour
         );
@@ -448,7 +448,7 @@ public:
         //- Supports reading/sending fields
         void readAllFields
         (
-            const boolList& haveMeshOnProc,
+            const boolUList& haveMeshOnProc,
             const faMeshSubset* subsetter,
             const faMesh& mesh,
             IOobjectList& objects
@@ -470,7 +470,7 @@ public:
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "faFieldDecomposerTemplates.C"
+    #include "faFieldDecomposer.txx"
 #endif
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
diff --git a/src/parallel/decompose/faDecompose/faFieldDecomposer.C b/src/parallel/decompose/faDecompose/faFieldDecomposer.cxx
similarity index 89%
rename from src/parallel/decompose/faDecompose/faFieldDecomposer.C
rename to src/parallel/decompose/faDecompose/faFieldDecomposer.cxx
index 3f7df059d8..c33fdad684 100644
--- a/src/parallel/decompose/faDecompose/faFieldDecomposer.C
+++ b/src/parallel/decompose/faDecompose/faFieldDecomposer.cxx
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 Wikki Ltd
-    Copyright (C) 2021-2024 OpenCFD Ltd.
+    Copyright (C) 2021-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -126,21 +126,17 @@ processorEdgePatchFieldDecomposer
 
 Foam::faFieldDecomposer::faFieldDecomposer
 (
-    const Foam::zero,
+    Foam::zero,
     const faMesh& procMesh,
-    const labelList& edgeAddressing,
-    const labelList& faceAddressing,
-    const labelList& boundaryAddressing
+    const labelUList& edgeAddressing,
+    const labelUList& faceAddressing,
+    const labelUList& boundaryAddressing
 )
 :
     procMesh_(procMesh),
     edgeAddressing_(edgeAddressing),
     faceAddressing_(faceAddressing),
-    boundaryAddressing_(boundaryAddressing),
-    // Mappers
-    patchFieldDecomposerPtrs_(),
-    processorAreaPatchFieldDecomposerPtrs_(),
-    processorEdgePatchFieldDecomposerPtrs_()
+    boundaryAddressing_(boundaryAddressing)
 {}
 
 
@@ -148,14 +144,14 @@ Foam::faFieldDecomposer::faFieldDecomposer
 (
     const faMesh& completeMesh,
     const faMesh& procMesh,
-    const labelList& edgeAddressing,
-    const labelList& faceAddressing,
-    const labelList& boundaryAddressing
+    const labelUList& edgeAddressing,
+    const labelUList& faceAddressing,
+    const labelUList& boundaryAddressing
 )
 :
     faFieldDecomposer
     (
-        zero{},
+        Foam::zero{},
         procMesh,
         edgeAddressing,
         faceAddressing,
@@ -169,19 +165,19 @@ Foam::faFieldDecomposer::faFieldDecomposer
 Foam::faFieldDecomposer::faFieldDecomposer
 (
     const label nTotalFaces,
-    const List<labelRange>& boundaryRanges,
+    const UList<labelRange>& boundaryRanges,
     const labelUList& edgeOwner,
     const labelUList& edgeNeigbour,
 
     const faMesh& procMesh,
-    const labelList& edgeAddressing,
-    const labelList& faceAddressing,
-    const labelList& boundaryAddressing
+    const labelUList& edgeAddressing,
+    const labelUList& faceAddressing,
+    const labelUList& boundaryAddressing
 )
 :
     faFieldDecomposer
     (
-        zero{},
+        Foam::zero{},
         procMesh,
         edgeAddressing,
         faceAddressing,
@@ -194,7 +190,7 @@ Foam::faFieldDecomposer::faFieldDecomposer
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-bool Foam::faFieldDecomposer::empty() const
+bool Foam::faFieldDecomposer::empty() const noexcept
 {
     return patchFieldDecomposerPtrs_.empty();
 }
@@ -211,16 +207,16 @@ void Foam::faFieldDecomposer::clear()
 void Foam::faFieldDecomposer::reset
 (
     const label nTotalFaces,
-    const List<labelRange>& boundaryRanges,
+    const UList<labelRange>& boundaryRanges,
     const labelUList& edgeOwner,
     const labelUList& edgeNeigbour
 )
 {
-    clear();
     const label nMappers = procMesh_.boundary().size();
-    patchFieldDecomposerPtrs_.resize(nMappers);
-    processorAreaPatchFieldDecomposerPtrs_.resize(nMappers);
-    processorEdgePatchFieldDecomposerPtrs_.resize(nMappers);
+
+    patchFieldDecomposerPtrs_.resize_null(nMappers);
+    processorAreaPatchFieldDecomposerPtrs_.resize_null(nMappers);
+    processorEdgePatchFieldDecomposerPtrs_.resize_null(nMappers);
 
     forAll(boundaryAddressing_, patchi)
     {
@@ -282,11 +278,11 @@ void Foam::faFieldDecomposer::reset
 
 void Foam::faFieldDecomposer::reset(const faMesh& completeMesh)
 {
-    clear();
     const label nMappers = procMesh_.boundary().size();
-    patchFieldDecomposerPtrs_.resize(nMappers);
-    processorAreaPatchFieldDecomposerPtrs_.resize(nMappers);
-    processorEdgePatchFieldDecomposerPtrs_.resize(nMappers);
+
+    patchFieldDecomposerPtrs_.resize_null(nMappers);
+    processorAreaPatchFieldDecomposerPtrs_.resize_null(nMappers);
+    processorEdgePatchFieldDecomposerPtrs_.resize_null(nMappers);
 
     // Create weightings now - needed for proper parallel synchronization
     //// (void)completeMesh.weights();
diff --git a/src/parallel/decompose/faDecompose/faFieldDecomposerTemplates.C b/src/parallel/decompose/faDecompose/faFieldDecomposer.txx
similarity index 100%
rename from src/parallel/decompose/faDecompose/faFieldDecomposerTemplates.C
rename to src/parallel/decompose/faDecompose/faFieldDecomposer.txx
diff --git a/src/parallel/decompose/faDecompose/faFieldDecomposerCache.C b/src/parallel/decompose/faDecompose/faFieldDecomposerCache.cxx
similarity index 99%
rename from src/parallel/decompose/faDecompose/faFieldDecomposerCache.C
rename to src/parallel/decompose/faDecompose/faFieldDecomposerCache.cxx
index 493a89e70c..caafa254b5 100644
--- a/src/parallel/decompose/faDecompose/faFieldDecomposerCache.C
+++ b/src/parallel/decompose/faDecompose/faFieldDecomposerCache.cxx
@@ -265,7 +265,7 @@ void Foam::faFieldDecomposer::fieldsCache::readAllFields
 
 void Foam::faFieldDecomposer::fieldsCache::readAllFields
 (
-    const boolList& haveMeshOnProc,
+    const boolUList& haveMeshOnProc,
     const faMeshSubset* subsetter,
     const faMesh& mesh,
     IOobjectList& objects
diff --git a/src/parallel/decompose/faDecompose/faMeshDecomposition.H b/src/parallel/decompose/faDecompose/faMeshDecomposition.H
index 88e54b1674..db892fb315 100644
--- a/src/parallel/decompose/faDecompose/faMeshDecomposition.H
+++ b/src/parallel/decompose/faDecompose/faMeshDecomposition.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 Wikki Ltd
-    Copyright (C) 2021 OpenCFD Ltd.
+    Copyright (C) 2021,2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -35,24 +35,20 @@ Author
     Hrvoje Jasak, Wikki Ltd.
 
 SourceFiles
-    faMeshDecomposition.C
+    faMeshDecomposition.cxx
 
 \*---------------------------------------------------------------------------*/
 
 #ifndef Foam_faMeshDecomposition_H
 #define Foam_faMeshDecomposition_H
 
-#include "polyMesh.H"
 #include "faMesh.H"
-#include "labelList.H"
-#include "PtrList.H"
-#include "point.H"
 
 namespace Foam
 {
 
 /*---------------------------------------------------------------------------*\
-                           Class faMeshDecomposition Declaration
+                     Class faMeshDecomposition Declaration
 \*---------------------------------------------------------------------------*/
 
 class faMeshDecomposition
@@ -61,8 +57,11 @@ class faMeshDecomposition
 {
     // Private Data
 
+        //- The area-region name
+        const word areaName_;
+
         //- Number of processors in decomposition
-        label nProcs_;
+        const label nProcs_;
 
         //- Is the decomposition data to be distributed for each processor
         bool distributed_;
@@ -128,6 +127,11 @@ class faMeshDecomposition
 
         void distributeFaces();
 
+        //- No copy construct
+        faMeshDecomposition(const faMeshDecomposition&) = delete;
+
+        //- No copy assignment
+        void operator=(const faMeshDecomposition&) = delete;
 
 public:
 
@@ -135,13 +139,27 @@ public:
 
         //- Construct from components.
         //- Values will come from the volume decomposition
-        //  \param mesh the fvMesh
-        //  \param nProcessors the number of processors
-        //  \param params additional parameters, sent to updateParameters
         faMeshDecomposition
         (
+            //! The area-region name
+            const word& areaName,
+            //! The underlying polyMesh
             const polyMesh& mesh,
+            //! The number of processors
             const label nProcessors,
+            //! Additional parameters, sent to updateParameters
+            const dictionary& params = dictionary::null
+        );
+
+        //- Construct from components (default area region).
+        //- Values will come from the volume decomposition
+        faMeshDecomposition
+        (
+            //! The underlying polyMesh
+            const polyMesh& mesh,
+            //! The number of processors
+            const label nProcessors,
+            //! Additional parameters, sent to updateParameters
             const dictionary& params = dictionary::null
         );
 
@@ -154,20 +172,17 @@ public:
 
     // Settings
 
+        //- The area-region name
+        const word& name() const noexcept { return areaName_; }
+
         //- Number of processor in decomposition
-        label nProcs() const noexcept
-        {
-            return nProcs_;
-        }
+        label nProcs() const noexcept { return nProcs_; }
 
         //- Is decomposition data to be distributed for each processor
-        bool distributed() const noexcept
-        {
-            return distributed_;
-        }
+        bool distributed() const noexcept { return distributed_; }
 
         //- Change distributed flag
-        bool distributed(const bool on) noexcept
+        bool distributed(bool on) noexcept
         {
             bool old(distributed_);
             distributed_ = on;
@@ -177,11 +192,11 @@ public:
         //- Are global face zones used
         bool useGlobalFaceZones() const noexcept
         {
-            return distributed_;
+            return hasGlobalFaceZones_;
         }
 
         //- Change global face zones flag
-        bool useGlobalFaceZones(const bool on) noexcept
+        bool useGlobalFaceZones(bool on) noexcept
         {
             bool old(hasGlobalFaceZones_);
             hasGlobalFaceZones_ = on;
@@ -208,7 +223,7 @@ public:
         void decomposeMesh();
 
         //- Write decomposition
-        bool writeDecomposition();
+        bool writeDecomposition() const;
 };
 
 
diff --git a/src/parallel/decompose/faDecompose/faMeshDecomposition.C b/src/parallel/decompose/faDecompose/faMeshDecomposition.cxx
similarity index 93%
rename from src/parallel/decompose/faDecompose/faMeshDecomposition.C
rename to src/parallel/decompose/faDecompose/faMeshDecomposition.cxx
index ff97ec03fd..ae2a7e1c64 100644
--- a/src/parallel/decompose/faDecompose/faMeshDecomposition.C
+++ b/src/parallel/decompose/faDecompose/faMeshDecomposition.cxx
@@ -31,7 +31,6 @@ License
 #include "dictionary.H"
 #include "labelIOList.H"
 #include "processorFaPatch.H"
-#include "faMesh.H"
 #include "OSspecific.H"
 #include "Map.H"
 #include "SLList.H"
@@ -42,9 +41,10 @@ License
 
 void Foam::faMeshDecomposition::distributeFaces()
 {
-    const word& polyMeshRegionName = mesh().name();
+    const word& polyMeshRegionName = faMesh::mesh().name();
 
-    Info<< "\nCalculating distribution of finiteArea faces" << endl;
+    Info<< "\nCalculating distribution of finite-area faces ["
+        << polyMesh::regionName(areaName_) << "]" << endl;
 
     cpuTime decompositionTime;
 
@@ -69,7 +69,7 @@ void Foam::faMeshDecomposition::distributeFaces()
             )
         );
 
-        IOobject ioAddr
+        IOobject ioFvAddr
         (
             "procAddressing",
             "constant",
@@ -82,8 +82,11 @@ void Foam::faMeshDecomposition::distributeFaces()
 
 
         // faceProcAddressing (polyMesh)
-        ioAddr.rename("faceProcAddressing");
-        labelIOList fvFaceProcAddressing(ioAddr);
+        ioFvAddr.resetHeader("faceProcAddressing");
+        const labelList fvFaceProcAddressing
+        (
+            labelIOList::readContents(ioFvAddr)
+        );
 
         labelHashSet faceProcAddressingHash;
         faceProcAddressingHash.reserve(fvFaceProcAddressing.size());
@@ -99,20 +102,17 @@ void Foam::faMeshDecomposition::distributeFaces()
         if (hasGlobalFaceZones_)
         {
             // owner (polyMesh)
-            ioAddr.rename("owner");
-            const label ownerSize = labelIOList(ioAddr).size();
+            ioFvAddr.resetHeader("owner");
+            const label ownerSize = labelIOList::readContentsSize(ioFvAddr);
 
-            for (int i = 0; i < ownerSize; ++i)
+            for (label i = 0; i < ownerSize; ++i)
             {
                 faceProcAddressingHash.insert(fvFaceProcAddressing[i]);
             }
         }
         else
         {
-            faceProcAddressingHash.insert
-            (
-                static_cast<labelList&>(fvFaceProcAddressing)
-            );
+            faceProcAddressingHash.insert(fvFaceProcAddressing);
         }
 
         forAll(faceLabels(), facei)
@@ -137,16 +137,18 @@ void Foam::faMeshDecomposition::distributeFaces()
 
 Foam::faMeshDecomposition::faMeshDecomposition
 (
+    const word& areaName,
     const polyMesh& mesh,
     const label nProcessors,
     const dictionary& params
 )
 :
-    faMesh(mesh),
+    faMesh(areaName, mesh),
+    areaName_(areaName.empty() ? polyMesh::defaultRegion : areaName),
     nProcs_(nProcessors),
     distributed_(false),
     hasGlobalFaceZones_(false),
-    faceToProc_(nFaces()),
+    faceToProc_(faMesh::nFaces()),
     procFaceLabels_(nProcs_),
     procMeshEdgesMap_(nProcs_),
     procNInternalEdges_(nProcs_, Zero),
@@ -168,6 +170,23 @@ Foam::faMeshDecomposition::faMeshDecomposition
 }
 
 
+Foam::faMeshDecomposition::faMeshDecomposition
+(
+    const polyMesh& mesh,
+    const label nProcessors,
+    const dictionary& params
+)
+:
+    faMeshDecomposition
+    (
+        polyMesh::defaultRegion,
+        mesh,
+        nProcessors,
+        params
+    )
+{}
+
+
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 void Foam::faMeshDecomposition::updateParameters
@@ -188,9 +207,10 @@ void Foam::faMeshDecomposition::decomposeMesh()
     // Decide which cell goes to which processor
     distributeFaces();
 
-    const word& polyMeshRegionName = mesh().name();
+    const word& polyMeshRegionName = faMesh::mesh().name();
 
-    Info<< "\nDistributing faces to processors" << endl;
+    Info<< "\nDistributing faces to processors ["
+        << polyMesh::regionName(areaName_) << "]" << endl;
 
     labelList nLocalFaces(nProcs_, Zero);
 
@@ -267,16 +287,21 @@ void Foam::faMeshDecomposition::decomposeMesh()
 
 
         // pointProcAddressing (polyMesh)
-        ioAddr.rename("pointProcAddressing");
-        labelIOList fvPointProcAddressing(ioAddr);
+        ioAddr.resetHeader("pointProcAddressing");
+        const labelList fvPointProcAddressing
+        (
+            labelIOList::readContents(ioAddr)
+        );
 
         Map<label> fvFaceProcAddressingHash;
 
         {
             // faceProcAddressing (polyMesh)
-            ioAddr.rename("faceProcAddressing");
-            labelIOList fvFaceProcAddressing(ioAddr);
-
+            ioAddr.resetHeader("faceProcAddressing");
+            const labelList fvFaceProcAddressing
+            (
+                labelIOList::readContents(ioAddr)
+            );
             fvFaceProcAddressingHash = invertToMap(fvFaceProcAddressing);
         }
 
@@ -296,9 +321,10 @@ void Foam::faMeshDecomposition::decomposeMesh()
                 ).val();
         }
 
-        // Create processor finite area mesh
+        // Create processor finite-area mesh
         faMesh procMesh
         (
+            areaName_,
             procFvMesh,
             labelList(procFaceLabels_[procI])
         );
@@ -315,18 +341,12 @@ void Foam::faMeshDecomposition::decomposeMesh()
             edgesHash.insert(patch.edges()[edgei], edgesHash.size());
         }
 
-        forAll(boundary(), patchi)
+        for (const auto& fap : faMesh::boundary())
         {
-            // Include emptyFaPatch
-            const label size = boundary()[patchi].labelList::size();
-
-            for (label edgei=0; edgei < size; ++edgei)
+            // Also include emptyFaPatch etc
+            for (const label edgei : fap.edgeLabels())
             {
-                edgesHash.insert
-                (
-                    patch.edges()[boundary()[patchi][edgei]],
-                    edgesHash.size()
-                );
+                edgesHash.insert(patch.edges()[edgei], edgesHash.size());
             }
         }
 
@@ -518,6 +538,8 @@ void Foam::faMeshDecomposition::decomposeMesh()
 
         forAll(patches, patchI)
         {
+            const faPatch& fap = patches[patchI];
+
             // Reset size and start index for all processors
             forAll(procPatchSize_, procI)
             {
@@ -526,7 +548,7 @@ void Foam::faMeshDecomposition::decomposeMesh()
                     procEdgeList[procI].size();
             }
 
-            const label patchStart = patches[patchI].start();
+            const label patchStart = fap.start();
 
 //             if (!isA<cyclicFaPatch>(patches[patchI]))
             if (true)
@@ -1030,9 +1052,10 @@ void Foam::faMeshDecomposition::decomposeMesh()
             )
         );
 
-        // create finite area mesh
+        // Create processor finite-area mesh
         faMesh procMesh
         (
+            areaName_,
             procFvMesh,
             labelList(procFaceLabels_[procI])
         );
@@ -1101,9 +1124,9 @@ void Foam::faMeshDecomposition::decomposeMesh()
 }
 
 
-bool Foam::faMeshDecomposition::writeDecomposition()
+bool Foam::faMeshDecomposition::writeDecomposition() const
 {
-    const word& polyMeshRegionName = mesh().name();
+    const word& polyMeshRegionName = faMesh::mesh().name();
 
     Info<< "\nConstructing processor FA meshes" << endl;
 
@@ -1144,23 +1167,29 @@ bool Foam::faMeshDecomposition::writeDecomposition()
             )
         );
 
-        labelIOList fvBoundaryProcAddressing
+        IOobject ioFvAddr
         (
-            IOobject
-            (
-                "boundaryProcAddressing",
-                "constant",
-                polyMesh::meshSubDir,
-                procFvMesh,
-                IOobject::MUST_READ,
-                IOobject::NO_WRITE
-            )
+            "procAddressing",
+            "constant",
+            polyMesh::meshSubDir,
+            procFvMesh,
+            IOobject::MUST_READ,
+            IOobject::NO_WRITE,
+            IOobject::NO_REGISTER
+        );
+
+        // boundaryProcAddressing (polyMesh)
+        ioFvAddr.resetHeader("boundaryProcAddressing");
+        const labelList fvBoundaryProcAddressing
+        (
+            labelIOList::readContents(ioFvAddr)
         );
 
 
-        // Create finite area mesh
+        // Create processor finite-area mesh
         faMesh procMesh
         (
+            areaName_,
             procFvMesh,
             labelList(procFaceLabels_[procI])
         );
@@ -1303,7 +1332,6 @@ bool Foam::faMeshDecomposition::writeDecomposition()
         maxProcPatches = max(maxProcPatches, nProcPatches);
 
         // Write the addressing information
-
         IOobject ioAddr
         (
             "procAddressing",
@@ -1317,19 +1345,19 @@ bool Foam::faMeshDecomposition::writeDecomposition()
 
         // pointProcAddressing
         ioAddr.rename("pointProcAddressing");
-        IOList<label>::writeContents(ioAddr, procPatchPointAddressing_[procI]);
+        labelIOList::writeContents(ioAddr, procPatchPointAddressing_[procI]);
 
         // edgeProcAddressing
         ioAddr.rename("edgeProcAddressing");
-        IOList<label>::writeContents(ioAddr, procEdgeAddressing_[procI]);
+        labelIOList::writeContents(ioAddr, procEdgeAddressing_[procI]);
 
         // faceProcAddressing
         ioAddr.rename("faceProcAddressing");
-        IOList<label>::writeContents(ioAddr, procFaceAddressing_[procI]);
+        labelIOList::writeContents(ioAddr, procFaceAddressing_[procI]);
 
         // boundaryProcAddressing
         ioAddr.rename("boundaryProcAddressing");
-        IOList<label>::writeContents(ioAddr, procBoundaryAddressing_[procI]);
+        labelIOList::writeContents(ioAddr, procBoundaryAddressing_[procI]);
     }
 
 
diff --git a/src/parallel/reconstruct/faReconstruct/Make/files b/src/parallel/reconstruct/faReconstruct/Make/files
index c0f15e7ecd..1d4f38d4e4 100644
--- a/src/parallel/reconstruct/faReconstruct/Make/files
+++ b/src/parallel/reconstruct/faReconstruct/Make/files
@@ -1,5 +1,5 @@
-processorFaMeshes.C
-faFieldReconstructor.C
-faMeshReconstructor.C
+processorFaMeshes.cxx
+faFieldReconstructor.cxx
+faMeshReconstructor.cxx
 
 LIB = $(FOAM_LIBBIN)/libfaReconstruct
diff --git a/src/parallel/reconstruct/faReconstruct/faFieldReconstructor.H b/src/parallel/reconstruct/faReconstruct/faFieldReconstructor.H
index 23e7e70415..fac2b77d49 100644
--- a/src/parallel/reconstruct/faReconstruct/faFieldReconstructor.H
+++ b/src/parallel/reconstruct/faReconstruct/faFieldReconstructor.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 Wikki Ltd
-    Copyright (C) 2022 OpenCFD Ltd.
+    Copyright (C) 2022-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -35,16 +35,16 @@ Author
     Hrvoje Jasak, Wikki Ltd.
 
 SourceFiles
-    faFieldReconstructor.C
-    faFieldReconstructorTemplates.C
+    faFieldReconstructor.cxx
+    faFieldReconstructor.txx
 
 \*---------------------------------------------------------------------------*/
 
 #ifndef Foam_faFieldReconstructor_H
 #define Foam_faFieldReconstructor_H
 
-#include "PtrList.H"
 #include "faMesh.H"
+#include "PtrList.H"
 #include "IOobjectList.H"
 #include "faPatchFieldMapper.H"
 #include "labelIOList.H"
@@ -63,19 +63,19 @@ class faFieldReconstructor
     // Private Data
 
         //- Reconstructed mesh reference
-        faMesh& mesh_;
+        const faMesh& mesh_;
 
         //- List of processor meshes
-        const PtrList<faMesh>& procMeshes_;
+        const UPtrList<faMesh>& procMeshes_;
 
         //- List of processor edge addressing lists
-        const PtrList<labelIOList>& edgeProcAddressing_;
+        const UPtrList<labelIOList>& edgeProcAddressing_;
 
         //- List of processor face addressing lists
-        const PtrList<labelIOList>& faceProcAddressing_;
+        const UPtrList<labelIOList>& faceProcAddressing_;
 
         //- List of processor boundary addressing lists
-        const PtrList<labelIOList>& boundaryProcAddressing_;
+        const UPtrList<labelIOList>& boundaryProcAddressing_;
 
         //- Number of fields reconstructed
         label nReconstructed_;
@@ -157,11 +157,11 @@ public:
         //- Construct from components
         faFieldReconstructor
         (
-            faMesh& mesh,                       // Target mesh
-            const PtrList<faMesh>& procMeshes,  // Source meshes
-            const PtrList<labelIOList>& edgeProcAddressing,
-            const PtrList<labelIOList>& faceProcAddressing,
-            const PtrList<labelIOList>& boundaryProcAddressing
+            const faMesh& mesh,                 // Target mesh
+            const UPtrList<faMesh>& procMeshes, // Source meshes
+            const UPtrList<labelIOList>& edgeProcAddressing,
+            const UPtrList<labelIOList>& faceProcAddressing,
+            const UPtrList<labelIOList>& boundaryProcAddressing
         );
 
 
@@ -179,7 +179,7 @@ public:
         reconstructField
         (
             const IOobject& fieldObject,
-            const PtrList<GeometricField<Type, faPatchField, areaMesh>>&
+            const UPtrList<GeometricField<Type, faPatchField, areaMesh>>&
         ) const;
 
         //- Read and reconstruct area field
@@ -194,7 +194,7 @@ public:
         reconstructField
         (
             const IOobject& fieldObject,
-            const PtrList<GeometricField<Type, faePatchField, edgeMesh>>&
+            const UPtrList<GeometricField<Type, faePatchField, edgeMesh>>&
         ) const;
 
         //- Read and reconstruct edge field
@@ -252,7 +252,7 @@ public:
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-#   include "faFieldReconstructorTemplates.C"
+#   include "faFieldReconstructor.txx"
 #endif
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
diff --git a/src/parallel/reconstruct/faReconstruct/faFieldReconstructor.C b/src/parallel/reconstruct/faReconstruct/faFieldReconstructor.cxx
similarity index 91%
rename from src/parallel/reconstruct/faReconstruct/faFieldReconstructor.C
rename to src/parallel/reconstruct/faReconstruct/faFieldReconstructor.cxx
index 57e2b46862..5e188dab19 100644
--- a/src/parallel/reconstruct/faReconstruct/faFieldReconstructor.C
+++ b/src/parallel/reconstruct/faReconstruct/faFieldReconstructor.cxx
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 Wikki Ltd
-    Copyright (C) 2022 OpenCFD Ltd.
+    Copyright (C) 2022-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -39,11 +39,11 @@ int Foam::faFieldReconstructor::verbose_ = 1;
 
 Foam::faFieldReconstructor::faFieldReconstructor
 (
-    faMesh& mesh,
-    const PtrList<faMesh>& procMeshes,
-    const PtrList<labelIOList>& edgeProcAddressing,
-    const PtrList<labelIOList>& faceProcAddressing,
-    const PtrList<labelIOList>& boundaryProcAddressing
+    const faMesh& mesh,
+    const UPtrList<faMesh>& procMeshes,
+    const UPtrList<labelIOList>& edgeProcAddressing,
+    const UPtrList<labelIOList>& faceProcAddressing,
+    const UPtrList<labelIOList>& boundaryProcAddressing
 )
 :
     mesh_(mesh),
diff --git a/src/parallel/reconstruct/faReconstruct/faFieldReconstructorTemplates.C b/src/parallel/reconstruct/faReconstruct/faFieldReconstructor.txx
similarity index 99%
rename from src/parallel/reconstruct/faReconstruct/faFieldReconstructorTemplates.C
rename to src/parallel/reconstruct/faReconstruct/faFieldReconstructor.txx
index 15d1fb3b63..1918b90a14 100644
--- a/src/parallel/reconstruct/faReconstruct/faFieldReconstructorTemplates.C
+++ b/src/parallel/reconstruct/faReconstruct/faFieldReconstructor.txx
@@ -28,7 +28,6 @@ License
 
 #include "faFieldReconstructor.H"
 #include "Time.H"
-#include "PtrList.H"
 #include "emptyFaPatch.H"
 #include "faPatchFields.H"
 #include "faePatchFields.H"
@@ -40,7 +39,7 @@ Foam::tmp<Foam::GeometricField<Type, Foam::faPatchField, Foam::areaMesh>>
 Foam::faFieldReconstructor::reconstructField
 (
     const IOobject& fieldObject,
-    const PtrList<GeometricField<Type, faPatchField, areaMesh>>& procFields
+    const UPtrList<GeometricField<Type, faPatchField, areaMesh>>& procFields
 ) const
 {
     // Create the internalField
@@ -271,7 +270,7 @@ Foam::tmp<Foam::GeometricField<Type, Foam::faePatchField, Foam::edgeMesh>>
 Foam::faFieldReconstructor::reconstructField
 (
     const IOobject& fieldObject,
-    const PtrList<GeometricField<Type, faePatchField, edgeMesh>>& procFields
+    const UPtrList<GeometricField<Type, faePatchField, edgeMesh>>& procFields
 ) const
 {
     // Create the internalField
diff --git a/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.H b/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.H
index 02253daa17..c8932c2655 100644
--- a/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.H
+++ b/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.H
@@ -40,7 +40,7 @@ Description
     but caution should be exercised before attempting large operations.
 
 SourceFiles
-    faMeshReconstructor.C
+    faMeshReconstructor.cxx
 
 \*---------------------------------------------------------------------------*/
 
@@ -214,10 +214,10 @@ public:
         static void writeAddressing
         (
             const IOobject& io,
-            const labelList& faBoundaryProcAddr,
-            const labelList& faFaceProcAddr,
-            const labelList& faPointProcAddr,
-            const labelList& faEdgeProcAddr
+            const labelUList& faBoundaryProcAddr,
+            const labelUList& faFaceProcAddr,
+            const labelUList& faPointProcAddr,
+            const labelUList& faEdgeProcAddr
         );
 
         //- Write proc addressing at the polyMesh faceInstances time
diff --git a/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C b/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.cxx
similarity index 96%
rename from src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C
rename to src/parallel/reconstruct/faReconstruct/faMeshReconstructor.cxx
index 8786ffb395..58524edf92 100644
--- a/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C
+++ b/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.cxx
@@ -56,15 +56,7 @@ void Foam::faMeshReconstructor::calcAddressing
     faBoundaryProcAddr_ = identity(nPatches);
 
     // Mark processor patches
-    for
-    (
-        label patchi = procMesh_.boundary().nNonProcessor();
-        patchi < nPatches;
-        ++patchi
-    )
-    {
-        faBoundaryProcAddr_[patchi] = -1;
-    }
+    faBoundaryProcAddr_.slice(procMesh_.boundary().nNonProcessor()) = -1;
 
 
     // ------------------
@@ -112,13 +104,13 @@ void Foam::faMeshReconstructor::calcAddressing
 
         PstreamBuffers pBufs;
 
-        if (Pstream::master())
+        if (UPstream::master())
         {
             // Determine the respective local portions of the global ordering
 
             labelList procTargets(globalFaceNum.totalSize());
 
-            for (const label proci : Pstream::allProcs())
+            for (const label proci : UPstream::allProcs())
             {
                 labelList::subList
                 (
@@ -139,7 +131,7 @@ void Foam::faMeshReconstructor::calcAddressing
             }
 
             // Send the local portions
-            for (const int proci : Pstream::subProcs())
+            for (const int proci : UPstream::subProcs())
             {
                 SubList<label> localOrder
                 (
@@ -158,11 +150,11 @@ void Foam::faMeshReconstructor::calcAddressing
 
         pBufs.finishedScatters();
 
-        if (!Pstream::master())
+        if (!UPstream::master())
         {
             labelList localOrder;
 
-            UIPstream fromProc(Pstream::masterNo(), pBufs);
+            UIPstream fromProc(UPstream::masterNo(), pBufs);
             fromProc >> localOrder;
 
             faFaceProcAddr_ = labelList(faFaceProcAddr_, localOrder);
@@ -235,7 +227,7 @@ void Foam::faMeshReconstructor::calcAddressing
             tmpFaces,
             singlePatchProcFaces,
             UPstream::msgType(),
-            Pstream::commsTypes::scheduled
+            UPstream::commsTypes::scheduled
         );
 
         globalPointsPtr().gather
@@ -531,11 +523,11 @@ void Foam::faMeshReconstructor::createMesh()
 
     // Serial mesh - no parallel communication
 
-    const bool oldParRun = Pstream::parRun(false);
+    const bool oldParRun = UPstream::parRun(false);
 
     completeMesh.addFaPatches(completePatches);
 
-    Pstream::parRun(oldParRun);  // Restore parallel state
+    UPstream::parRun(oldParRun);  // Restore parallel state
 }
 
 
@@ -550,7 +542,7 @@ Foam::faMeshReconstructor::faMeshReconstructor
     procMesh_(procMesh),
     errors_(0)
 {
-    if (!Pstream::parRun())
+    if (!UPstream::parRun())
     {
         FatalErrorInFunction
             << "Can only be called in parallel!!" << nl
@@ -612,7 +604,7 @@ Foam::faMeshReconstructor::faMeshReconstructor
     procMesh_(procMesh),
     errors_(0)
 {
-    if (!Pstream::parRun())
+    if (!UPstream::parRun())
     {
         FatalErrorInFunction
             << "Can only be called in parallel!!" << nl
@@ -681,10 +673,10 @@ void Foam::faMeshReconstructor::writeAddressing() const
 void Foam::faMeshReconstructor::writeAddressing
 (
     const IOobject& io,
-    const labelList& faBoundaryProcAddr,
-    const labelList& faFaceProcAddr,
-    const labelList& faPointProcAddr,
-    const labelList& faEdgeProcAddr
+    const labelUList& faBoundaryProcAddr,
+    const labelUList& faFaceProcAddr,
+    const labelUList& faPointProcAddr,
+    const labelUList& faEdgeProcAddr
 )
 {
     // Write copies
diff --git a/src/parallel/reconstruct/faReconstruct/processorFaMeshes.H b/src/parallel/reconstruct/faReconstruct/processorFaMeshes.H
index fb262d2bf0..04beddf100 100644
--- a/src/parallel/reconstruct/faReconstruct/processorFaMeshes.H
+++ b/src/parallel/reconstruct/faReconstruct/processorFaMeshes.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 Wikki Ltd
+    Copyright (C) 2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -33,7 +34,7 @@ Author
     Zeljko Tukovic, FSB Zagreb
 
 SourceFiles
-    processorFaMeshes.C
+    processorFaMeshes.cxx
 
 \*---------------------------------------------------------------------------*/
 
@@ -59,8 +60,11 @@ class processorFaMeshes
 {
     // Private Data
 
-        //- List of processor finite volume meshes
-        const UPtrList<fvMesh>& fvMeshes_;
+        //- The area-region name
+        const word areaName_;
+
+        //- List of processor volume meshes (could/should be polyMesh)
+        const UPtrList<fvMesh>& volMeshes_;
 
         //- List of processor finite area meshes
         PtrList<faMesh> meshes_;
@@ -95,16 +99,30 @@ public:
     // Constructors
 
         //- Construct from components
-        explicit processorFaMeshes(const UPtrList<fvMesh>& procFvMeshes);
+        explicit processorFaMeshes
+        (
+            //! The processor volume meshes (could/should be polyMesh)
+            const UPtrList<fvMesh>& procVolMeshes,
+            //! The area-region name
+            const word& areaName = word()
+        );
 
 
     // Member Functions
 
+        //- The area-region name
+        const word& name() const noexcept { return areaName_; }
+
+        //- The number of processors used
+        label nProcs() const noexcept { return volMeshes_.size(); }
+
+        //- The processor finite-area meshes
         const PtrList<faMesh>& meshes() const noexcept
         {
             return meshes_;
         }
 
+        //- The processor finite-area meshes
         PtrList<faMesh>& meshes() noexcept
         {
             return meshes_;
diff --git a/src/parallel/reconstruct/faReconstruct/processorFaMeshes.C b/src/parallel/reconstruct/faReconstruct/processorFaMeshes.cxx
similarity index 86%
rename from src/parallel/reconstruct/faReconstruct/processorFaMeshes.C
rename to src/parallel/reconstruct/faReconstruct/processorFaMeshes.cxx
index 08d3ed6554..ccd5f2ee5f 100644
--- a/src/parallel/reconstruct/faReconstruct/processorFaMeshes.C
+++ b/src/parallel/reconstruct/faReconstruct/processorFaMeshes.cxx
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 Wikki Ltd
-    Copyright (C) 2022-2023 OpenCFD Ltd.
+    Copyright (C) 2022-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -37,17 +37,23 @@ void Foam::processorFaMeshes::read()
     // Make sure to clear (and hence unregister) any previously loaded meshes
     // and fields
 
-    boundaryProcAddressing_.free();
-    faceProcAddressing_.free();
-    edgeProcAddressing_.free();
-    pointProcAddressing_.free();
-    meshes_.free();
+    const label numProc = volMeshes_.size();
 
+    boundaryProcAddressing_.resize_null(numProc);
+    faceProcAddressing_.resize_null(numProc);
+    edgeProcAddressing_.resize_null(numProc);
+    pointProcAddressing_.resize_null(numProc);
+    meshes_.resize_null(numProc);
 
-    forAll(fvMeshes_, proci)
+    for (label proci = 0; proci < numProc; ++proci)
     {
         // Construct from polyMesh IO information
-        meshes_.emplace_set(proci, fvMeshes_[proci]);
+
+        meshes_.set
+        (
+            proci,
+            new faMesh(areaName_, volMeshes_[proci])
+        );
 
         // Read the addressing information
 
@@ -91,15 +97,12 @@ void Foam::processorFaMeshes::read()
 
 Foam::processorFaMeshes::processorFaMeshes
 (
-    const UPtrList<fvMesh>& procFvMeshes
+    const UPtrList<fvMesh>& procVolMeshes,
+    const word& areaName
 )
 :
-    fvMeshes_(procFvMeshes),
-    meshes_(procFvMeshes.size()),
-    pointProcAddressing_(meshes_.size()),
-    edgeProcAddressing_(meshes_.size()),
-    faceProcAddressing_(meshes_.size()),
-    boundaryProcAddressing_(meshes_.size())
+    areaName_(areaName.empty() ? polyMesh::defaultRegion : areaName),
+    volMeshes_(procVolMeshes)
 {
     read();
 }