diff --git a/applications/solvers/multiphase/compressibleInterFoam/twoPhaseMixtureThermo/twoPhaseMixtureThermo.C b/applications/solvers/multiphase/compressibleInterFoam/twoPhaseMixtureThermo/twoPhaseMixtureThermo.C
index 192dee724..d2a3ca2c2 100644
--- a/applications/solvers/multiphase/compressibleInterFoam/twoPhaseMixtureThermo/twoPhaseMixtureThermo.C
+++ b/applications/solvers/multiphase/compressibleInterFoam/twoPhaseMixtureThermo/twoPhaseMixtureThermo.C
@@ -26,7 +26,7 @@ License
 #include "twoPhaseMixtureThermo.H"
 #include "gradientEnergyFvPatchScalarField.H"
 #include "mixedEnergyFvPatchScalarField.H"
-
+#include "collatedFileOperation.H"
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
 
@@ -50,6 +50,12 @@ Foam::twoPhaseMixtureThermo::twoPhaseMixtureThermo
     thermo1_(nullptr),
     thermo2_(nullptr)
 {
+    // Note: we're writing files to be read in immediately afterwards.
+    //       Avoid any thread-writing problems.
+    float bufSz =
+        fileOperations::collatedFileOperation::maxThreadFileBufferSize;
+    fileOperations::collatedFileOperation::maxThreadFileBufferSize = 0;
+
     {
         volScalarField T1
         (
@@ -80,6 +86,10 @@ Foam::twoPhaseMixtureThermo::twoPhaseMixtureThermo
         T2.write();
     }
 
+    fileOperations::collatedFileOperation::maxThreadFileBufferSize =
+        bufSz;
+
+
     thermo1_ = rhoThermo::New(U.mesh(), phase1Name());
     thermo2_ = rhoThermo::New(U.mesh(), phase2Name());
 
diff --git a/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C b/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C
index 121b4b8da..486290c8d 100644
--- a/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C
+++ b/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C
@@ -859,7 +859,7 @@ bool Foam::decomposedBlockData::writeBlocks
         label startProc = 1;
         label nSendProcs = nProcs-1;
 
-        while (nSendProcs > 0)
+        while (nSendProcs > 0 && startProc < nProcs)
         {
             nSendProcs = calcNumProcs
             (
@@ -873,7 +873,7 @@ bool Foam::decomposedBlockData::writeBlocks
                 startProc
             );
 
-            if (startProc == nProcs || nSendProcs == 0)
+            if (nSendProcs == 0)
             {
                 break;
             }
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
index 07a19f368..2d6f39ebd 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
@@ -265,7 +265,11 @@ void Foam::OFstreamCollator::waitForBufferSpace(const off_t wantedSize) const
             }
         }
 
-        if (totalSize == 0 || (totalSize+wantedSize) <= maxBufferSize_)
+        if
+        (
+            totalSize == 0
+         || (wantedSize >= 0 && (totalSize+wantedSize) <= maxBufferSize_)
+        )
         {
             break;
         }
@@ -354,7 +358,8 @@ bool Foam::OFstreamCollator::write
     IOstream::streamFormat fmt,
     IOstream::versionNumber ver,
     IOstream::compressionType cmp,
-    const bool append
+    const bool append,
+    const bool useThread
 )
 {
     // Determine (on master) sizes to receive. Note: do NOT use thread
@@ -374,7 +379,7 @@ bool Foam::OFstreamCollator::write
         Pstream::scatter(maxLocalSize, Pstream::msgType(), localComm_);
     }
 
-    if (maxBufferSize_ == 0 || maxLocalSize > maxBufferSize_)
+    if (!useThread || maxBufferSize_ == 0 || maxLocalSize > maxBufferSize_)
     {
         if (debug)
         {
@@ -589,4 +594,20 @@ bool Foam::OFstreamCollator::write
 }
 
 
+void Foam::OFstreamCollator::waitAll()
+{
+    // Wait for all buffer space to be available i.e. wait for all jobs
+    // to finish
+    if (Pstream::master(localComm_))
+    {
+        if (debug)
+        {
+            Pout<< "OFstreamCollator : waiting for thread to have consumed all"
+                << endl;
+        }
+        waitForBufferSpace(-1);
+    }
+}
+
+
 // ************************************************************************* //
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H
index 92ef9068b..594634199 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H
@@ -206,8 +206,12 @@ public:
             IOstream::streamFormat,
             IOstream::versionNumber,
             IOstream::compressionType,
-            const bool append
+            const bool append,
+            const bool useThread = true
         );
+
+        //- Wait for all thread actions to have finished
+        void waitAll();
 };
 
 
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
index c7c6830ac..614e846af 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
@@ -556,14 +556,32 @@ bool Foam::fileOperations::collatedFileOperation::writeObject
         }
         else
         {
+            // Re-check static maxThreadFileBufferSize variable to see
+            // if needs to use threading
+            bool useThread = (maxThreadFileBufferSize > 0);
+
             if (debug)
             {
                 Pout<< "collatedFileOperation::writeObject :"
                     << " For object : " << io.name()
-                    << " starting collating output to " << pathName << endl;
+                    << " starting collating output to " << pathName
+                    << " useThread:" << useThread << endl;
             }
 
-            threadedCollatedOFstream os(writer_, pathName, fmt, ver, cmp);
+            if (!useThread)
+            {
+                writer_.waitAll();
+            }
+
+            threadedCollatedOFstream os
+            (
+                writer_,
+                pathName,
+                fmt,
+                ver,
+                cmp,
+                useThread
+            );
 
             // If any of these fail, return (leave error handling to Ostream
             // class)
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C
index df919680f..c35ba0c1f 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2017 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2017-2018 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -35,13 +35,15 @@ Foam::threadedCollatedOFstream::threadedCollatedOFstream
     const fileName& pathName,
     streamFormat format,
     versionNumber version,
-    compressionType compression
+    compressionType compression,
+    const bool useThread
 )
 :
     OStringStream(format, version),
     writer_(writer),
     pathName_(pathName),
-    compression_(compression)
+    compression_(compression),
+    useThread_(useThread)
 {}
 
 
@@ -57,7 +59,8 @@ Foam::threadedCollatedOFstream::~threadedCollatedOFstream()
         IOstream::BINARY,
         version(),
         compression_,
-        false                   // append
+        false,                  // append
+        useThread_
     );
 }
 
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.H b/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.H
index e296e1132..f9b02eed6 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.H
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.H
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2017 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2017-2018 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -60,6 +60,8 @@ class threadedCollatedOFstream
 
         const IOstream::compressionType compression_;
 
+        const bool useThread_;
+
 
 public:
 
@@ -72,7 +74,8 @@ public:
             const fileName& pathname,
             streamFormat format=ASCII,
             versionNumber version=currentVersion,
-            compressionType compression=UNCOMPRESSED
+            compressionType compression=UNCOMPRESSED,
+            const bool useThread = true
         );