diff --git a/.github/workflows/build_mpich_source.yml b/.github/workflows/build_mpich_source.yml
index f510fdcd758..69acbd8f597 100644
--- a/.github/workflows/build_mpich_source.yml
+++ b/.github/workflows/build_mpich_source.yml
@@ -1,7 +1,9 @@
 # Build MPICH from source using the latest commit on the
-# 'main' branch and cache the results. The result is installed
-# to (or restored to) '${{ runner.workspace }}/mpich' and
-# an artifact called 'mpich' is saved for later use.
+# 'main' branch and cache the results. The result is compressed
+# into a 'mpich.tar' archive to preserve permissions and
+# then is uploaded as the artifact 'mpich' which can later
+# be downloaded with 'actions/download-artifact' and then
+# uncompressed with 'tar xvf mpich.tar -C <directory>'
 
 # Triggers the workflow on a call from another workflow
 on:
diff --git a/.github/workflows/build_openmpi_source.yml b/.github/workflows/build_openmpi_source.yml
index 359dfa302c8..5c13d4e8c8b 100644
--- a/.github/workflows/build_openmpi_source.yml
+++ b/.github/workflows/build_openmpi_source.yml
@@ -1,5 +1,11 @@
 # Build OpenMPI from source using the latest commit on the
-# 'main' branch and cache the results. The result is installed
+# 'main' branch and cache the results. The result is compressed
+# into a 'openmpi.tar' archive to preserve permissions and
+# then is uploaded as the artifact 'openmpi' which can later
+# be downloaded with 'actions/download-artifact' and then
+# uncompressed with 'tar xvf openmpi.tar -C <directory>'
+
+installed
 # to (or restored to) '${{ runner.workspace }}/openmpi' and
 # an artifact called 'openmpi' is saved for later use.
 
diff --git a/.github/workflows/cmake-par-source.yml b/.github/workflows/cmake-par-source.yml
index 9340698df65..8a535b99eff 100644
--- a/.github/workflows/cmake-par-source.yml
+++ b/.github/workflows/cmake-par-source.yml
@@ -54,7 +54,10 @@ jobs:
         uses: actions/download-artifact@fa0a91b85d4f404e444e00e005971372dc801d16 # v4.1.8
         with:
           name: openmpi
-          path: ${{ runner.workspace }}/openmpi
+
+      - name: Untar MPI installation (OpenMPI)
+        run: |
+          tar xvf openmpi.tar -C ${{ runner.workspace }}/openmpi
 
       - name: Set path (OpenMPI)
         shell: bash
@@ -162,11 +165,14 @@ jobs:
           sudo apt-get install ninja-build
           sudo apt install libaec0 libaec-dev
 
-      - name: Get MPICH installation
+      - name: Get MPI installation (MPICH)
         uses: actions/download-artifact@fa0a91b85d4f404e444e00e005971372dc801d16 # v4.1.8
         with:
           name: mpich
-          path: ${{ runner.workspace }}/mpich
+
+      - name: Untar MPI installation (MPICH)
+        run: |
+          tar xvf mpich.tar -C ${{ runner.workspace }}/mpich
 
       - name: Set path (MPICH)
         shell: bash