diff --git a/etc/bashrc b/etc/bashrc
index 965a08265..684aba392 100644
--- a/etc/bashrc
+++ b/etc/bashrc
@@ -71,13 +71,12 @@ fi
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 export WM_PROJECT_INST_DIR=$FOAM_INST_DIR
 export WM_PROJECT_DIR=$WM_PROJECT_INST_DIR/$WM_PROJECT-$WM_PROJECT_VERSION
-export WM_PROJECT_USER_DIR=$HOME/$WM_PROJECT/$USER-$WM_PROJECT_VERSION
+: ${WM_PROJECT_USER_DIR:=$HOME/$WM_PROJECT/$USER-$WM_PROJECT_VERSION}; export WM_PROJECT_USER_DIR
 
 
 # Location of third-party software
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-export WM_THIRD_PARTY_DIR=$WM_PROJECT_INST_DIR/ThirdParty-$WM_PROJECT_VERSION
-
+: ${WM_THIRD_PARTY_DIR=$WM_PROJECT_INST_DIR/ThirdParty-$WM_PROJECT_VERSION}; export WM_THIRD_PARTY_DIR
 
 # Operating System/Platform
 # ~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -95,7 +94,7 @@ export WM_COMPILER_LIB_ARCH=
 
 # Compilation options (architecture, precision, optimised, debug or profiling)
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-export WM_NCOMPPROCS=2
+: ${WM_NCOMPPROCS:=2}; export WM_NCOMPPROCS
 
 # WM_ARCH_OPTION = 32 | 64
 : ${WM_ARCH_OPTION:=64}; export WM_ARCH_OPTION