diff --git a/src/LIB/SURCOUCHE/src/mode_io_manage_struct.f90 b/src/LIB/SURCOUCHE/src/mode_io_manage_struct.f90
index 7d43dfb8176462f7326b09fb92d2b6e176ff37bd..2b63ec0cfbd07f074e514b0e2cc7ce9c50156588 100644
--- a/src/LIB/SURCOUCHE/src/mode_io_manage_struct.f90
+++ b/src/LIB/SURCOUCHE/src/mode_io_manage_struct.f90
@@ -1168,9 +1168,11 @@ SUBROUTINE IO_File_add2list( TPFILE, HNAME, HTYPE, HMODE,
   USE NETCDF, ONLY: NF90_QUANTIZE_BITGROOM, NF90_QUANTIZE_BITROUND, NF90_QUANTIZE_GRANULARBR
 !
 #endif
-USE MODD_BAKOUT,         ONLY: LBAK_COMPRESS, NBAK_COMPRESS_LEVEL, LBAK_REDUCE_FLOAT_PRECISION, &
-                               LOUT_COMPRESS, NOUT_COMPRESS_LEVEL, LOUT_REDUCE_FLOAT_PRECISION, &
-                               COUT_COMPRESS_LOSSY_ALGO, LOUT_COMPRESS_LOSSY, NOUT_COMPRESS_LOSSY_NSD
+USE MODD_BAKOUT,         ONLY: LBAK_COMPRESS, NBAK_COMPRESS_LEVEL, LBAK_REDUCE_FLOAT_PRECISION,        &
+                               LOUT_COMPRESS, NOUT_COMPRESS_LEVEL, LOUT_REDUCE_FLOAT_PRECISION,        &
+                               COUT_COMPRESS_LOSSY_ALGO, LOUT_COMPRESS_LOSSY, NOUT_COMPRESS_LOSSY_NSD, &
+                               LOUT_FILESPLIT_DISABLE
+
 USE MODD_CONF,           ONLY: CPROGRAM
 USE MODD_CONFZ,          ONLY: NB_PROCIO_R, NB_PROCIO_W
 USE MODD_DYN_n,          ONLY: DYN_MODEL
@@ -1357,6 +1359,8 @@ else
       ! Disable Z-split files for output files with no write of the main domain
       ! Boxes/subdomains are assumed to be too small to be usefully split vertically
       if ( htype == 'MNHOUTPUT' .and. .not. out_model(imi)%lout_bigbox_write ) gsplit_ioz = .false.
+      ! Force no split if asked in NAM_OUTPUT
+      if ( htype == 'MNHOUTPUT' .and. lout_filesplit_disable(imi) ) gsplit_ioz = .false.
     end if
   end if
 end if
diff --git a/src/MNH/modd_bakout.f90 b/src/MNH/modd_bakout.f90
index 8048bb60124d8a631dafdbdb4695e64292da1863..03c203d7d8b94609bf6e346b0ced8c36423e0264 100644
--- a/src/MNH/modd_bakout.f90
+++ b/src/MNH/modd_bakout.f90
@@ -117,4 +117,6 @@ INTEGER, DIMENSION(:,:), ALLOCATABLE :: NOUT_BOX_JSUP
 INTEGER, DIMENSION(:,:), ALLOCATABLE :: NOUT_BOX_KINF
 INTEGER, DIMENSION(:,:), ALLOCATABLE :: NOUT_BOX_KSUP
 
+! Flag to disable output file splitting (supersedes NB_PROCIO_W option from NAM_CONFZ)
+LOGICAL, DIMENSION(JPMODELMAX) :: LOUT_FILESPLIT_DISABLE = .FALSE.
 END MODULE MODD_BAKOUT
diff --git a/src/MNH/modn_output.f90 b/src/MNH/modn_output.f90
index c76dd237299d3ba25a3023e5bcd053cdc3293bf2..76833605c059b145a93cfcab84ad7aa13e003677 100644
--- a/src/MNH/modn_output.f90
+++ b/src/MNH/modn_output.f90
@@ -59,7 +59,8 @@ NAMELIST/NAM_OUTPUT/LOUT_BEG,LOUT_END,&
                    LOUT_BOTTOM_ABSORBING_LAYER_REMOVE, LOUT_TOP_ABSORBING_LAYER_REMOVE, &
                    LOUT_UNPHYSICAL_HOR_CELLS_REMOVE, LOUT_UNPHYSICAL_VER_CELLS_REMOVE,  &
                    LOUT_PHYSICAL_SIMPLIFIED, &
-                   NOUT_BOX_IINF, NOUT_BOX_ISUP, NOUT_BOX_JINF, NOUT_BOX_JSUP, NOUT_BOX_KINF, NOUT_BOX_KSUP
+                   NOUT_BOX_IINF, NOUT_BOX_ISUP, NOUT_BOX_JINF, NOUT_BOX_JSUP, NOUT_BOX_KINF, NOUT_BOX_KSUP, &
+                   LOUT_FILESPLIT_DISABLE
 
 LOGICAL, SAVE, PRIVATE :: LOUTPUT_NML_ALLOCATED = .FALSE.