diff --git a/docs/Developer.md b/docs/Developer.md
index 0a2043702f9e76a0dbb9a2c6bda8033adbefde2f..9059eccfe50312ef8b2fa01dd2cd19eed0dfa67e 100644
--- a/docs/Developer.md
+++ b/docs/Developer.md
@@ -91,14 +91,18 @@ Workflow details (getting the source code in blue, pull request in red, integrat
 
 ### Special notes for building the model from PHYEX before cycle 49t2
 
-The model version hosted in IAL is incompatible with the content of the PHYEX repository.
+Because the interfaces between the physics and the rest of the model can change, one have to choose the right version of IAL to use with PHYEX.
+The file 'src/arome/ial\_version.json' contains a description of this IAL version.
+
+If no IAL version suits correctly, this json file is accompanied by the 'ext' directory and/or by the 'src/arome/gmkpack\_ignored\_files' file.
+
 To build the model, you must:
 
-- take the source code of cycle 48t3
-- remove the directories 'mpa/\*/internals' and 'mpa/\*/modules'
-- put the PHYEX directories 'aux', 'conv', 'micro' and 'turb' into a new directory (at the same level as 'mpa') named 'phyex'
-- dispatch the code contained in 'ext' into the subdirectories of 'arpifs'
-- remove the files listed in the PHYEX repository in the 'src/arome/gmkpack\_ignored\_files' file
+- checkout the IAL source code using the version described in the file src/arome/ial\_version.json
+- remove the directories 'mpa/\*/internals' and 'mpa/\*/modules' (if they still exist in IAL, eg: 48t3)
+- put the PHYEX directories 'aux', 'conv', 'micro' and 'turb' into a directory (at the same level as 'mpa') named 'phyex'
+- if the 'ext' directory exists, dispatch its content into the subdirectories of IAL
+- remove from the source tree the files listed in the 'src/arome/gmkpack\_ignored\_files' file
 
 ## Contribution workflow for MESO-NH developers
 
diff --git a/docs/Integrator.md b/docs/Integrator.md
index 5716ceadb28b330fd072e9b7e7829c4e9ec222c2..6726f35b039868206d1e4f3395b316ac7703e4b7 100644
--- a/docs/Integrator.md
+++ b/docs/Integrator.md
@@ -47,6 +47,14 @@ Details for point 6:
     - when asked by the IAL integrator, builds a new arome specific branch (see [below](#code-preparation))
     - when an arome specific branch is used in an official cycle, the arome specific branch is tagged accordingly
 
+### PHYEX - IAL compatibility
+
+Because the interfaces between the physics and the rest of the model can change, the right version of IAL to use with PHYEX must be referenced in the 'src/arome/ial\_version.json' file.
+
+If no IAL version is able to receive directly the PHYEX physics, an 'ext' directory can be added to hold the files that must be modified on top of the IAL version described in the 'src/arome/ial\_version.json' file.
+
+In addition, if some files must be excluded from the IAL compilation, they must be listed in the 'src/arome/gmkpack\_ignored\_files' file.
+
 ## Normal workflow for a contribution developed in MESONH
 
 The developer sends its pull request on the Méso-NH repository (the physics source code is embedded in the model source code).