diff --git a/domain/modelling/generators/heating_recommendation.py b/domain/modelling/generators/heating_recommendation.py
index 452f63914..3af1108b3 100644
--- a/domain/modelling/generators/heating_recommendation.py
+++ b/domain/modelling/generators/heating_recommendation.py
@@ -670,10 +670,14 @@ def _ashp_eligible(epc: EpcPropertyData, restrictions: PlanningRestrictions) ->
     installability — the Optimiser owns the economics (ADR-0024), so floor area,
     built form, fuel, and fabric are deliberately not gates. A conservation area
     does not exclude ASHP (offered with a planning caveat); a listed/heritage
-    protection (`blocks_internal`) does."""
+    protection (`blocks_internal`) does. Community heating (SAP Table 4a codes
+    301–304 or category 6) is excluded by topology: replacing a shared heat
+    network with an individual ASHP is never appropriate."""
     main: MainHeatingDetail = epc.sap_heating.main_heating_details[0]
     if main.main_heating_category == _HEAT_PUMP_CATEGORY:
         return False
+    if is_heat_network_main(main):
+        return False
     if restrictions.blocks_internal:
         return False
     return _is_house_or_bungalow(epc)