diff --git a/src/house_type.h b/src/house_type.h
--- a/src/house_type.h
+++ b/src/house_type.h
@@ -12,8 +12,8 @@
 #ifndef HOUSE_TYPE_H
 #define HOUSE_TYPE_H
 
-typedef uint16 HouseID;
-typedef uint16 HouseClassID;
+typedef uint16 HouseID; ///< OpenTTD ID of house types.
+typedef uint16 HouseClassID; ///< Classes of houses.
 
 struct HouseSpec;