diff --git a/Editor/Editor Undo.cpp b/Editor/Editor Undo.cpp
index 46a3062a..fb0b1a29 100644
--- a/Editor/Editor Undo.cpp	
+++ b/Editor/Editor Undo.cpp	
@@ -509,7 +509,11 @@ BOOLEAN AddToUndoListCmd( INT32 iMapIndex, INT32 iCmdCount )
 		{
 			// this loop won't execute for single-tile structures; for multi-tile structures, we have to
 			// add to the undo list all the other tiles covered by the structure
+#if 0//dnl ch83 080114
 			iCoveredMapIndex = pStructure->sBaseGridNo + pStructure->pDBStructureRef->ppTile[ubLoop]->sPosRelToBase;
+#else
+			iCoveredMapIndex = AddPosRelToBase(pStructure->sBaseGridNo, pStructure->pDBStructureRef->ppTile[ubLoop]);
+#endif
 			AddToUndoList( iCoveredMapIndex );
 		}
 		pStructure = pStructure->pNext;
@@ -537,11 +541,19 @@ void CheckMapIndexForMultiTileStructures( UINT32 usMapIndex )
 				// for multi-tile structures we have to add, to the undo list, all the other tiles covered by the structure
 				if (pStructure->fFlags & STRUCTURE_BASE_TILE)
 				{
+#if 0//dnl ch83 080114
 					iCoveredMapIndex = usMapIndex + pStructure->pDBStructureRef->ppTile[ubLoop]->sPosRelToBase;
+#else
+					iCoveredMapIndex = AddPosRelToBase(usMapIndex, pStructure->pDBStructureRef->ppTile[ubLoop]);
+#endif
 				}
 				else
 				{
+#if 0//dnl ch83 080114
 					iCoveredMapIndex = pStructure->sBaseGridNo + pStructure->pDBStructureRef->ppTile[ubLoop]->sPosRelToBase;
+#else
+					iCoveredMapIndex = AddPosRelToBase(pStructure->sBaseGridNo, pStructure->pDBStructureRef->ppTile[ubLoop]);
+#endif
 				}
 				AddToUndoList( iCoveredMapIndex );
 			}
diff --git a/Tactical/Rotting Corpses.cpp b/Tactical/Rotting Corpses.cpp
index 5ff3e7e6..045c6066 100644
--- a/Tactical/Rotting Corpses.cpp	
+++ b/Tactical/Rotting Corpses.cpp	
@@ -659,9 +659,11 @@ INT32	AddRottingCorpse( ROTTING_CORPSE_DEFINITION *pCorpseDef )
 		for (ubLoop = 0; ubLoop < pDBStructureRef->pDBStructure->ubNumberOfTiles; ubLoop++)
 		{
 			ppTile = pDBStructureRef->ppTile;
-
+#if 0//dnl ch83 080114
 			sTileGridNo = pCorpseDef->sGridNo + ppTile[ ubLoop ]->sPosRelToBase;
-
+#else
+			sTileGridNo = AddPosRelToBase(pCorpseDef->sGridNo, ppTile[ubLoop]);
+#endif
 			//Remove blood
 			RemoveBlood( sTileGridNo, pCorpseDef->bLevel );
 		}
diff --git a/TileEngine/Explosion Control.cpp b/TileEngine/Explosion Control.cpp
index 1aae29f3..f9a27f86 100644
--- a/TileEngine/Explosion Control.cpp	
+++ b/TileEngine/Explosion Control.cpp	
@@ -838,7 +838,11 @@ BOOLEAN ExplosiveDamageStructureAtGridNo( STRUCTURE * pCurrent, STRUCTURE **ppNe
 					{
 						if ( !(ppTile[ ubLoop ]->fFlags & TILE_ON_ROOF ) )
 						{
+#if 0//dnl ch83 080114
 							sStructGridNo = pBase->sGridNo + ppTile[ubLoop]->sPosRelToBase;
+#else
+							sStructGridNo = AddPosRelToBase(pBase->sGridNo, ppTile[ubLoop]);
+#endif
 							// there might be two structures in this tile, one on each level, but we just want to
 							// delete one on each pass
 
@@ -1461,8 +1465,11 @@ void ExplosiveDamageGridNo( INT32 sGridNo, INT16 sWoundAmt, UINT32 uiDist, BOOLE
 
 					for ( ubLoop = BASE_TILE; ubLoop < ubNumberOfTiles; ubLoop++)
 					{
+#if 0//dnl ch83 080114
 						sNewGridNo = sBaseGridNo + ppTile[ubLoop]->sPosRelToBase;
-
+#else
+						sNewGridNo = AddPosRelToBase(sBaseGridNo, ppTile[ubLoop]);
+#endif
 						// look in adjacent tiles
 						for ( ubLoop2 = 0; ubLoop2 < NUM_WORLD_DIRECTIONS; ubLoop2++ )
 						{
diff --git a/TileEngine/Render Fun.cpp b/TileEngine/Render Fun.cpp
index 4fa62e70..26dc5a37 100644
--- a/TileEngine/Render Fun.cpp	
+++ b/TileEngine/Render Fun.cpp	
@@ -216,8 +216,11 @@ void ExamineGridNoForSlantRoofExtraGraphic( INT32 sCheckGridNo )
 		for ( ubLoop = 0; ubLoop < pBase->pDBStructureRef->pDBStructure->ubNumberOfTiles; ubLoop++ )
 		{
 			ppTile = pBase->pDBStructureRef->ppTile;
+#if 0//dnl ch83 080114
 			sGridNo = pBase->sGridNo + ppTile[ ubLoop ]->sPosRelToBase;
-
+#else
+			sGridNo = AddPosRelToBase(pBase->sGridNo, ppTile[ubLoop]);
+#endif
 			if (sGridNo < 0 || sGridNo > WORLD_MAX)
 			{
 				continue;
diff --git a/TileEngine/Structure Internals.h b/TileEngine/Structure Internals.h
index 3d86fe57..d3980a9a 100644
--- a/TileEngine/Structure Internals.h	
+++ b/TileEngine/Structure Internals.h	
@@ -123,6 +123,8 @@ extern UINT8 AtHeight[PROFILE_Z_SIZE];
 #define TILE_ON_ROOF						0x01
 #define TILE_PASSABLE						0x02
 
+#define AddPosRelToBase(sBaseGridNo, pTile) (pTile->sPosRelToBase ? (sBaseGridNo + pTile->bXPosRelToBase + pTile->bYPosRelToBase * WORLD_COLS) : sBaseGridNo)//dnl ch83 080114
+
 typedef struct TAG_STRUCTURE_TILE
 {
 	INT16			sPosRelToBase;	// "single-axis"
diff --git a/TileEngine/structure.cpp b/TileEngine/structure.cpp
index f00daeaf..1139bc8d 100644
--- a/TileEngine/structure.cpp
+++ b/TileEngine/structure.cpp
@@ -636,7 +636,11 @@ BOOLEAN OkayToAddStructureToTile( INT32 sBaseGridNo, INT16 sCubeOffset, DB_STRUC
 	INT32						sOtherGridNo;
 
 	ppTile = pDBStructureRef->ppTile;
+#if 0//dnl ch83 080114
 	sGridNo = sBaseGridNo + ppTile[ubTileIndex]->sPosRelToBase;
+#else
+	sGridNo = AddPosRelToBase(sBaseGridNo, ppTile[ubTileIndex]);
+#endif
 	if (sGridNo < 0 || sGridNo > WORLD_MAX)
 	{
 		return( FALSE );
@@ -742,11 +746,16 @@ BOOLEAN OkayToAddStructureToTile( INT32 sBaseGridNo, INT16 sCubeOffset, DB_STRUC
 							}
 							for (bLoop2 = 0; bLoop2 < pDBStructure->ubNumberOfTiles; bLoop2++)
 							{
+#if 0//dnl ch83 080114
 								if ( sBaseGridNo + ppTile[bLoop2]->sPosRelToBase == sOtherGridNo)
 								{
 									// obstacle will straddle wall!
 									return( FALSE );
 								}
+#else
+								if(AddPosRelToBase(sBaseGridNo, ppTile[bLoop2]) == sOtherGridNo)
+									return(FALSE);// obstacle will straddle wall!
+#endif
 							}
 						}
 					}
@@ -988,7 +997,11 @@ STRUCTURE * InternalAddStructureToWorld( INT32 sBaseGridNo, INT8 bLevel, DB_STRU
 			MemFree( ppStructure );
 			return( NULL );
 		}
+#if 0//dnl ch83 080114
 		ppStructure[ubLoop]->sGridNo = sBaseGridNo + ppTile[ubLoop]->sPosRelToBase;
+#else
+		ppStructure[ubLoop]->sGridNo = AddPosRelToBase(sBaseGridNo, ppTile[ubLoop]);
+#endif
 		if (ubLoop != BASE_TILE)
 		{
 			#ifdef JA2EDITOR
@@ -1196,7 +1209,11 @@ BOOLEAN DeleteStructureFromWorld( STRUCTURE * pStructure )
 	// Free all the tiles
 	for (ubLoop = BASE_TILE; ubLoop < ubNumberOfTiles; ubLoop++)
 	{
+#if 0//dnl ch83 080114
 		sGridNo = sBaseGridNo + ppTile[ubLoop]->sPosRelToBase;
+#else
+		sGridNo = AddPosRelToBase(sBaseGridNo, ppTile[ubLoop]);
+#endif
 		// there might be two structures in this tile, one on each level, but we just want to
 		// delete one on each pass
 		pCurrent = FindStructureByID( sGridNo, usStructureID );