diff --git a/OpenRA.FileFormats/Map/TileSet.cs b/OpenRA.FileFormats/Map/TileSet.cs
index 59ad5bc27e..78f6e76c0a 100644
--- a/OpenRA.FileFormats/Map/TileSet.cs
+++ b/OpenRA.FileFormats/Map/TileSet.cs
@@ -19,7 +19,6 @@ namespace OpenRA.FileFormats
 	public class TerrainTypeInfo
 	{
 		public string Type;
-		public bool Buildable = true;
 		public bool AcceptSmudge = true;
 		public bool IsWater = false;
 		public Color Color;
diff --git a/OpenRA.Mods.RA/Buildings/Building.cs b/OpenRA.Mods.RA/Buildings/Building.cs
index e23949608e..65a4283758 100755
--- a/OpenRA.Mods.RA/Buildings/Building.cs
+++ b/OpenRA.Mods.RA/Buildings/Building.cs
@@ -22,7 +22,7 @@ namespace OpenRA.Mods.RA.Buildings
 	public class BuildingInfo : ITraitInfo
 	{
 		public readonly int Power = 0;
-		public readonly bool WaterBound = false;
+		public readonly string[] TerrainTypes = {};
 		public readonly int Adjacent = 2;
 		public readonly string Footprint = "x";
 		public readonly int2 Dimensions = new int2(1, 1);
diff --git a/OpenRA.Mods.RA/Buildings/Util.cs b/OpenRA.Mods.RA/Buildings/Util.cs
index 4ec4863c7c..c8c743bdfd 100755
--- a/OpenRA.Mods.RA/Buildings/Util.cs
+++ b/OpenRA.Mods.RA/Buildings/Util.cs
@@ -16,20 +16,17 @@ namespace OpenRA.Mods.RA.Buildings
 {
 	public static class BuildingUtils
 	{
-		public static bool IsCellBuildable(this World world, int2 a, bool waterBound)
+		public static bool IsCellBuildable(this World world, int2 a, BuildingInfo bi)
 		{
-			return world.IsCellBuildable(a, waterBound, null);	
+			return world.IsCellBuildable(a, bi, null);
 		}
 		
-		public static bool IsCellBuildable(this World world, int2 a, bool waterBound, Actor toIgnore)
+		public static bool IsCellBuildable(this World world, int2 a, BuildingInfo bi, Actor toIgnore)
 		{
 			if (world.WorldActor.Trait<BuildingInfluence>().GetBuildingAt(a) != null) return false;
 			if (world.ActorMap.GetUnitsAt(a).Any(b => b != toIgnore)) return false;
 			
-			if (waterBound)
-				return world.Map.IsInMap(a.X,a.Y) && world.GetTerrainInfo(a).IsWater;
-
-			return world.Map.IsInMap(a.X, a.Y) && world.GetTerrainInfo(a).Buildable;
+			return world.Map.IsInMap(a) && bi.TerrainTypes.Contains(world.GetTerrainType(a));
 		}
 
 		public static bool CanPlaceBuilding(this World world, string name, BuildingInfo building, int2 topLeft, Actor toIgnore)
@@ -37,7 +34,7 @@ namespace OpenRA.Mods.RA.Buildings
 			var res = world.WorldActor.Trait<ResourceLayer>();
 			return FootprintUtils.Tiles(name, building, topLeft).All(
 				t => world.Map.IsInMap(t.X, t.Y) && res.GetResource(t) == null &&
-					world.IsCellBuildable(t, building.WaterBound, toIgnore));
+					world.IsCellBuildable(t, building, toIgnore));
 		}
 
 		public static IEnumerable<int2> GetLineBuildCells(World world, int2 location, string name, BuildingInfo bi)
@@ -45,7 +42,7 @@ namespace OpenRA.Mods.RA.Buildings
 			int range = Rules.Info[name].Traits.Get<LineBuildInfo>().Range;
 			var topLeft = location;	// 1x1 assumption!
 
-			if (world.IsCellBuildable(topLeft, bi.WaterBound))
+			if (world.IsCellBuildable(topLeft, bi))
 				yield return topLeft;
 
 			// Start at place location, search outwards
@@ -60,7 +57,7 @@ namespace OpenRA.Mods.RA.Buildings
 						continue;
 
 					int2 cell = topLeft + i * vecs[d];
-					if (world.IsCellBuildable(cell, bi.WaterBound))
+					if (world.IsCellBuildable(cell, bi))
 						continue; // Cell is empty; continue search
 
 					// Cell contains an actor. Is it the type we want?
diff --git a/OpenRA.Mods.RA/HackyAI.cs b/OpenRA.Mods.RA/HackyAI.cs
index 28b3fd129f..69fa6fd3e2 100644
--- a/OpenRA.Mods.RA/HackyAI.cs
+++ b/OpenRA.Mods.RA/HackyAI.cs
@@ -34,6 +34,7 @@ namespace OpenRA.Mods.RA
 		public readonly string Name = "Unnamed Bot";
 		public readonly int SquadSize = 8;
 		public readonly int AssignRolesInterval = 20;
+		public readonly string RallypointTestBuilding = "fact";		// temporary hack to maintain previous rallypoint behavior.
 
 		string IBotInfo.Name { get { return this.Name; } }
 
@@ -64,6 +65,7 @@ namespace OpenRA.Mods.RA
 		int ticks;
 		Player p;
 		PowerManager playerPower;
+		readonly BuildingInfo rallypointTestBuilding;		// temporary hack
 
 		int2 baseCenter;
 		XRandom random = new XRandom(); //we do not use the synced random number generator.
@@ -76,6 +78,8 @@ namespace OpenRA.Mods.RA
 		public HackyAI(HackyAIInfo Info)
 		{
 			this.Info = Info;
+			// temporary hack.
+			this.rallypointTestBuilding = Rules.Info[Info.RallypointTestBuilding].Traits.Get<BuildingInfo>();
 		}
 
 		enum BuildState
@@ -342,7 +346,9 @@ namespace OpenRA.Mods.RA
 
 		bool IsRallyPointValid(int2 x)
 		{
-			return world.IsCellBuildable(x, false);
+			// this is actually WRONG as soon as HackyAI is building units with a variety of
+			// movement capabilities. (has always been wrong)
+			return world.IsCellBuildable(x, rallypointTestBuilding);
 		}
 
 		void SetRallyPointsForNewProductionBuildings(Actor self)
@@ -366,7 +372,7 @@ namespace OpenRA.Mods.RA
 		//won't work for shipyards...
 		int2 ChooseRallyLocationNear(int2 startPos)
 		{
-			var possibleRallyPoints = world.FindTilesInCircle(startPos, 8).Where(x => world.IsCellBuildable(x, false)).ToArray();
+			var possibleRallyPoints = world.FindTilesInCircle(startPos, 8).Where(IsRallyPointValid).ToArray();
 			if (possibleRallyPoints.Length == 0)
 			{
 				Game.Debug("Bot Bug: No possible rallypoint near {0}", startPos);
diff --git a/OpenRA.Mods.RA/Orders/PlaceBuildingOrderGenerator.cs b/OpenRA.Mods.RA/Orders/PlaceBuildingOrderGenerator.cs
index 7c88fb9197..cab8c6b98c 100755
--- a/OpenRA.Mods.RA/Orders/PlaceBuildingOrderGenerator.cs
+++ b/OpenRA.Mods.RA/Orders/PlaceBuildingOrderGenerator.cs
@@ -22,13 +22,14 @@ namespace OpenRA.Mods.RA.Orders
 		readonly Actor Producer;
 		readonly string Building;
 		readonly IEnumerable<Renderable> Preview;
-		BuildingInfo BuildingInfo { get { return Rules.Info[ Building ].Traits.Get<BuildingInfo>(); } }
+		readonly BuildingInfo BuildingInfo;
 		Sprite buildOk, buildBlocked;
 
 		public PlaceBuildingOrderGenerator(Actor producer, string name)
 		{
 			Producer = producer;
 			Building = name;
+			BuildingInfo = Rules.Info[Building].Traits.Get<BuildingInfo>();
 			
 			Preview = Rules.Info[Building].Traits.Get<RenderBuildingInfo>()
 								.RenderPreview(Rules.Info[Building], producer.Owner);
@@ -97,7 +98,7 @@ namespace OpenRA.Mods.RA.Orders
 				var res = world.WorldActor.Trait<ResourceLayer>();
 				var isCloseEnough = BuildingInfo.IsCloseEnoughToBase(world, world.LocalPlayer, Building, topLeft);
 				foreach (var t in FootprintUtils.Tiles(Building, BuildingInfo, topLeft))
-					cells.Add( t, isCloseEnough && world.IsCellBuildable(t, BuildingInfo.WaterBound) && res.GetResource(t) == null );
+					cells.Add( t, isCloseEnough && world.IsCellBuildable(t, BuildingInfo) && res.GetResource(t) == null );
 			}
 
 			foreach( var c in cells )
diff --git a/OpenRA.TilesetBuilder/Form1.cs b/OpenRA.TilesetBuilder/Form1.cs
index cd78cfc50a..dd2d26bdeb 100644
--- a/OpenRA.TilesetBuilder/Form1.cs
+++ b/OpenRA.TilesetBuilder/Form1.cs
@@ -147,7 +147,6 @@ namespace OpenRA.TilesetBuilder
 			var terraintype = new TerrainTypeInfo()
 			{
 				Type = "Clear",
-				Buildable = true,
 				AcceptSmudge = true,
 				IsWater = false,
 				Color = Color.White
diff --git a/mods/cnc/rules/defaults.yaml b/mods/cnc/rules/defaults.yaml
index 0955613383..590a3a35b4 100644
--- a/mods/cnc/rules/defaults.yaml
+++ b/mods/cnc/rules/defaults.yaml
@@ -207,6 +207,7 @@
 		Footprint: x
 		BuildSounds: constru2.aud, hvydoor1.aud
 		SellSounds: cashturn.aud
+		TerrainTypes: Clear,Road
 	SoundOnDamageTransition:
 		DamagedSound: xplos.aud
 		DestroyedSound: xplobig4.aud
@@ -295,6 +296,7 @@
 		Footprint: x
 		BuildSounds: hvydoor1.aud
 		Adjacent: 7
+		TerrainTypes: Clear,Road
 	TargetableBuilding:
 		TargetTypes: Ground
 	Wall:
diff --git a/mods/cnc/tilesets/desert.yaml b/mods/cnc/tilesets/desert.yaml
index 4f1f11efef..b8314c4b3b 100644
--- a/mods/cnc/tilesets/desert.yaml
+++ b/mods/cnc/tilesets/desert.yaml
@@ -7,58 +7,47 @@ General:
 Terrain:
 	TerrainType@Clear:
 		Type: Clear
-		Buildable: True
 		AcceptSmudge: True
 		Color: 134, 95, 69
 	TerrainType@Water:
 		Type: Water
 		IsWater: true
-		Buildable: False
 		AcceptSmudge: False
 		Color: 93, 165, 206
 	TerrainType@Road:
 		Type: Road
-		Buildable: True
 		AcceptSmudge: True
 		Color: 168, 123, 83
 	TerrainType@Rock:
 		Type: Rock
-		Buildable: False
 		AcceptSmudge: False
 		Color: 116, 90, 63
 	TerrainType@Tree:
 		Type: Tree
-		Buildable: False
 		AcceptSmudge: False
 		Color: 28, 32, 36
 	TerrainType@River:
 		Type: River
-		Buildable: False
 		AcceptSmudge: False
 		Color: 111, 132, 139
 	TerrainType@Rough:
 		Type: Rough
-		Buildable: False
 		AcceptSmudge: True
 		Color: 68, 68, 60
 	TerrainType@Wall:
 		Type: Wall
-		Buildable: False
 		AcceptSmudge: True
 		Color: 208, 192, 160
 	TerrainType@Beach:
 		Type: Beach
-		Buildable: False
 		AcceptSmudge: False
 		Color: 176, 156, 120
 	TerrainType@Tiberium:
 		Type: Tiberium
-		Buildable: False
 		AcceptSmudge: True
 		Color: 161, 226, 28
 	TerrainType@BlueTiberium:
 		Type: BlueTiberium
-		Buildable: False
 		AcceptSmudge: True
 		Color: 84, 252, 252
 
diff --git a/mods/cnc/tilesets/temperat.yaml b/mods/cnc/tilesets/temperat.yaml
index 627eb6f53c..d38917bdc3 100644
--- a/mods/cnc/tilesets/temperat.yaml
+++ b/mods/cnc/tilesets/temperat.yaml
@@ -7,58 +7,47 @@ General:
 Terrain:
 	TerrainType@Clear:
 		Type: Clear
-		Buildable: True
 		AcceptSmudge: True
 		Color: 40, 68, 40
 	TerrainType@Water:
 		Type: Water
 		IsWater: true
-		Buildable: False
 		AcceptSmudge: False
 		Color: 92, 116, 164
 	TerrainType@Road:
 		Type: Road
-		Buildable: True
 		AcceptSmudge: True
 		Color: 88, 116, 116
 	TerrainType@Rock:
 		Type: Rock
-		Buildable: False
 		AcceptSmudge: False
 		Color: 68, 68, 60
 	TerrainType@Tree:
 		Type: Tree
-		Buildable: False
 		AcceptSmudge: False
 		Color: 28, 32, 36
 	TerrainType@River:
 		Type: River
-		Buildable: False
 		AcceptSmudge: False
 		Color: 92, 140, 180
 	TerrainType@Rough:
 		Type: Rough
-		Buildable: False
 		AcceptSmudge: True
 		Color: 68, 68, 60
 	TerrainType@Wall:
 		Type: Wall
-		Buildable: False
 		AcceptSmudge: True
 		Color: 208, 192, 160
 	TerrainType@Beach:
 		Type: Beach
-		Buildable: False
 		AcceptSmudge: False
 		Color: 176, 156, 120
 	TerrainType@Tiberium:
 		Type: Tiberium
-		Buildable: False
 		AcceptSmudge: True
 		Color: 161, 226, 28
 	TerrainType@BlueTiberium:
 		Type: BlueTiberium
-		Buildable: False
 		AcceptSmudge: True
 		Color: 84, 252, 252
 
diff --git a/mods/cnc/tilesets/winter.yaml b/mods/cnc/tilesets/winter.yaml
index c6f6b3422e..233e65d54c 100644
--- a/mods/cnc/tilesets/winter.yaml
+++ b/mods/cnc/tilesets/winter.yaml
@@ -7,58 +7,47 @@ General:
 Terrain:
 	TerrainType@Clear:
 		Type: Clear
-		Buildable: True
 		AcceptSmudge: True
 		Color: 40, 68, 40
 	TerrainType@Water:
 		Type: Water
 		IsWater: true
-		Buildable: False
 		AcceptSmudge: False
 		Color: 92, 116, 164
 	TerrainType@Road:
 		Type: Road
-		Buildable: True
 		AcceptSmudge: True
 		Color: 88, 116, 116
 	TerrainType@Rock:
 		Type: Rock
-		Buildable: False
 		AcceptSmudge: False
 		Color: 68, 68, 60
 	TerrainType@Tree:
 		Type: Tree
-		Buildable: False
 		AcceptSmudge: False
 		Color: 28, 32, 36
 	TerrainType@River:
 		Type: River
-		Buildable: False
 		AcceptSmudge: False
 		Color: 92, 140, 180
 	TerrainType@Rough:
 		Type: Rough
-		Buildable: False
 		AcceptSmudge: True
 		Color: 68, 68, 60
 	TerrainType@Wall:
 		Type: Wall
-		Buildable: False
 		AcceptSmudge: True
 		Color: 208, 192, 160
 	TerrainType@Beach:
 		Type: Beach
-		Buildable: False
 		AcceptSmudge: False
 		Color: 176, 156, 120
 	TerrainType@Tiberium:
 		Type: Tiberium
-		Buildable: False
 		AcceptSmudge: True
 		Color: 161, 226, 28
 	TerrainType@BlueTiberium:
 		Type: BlueTiberium
-		Buildable: False
 		AcceptSmudge: True
 		Color: 84, 252, 252
 
diff --git a/mods/ra/rules/defaults.yaml b/mods/ra/rules/defaults.yaml
index 7d150a7f5e..df82fc9974 100644
--- a/mods/ra/rules/defaults.yaml
+++ b/mods/ra/rules/defaults.yaml
@@ -174,6 +174,7 @@
 	Building:
 		Dimensions: 1,1
 		Footprint: x
+		TerrainTypes: Clear,Road
 	GivesBuildableArea:
 	Capturable:
 	SoundOnDamageTransition:
@@ -205,6 +206,7 @@
 		Footprint: x
 		BuildSounds: placbldg.aud
 		Adjacent: 7
+		TerrainTypes: Clear,Road
 	SoundOnDamageTransition:
 		DamagedSound: sandbag2.aud
 		DestroyedSound: sandbag2.aud
diff --git a/mods/ra/rules/structures.yaml b/mods/ra/rules/structures.yaml
index f38ae85620..697d3ccb36 100644
--- a/mods/ra/rules/structures.yaml
+++ b/mods/ra/rules/structures.yaml
@@ -85,7 +85,7 @@ SPEN:
 		Footprint: xxx xxx xxx
 		Dimensions: 3,3
 		Adjacent: 8
-		WaterBound: yes
+		TerrainTypes: Water
 	-GivesBuildableArea:
 	Health:
 		HP: 1000
@@ -140,7 +140,7 @@ SYRD:
 		Footprint: xxx xxx xxx
 		Dimensions: 3,3
 		Adjacent: 8
-		WaterBound: yes
+		TerrainTypes: Water
 	-GivesBuildableArea:
 	Health:
 		HP: 1000
@@ -1046,7 +1046,7 @@ SYRF:
 		Footprint: xxx xxx xxx
 		Dimensions: 3,3
 		Adjacent: 8
-		WaterBound: yes
+		TerrainTypes: Water
 	-GivesBuildableArea:
 	Health:
 		HP: 30
@@ -1066,7 +1066,7 @@ SPEF:
 		Footprint: xxx xxx xxx
 		Dimensions: 3,3
 		Adjacent: 8
-		WaterBound: yes
+		TerrainTypes: Water
 	-GivesBuildableArea:
 	Health:
 		HP: 30
diff --git a/mods/ra/tilesets/interior.yaml b/mods/ra/tilesets/interior.yaml
index 1952a4abfe..26f2c22f77 100644
--- a/mods/ra/tilesets/interior.yaml
+++ b/mods/ra/tilesets/interior.yaml
@@ -7,53 +7,43 @@ General:
 Terrain:
 	TerrainType@Clear:
 		Type: Clear
-		Buildable: True
 		AcceptSmudge: True
 		Color: 40, 68, 40
 	TerrainType@Water:
 		Type: Water
 		IsWater: true
-		Buildable: False
 		AcceptSmudge: False
 		Color: 92, 116, 164
 	TerrainType@Road:
 		Type: Road
-		Buildable: True
 		AcceptSmudge: True
 		Color: 88, 116, 116
 	TerrainType@Rock:
 		Type: Rock
-		Buildable: False
 		AcceptSmudge: False
 		Color: 68, 68, 60
 	TerrainType@Tree:
 		Type: Tree
-		Buildable: False
 		AcceptSmudge: False
 		Color: 28, 32, 36
 	TerrainType@River:
 		Type: River
-		Buildable: False
 		AcceptSmudge: False
 		Color: 92, 140, 180
 	TerrainType@Rough:
 		Type: Rough
-		Buildable: False
 		AcceptSmudge: True
 		Color: 68, 68, 60
 	TerrainType@Wall:
 		Type: Wall
-		Buildable: False
 		AcceptSmudge: True
 		Color: 208, 192, 160
 	TerrainType@Beach:
 		Type: Beach
-		Buildable: False
 		AcceptSmudge: False
 		Color: 176, 156, 120
 	TerrainType@Ore:
 		Type: Ore
-		Buildable: False
 		AcceptSmudge: True
 		Color: 148, 128, 96
 
diff --git a/mods/ra/tilesets/snow.yaml b/mods/ra/tilesets/snow.yaml
index 23f582313c..f5ab82e895 100644
--- a/mods/ra/tilesets/snow.yaml
+++ b/mods/ra/tilesets/snow.yaml
@@ -7,53 +7,43 @@ General:
 Terrain:
 	TerrainType@Clear:
 		Type: Clear
-		Buildable: True
 		AcceptSmudge: True
 		Color: 196, 196, 196
 	TerrainType@Water:
 		Type: Water
 		IsWater: true
-		Buildable: False
 		AcceptSmudge: False
 		Color: 92, 116, 164
 	TerrainType@Road:
 		Type: Road
-		Buildable: True
 		AcceptSmudge: True
 		Color: 88, 116, 116
 	TerrainType@Rock:
 		Type: Rock
-		Buildable: False
 		AcceptSmudge: False
 		Color: 68, 68, 60
 	TerrainType@Tree:
 		Type: Tree
-		Buildable: False
 		AcceptSmudge: False
 		Color: 28, 32, 36
 	TerrainType@River:
 		Type: River
-		Buildable: False
 		AcceptSmudge: False
 		Color: 92, 140, 180
 	TerrainType@Rough:
 		Type: Rough
-		Buildable: False
 		AcceptSmudge: True
 		Color: 68, 68, 60
 	TerrainType@Wall:
 		Type: Wall
-		Buildable: False
 		AcceptSmudge: True
 		Color: 208, 192, 160
 	TerrainType@Beach:
 		Type: Beach
-		Buildable: False
 		AcceptSmudge: False
 		Color: 176, 156, 120
 	TerrainType@Ore:
 		Type: Ore
-		Buildable: False
 		AcceptSmudge: True
 		Color: 148, 128, 96
 
diff --git a/mods/ra/tilesets/temperat.yaml b/mods/ra/tilesets/temperat.yaml
index 4dd951c41c..7e2729469c 100644
--- a/mods/ra/tilesets/temperat.yaml
+++ b/mods/ra/tilesets/temperat.yaml
@@ -7,53 +7,43 @@ General:
 Terrain:
 	TerrainType@Clear:
 		Type: Clear
-		Buildable: True
 		AcceptSmudge: True
 		Color: 40, 68, 40
 	TerrainType@Water:
 		Type: Water
 		IsWater: true
-		Buildable: False
 		AcceptSmudge: False
 		Color: 92, 116, 164
 	TerrainType@Road:
 		Type: Road
-		Buildable: True
 		AcceptSmudge: True
 		Color: 88, 116, 116
 	TerrainType@Rock:
 		Type: Rock
-		Buildable: False
 		AcceptSmudge: False
 		Color: 68, 68, 60
 	TerrainType@Tree:
 		Type: Tree
-		Buildable: False
 		AcceptSmudge: False
 		Color: 28, 32, 36
 	TerrainType@River:
 		Type: River
-		Buildable: False
 		AcceptSmudge: False
 		Color: 92, 140, 180
 	TerrainType@Rough:
 		Type: Rough
-		Buildable: False
 		AcceptSmudge: True
 		Color: 68, 68, 60
 	TerrainType@Wall:
 		Type: Wall
-		Buildable: False
 		AcceptSmudge: True
 		Color: 208, 192, 160
 	TerrainType@Beach:
 		Type: Beach
-		Buildable: False
 		AcceptSmudge: False
 		Color: 176, 156, 120
 	TerrainType@Ore:
 		Type: Ore
-		Buildable: False
 		AcceptSmudge: True
 		Color: 148, 128, 96