Fixes #7877

code/game/objects/structures/door_assembly.dm

@@ -248,6 +248,10 @@
 							glass = 1
 				else if(istype(S, /obj/item/stack/sheet/mineral) && S.sheettype)
 					var/M = S.sheettype
+					// Ugly hack, will suffice for now. Need to fix it upstream as well, may rewrite mineral walls. ~Z
+					if(M in list("mhydrogen","osmium","tritium","platinum","iron"))
+						user << "You cannot make an airlock out of that material."
+						return
 					if(S.get_amount() >= 2)
 						playsound(src.loc, 'sound/items/Crowbar.ogg', 100, 1)
 						user.visible_message("[user] adds [S.name] to the airlock assembly.", "You start to install [S.name] into the airlock assembly.")

code/game/objects/structures/girders.dm

@@ -26,7 +26,7 @@
 	var/damage = Proj.damage
 	if(!istype(Proj, /obj/item/projectile/beam))
 		damage *= 0.4 //non beams do reduced damage
-	
+
 	health -= damage
 	..()
 	if(health <= 0)
@@ -144,6 +144,10 @@
 
 		if(S.sheettype)
 			var/M = S.sheettype
+			// Ugly hack, will suffice for now. Need to fix it upstream as well, may rewrite mineral walls. ~Z
+			if(M in list("mhydrogen","osmium","tritium","platinum","iron"))
+				user << "You cannot plate the girder in that material."
+				return
 			if(!anchored)
 				if(S.amount < 2) return
 				S.use(2)
@@ -271,11 +275,11 @@
 	//Girders only provide partial cover. There's a chance that the projectiles will just pass through. (unless you are trying to shoot the girder)
 	if(Proj.original != src && !prob(cover))
 		return -1 //pass through
-	
+
 	//Tasers and the like should not damage cultgirders.
 	if(!(Proj.damage_type == BRUTE || Proj.damage_type == BURN))
 		return
-	
+
 	health -= Proj.damage
 	..()
 	if(health <= 0)