Hideout walls (the metal ones) have 50 armor. Against terrain, HE does flat 50% base damage, and firearms around 2/3-4/3 of their base damage. Outer ship's wall has 100 armor, inner 70. Shacks etc. have usually 15-30 armor, but it varies a lot between all these tilesets taken from various sources. Playing on lowest diff. may decrease that terrain armor values, maybe? But I have no other idea.
I will update the tileset just in case something got corrupted, though.