I'd say this is not exactly a properly made tilemap, at least in the context of constructs tilemaps. This tilemap seems to assume that tiles can simply be stacked over each other (as if you have multiple layers of tilemaps) whereas the tilemap in construct is 1 layer, so tiles cannot stack, period. You can either create the missing tiles you need on your own or you can stack multiple tilemaps on top of each other to emulate the layering (I do not recommend that, it's going to be arduous to work with)