So I've created a basic world in CAW & have no issue with the lots I created while in CAW. But when I export the world & try to place a 64x64 lot in the empty spaces I intentionally left open for future lot placement, it says "Can't place on road." Now I KNOW it's a 64 wide & 130 long block, because that's how I placed the roads in CAW.
Also, I placed trees in other parts of the world (in the empty "blocks" I left) & can't place lots over SOME of them because it says it's unroutable terrain! Seeing as how it's a flat island, I didn't use a lick of Sims non-routable paint & there are no spawners there, so I'm baffled. Yet, in the next block over, I can place a lot, over the damn trees.
I've repeatedly run "Rebuild Routing Data," & checked the routing with Show Routing Data, & it all checks out fine. I've created a few other worlds & never had issues like this.
Any thoughts?

@Jouet: I think you need some more flat space around that area for it to work. Say you flattened an area in CAW that is exactly 64x64, but then the terrain has a slight bump outside this area and/or you have it boxed in on all four sides with road. The World Editor is a lot more finicky in terms of how you can place lots than in CAW. That is to say, in CAW, you can place lots anywhere you like, even if the terrain is slightly bumpy and the lot is boxed in by road. But in World Editor, the flattened area has to be a bit wider than 64x130, like maybe 70x140 or something, and the lot can't be "boxed in" on all four sides with road. Otherwise, when you try to position the lot, WE will complain that you can't place it.

You can just place the lot in caw and leave it unbuild. It can be hard to find the reason it doesn't work.

@Volvenom, you are right but there might be some special reason why OP wants to do it this way. I can't speak for OP personally but I know that in some revisions that I'm doing for my worlds, I'm doing exactly what he's doing in case people have IP installed and want to be able to place their own houseboat lots.