I can't place my beach lots at the beach. I use the Belladonna Cave template and as you can see in the picture, empty lots are fine, I just can't place lots where I already built something.

I know this is a common problem and there are a lot of threads about it, but nothing seems to work for me (I edited the terrain etc.). I really don't wanna rebuild everything, is there any way to make the lots placeable, maybe through a mod? I don't really know what the problem behind this is or if this is considered a bug

As far as I know, nope. Beach lots are fussy and are only guaranteed to place in the same spot on the same neighborhood map on which they were originally built. The issue with them is that, in order for them to place, the overall shape of the saved lot -- particularly the slope of it from road to waterline -- has to very closely match the shape of the spot on the terrain that you want to place it on. Beach lots do not warp the underlying terrain to match themselves, as non-beach-lots do, so there needs to be enough of a match in order for the beach lot to be placed in a given spot. Unfortunately, editing the terrain to do this doesn't always work because, for one thing, editing terrain in neighborhood view isn't nearly as precise as the tools one uses to change the terrain when building on a placed lot...

...Unless you're completely flattening an area. So, the method I use to make "universal" beach lots is to always completely flatten all beach areas of every empty neighborhood first, before I build or place any lots in a neighborhood. (Vimpse wrote up a tute here.) That way, any beach lot I build can be stuffed in my lot catalog and used pretty much anywhere, so long as the beach areas have been flattened. The other option is to place an empty non-beach lot somewhere in the neighborhood, and then move it and make it into a beach lot using the Lot Adjuster, then build on it. (I wrote up a mini-tute to make a waveless beach lot here, but you can add the waves with another download if you want. But! That method also generally works best with flattened lots.) Unfortunately, those methods aren't going to help you if your pre-built beach lots are not flat. It's also not going to help you if you want lots with houses built on beachside cliffs and such. Lots like that would likely need to be built individually in each neighborhood you want to use them in.

I'm sorry I don't have better news for you, but I'm pretty sure this isn't something that can be changed with a mod because where lots can be placed is hard-coded into the game. There might be some way to very finely mess with an existing lot's shape in SimPE but if there is, knowing how to do so is above my pay grade.

How much terrain changing did you do? I downloaded some tiny beach lots a few days ago and it took a LOT of terrain changing before one would place and then I realized the whole road area needed to be lower. Once I figured that out then figured it needed to be shorter to the water they started placing, but it's possible you need to keep on trying with the terrain shaping. I partly used Vimpse's tutorial that iCad linked to above.

Thanks for the responses, maybe I can fix it somehow. At least now I know where the problem is - all my lots have many hills and so on.

I basically tried to lower or raise only some parts in neighborhood mode because at first I thought the lot was not close enough to the water. So I made the terrain lower and when that didn't work I tried the opposite. I didn't really do much because I wasn't sure if the water was the problem or the general height

according to a Sims Resource tutorial, beach lots would need to be placed on similar terrain as the terrain it was build on. and according to the same tutorial, rotating would like mess up the lot.
http://wiki.thesimsresource.com/ind...s_of_Beach_Lots

Yes and yes, but you can fool the lot into placing on a different beach by modifying the terrain since its the different terrain that is stopping it placing not simply that its a different beach.