A few years ago we had a swim spa and I installed a 12 x 20 slab (6" thick).

We sold the swim spa and currently have a conventional spa which I am in the process of selling due to low use.

I am considering building a shed on the slab vs tearing it out.

Our township does not require a building permit for sheds under 200 sq ft but it does state that foundations should have a rat wall.

https://www.doityourself.com/forum/a...1&d=1520692532

I'm sure that many homeowners who install small sheds even install a slab and even less probably install the required rat walls.

So I guess my inquiry is, why is a slab without a rat wall ok for a swim spa, patio, side walk, etc but once I build a structure (shed) it now is required?

I also noticed that their generic wall section they have on the building permit shows the structure sitting on the rat wall/foundation vs on the slab like I would be building.

 

Maybe they think the items stored within the building will attract animals. Or how water coming off a building with no gutters might erode the slab... which might attract burrowing animals.