NatSol is not aware of any genuine composting toilet which fits in the space taken up by a WC. There are some toilets which are not much larger but these are usually incinerating or dehydrating toilets or “bucket” toilets. The critical dimension in most situations is not the floor area taken up by a composting toilet but the space required below the floor. In particular, the depth of vault required. NatSol toilets can be constructed with as little as 750mm vault depth and because there is no requirement with an NatSol toilet for drainage from the bottom of the vault it is possible for the vault to extend below ground level.