DIY Doctor UK DIY Forums

We are converting part of an old adjacent barn into a shower room and utility area. The barn is over 200 years old and is built without dpc or foundations on bedrock. The Structural Engineer said that there was no damp in the current concrete floor but the Building Inspector is insisting that we put in a DPC. We are pensioners and are doing as much as we can ourselves to save money so we thought a liquid, bitumen type DPC would probably be easier and cheaper. We have planned to paint the vertical surfaces to a height of 1m as well as the floor and all the walls will then be covered by insulated stud walling/plaster and the floor is to be tiled with ceramic tiles. All the bitumen products I have seen require a 50mm screed to be applied to the finished floor and plaster to the walls. Is this necessary if we are tiling the floor and covering the walls?

the screed is to protect the buitumin seal,but if the floor is already laid you can lay a self level compound over the buitumin to protect it,before tiling.
With the walls, if you are plastering it the render will protect the seal