my house is an end terrace. my stairs are on the joining wall. so not outside wall. i have a problem with damp at the foot of the stairs making the paint fall off. it looks like it has all ready been treated before as you can see the bungs in the wall. does this just need redoing. how ever i did take up the last two steps and found that it is only mud underneath would this need digging dawn and a plastic membrane laying then filling back up with concrete? rest of house is fine.