Investigating the damp under the stairs.

Hi folks,

This post covers what I have been doing over the last two weekends and brings the blog up to date.

We had a problem with damp under the stairs last year. The this wall joins the house next door, is four feet below grade and was tanked when the house was renovated some years ago. The tanking has been breached by a wrongly installed chemical damp proof course this was high lighted when the gutters were removed from the house next door causing water to run down the back wall of our house and soak into the wall. The wall dried out when the gutters were replaced. This year the rising water main was broken and we had six inches of standing water against the back wall of the house which found its way in. This has caused the plaster to crumble on the back wall and you can smell the damp in the house now. There was also an electric socket in the corner which is now soaking and a bit dangerous to be fair.
It took me the best part of a morning to find where this socket was supplied from, it was a spur from the ring main in the kitchen. I isolated the power and removed it, the cable is still in the wall but both ends are isolated from the supply. This cable was pretty dangerous it had been pieced three time by concrete nails, if the guy who did this had invested a fraction of the cost of his nail gun in a cable detector this wouldn't have happened.

I stripped the top 1/2" of concrete off which turned out to be a skim coat hiding more concrete. I chiseled out two holes 1 1/2" deep to find the stone wall underneath but didn't find it.

I was worried that the old wall had been removed and replaced with a solid block wall but I noticed two drill holes at eye level when I removed the concrete render. They seemed to have a void behind them so I enlarged one and found a void with stone on one side and brick on the other. I think this is the old back window that has been bricked up when the extension was built.

I started stripping away the concrete to find the original stone wall to allow it to dry out. I needed to chisel away an 1 1/2" of concrete to expose the stone which was damp but started to dry out once it was exposed.

I stripped the concrete around the door frame in a band trying to find the end of the wall.

I moved in to the extension to expose the other side of the wall. This would have been the outside wall of the old house. It smells really damp here so I lifted the floor tiles here and found three more layers of floor covering all damp. Underlay; lino and vinyl floor tiles all holding water like a sponge and stinking. So I lifted all of this and removed the wall tiles from this area as well which were concealing damp plaster.

I then stripped the bottom 12" of concrete from this side of the wall to allow it to dry out. I also uncovered a void at the base of the wall in the corner, I think the builder who laid the slab for the extension removed a protruding stone from the wall here. I will leave it open for now it will allow any water to drain away. The exposed stone was very damp but soon as it was exposed it started to dry out.

I intend to strip all the concrete from this wall and re point it with lime mortar. I will fill in the window void will new stone.

I want to observe the wall over the coming winter to see how bad the damp gets and do some research on tanking systems. I would prefer a system that allows the wall to breath and lets the ground water drain away.

It would be a shame to cover this lovely stone wall over again but I may have to reinstate the tanking but only to just above grade above this I want to leave it bare so it can breath.

A lot of hard work has gone into stripping this over the last two weekends using a lump hammer and cold chisel. Slow work but it doesn't damage the stone.

KBO.