DIY Doctor UK DIY Forums

Hi, we live in 3 storey terraced house. The old part of the house is 3 storey (200 year old, sandstone, probably sitting on sandstone bed), The front of the basement opens road level, the rear is earth under the extension.

To the rear of the of the property we have a 70's 2 storey extension, to the upper two floors of the old house. So I cannot treat any basement issues from it's outside walls.

To the rear of the 2 storey extension we have just built a single storey extension, of which it's foundations had to go all the way down to bedrock (I guess the same level as basement floor) because of neighbouring issues.

So, the issues - general dampness in the basement - I have been using a dehumidifier as a temporary solution - but need a longer term fix. There is no "running" water on the back wall of the extension but certainly damp - do we need to have tanking membrane - how would moisture escape, or would a tanking slurry/paint on solution work?

We also have dampness on the bottom of the walls on the first floor, these are the old house rear walls that are now internal - will this need treating with an injection cream?

One other point is because of our new extension all rainwater from the gutters now go to a soak away to comply with building reg, rather than into mains drainage as it was. Are we going to see an increase in dampness in the basement (there has been no great evidence of this as yet, it is downhill (thats the way the sandstone bedrock is running) from the soak away. I didn't think about the basement when we put the soak away in.

Any advice welcome as I plan to DIY it.

many thanks

Matt

Address the drainage problem first and pipe it to the sewer, This will help stop a lot of water entering the basement. As for the walls there are many products that you can buy for the job, a membrane will stop the damp from entering the basement, and I think this is your best solution, As for the internal walls a chemical injection is required.

Thanks, do I need to worry about the soak away?, after all it has made little difference in the year that we have had it i.e. no increase in running water in the basement retaining wall, I'm just wondering if it's something we shouldn't have done. I'm guessing that our contribution to water in the ground 5 meters away from our house in nothing compared to the land further afield.

If we went for a membrane system in the basement, does it have to have a sump? also can just the rear face be done, and injection cream to the side walls and stone partition wall (basement is two rooms). Or does the whole of the basement including the road wall need membrane?

Also the neighbour to the right of us (has an identical house) has had his basement tanked. The neighbour to the left, his house is a storey down (only 2 storey house) i.e. his lounge is adjacent to our basement. If I were to tank, would I push the risk of damp into his property and should I forewarn him - is there anything he can object to or us be liable for?

if you have had no issues with ground water entering the basement throughout winter, then its not a concern, you do not need a pump unless the water is severe, if your using the membrane then for best results its best to do the whole room, there is no need to inform your neighbour you will not make any difference to his property

Great thanks.

One other issue that has come to light, is that there is a brick cavity wall (now internal completely) that joins at right angles to one of the old stone walls. This brick cavity is now showing signs of damp on both sides of the wall - for about 3ft up and 2ft along the wall.

I'm guessing that because the air in the cavity is cold, the dampness in the stone is being drawn there, would that be correct.

And how can I remedy this? It's a two storey internal wall now.

sika do a waterproof cement slurry that you can paint on the wall, I have used it before and was impressed with the results, I would recommend it

Yes I heard that too. Trouble is, we are just about to fit a kitchen on one side on the wall. We should have dealt with it but we thought it was caused by the radiator that used to be there. The other side is under the stairs so no problem on that side. Would it help to put and air brick in? Would that help the wall dry out?

yes any airflow is a help as it dries out moisture