Damp Sub Floor

[Sepher]

Hi All,

I moved into my house about 2 years ago, and during the renovations I had an issue with the sub floor which was causing musty damp smells in the house. I narrowed this down to an area where all 3 service pipes came into the house, and it appeared the hole had collapsed and was letting water in so this got filled in with a ton of waterproof expandable foam. I had the whole subfloor cleared out, I got a few of sacks of soil out of it. I then laid down cat litter around the floor to dry it out quicker as it was very damp. After a heavy rainfall I noticed this cat litter had all turned to mush without any water entering the subfloor. I then assumed that there was a broken or no DPC for my subfloor as water appeared to be coming up from underneath.

This hasn't caused any issues for the past year so. However lately we've had some really bad rain falls and unfortunately it collected out the front and breached my air bricks and went under the house. Hence now the house stinks of damp earth which is really annoying. I have also laid down all my flooring and fixed all floorboards since so I dont particularly want to take it all up again.

My plan of action is to first sort out the issue with the air bricks and get them raised higher, secondly I want to add extra air bricks onto the side of the house to introduce a cross flow (I'm semi detached house). I don't think the air flow is working correctly because I have an old lean to on the back of the house of which the outside wall has the air bricks blocked up I presume this was done because they are literally on the ground. Eventually this lean too is being replaced and I'll sort out the back air bricks. However the air bricks on the back of the house inside the lean too are fine.

So I really just to know if this 1960 house is normal to have a sub floor with no DPC in it? The house is sitting on a concrete raft as far as I'm aware. I don't suffer from any damp or condensation problems in the house and never have, so does it sound like the sub floor is not drying out and will introducing more air bricks will help it dry out quicker?

Cheers, sorry for the long post!

 

[vinn]

DPC's are in walls - DPC comes in rolls. DPM's are sheet membranes that typically go under a concrete slab.
There's rarely a call for spreading a DPM below a suspended floor in a new house.
But you could cover your sub area exposed soil with a membrane - lap it up the walls a few inches, it will contain the ground moisture from condensing on your floor.
You will need an access trap/hatch to the sub-area.

Your lengthy details about air bricks etc would be better understood if you posted photos of the three elevations at low level.
Air bricks and joist tails should best practice sit on the DPC.
Water tables and ground water from various sources is changeable, and can change overnight: the location of the house will have much to do with its appearance.

 

[Sepher]

Cheers for reply. So two pictures of front, the house floor level is basically where the cladding starts. Had a builder round today to quote to raise the airbricks by one brick as the flood went halfway past the airbrick.

Then one picture of down the side, I don't know what this rendering is over brick but I'm going to get 3-4 airbricks put down this side and then the render will be all painted and sealed.

Was also advised to dig a pit in front of the concrete raft (foundations, protrudes 1 meter round house) to stop the water flooding out the front. However I've looked online and it states that soakaway pits need to be a minimum of 5 meters from front of house which isn't feasible as I have a tarmac driveway just after 4 metres and by then the ground is higher up.

 

[vinn]

If your house is located on a hillside then that might be the root cause of your damp difficulties.

Are you saying that all or part of your house was built on a concrete raft - & that the wall or walls were set back 1m from the edge of this raft?
But you still have soil in the sub-area?
Is your sub-area covered with a layer of concrete?
Is this raft or concrete projection visible on the ground surface or is it located at some depth?
Is the ground surface in photo 3. (the photo with the red render) the raft projection you are talking about?

Photos of the hole area plugged with foam might help - believe me, masses of foam doesn't sound like a satisfactory solution.

The black (bitumen) painted area - is that render?
Likewise the red painted area render plinth seems to have been painted with plastic paints - bad, only masonry paints should be used. Dont seal anything.
Plus all render ground contact should be cut back by say 150mm.

Can you definitely indicate where your DPC bed is in the photos?

I dont understand what you say about the rear elevation & air bricks?