Rising damp coming through chipboard on concrete floor
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Looking at post #22, it's strange that the worst damp is on the inner leaf, and not directly on the outer wall. How much lower is your inner level, compared to the outside steps. French drains are good if the inner and outer levels are the same, but they don't always work very well as they can get silted up over time, and sometimes, a drain channel works better. The other issue with a french drain, is you've got to be able to get down to earth level (ideally with no clay) so that the water can drain into the ground; if you can't do that, then you need a pipe with holes bedded in gravel to take the water out to a drain somewhere. Have a look at the paving expert website for ideas on french drain types.
As you're lower on the inside in some places, you'd need to go down quite a way to make sure you get past the inner ground level, and then throw either bitumen or synthepruf the outer wall, and then concrete with a waterproofer added to get you up to the drain channel height. You may also need to hack off the plaster internally and inject a silicon cream dpc, and then tank as well, but it's odd that the ooutside levels weren't considered when the extension was done, but it's possible that the paving was done afterwards, and that bridged the dpc.
Moisture meters don't always tell the true story, but they do let you see the highest and lowest wet points, and that helps determine the worst areas, and even a wood meter will help you do this. And in addition to dealing with the outside levels and drains, you may end up tanking the walls as the only way of dealing with this, and putting down a butumen type dpc, and then adding self leveling compound on top of it.
As you're lower on the inside in some places, you'd need to go down quite a way to make sure you get past the inner ground level, and then throw either bitumen or synthepruf the outer wall, and then concrete with a waterproofer added to get you up to the drain channel height. You may also need to hack off the plaster internally and inject a silicon cream dpc, and then tank as well, but it's odd that the ooutside levels weren't considered when the extension was done, but it's possible that the paving was done afterwards, and that bridged the dpc.
Moisture meters don't always tell the true story, but they do let you see the highest and lowest wet points, and that helps determine the worst areas, and even a wood meter will help you do this. And in addition to dealing with the outside levels and drains, you may end up tanking the walls as the only way of dealing with this, and putting down a butumen type dpc, and then adding self leveling compound on top of it.
Bottom right of the posts shows the post number. This one should be #34. 0 to 7ft is too general. What's the difference in height outside at each point of the dampness in the wall. I suspect you need to call in a builder so you've got someone on site to ascertain the problem.
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Got it.
Yes, well we don't know how damp the outer wall is.
Its pebbledashed on the outside, and the inside of the outer wall isnt accessable.
Its a strange arrangement, with 3 ft deep airing cupboard between the inner and outer.
At the point where the worst damp is, the corresponding outer wall is about 4 ft underground, where the second step up is, on the upper steps.
Yes, well we don't know how damp the outer wall is.
Its pebbledashed on the outside, and the inside of the outer wall isnt accessable.
Its a strange arrangement, with 3 ft deep airing cupboard between the inner and outer.
At the point where the worst damp is, the corresponding outer wall is about 4 ft underground, where the second step up is, on the upper steps.
Ive hacked away at the exposed dpc to see how they've done it.
Seems like they put a membrane between the steps/raised paving, and the house wall.
But ruined it by concreting 4 inches over the top of the overlap?
I imagine that could be fixed by hacking out the 4" of concrete and laying a slot drain in its place?
Seems like they put a membrane between the steps/raised paving, and the house wall.
But ruined it by concreting 4 inches over the top of the overlap?
I imagine that could be fixed by hacking out the 4" of concrete and laying a slot drain in its place?
Now, its looking like the central heating!
Removed the piles of bedding etc from the airing cupboard, and the paint has blistered up just below the rad inlet.
This is the inside of the true outer wall, probably only a few inches undergound.
Plaster crumbly, meter reads 18% compared to 10% just above the pipe.
The rad. pipe has verdigris, and maybe feels damp, hard to tell for sure.
Removed the piles of bedding etc from the airing cupboard, and the paint has blistered up just below the rad inlet.
This is the inside of the true outer wall, probably only a few inches undergound.
Plaster crumbly, meter reads 18% compared to 10% just above the pipe.
The rad. pipe has verdigris, and maybe feels damp, hard to tell for sure.
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You don't need to go by the digits reading.
Observe the top of the meter. It will most likely have a glass window. Rub it clean. Observe that there is an air bubble in it. All the time water is flowing, the bubble will turn.
You will need a torch, a rag or small paintbrush, and possibly a ladle or plastic mug if the meter pit is filled with water.
Observe the top of the meter. It will most likely have a glass window. Rub it clean. Observe that there is an air bubble in it. All the time water is flowing, the bubble will turn.
You will need a torch, a rag or small paintbrush, and possibly a ladle or plastic mug if the meter pit is filled with water.
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