House built 1m below ground level - Damp what else?

[Demolition Derby]

I am looking for a little enlightenment having read most of the things to do with damp on this website and not being able to find an answer to my question I have relented and registered so I can ask my question! I have by the way enjoyed laughing out loud at some of the comments made in various threads. It just shows you how there are still people out there with a sense of humour, to business:

House - approx 200 years old, was 3 cottages now one house. Both sides and the back of the house is below ground level. At the back there is a walkway with retaining wall. At one side the garden is seperated from the house by further concrete path. There are air bricks at outside ground level. There is a wooden floor inside 1m below ground level. This end of the house is relatively damp free.

The other (problem) side of the house, is extremely damp inside, strangely, the wall is (vertically speakng) half wall half stone, with facing stone externally. We have taken the plaster and concrete (yes concrete) off the wall, it had all the symptoms of damp. The floor at this end is sandstone flags laid on sand/earth (again 1m below ground level).

We plan to excavate what looks like an old french drain covered by road planings outside. No visible signs of any ventilation we are just wondering whether we would acheive anything with airbricks.

Any advice on what we can do to make these rooms liveable again would be appreciated basically the damp area affects the floorspace of what would have been one cottage.

I look forward to your comments

 

[MdB]

Any chance of some pictures? They help a lot in understanding the problem.

 

[chuckey]

If I understand you correctlly the damp end is 1m below ground level with a sandstone flag floor? Dig out the blocked french drain first, the real problem is with the road, because it and its traffic vibrations will exert a side ways pressure on you french drain unless its greater then 6' from it, depending on the soil type.
I would go for a DPC membrane against the house with a gravel in fill and another plastic/porous membrane on the out side. A perforated 3" drain at the bottom to allow any water to drain away to a lower level. This system should allow for total settlement on the outside without the main drainage pipe getting blocked, unlike french drains.
Oh yes some sandstone is very porous, I would lift them and install insulation and a DPC.
Frank

 

[Demolition Derby]

Thanks for your opinion, you read my garbles right, certainly your comment on the traffic is appreciated, the yard area was a hive of activity for tractors and wagons it is a bit more sedate now but we still have a tractor and the odd delivery wagon.

There were groans here when you mentioned lifting the sandstone we had already lifted a 'small' corner bit it's only 2 inches thick! Any tips on successful removal and replacement would be appreciated.

Re the drain advice there is already a small drain serving a downpipe at the lower end of the side of the house I think it will not be low enough (I'll scrap that as I'm answering my own question)

I will post some photos tomorrow as requested previously

 

[Matt Green]

If the ground levels around the house can be reduced below the level of the sandstone floor, it would then be the highest point, rather than the lowest. That would dramatically reduce water movement through it.

Also, putting DPM under the flags will result in any water trapped beneath it evaporating through the base of the walls.

I'd be inclined to concentrate your efforts in reducing the ground levels around the building either by permanent reuction of French drains.


Matt

 

[Demolition Derby]

Ok these are not exactly in the order I wanted but hey I got this far without too much ado. The photo below is to show the floor, the white looking patch is not sunlight but the dry part of the floor.

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This photo shows the wall with the plaster on at the other end of the room which has a wall in between which we are taking down.

On this pic you can see the half stone, half wall scenario, the wall on the right hand side of the pic is barely touching the back wall and this is the wall to be removed. Again you can see where the stone is dry and where it is wet to touch.

And lastly this photo shows the external wall and on the right hand side there are steps down to the back of the house you can just about see how much higher the ground is than the room. You can see the potential problem in excavating it.