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damp on external end terrace wall with floor below st level

Postby Azureblue8 » Thu Sep 02, 2010 9:40 pm

My husband and I are in the process of buying a flat but we might have a serious damp problem. Would really appreciate any advice as we have a sneaky suspicion it might end up costing us more than we bargained for!!

Flat notes:
The flat is an end of terrace.
The house was built in 1860.
The floor of the flat is below street level (by about 1 metre).
The total height of the flat is about 1.2 meters

A damp specialist took a damp reading with their meter which showed damp up to a metre across the wall of the living room which continues into the bedroom. This is an external wall and the end of terrace wall.

The damp specialist said they would take the skirting boards off and drill holes that are placed 6 inches above the floor. The holes will be drilled in a horizontal line. They will fill the holes which will stop the damp rising. They also intend to add vertical tanking at the edge of each wall then replaster.

On another link of this forum someone said "beware of damp specialists because they will just want to inject the wall with a chemical and give you a guarantee for that part of the wall - the damp will naturally want to move elsewhere so if it pops up on a seperate wall, the guarantee won't cover it."

A website says:
"Injection damp proof remedies seldom work properly. The process involves pumping silicon into a wall under pressure, saturating the brick or stonework with a waterproof material. However, the mortar between stone or brick and any voids in the structure still allow moisture through, especially if this is under pressure from the ground behind. Rendering with a waterproof additive is then applied to seal off the moisture. However, even if very well undertaken, this type of repair tends to have a limited lifespan."

As the street is higher than the flat floor level, how will six inches of damp proofing stop the damp from coming in above it? We are concerned that it wont. And then the guarantee wont cover it.

It has been suggested by a building surveyor friend of ours (he hasnt seen the property) that we could consider digging down externally and creating a channel between the exterior wall and the ground outside. A website on this matter says "water ingress can be reduced by introducing a damp proof membrane (DPM), usually of polypropylene sheeting, against the external face of the retaining wall with a land drain at the bottom. Without the ability to connect this membrane to a horizontal damp membrane across the floor, the results will never be perfect, but good results can be achieved."

However we have concerns as it is an end of terrace flat and the end of terrace wall may well be supported by the road outside. The house has stood for 150 years and we may cause more serious structural damage if we take this course of action, but it seems the only course for this kind of damp problem??

Can anyone offer any advice/experience to this please???
Most grateful as its sink or swim with this one!!
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Simply Build It

Postby stoneyboy » Sun Sep 05, 2010 10:16 pm

To be blunt - don't buy this flat it will always be cold and damp.
If you must buy the external DPM is a valid solution.
You could consider tanking with an air gap as described here
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