Damp damage: incorrect CWI?

Furts

If you are investigating yourself, or engaging a damp company to drill and inject, it would be worthwhile examining the construction of the wall to the drive. This would be done from inside the room.

A boroscope should shed light on matters. If not drill and remove a small piece of wall. You may find this wall is a solid retaining wall without any CWI. The solidity could be a cavity wall with concrete put down the cavity, or more likely a blockwork wall. There should be a tanking membrane so your drilling and investigation could penetrate this. But since you have apparent damp this would be a minor matter in the overall picture.

As I mentioned you have a complex building detail and one that will not be easy to reach a conclusion. Injecting a damp treatment may work in the short term, but longer term this does not appear to be the answer.

Lungboy

I've had the report from the damp survey:

"From our observations and random damp meter tests to area defined, damp sources present at the time of the survey were:-

Rising damp - due to the lack of an effective damp proof course/bridging of original damp proof course by driveway, dampness was found to be rising in the walls hatched red on the attached sketch plan.
Ground water penetration - dampness was also penetrating on a horizontal plane where ground/abutting floor levels are at a higher level as marked xxx on the attached sketch plan.

Our damp proof course will be installed above these higher levels. All internal wall surfaces below the damp proof course level will require the application of a vertical waterproof membrane prior to replastering (see separate vertical waterproof membrane/replastering estimate).

Perished plaster - due to the effects of dampness, the internal wall plaster has become salt contaminated/perished. Therefore, a minimum height of 1.2m of internal wall plaster, but at least 600mm into sound plaster, should be hacked off all walls that are being injected, and renewed to our specification (see separate quotation). Penetrating dampness - All sources of penetrating dampness e.g. defective chimneys, flashings, roof coverings, rainwater goods, rendering/pointing, window cills and door openings etc. should be remedied during external repair and maintenance works by the client’s builder. We would like to point out that concealed timbers in contact with damp walls are also at risk to fungal decay. The property may be prone to condensation during winter months due to high water vapour generation from cooking, washing etc.

Extractor fans in kitchens and bathrooms are useful by removing water vapour at source. If a persistent condensation problem exists, the use of a dehumidifier would be very effective in controlling condensation. Deflection noted to hall floor to base of stairs, possibly indicating decay caused by dampness noted to walls.

RECOMMENDATION We recommend that a chemical damp proof course be injected, and this report should be read in conjunction with our STANDARD SPECIFICATION ATTACHED. Our quotation for the injection of the damp proof course into the walls, hatched in red on the attached plan, amounts to :- QUOTATION: £310.00 + VAT"

Plus the tanking membrane, which is another £900 + VAT. Ouch.

Furts

Lungboy wrote: »

I've had the report from the damp survey:

. Penetrating dampness - All sources of penetrating dampness e.g. defective chimneys, flashings, roof coverings, rainwater goods, rendering/pointing, window cills and door openings etc. should be remedied during external repair and maintenance works by the client’s builder.

Here lies the cop out for the damp company . The work is not investigated, and the source of your damp is unproven - indeed it has not been investigated! I have already referred to this in my #9.

These additional works, if required, will bump up your costs above the current quote. They should all be done before any damp proofing company is allowed near the home.

The ventilation and fan use also needs fully investigating on the same basis.

Damp proofing companies are sales driven smoke and mirrors outfits. Your experience fully justifies peoples poor perceptions of them.

Lungboy

The independent damp surveyor just left. As expected, he said tanking/DPC would not stop the problem, just move it elsewhere in the house. He also didn't think the driveway was too big an issue, as the flank wall is not damp away from the corner, and the drive has been cambered slightly to deflect water away from the wall. He reckons it's the front corner by the flowerpot, the crazy paving is pretty much impermeable along the front so water pools in that corner, and there's a small hole in the paving there, so all water that ends up at the front of the house is draining via that hole and into the ground directly in front of the damp corner. He says some work to change the camber of the paved area, plus a proper drain to divert the water away and into the main drain should fix it.