How much for new Damp Proof Course.

as a plasterer whom has done a lot of re plastering for damp proofing companies my oppinion is there is no such thing as rising damp its a myth.ask your self how bridges in venice are still standing and also why doesnt the damp come out at the end of the buildings .there is always another reason.the reason dpc seem to work is the replastering with vey good waterproofing additives.

http://www.askjeff.co.uk/rising_damp.html

For an alternative view to Jeff Howell's this makes an interesting read - http://www.buildingpreservation.com/index.php?option=com_content&view=article&id=80:the-truth-about-rising-damp&catid=3

Rising damp can often occur in properties that have a DPC when ground levels are raised above DPC level - commonly in the case of concrete driveways etc... In such cases the problem could be dealt with by lowering the ground level. But in the case of a concrete driveway wouldn't it be a hell of a lot easier just to inject some Dryzone? Is injecting a DPC really THAT evil?

I've actually been looking into this regarding a damp problem in my own house.

It turns out that the 150mm is derived from a British Standard regarding the installation of damp-proof courses in new houses. It is supposed to be high enough to prevent rain splashes from bouncing off hard surfaces (e.g. concrete driveways) and bridging the DPC. Therefore, you can install the DPC lower if you waterproof the wall (with a tanking slurry, render, or water repellent) up to 150mm.

Replastering can be minimised if it is delayed for approx. 6 months. BS6576 states that:

“Where the plaster appears to be in sound condition, the extent of plaster to be removed may be minimised by delaying any decision to replaster until the drying period is complete. In such cases the surveyor should offer clear advice on the risks arising of possible damage to decorations in the future.”

If you assume that you have to replaster then I agree that DPC injection can be pretty disruptive. But if you have time on your side it isn't necessarily the case.

Hi
The OP said the house was built circa 1900 and the external walls are solid. The age of the house is more recent than the 1875 stated by 25rts as when dpc's were supposed to be mandatory and we know path levels are high but we do not do not know the level of the dpc if present.

The recommendations of the British Standards, Building Regulations and Building Research Establishment (BRE) Digests is where possible the min height between dpc and external paths should be 150mm. This is for good reason especially with solid walls to prevent rainwater bouncing off hard ground against house walls and bridging the dpc in addition to allowing a reasonable depth to cope with any debris accumulating against house walls doing likewise.

Personally if at all possible I would not recommend putting a dpc in lower than this 150mm distance as it is not only asking for trouble for the above reasons but also only likely to be picked up as a fault by any competant surveyor looking at the property at a later date who could then recommend not that that the dpc be raised but that the entire driveway / paths should be lowered at considerable cost to the owner of the house at that time.

Chemical damp proof courses (dpc's) are not 'evil' and indeed where appropriate can in conjunction with an appropriate re-plastering system be extremely useful in controlling active rising dampness where such is proven to be occurring to an existing wall to a point that may be preceived as being adequately dry. Whether a new dpc is appropriate in this case we do not know.

Solid external walls are inherently prone to condensation on their surfaces and within the depth of the wall itself. They are also inherently prone to penetrating dampness which in this case appears to be compounded by the high path levels noted above. We do not know to what degree dampness if present at all is affecting internal areas.

If a chemical dpc is justified then the recommendation is for the same contractor to undertake appropriate re-plastering as there is a reliance on the re-plastering system to hold back residual ground salts within the wall and some degree of rising dampness that would still occur due to inherent limitations of the chemical dpc systems. Having the same contractor undertake both chemical dpc and re-plastering prevents split liability where one contractor is arguing with another over who would be to blame for any continued dampness associated with rising damp / degraded plaster should areas not dry down / plaster degrade at a later date.

If dampness is present internally to these solid walls as stated previously it would be prudent to check all manner of things and try and resolve what is obvious and the cheapest things first if time is not an issue. If the plaster is no good and needs to come off then it may be worth considering whether what goes back, be that re-plastering or dry lining needs to be waterproof given the risk of penetrating dampness, in addition whether the insulation to such solid walls which are prone to being cold could be improved at the same time. If the owner of the property wishes to put a new chemical dpc into the walls whilst the area is opened up simply as a precautionary measure that would be their choice.

Hope this helps, kindest regards to all, David Aldred Independent damp and timber surveyor.