Damp proof course - is it a necessity?

The_Wall

David,

Is there anywhere I can get more information about the paste type DPC's that can be done by any competant DIY person? Especially on how to apply it, and any potential pitfalls.

The reason being that I know I need to do something about the DPC on our house, as it has not been joined up to the existing DPC where the conservatory was built, and the original DPC is in poor condition.

I like to think I'm a competant DIYer, well I'm still alive

dampdaveski

Mr wall ;o)
without getting into the whys and wherefores of the original post
a sample of them are
www.nvirol.co.uk
www.dampshop.com
www.twistfix.co.uk (bit expensive)

also just ebay or google dpc cream or damproofing cream
there are dozens and dozens of them, most are jumping on the bandwagon, and are resellers, most charge stupidly naughty prices, and a lot are inbred halfwits who should be dragged out into the street and slapped with a wet kipper!
I've used nvirol several times and have been happy with them, i'm sure there are lots of others who are smashing too
hope this bit helps
DD

kerri247

I am not an expert and like you am new to house renovation but this is my 'damp' story..
I have just bought a property built in 1888 and the homebuyers report suggested 'evidence of damp'. I have had 3 damp & timber companies report on it and all suggest the usuall fixes and none mention fixing the cause of the damp. Therefore I am now following the advice of my builder who suggests fixing the cause first (leaky windows, lowering a patio higher than the inside floors, fixing broken guttering), monitoring the results before paying out for expensive dpc treatment.

keystone

kerri247 wrote: »

the homebuyers report suggested 'evidence of damp'.

LoL. So much CYA in this "industry" now that the report would probably say "evidence of damp" if it had rained two minutes before he got there.

Cheers

David_Aldred

Hi,
Assuming chemical injection has been justified and proven in a particular case to be appropriate:

Not all creams are quite the same strength with Safeguard and Wykamol some of the strongest out there with regard to % active ingrediant though there are plenty of others - just ask and shop around. Good manufacturers will even come to site and show you how to apply the product.

Each manufacturer has their own installation instructions and you are best following them for the product you use. Have a look on their web sites but also trot down to your local library and you should be able to read the British Standard BS6576 on line and make your own notes from it which you should try to comply with as much of possible especially with regard to the level you inject at, the depth of injection, the size of drillings, clearing cavities and ensuring linking of any solid floor damp proof membrane into the wall dpc.

If you cannot seal the solid floor damp proof memebrane into the wall dpc then at the very least seal the solid floor / wall joint ensuring all timber - i.e. skirting / base of door casings / base of stairs etc is physically isolated from the dampness with a flexible impervious material and that the plaster is kept away from the floor / wall joint. Where possible inject below floor joist level or if not appropriate, suitably isolate the floor joists from dampness.

If injecting the Party Wall or adjacent to it you need to comply with the Party Wall Act. Some of the carriers used to transport the active ingredient such as paraffin / solvents can be disruptive to asphalts, bitumens (including the original bitumen dpc the house was built with, which if you are on the ball you will note can be counter productive since the original dpc is the more reliable) and can also be troublesome to electrical insulation and similar sheathing found to other things so be mindful of this.

There is no point injecting a hard dense facing brick as this will be a waste of time and money. In such circumstances aim to inject the more permeable and continuous mortar and this preferably to be done in two courses plus vertical mortar beds between though as I said check all of this with the specific manufacturer. The mortar bed is the continuous material so it often makes sense that rising damp would run through permeable mortar first rather than jump from mortar to brick to mortar. Permeable brick can be injected if suitable - again check with manufacturer as to which they recommend and the pattern / depth of injection etc. Random rubble walls are a nightmare to inject effectively and require special consideration. Inject cavity walls from both sides and inject party walls from both sides if you can get permision.

I am always a bit dubious about the value of injecting the outer leaf of a cavity wall since it gets wet with rain anyway and if the cavity is clear the wall can really do what it likes as it shouldn't effect the internal wall. Nevertheless it is a requirement of BS6576 that both leaves be injected and if rising dampness is present I guess it stops any disruptive salts causing damge to the face of brickwork above dpc level.

Note that most chemical dpc's are pore lining materials not pore blocking and as such any moisture under hydrostatic pressure will push straight through them and this is one reason why original sheet memebrane dpc's are better than chemicals. For example injecting vertically the junction of a garden wall to the main house wall is unlikley to hold back moisture from the garden wall soaking down and into the house wall so this needs special considration.

Also bear in mind that the dpc fluid will not permeate everywhere and there will be inherant weaknesses in the system and it is therefore the re-plastering that has to hold back such moisture and any disruptive salts within the wall. Out of preferance the people injecting should always be the people re-plastering so there is no split liability. If you leave hygroscopic plaster on the wall it won't dry down.

I shouldn't really say this but I have seen operatives upon a few occasions drill the holes and not actually put any chemical dpc fluid in the wall at all but simply wet the surface to look like they have injected it because the boss wouldn't give them enough time to do the job properly. The reliance was on the re-plastering to hold anything and everything back and in most cases if done right it often can, which tends to show how much relaince there is upon the plastering compared to the actual dpc injection.

If you think you can inject enough dpc fluid into a party wall chimney breast (or indeed most fireplaces) especially two chimney breasts back to back through all that infill and wet hearth to establish an effective chemical dpc then you are kidding yourself.

People will say I had a chemical dpc and it must have been rising dampness because the wall is now dry which is a load of rubbish really since the waterproof grade plastering able to hold salts back will also hold back moisture from a number of sources that could be present.

One advantage of the creams is that you can actually see the cream being put into the holes and it doesn't take days to inject a house like it did with pumps. Be mindful that if the wall is wet and you apply a waterproof grade plaster to it and this wall happens to be a party wall you may well make next doors side of this wall wetter and could in theory run a risk of being held liable. These are general notes of principle and not exhaustive and may not apply to your particular case so as I said at the outset if you are going to use these creams get the manufacturer down on site and run through the particular method of application they recommend.

I hope this helps, kindest regards, David Aldred independent dampness and timber surveyor

squirrelchops

I agree with kerry247. I bought a house in 2005 that on the surveyors report had damp.

However, the house had also been empty for 6 months and there was a leaking pipe in the kitchen that had caused a damp wall we found after we had moved in.

Anyway....the issue of needing a DPC got me £1000 knocked off the sale price. I had been prepared to het a DPC but after lived there for a couple of months I proceeded to get some quotes and at this point the reply was 'you don't have damp'!!!

Ok so I had wood worm but the issue of the damp went once the house had the pipe fixed and had a chance to get warm again. Oh and also new windows and sorting the guttering helped too.

David_Aldred

Hi Squirrel,
Good on you - always the best way - look at what is obvious other than dpc failure and resolve that then monitor for drying down. As for woodworm don't get met started on that one (laughing). Kindest regards, David Aldred independent dampness and timber surveyor

dampdaveski

David_Aldred wrote: »

. As for woodworm don't get met started on that one (laughing). Kindest regards, David Aldred independent dampness and timber surveyor

Please god nooooooooooooo :beer:
though it would be interesting to see what you think of jeff's opinion that woodworm will disappear if you put central heating in! (reply as a pm if you prefer )

The_Wall

David,

Thanks for the detailed information but having read it, given that we do have a solid floor and I have no idea if the membrane is tied into the DPC and there is a party wall, in addition to your post on cavity wall insulation, which we also have. I'm now going into full "don't panic Mr. Mannering" mode. :eek:

Seriously though I do not even think that there is damp, just the potential for it. So if I got someone, reputable of course, from your profession would they do an assessment, and make recommendations?

David_Aldred

Hi - that is the trouble with forum posts as opposed to chats over the phone it is easy to go aaaagh! The main two worries with damp are products of mould which will make you poorly and wood that becomes damp will decay. Trying to save you money here if you are concerned you could:
a) get a reputable contractor in with one of their free surveys and ask them to show you any areas of wood such as skirting where the moisture cotent of it is above 20% and also to show you where they find above average readings and pencil them on the wall and then discuss what the contractor suggests on here or by phone or private e-mail, or b) bit more expensive get yourself a good quality second hand conductivity meter off e-bay and take the readings yourself and discuss or c) get an independent freelance or consultant surveyor from the Property Care Association (PCA) to come and have a look and give you verbal comments cheaply or full written report bit more expensive. You pays your money and you takes your choice hope this helps kindest regards David Aldred independent dampness and timber surveyor