Damp Proof Course - What to do ?

[oksamurai]

Hi all, I'm a FTB buying a 1930s semi. The mortgage provider requested I instruct a Specialist to investigate after the mortgage valuation/survey found rising damp at the property. I've received a report back from the Specialist who I made sure was wholly independent and not a contractor and he believes a chemical damp proof course is required at the property.

I'm unsure if a DPC should be the first course of action as from reading more about this issue, I suspect in my case the damp is caused mainly by the laying of a tarmac driveway. This has caused the external ground level outside to be raised, and breach the height of the original blue engineering bricks/damp proof course. There are 2 layers of blue bricks, the tarmac only breaches half of the first layer. At the front of the house, the tarmac is also partly blocking the sub floor vents.

To be fair, the specialist did point out the high external ground level was a major contributory factor so I don't understand the reason a DPC is required as a first course of action. Surely it would make more sense to lower the ground level approximately 150 mm below the DPC as he is also recomending, and then monitor the situation before attempting costly remedial DPC that is probably not required.

I don't know what to do, as I know I have condition in my mortgage offer stating I need to carry out any remedial work as advised and there is also a retention in place to make sure I do. I'm conflicted as I don't personally believe the damp problem is serious, as the ground floor has mainly oldish wallpaper throughout and it does not look like the wallpaper is peeling off at all and the skirting boards look in good condition. It's definitely not like the seller has tried to hide the damp by skimming or painting over the problem. Damp is only visible in a small corner of the porch where plaster has peeled off which alerted the mortgage valuer.

I would love to know what others think. How much would it cost to lower the tarmac level ? Is it something I can do myself ? or does it require special machinery ? or should I just get the DPC done and forget about lowering the driveay at all. In theory will the DPC eliminate any damp completely, even though the problem will still exist with the high external ground level.

Thanx in advance everyone.

 

[tony1851]

This post just goes to show what a mess an idiot surveyor can make of what is probably a very minor problem.

 

[dann09]

What do you mean by a "Specialist" who is "wholly independent"? How did you come to that judgement?
AAMOI: you are in range of a truly independent, & experienced, damp surveyor-Patrick Doyle.

What kind or type of "chemical damp proof course" did he recommend?

Notwithstanding the blue brick courses, 1930's houses would often have a bitumen DPC - injecting some kinds of chemical DPC will degrade the bitumen.

You will also have a cavity to, hopefully, protect the inner skin.

You could cut a channel thro the tarmac/driveway with a circular saw and a suitable blade. You could also install a French drain. Research these procedures on here.

 

[nebjamin]

I have a very similar problem, which I am currently in the process of rectifying.

1930s house, solid walls, bit of rising damp along one side where the previous idiot owners have laid 2 layers of tarmac over the original concrete path, partially blocking one airbrick.

I would say that the level is about 2" above where it was when the house was built.

In my case the tarmac is actually loose and hollow sounding. It's easy to just lift it up with a garden spade.

Anyway, regards cost, I have had a couple of quotes for remedial work. A french drain including new gulley about £300 all the way to brand new 60m2 patio incl new drainage and lowering of ground levels to 150mm below DPC about 7-8k.

TBH if you have spare time, it's probably easy to do this yourself - it's just digging.

I would second the advice of others and steer clear of the DPC. We had damp dudes in to quote for remedial work who recommended a chemical DPC (surprise!) (on the basis of which we lowered our offer). After we moved in I had an independent damp survey done (for about £150) and he just said to lower the ground levels or install a french drain.