Dealing with high ground levels

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Hello there, first post here. I was hoping to get some advice regarding some apparent damp problems around the front and side or our new home.

We had a homebuyers survey which stated that damp meter readings indicated there were high levels of damp along the side of the house., particularly the front corner around the downstairs shower room. There was also signs of damp/blown plaster on the internal wall dividing the hallway and downstairs shower.

Our surveyor indicated that the ground levels around the property were too high - a paved driveway to the front of the house and a concrete path running down the side of the house, meaning the DPC was only 1 course of bricks high instead of 2. He recommended a french drain be constructed down the side.

Skeptical as I am of them - we decided to get a damp proofing company to do one of their free surveys anyway to see what they said - the company we called out had previously done some damp proofing work on the property in 1997 - they had injected a damp proof course in the front bay window and in the rear corner of the dining room (no longer an external wall due to newer conservatory).

Their findings were:
* Dampness around shower room likely to be due to a leak in the shower. Recommended rectifying the problem and a small amount of re-plastering where it had blown on the internal wall.

* High readings to rear corner of dining room due to "lack of effective damp proof course" - inject chemical DPC and internal re-plastering up to 1m. May have also been due to a leak in the conservatory which has since been rectified.

* Ground levels too high down front and side and likely contributing towards high damp readings under the stairs. Recommend ground levels are lowered and French drain installed.

OK, so far so good. The shower is badly done and the tiling/grout looks shot. Line of staining/blown plaster on internal wall is in line with tiled shower floor so it seems obvious the shower is knackered. We plan to rip this out and get it redone properly. I suspect this is also contributing towards dampness in exterior walls.

Despite saying the damp on the side of the house was due to high ground levels and recommending a french drain, they also recommended injecting a chemical DPC along the entire side of the house. WHY? Seems unnecessary to me. The house has a DPC, its just being compromised by the high ground level, surely? The ground levels at the rear corner are a bit high too but the ground is covered in shingle, not concrete so not sure that's the problem here.

The bottom 3 courses of bricks on the outside appear to have been coated with some kind of treatment - red in colour, presumably some attempt to waterproof it. Its chipping away in a few places and I counted 8 blown bricks around the perimeter of the house which need replacing. The house also only appears to have two air bricks - one in the front bay and one on the side. It may have had one on the rear at some point but has probably been covered by a rear extension or the conservatory.

So it seems clear we need to sort out the shower, maybe fit a couple of extra air bricks and replace the spalled bricks. I'm inclined to think the chemical DPC is not worth it (we were quoted £293 + VAT for the chemical DPC and £450 + VAT for about 1.5 sq/m or re-plastering!!!).

We've had some quotes for creating a french drain and they've been around the £700 mark which seems very high to me. Is that high? I don't really want to spend that much on a shingle filled trench and I'm wondering if its really necessary. Only one course between ground and the DPC is obviously not ideal but other than a few spalled bricks, and some small amounts of black mould along the bottom of the wall in the cupboard under the stairs, the walls seem dry enough to me inside and out (its a cavity wall). I see no signs of dampness in the kitchen.

What should I do? I should be able to manage replacing the spalled bricks myself and fitting an air brick. Would it be worth re-painting the bottom few courses in some kind of waterproofing agent? I appreciate this wouldn't be a permanent fix but it seems like it might do the job for a while.

Am I being too quick to dismiss the chemical DPC option? £293 + VAT is half the price of constructing the French drain. They didn't recommend any re-plastering internally down the side of the house due to difficulty of access - shower rooms, stairs, boiler/pipework and fitted kitchen all being in the way. It would at least solve the problem of high ground levels by moving the DPC up the wall. I can get somebody else to re-plaster in the corner of the dining room if its even necessary.
 
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If your house has cavity walls then it should not matter if the outer skin is wet as the cavity should keep the inner skin dry UNLESS the cavity has been bridged which tends to be at the bottom of it due to the original builders dropping mortar/rubbish down the cavity.
If you have solid walls, its a very different matter, I would go for the french drain. The only difficult part is running a diamonnd disc down the edge of the path (you could get a builder to do this for you), the rest of it is just digging it out and filling with gravel, a good bit of exercise?.
Do the shower and the drain and give it 6 months to "dry out", then make a decision on the DPC.
Frank
 
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If your house has cavity walls then it should not matter if the outer skin is wet as the cavity should keep the inner skin dry UNLESS the cavity has been bridged which tends to be at the bottom of it due to the original builders dropping mortar/rubbish down the cavity.

It is cavity wall although if I'm understanding this correctly, the high ground level means that rain can bounce off the path and reach the bricks above the DPC (which is only one course high) thus bridging the DPC that way. Is that correct?

That said, what you are saying makes sense - if the cavity is clear then the water shouldn't be making it through to the inner leaf.

I do wonder if there might be another cause for the black mould in the cupboard under the stairs - its not bad and will probably scrub off easily enough. The cupboard gets quite warm as it houses the boiler - would this air be humid? Could it perhaps just be due to condensation? If the mould comes back after cleaning, would it be better to just paint the bottom of the wall with some anti-mould/damp paint instead?

So in other words, you think its not worth doing the french drain if we have a cavity wall?

Out of curiosity I've invited another local damp proofing company out to do a free survey on Thursday. I wasn't present when the other company did their survey. I fully expect them to just run a damp meter over the walls and give me a sales pitch for chemical DPCs but I thought there was no harm in seeing what they have to say.

Incidentally, the builder who quoted me £700 to dig the french drain (as well as some other things) has now offered to construct the french drain, fit a lintel above our rear porch door (the frame was sagging) and fit a few more air bricks for a total price of £500 all in. Seems like a very good deal to me but only if the drain is necessary!
 
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The whole reason for a 50mm cavity is that the building control people believe that rain can penetrate the outer skin and run down the inside of the outside skin, safely into the ground under the DPC. Its funny that the rest of Europe do not believe this and use solid walls. Perhaps our bricks and or workmanship is poor.
Frank
 
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The whole reason for a 50mm cavity is that the building control people believe that rain can penetrate the outer skin and run down the inside of the outside skin, safely into the ground under the DPC. Its funny that the rest of Europe do not believe this and use solid walls. Perhaps our bricks and or workmanship is poor.
Frank
The issue isn't whether or not the wall is solid, it's how thick it is. Water can penetrate a 100mm wall but not a 215mm wall. They don't often build a solid 100mm structural wall in Europe and expect it to keep out the rain.
 
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So to sum up, if no major signs of dampness on internal walls, nothing much to worry about?

Regarding the spalled bricks, is it likely due to bad pointing, water getting into bricks and then freezing, blowing off the face? Replace them and jobs a goodun?

And don't bother with French drain or would it not harm to have it done?

When mr damp specialist surveyor comes and runs his damp meter up the internal walls and claims I've got rising damp, do I just smile and nod and then send them on their way? Should I assume that any damp surveyor who makes a diagnosis based solely on a damp meter reading is a cowboy? If the surveyor is decent and knows his stuff, what should I expect from them? Any good questions to ask?
 
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Well, I just spoke to the builder who had quoted me to do the job. After saying I didn't think we needed to run the drain around the front as it already had a chemical DPC, he offered to do the side, fit our porch lintel and a few air bricks for £300 all in so I've decided to go for it. He said even if there weren't many signs of internal dampness, the concrete still shouldn't be right up to building and it would be a good preventative measure.

Given he was going to charge us £150 to fit the lintel (which was already half of what I'd been quoted by other builders) it seems to be a no-brainer.
 
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Another follow-up - we decided to proceed with the french drain to the side of the property only. The concrete path has been cut back about a foot away from the house and dug down a few courses below the DPC, lined with a weed membrane and back-filled with pea shingle. I have to say it looks a lot better for it too.

The same builders also replaced the two existing cracked grated air vents with newer plastic air bricks and fitted two more for us - another on the other side of the front bay window and one to the rear of the property.

Unfortunately they don't seem to have fitted cavity liners - is this likely to be a major issue? I lifted the floorboards in the lounge - the one that has been there for ages (just replaced) doesn't have one anyway and neither does the new one they fitted for me. I removed all the rubble and muck from behind the air bricks to make sure they don't get blocked up and there was a noticeable draft coming in to the sub-floor. It also seemed quite dry.

Does this sound like its sufficiently ventilated? I can post some photos.
 
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