Need to lower exterior ground level without mass excavation

[kingandy2nd]

Hi all,

Our new house has had concrete laid in the rear yard which has raised the height of the outside ground level to only about 5cms below the interior ground level.

Now I know this can cause all sorts of problems with water bridging the DPC etc, etc but I'm reluctant to remove all the concrete because it'll be hard work and I was only planning to put pebbles over the area around the house anyway. The wall with the window already has some evidence of damp patches.

My idea is to use my angle grinder and masonry disk to cut a channel about 10-15 cms away from the walls then remove the concrete from this area all the way around the house. Effectively creating a concrete free channel around the house. Then I'm going to dig down to the soil layer around this 'border' in order to allow any rain water to soak away into the ground.

Finally I was going to fill the channel with some larger pebbles, and top off with the pebbles I was going to use over the rest of the area.

Anyone have any feedback or suggestions on whether this might work?

 

[gregers]

done this a few times over the years when i was in the the preservation industry,you might have to shutter up the rest of the concrete to stop it collapsing over time.but before you do any of this is your house cavity or solid brick construction?if its cavity then the reason you might have damp coming through is because the cavity could be full up with crud and bridging into the inner skin.

 

[Shytalkz]

External ground should be 150 below DPC level and that it's clearly not should have been picked up on your valuation/HBR by the surveyor, assuming that you had one done and weren't a cash purchaser relying on your own wits (not wise). That's not to say that it will definitely cause a problem, but the odds are reduced, depending on location, prevailing rain/wind direction etc.

If there was a survey, you could go and have words and suggest that he might like to contribute to the cost of the work to rectify the situation. If they wriggle by saying it was only a valuation report and that the report was done for your BS and there is therefore no duty of care to you, quote Merrett v Babb at them and that should make them shudder. And tell the BS too.

Your idea of addressing this is a reasonable one, in principle and depending on the specific circumstances; just don't go down too deep (225 to 300mm is fine, assuming that you're not at, or near, or deeper than the foundations at that depth) and line the excavation with Terram or a similar geotextile, to stop fine grains leeching into the drainage medium and eventually silting it up. Fill the excavation with pea shingle.

 

[kingandy2nd]

Cash purchaser… I wish!

We had a valuation done on the place, and the surveyor made loose reference to “needing to get a professional to address the damp areas at the rear of the property”. You know - the kind of comment that really doesn’t provide any useful insight to the buyer but is sufficient to allow the surveyor to weasel out of any claims against them.

This is my girlfriend and I’s second run on the property ladder and we’re climbing up the hard way by buying run-down (but mortgage-able) houses and fixing them up as we go. One of the conditions of the mortgage of the first place was to lower the exterior ground level to below 150mm of the ground floor level. This resulted in me having to dig up about 2 tonnes of concrete, then filling the rest of the 8 tonne skip with soil I had to remove in order to level the yard up. Therefore I knew before we even got a survey on this place that some work was on the cards, but I really don’t want I don’t want to go down the dig down and level off route again!!

Thanks for the info on the legal precedent – I will remember it in case of any future need. However, in this instance it’s easier and quicker for me to just crack on and get the work done.

Thanks too for the geotextile tip, I hadn’t thought about that, and will definitely include it in my work.