Water Pouring Through Airbricks into Subfloor

[coofercat]

Last night we had a horrendous storm - probably one of the most powerful I've ever seen. We live on a hill, and the road outside looked like a river - the drains were temporarily overwhelmed but otherwise had water swirling around them like a whirlpool.

Around the back, our patio had about a half inch of water on it. It's got a few slopes to get water away from the house, but there too the drain was overwhelmed for a while (partly because of leaves and whatnot sitting on it). For whatever reason, when we had the patio put down they put the slabs right up to some subfloor airbricks (albeit with a slope away from the house). With all that standing water, it looks very much like it's been pouring through them and into the subfloor.

I haven't seen all of the subfloor, but from memory we have a concrete slab about a foot below the floor joists. There are some supporting walls in there, obviously where the walls of the house are, but also running along the middle of the rooms (presumably to help support the floor). There are quite a few airbricks (most of which are a good few inches above the ground), so I suspect it's quite well ventilated. We've put UFH in, so there's 100mm of kingspan between the floor joists and then pipework and chipboard floor and either carpet or wooden floor.

I should also mention that the water table is a long way below our house - we're on a slope, so the back is higher than the front, and it slopes down to the left a little too. I've checked the airbricks in other downpours before, and so far they've been dry - but standing water on the patio is a new thing, and the root cause here, I think. We're in a 1920s detached brick built house.

I'm guessing we have a puddle of water under our floors right now. As it's (sort of) summer, I'm guessing it'll dry up in the coming weeks. However, what problems should I be looking out for? I'm assuming any problems are going to be an insurance job to fix now, as getting access is nigh-on impossible without major upheaval. Any help much appreciated!

[Barry_Convex]

It's really a case of how much water got in, which is anyone's guess I suppose. It's a common patio problem and ideally wants the patio dropping but I'm assuming that's not going to happen?

So take out the offending air bricks and see if you see inside. If it's a lot of water hire a pump. If only a little maybe wing it. Either way take out the two bricks above the removed air brick and install a staggered air vent to raise the outer skin vent level.

That's just off the top of my head. May give access to inspect extent of issue, AND remove need to mess with floor AND resolve wider cause.

Otherwise you may get a short term rising damp issue and damage to plaster and or timber, not to mention a nasty damp smell.

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[Barry_Convex]

And report it to the water board? May have a wider drain issue which can be resolved Street - side?

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[coofercat]

Thanks folks - rising damp - I hadn't thought of that, and whilst it may be extreme, it's a possibility I guess. There are some cables and whatnot under the floor too, so I guess they could go wonky over time too. I've bashed the credit card at Amazon and bought a endoscope for my phone - not sure if it'll be any use for getting down there, but I figured it's worth 24 quid to find out (I've got some cables to pull through conduit in the garden, so it'll help there too).

I didn't know a staggered vent was 'a thing' - Short of taking up the whole patio, then smashing up the concrete underneath and re-laying the whole thing, the levels aren't going to change, so protecting the vents seems like the best course of action. I'll see if there's some way we can keep the drain in the patio clear of debris too though - that would at least give it more of a chance to work properly.

I took video of the road and the drain out there too - it's been something of a constant issue with the council & co. (the road gets double-decker buses, occasionally on the pavements so the whole thing is a bit of a mess) - more for the people opposite because they get the overflow coming down to them when the drain stops working. However, I'll be tackling that issue too.

[Barry_Convex]

This is the vent :
http://manthorpebuildingproducts.co.uk/ ... loor-vents

I've never fitted one myself but they're perfect for this.

In hindsight rising damp may be a bit extreme from one occasion, there would need to be a lot of water to soak the bricks high enough. But if it keeps happening? Who knows?

People do simply put a small single course of bricks around vents to prevent this but it looks ugly as hell and fills with leaves and crap if you don't keep an eye on it.

Not sure about the cables but my hunch is that any sleeving will be water tight and not degrade simply in water for a few weeks. I assume you would have discovered already if there were a critical junction down there.

Good call on the endoscope [emoji106]

[coofercat]

Thanks for the link - I can see how that would work - it's a really cool solution.

On closer inspection, there are 2 airbricks that are 'at risk'. One is on a non-original part of the house, and has a course of bricks above it, and then the DPC above those - so I guess the telescopic vent could be put there (weirdly, at that part the bricks aren't in an offset brick pattern either, so it's a matter of taking the vent and the brick above out).

The other is more of an issue - it's on the original house and has the DPC right above it (I'm not sure we'd want to break the DPC for a vent). However, it's quite close to the corner of the house. Around the corner there are some small planting beds (full of weeds right now), so if I lower the level of earth there, we could put a regular vent in right below the DPC - so long as we take care of it so that we don't end up with a puddle in the bed, we could be okay (maybe replace the whole thing with a french drain or something - it's not very big). We could then just block up the 'at risk' vent on the patio.

The camera is due to arrive later today, but I had a brainwave if I do need to get water out. Since the house is on a hill, I could (possibly) just poke a plastic tube in through one of the vents at the front, and then suck the water through the tube and just syphon it all out with gravity. A little project for the weekend if it's required ;-)

Thanks again for the help - I feel like I've gone from 'clueless and a bit worried' to 'sort of know what to do'