Flooded Air Raid Shelter Under House

16 Jun 2013
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United Kingdom
Asking on behalf of my mother..

Her 1930s house has an air raid shelter underneath the back lounge. There is even a small trapdoor under the lounge carpet and a sloped wall so the occupants could slide into the shelter in an emergency (never tried the slide myself as it is steep!)
There is also access from outside, just next to the back lounge outer wall.
The shelter is about 6-7ft high.

The problem is, most of the time the shelter is flooded, with about 2ft of water. Pretty sure it's the water table as the shelter hatch outside is well sealed. The walls inside the shelter are plain concrete, I assume water just seeps through it.
I recall when I was a kid and lived there about 30 years ago, it was frequently dry, as I used to play in it. But most times when I am over now, it is flooded. It might dry out in a dry summer but it's rare these days - is the water table generally higher nowadays?

Just wondering if anyone has advice on what could be done to remedy the situation?
She doesn't use the space so could it just be filled in or would that cause the water to get higher (and start affecting the lounge floor)?
Could it be damp proofed somehow? Seems like it would need to hold back a significant amount of water.
Someone suggested a pump but that seems a pain to have to rely on.

We aren't necessarily looking to remedy it now as it's not been a problem other than being an unusable space. Just curious for when the time comes to sell the place and there might be something that can be done to avoid survey issues.

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You could fit a sump pump, with a float switch. Preferably in a bucket-sized hole in the floor so water is always below floor level.

Unless the water is being constantly replenished from a leak (quite common in older houses, and xhould be fixed anyway) it shouldn't be wetter now than in the past.
Unfortunately, despite you thinking a pump is a pain - that (fitted as John suggests) is about the only option to remove the water.
Initially anyway, remove the water then get down there and have a good look for where it is coming from.

You may also be able to insulate under the floor then too.
If you are sure its the water table just backfill it with suitable material. Re a pump, depending on the inflow you could end up trying to pump down the entire water table in the area.
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If you are sure its the water table just backfill it with suitable material. Re a pump, depending on the inflow you could end up trying to pump down the entire water table in the area.

I am suspicious of the idea that water table has risen by several feet since OP was a lad.

A leak from 80 year old plumbing, however, is quite common.
Masonry can become more porous over time, due to several factors. To a lesser extent, the ground conditions can change over similar time periods.
One solution I saw, to make such a space usable, was to have galvanised angle iron, bolted and sealed to the floor, so as to make a drainage channel around the perimeter of the wall. That then discharged into a sump, containing a sump pump.

First solution is to have the water analysed, to see if it is ground water, drainage water, or a tap water leakage.
Thanks for the replies. A leak from somewhere didn't really cross my mind, I guess because the water dries up occasionally in summer. If it was that though, I'd have thought it would be at a fairly constant level? Worth checking though.

If the leak wasn't obvious from inside the shelter, could it be a leak underground that causes water to seep into the shelter through the walls?

For the pump solution, would it be pumped into a nearby drain? I know they can be strict on what goes into drains, not sure where else it would go though.

And I am over tomorrow so if I remember I'll get some photos! Just need to dig out the speedos.

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