Damp/flooding problem in underground concrete bunker

[Nigel Watts]

In the second world war my grandfather built an air raid shelter in his back garden, just big enough for a bunk bed. It was made of poured, shuttered concrete and was about three quarters underground, with earth piled on top. There was originally a ventilation pipe on top and some kind of square window or escape hole high in the wall. It was located just beyond the back wall of his garage.

In the late 1960s my father extended his garage over the shelter which became a cellar under it where he stored wine. The ventilation pipe in the ceiling was dispensed with and the window/escape hole bricked up. The concrete stairs are fully within the garage, which has a watertight roof.

When visiting my mother today I went down to inspect the cellar and found it to be about eight inches deep in stagnant water. It has been known to flood before. It has no drain and the the drains leading from the house to the street are nowhere near it (and would be too shallow to connect to in any case). It is possible that the garage gutters are in poor shape.

The wine stored in the cellar may still be drinkable, but the labels have all gone mouldy and the wooden wine racks are rotting dangerously away.

Any ideas for fixing the damp/flooding problem?

 

[stephenh]

Nigel - either :

Get the cellar 'tanked' by a reputable firm that is registered with e.g. 'Sovereign' - quite expensive..

or

Dig out a sump and install an electric pump with a float switch( like a bilge pump on a yacht) - this you could do yourself by hiring a Kango etc.

BTW I live in N19 - if you would like some advice from a retired surveyor in exchange for a pint I would be quite happy to oblige.

Good luck

Stephenh

 

[MatthewC]

The wine stored in the cellar may still be drinkable, but the labels have all gone mouldy and the wooden wine racks are rotting dangerously away.

Any ideas for fixing the damp/flooding problem?

Can't really help with the specific damp problem, but I can help you either to identify wine in label-less bottles, or else to dispose of it entirely!

(Thought I'd say that before Penners)

 

[Nigel Watts]

Nigel - either :

Get the cellar 'tanked' by a reputable firm that is registered with e.g. 'Sovereign' - quite expensive..

or

Dig out a sump and install an electric pump with a float switch( like a bilge pump on a yacht) - this you could do yourself by hiring a Kango etc.

BTW I live in N19 - if you would like some advice from a retired surveyor in exchange for a pint I would be quite happy to oblige.

Good luck

Stephenh

Great advice - thanks. Although I live in N7 the bunker in question is unfortunately in North Essex

 

[chuckey]

I've had a go at tanking two buildings, both seem to be successful. The first method was using a bitumen product that you slop on as heavily as possible, needs a couple of days to dry out then another coat, and repeat again. Only problem I found was that the finished coat remained sticky, on the walls it was plastered, on the floor I put down Baco-foil, so I could walk on it. The other product I used was a SBR cement additive (whoops I've used the C word ). This you mix with same volume "C" and paint on. Needs two coats. Goes off in a couple of days between coats. Non sticky finish, I prefer to use this rather then the bitumen. Bitumen stuff costed £50 /20l in 2003, SBR £20/5l at present.
For an Anderson type shelter, if you don't get asphyxiated, a mornings work/coat, wash brushes out in water. Wear a hat!
Frank

 

[Penners]

I can help you either to identify wine in label-less bottles, or else to dispose of it entirely!
(Thought I'd say that before Penners)

Damn!

Nigel - stephenh's advice seems good, although before I undertook tanking I think I would want to be very sure that I knew where the water had come from - and thus that tanking would cure the problem. Alternatively, the idea of a sump with a pump, while not solving the essential problem, would deal with its consequences regardless of the source of the water.

 

[Nigel Watts]

The soil is quite sandy and the water table is almost certainly some way below the floor of the cellar. Would some kind of soakaway work here I wonder?

 

[Penners]

Only one way to find out!

But if the water table is low enough for a soakaway to work from the cellar, how is the cellar filling with water in the first place?

 

[Nigel Watts]

But if the water table is low enough for a soakaway to work from the cellar, how is the cellar filling with water in the first place?

The floor, walls and ceiling are all concrete except for the bricked-up hole high on the wall at one end. I suspect this bricked up bit is the entry point for the water which, one inside, cant escape because there is no drain and no ventilation.

 

[Flyfisher]

. . . in which case, tanking may not be the answer (bringing us neatly back to Penner's point - proving the source of the water).

Indeed, with sandy, free-draining soil and a low water table, my suspicion would be that the water-tightness of the bunker is the real problem here. A simple drain hole at the lowest point of the bunker might be all you need to solve the flooding problem.

 

[philpjuk100]

Have found that the electric pumps are a bit unreliable in this situation and need checking every now and then.I think its due to standing idle for so long allowing debris/spiders etc jam the impeller,one I used in an inspection pit used to give problems yet an identical pump(but without the float switch) on a timer worked in my pond without any trouble for years(the bilge pump in my boat is also unreliable and is changed every season)phil.