Underground chamber.... which makes for a stronger wall?

15 May 2013
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United Kingdom
Hi all,

I'm thinking of building a small bunker as a man cave maybe 6 x 3m at most. I was going to use butyl liner and tanking slurry to stop the water ingress but im not sure which type of block to go for.

A) 4inch concrete blocks laid on their side

B) 9 inch hollows filled and rebarred into the slab

Would the 9inch hollows be cheaper and stronger or would the cost of filling them with concrete negate the savings. I would of thought the tanking slurry would work better on the solid concrete blocks. The roof will be a suspended reinforced concrete slab on rsj's.

Any advice is greatly appreciated

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Hello Mr Fritzle,

Just curious as to the bunker idea. Would it not be easier to build something above ground?

Sounds like a lot of work unless you need discretion at all times
I think i've exhausted the PD rights of the property above ground :D It would just be built for fun, mainly because I enjoy the challenge
Reinforced concrete. You are allowed up to 30 sq metres internal floor space.

Similar threads if you search "bunker"

It will be damp.
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If it's a suspended concrete slab, 4" 7N blocks laid flat would do.

With regard to permitted development; there are a number of appeal cases regarding basements and the majority determine that a basement is not P.D.
Have you looked at the various 'Bury a shipping container' projects online? Might give you some inspiration and ideas at the least.
You can't just bury a shipping container. the strength is in the corner posts. The weight of overburden will crush the roof
Check the height of the water table in the ground. A lightweight, large volume construction could float out of the ground if the water table is close to the surface.
Thanks for the replies. This building will have some weight to it so shouldnt float out the ground. Ive done a similar subterranean building previously (just 1 metre deep not 2-2.5m deep) and thats all ok around 8years later. I have a drain nearby so was thinking of hooking a pipe from the french drain surrounding the bunker (maybe 1-2metres down) into the drain so the hole would only ever be a 1/3 full after heavy rain.

Ive heard horror stories about sinking shipping containers in the ground, if I lived in Arizona then I might take the risk but not here in the UK.

Thanks for the advice Tony. I think a block and beam floor will be easier and still do the job so I shall look into this. As for planning I shall make some enquiries. I have a large garden in the middle of nowhere and am not planning on moving for a long long time so worst case I could fill it in upon selling up.
With regard to permitted development; there are a number of appeal cases regarding basements and the majority determine that a basement is not P.D.
Is a basement the same as a subterranean fallout shelter in the garden?

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