Planning permission (underground)?

[toasty]

Fair point RE the shock wave and concrete vs blocks, but in fairness it's only going to be a storeroom, if and when the nuclear attack comes i think I'd rather be stood in the street than trying to survive underground.

I was thinking of standard concrete blocks layed on their sides so giving quite a bit of strength

 

[Static]

As i said before, it is liable to fail and crush you/whatever you are storing just from the weight of earth pressing against it. Not counting water pressure etc.

 

[splinter]

There is a system ,which uses hollow inter-locking polystrene blocks ,re-bars are pushed down the hollow sections and this is then filled with concrete.Cheaper than using formwork and stronger that blockwork

 

[SparkyMarky]

Have you been watching re-runs of Grand Designs?

I remember seeing this sort of construction on there once. I also seem to remember that it went slighly pear shaped at one point and the guy ended up with some odd bulges in the wall where the polystyrene split!

 

[toasty]

TBH I think I'll build with standard concrete blocks on their sides, giving an eight inch thick wall. I very much doubt the weight of the soil 10 feet down will cause that to collapse, I'll pour a nice thick 1 foot slab for the floor with mesh in it and wrap the lot in a couple layers of DPC.

As for the roof, block and beam seem the way forward, in my case covered in DPC and then a good layer of concrete on top.

My mate, who is a very experienced and skilled builder reckons I should pour in clean stone around the structure to aid drainage

I've already managed to sign up quite a few mates/family to help with the project, I'm really quite excited. Just need to stock up on spam and dried fruit now.

 

[Static]

Ok, when bored try this as an experiment: build a garage door sized panel of blockwork laid flat as you are suggesting, then after its set for a week lay it down on a couple of sturdy benches/walls, then tip some earth ontop of it say 6 tonnes and watch it snap in 2-3 pieces along the mortar joints.
Then imagine building an underground chamber from blocks laid flat with 3-6 tonnes of earth pressure on the sides and you in the middle. Your relying on the horzontal strength of the mortar which is pretty poor.
The walls will need strengthening or thickening, also go for engineering bricks rather than blocks if you are set on forming the walls from masonry. Personally i wouldnt mess about, i would go for reinforced concrete the cost will more than likely end up the same in the end.

 

[SparkyMarky]

Have you checked the level of the water table in your garden? I know is's only a foot or so down in mine. If I tried to dig a bunker in my garden I'd be up to my armpits in water before I'd even dug the hole....

 

[toasty]

Static,

I see what you are saying, however, I've seen walls built of blocks laid on their sides as I've suggested holding back huge volumes of earth at the sides of roads etc...

The roof of the bunker will be a completely different story I'll use a block and beam type thing.

 

[SparkyMarky]

Static,

I see what you are saying, however, I've seen walls built of blocks laid on their sides as I've suggested holding back huge volumes of earth at the sides of roads etc...

...But what you probably can't see is the big buttresses and gabions behind the blocks which are actually holding back the ground. Normally the block/bricks you see on road cuttings are just for aesthetics.

I'd really recommend you consult a structural engineer on this. The type of construction you need for the walls will depend on soil type, density, water table height and numerous other things, and not just something which you've seen somewhere else which looks about right....

 

[JohnD]

I was wondering how this was coming along?

 

[toasty]

John.

If I dug up the garden now, I'd be a dead man.

This is a project for the winter, but it should be a go-er.
-Dan

 

[daysleeper]

Make sure you take lots of photos and bung them on a webpage so we can all watch.

 

[legs-akimbo]

Any new build house in the rural areas of Germany are constructed as a matter of course with a basement. I spent three years in Berlin working for a company that built houses with said basements, some were reinforced concrete while others were blocks similar to a regular clinker, that were laid on flat. The difference however was that opposed to a 9" thickness the blockwork was constructed by laying two courses of block flat with a course of block laid in the regular fashion at the side of them (4") with an inch gap in between the two thus giving a 14 " thick wall. The following course was alternated by laying the blocks flat over the 4" upstanding block and two courses flat to the sides of this. In essence two courses flat block internal side then alternate to the external so that it is all tied together and you have a strong retaining structure which is very simple to build. The external structure is then black jacked and covered with a special membrane and coated with a tanking bitumen before being backfilled. A job of this description can not be undertaken at half measures as the whole concept is undermined if poorly constructed and you will end up with a claustrophobic saturated hole in the ground fit for nothing but a glorified coal bunker, £2,00- 3,000 is way way off the mark for what is actually a complex piece of engineering.

 

[Deluks]

This hatch lark sounds a bit iffy if you need to get stuff in and out. Like a loft hatch reversed in a way. Why not build a concrete staircase going down to a door at the side of the structure. Will be much easier to get in and out and will make the space more usable. You need only lose a strip of lawn about 2'8" x 9'

Alternatively, invest in a disabled platform lift, then your underground shed will be like some sort of James Bond villains lair

 

[morris8]

hey, did ever do the bunker? did you need planning permission?
please let me know