We have a large double garage built into the side of the hill, I would imagine it was build around 1970-1980 it has breezeblock walls with an enormous RSJ inside and a 2 foot thick reinforced concrete roof....

At present there is nothing on top of it. However the lawn above is much higher than the roof.


What I want to do is build a retaining wall allong the front of the roof and scrape the soil from the lawn onto the roof to level out the area.

A comercial structural engineering company that one of my friends works for has quoted £450 to do a site visit and write a report etc, but would charge extra to redesign te roof etc.


Has anyone any experience of doing this sort of thing?

Do I need planning etc to move some soil onto the roof?

Any thoughts would be appreciated.

You’ll need some good damp proofing. Why is the roof so thick? Is it a nuclear bomb shelter or was it originally designed to be buried or had originally been buried in the past?

How many garages have a 2 foot thick concrete for a roof anyway?! How much more concrete do you think you need???

[Edited on 8/9/09 by Mr Whippy]

astroturf?

just a thought...Osama bin laden may be using your garage as a bunker so take care going in alone

I assume the roof was intended to carry the load of soil but for some reason was never compelted... but I cant be sure the structure will be strong enough....


I had thought about damp... A thick waterproof membrane on the roof, followed by a thin (ish) layer of concrete poured on a gradient to force the water to flow off the burried roof... another waterproof membrane and then the soil, piled on top...

It would only be about 80-100cm deep... but thats quite a bit of weight!

Working on a typical double garage size of 5.5m x 6.7m, that would be roughly 60 to 75 tonnes of soil on there. If the roof really is 2' thick, there could already be more than 25 tonnes of concrete there. I would get a Structural Engineer to look at it first as, if it does come down, 100 tonnes of concrete and soil isn't something you will shift with a dustpan and brush.

quote:

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Originally posted by tegwin
It would only be about 80-100cm deep... but thats quite a bit of weight!

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Be Advised---Dont do it without a professional Engineer accessing the situation. Better to be safe than sorry.

quote:

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Originally posted by Richard Quinn
100 tonnes of concrete and soil isn't something you will shift with a dustpan and brush.

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simple first question - how much weight can a breeze block wall support?

Once you know that you'll have an idea if it can take the roof weight, seems a hell of a lot to a complete numpty like me!

This might be useful

http://www.livingroofs.org/

Planning wise you might get away with it under permitted development. Geotechnically speaking I have an engineer who works for me if you need advice.

Forget the grass it's a PITA it grows and needs cutting. Put a deck on it.

How do you know its reinforced?

Have you had a section cut out and looked inside?

Its not a case of how much can a breeze block support there are many types all with different strengths.

You don't know if the roof is only designed to support its own weight only

I too work in the construction industry I am not a structural engineer but an electrical consultant, I would confirm that £400-£500 plus vat a day is a reasonable charge for a fully qualified consultant engineer personally I charge £400.00 plus vat per day.

Please, Please, get an expert to look at it.

Also take weeks of rain, 2 m snow and ice into account! It would be a pity if your bomb shelter caves in and crushes your 7!