What floor can i use when building a garage basement

27 Sep 2011
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United Kingdom

Long time reader, and now first time poster. I've searched for a while online and cannot see a clear answer to my query, so here goes.

I am looking to rebuild a standalone garage at the end of my garden. It measures about 4m across, by 3m deep. However, i want to dig out a basement at the same time.

What is the most cost effective way to build the floor at the ground level which can take the weight of possibly 2 cars? I'd rather not put in a whole load of steels, which i expect will cost me a fair bit. Other options are timber beams, but without going into the calculations, i'm expecting they'll end up being quite thick and sacrifice some headroom. I've read something about concrete sheets that can be strong enough, but i'm not sure what they're called or where to get them.

So, does anyone have any suggestions? Any help greatly appreciated.
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Is this a basement or a car pit? Cos doing a basement without "getting into the calculations" is slightly crazy and may end up costing someone their life..
It's going to be a proper basement using up as much of the ground area of the full garage as possible. Of course i'm not proposing the build of such a construction without engineering calculations to determine its ability to carry the required weight.

At this stage i'm looking for some ideas of the cheapest way to get this done so when i take it to a structural engineer i can have an informed discussion.
Reinforced concrete basement retaining walls, hollow core slab to form the ground floor and then traditional brick walls and truss roof.. job done
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Just finished one of these though slightly larger and close to what Static has just outlined.
Structural steel and kingspan cladded. Reinforced concrete basement and all upper walls shuttered also. Also has enough height for a second floor which will probably be added later and a big hole in the slabs for the car pit.

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