OT - Concrete Slab Strength
Turbo Mini Forums

I am currently trying to get a garage built and because of the trees in the garden I need to put a slab down for the floor. Does anybody know how to calculate what strengthening steels I will need in the slab? The slab will be 6.6m x 6.6m and just have normal garage type loads on it.

Cheers

Ben

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Try looking here
http://www.doityourself.com/stry/buildgaragefoundatio

Own the day

I know I'm going to get flamed for the lack of photos accompanying this post but my sister is a structural engineer.
I sent her your post via email and enquired whether it would be affected by the soil type and location of the trees.
This is her response:
"Yes - the foundations/floor slab will only be affected if the soil type is shrinkable (clay/mudstone or silt) if it's on sand or rock then the trees can be ignored.
If it is clay then it depends on the tree sizes and their position relative to the garage.
Incidentally I guess from the way he's phrased this he's looking at a suspended floor slab because the foundations need deepening rather than a raft?"
Hope that this helps in some way?

Regards

Dave

What, a sister...... who is an engineer..... and no photos ???

Back to the point, I have a similar problem with the workshop I'm going to build "soon", I've discussed it with my Building Inspector and his concern is also the trees all around my site, because I am also on clay (shrinkable).

Mine is going to be a steel portal frame on individual foundation pads and he has asked me for a detailed map of all trees within 30m, their species and height.

He says he has tables then to look-up the foundation pad depths (from the tree information) and will "advise" me what to submit.

The information to calculate rebar sizes, I found in a book I borrowed from one of the Civil Engineers at work, but I've long since given it back and I can't remember it's title.

Schrödinger's cat - so which one am I ???

I had problems with trees and clay soil when I built my garage, 3m deep foundations FTL, this also meant I had to use a beam and block floor and a bloody great steel beam in the floor to break the spans, so just be aware it can get very expensive just to get out of the ground, but it was worth it in the end.



Note: great big conifer tree in the back ground in my neighbours garden

Thanks for all your replies. It basically told me to contact a professional, which I have done. The quote for the build is with a slab, not footings, so now I just need some drawings and supporting calcs. Oh the joy.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

thats one hell of a spec and garage to go on top - did you consider a basement for storage and a pit?

On 30th Oct, 2008 MarkLD said:
I had problems with trees and clay soil when I built my garage, 3m deep foundations FTL, this also meant I had to use a beam and block floor and a bloody great steel beam in the floor to break the spans, so just be aware it can get very expensive just to get out of the ground, but it was worth it in the end.



Note: great big conifer tree in the back ground in my neighbours garden

best of luck Ben. Its a pretty staight forward design job for someone but the last few engineers I've used have completely over engineered their design to protect their PI insurance me thinks!

Would have loved to make a basement but I just ran out of money, it cost me a fortune just getting the soil shipped away from the drive and foundations as it was:(

On 30th Oct, 2008 Rob Gavin said:

thats one hell of a spec and garage to go on top - did you consider a basement for storage and a pit?

On 30th Oct, 2008 MarkLD said:
I had problems with trees and clay soil when I built my garage, 3m deep foundations FTL, this also meant I had to use a beam and block floor and a bloody great steel beam in the floor to break the spans, so just be aware it can get very expensive just to get out of the ground, but it was worth it in the end.


Note: great big conifer tree in the back ground in my neighbours garden

Mark ld what you could have done is say to a local farmer do you want the top soil.

we got rid of 1800 tonnes of the stuff. (we had to dig into quite a steep slope for our garage) for free, we just had to drive the tractor and trailer to and from his field and tip it that was about it.

hardly, no offence but thats ridiculous sam

have you guys never seen the shawshank redemption?

should have just hidden the dirt in your pants and dropped it when exercising in the yard

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