Foundation size for garage

[spada01]

I'm building a 1 1/2 size garage in lightweight Celcon blocks. The roof comes in at about 600kg and it's a single block thick (with midway supports). It's also 14m2 so no BC

What size foundation should I use? 200 wide, 400 deep or 300 wide and 600 deep?

 

[RedHerring2]

Why not work as close as you can afford to BR anyway. If it's a little extra effort it doesn't cost that much extra.
I believe footings should allow 125mm either side of the wall. Minimum thickness would be 275mm. Possibly, mnimum depth would be 600mm to top of footings. But so much depends on your local conditions.

Perhaps more experienced/qualified may confirm.

Don't forget to allow for the pier footings while your at it.

 

[^woody^]

Foundation depth is more to do with the ground under them, than the weight on them.

The type of ground determines the depth, along with surrounding vegetation, and if you don't want the garage bobbing up and down every year, then its best to ensure that the foundations are deep enough.

I'd start the bidding at 500mm and see if that is good enough

You don't say if you are doing a brick, strip or narrow strip foundation, so width will depend on the type

 

[Static]

Would aim at 450mm wide footing with depth around 300mm making sure the bottom of the concrete is at least 450mm below ground level to avoid frost heave.. based on a fair quality of bearing soil.. so dig deeper if you hit poor soil..

Will the floor sit on this foundation as well?

 

[spada01]

No - the floor is an old concrete slab that currently sits on soil and is completely intact and without cracks despite having parked my car there for a long time, so I'm not going to replace this, just the foundation

45 deep by 30 wide sounds reasonable and for such a light garage adequate enough. Right - off to break up the old foundation then dig, board out and lay the new one.

Thanks for your advice folks

 

[RonnyRaygun]

45 deep by 30 wide sounds reasonable and for such a light garage adequate enough. Right - off to break up the old foundation then dig, board out and lay the new one.

Before you start...Static said 45 wide by 30 deep, not the other way round! And 450 below ground level...

 

[spada01]

Resurrecting an old post - is it worth putting rebar into the foundations along it's length and at the corners? It's cheap enough and I'm happy to bend, but is it going to be a complete waste of time?

 

[ChapiTheBricky]

min 200mm deep concrete
min 150mm scarcement each side of outside edge of walls(if you know what i mean)
min 200mm frost cover (200mm from top of concrete to existing ground level)
i would put re-inforcement in, you would probably get away without it, but it's cheap and doesn't take long so why not?