Concrete garage base thickness.

[Adam68]

True. But on sh it ground......

The ground is lawn but will be compacted with hardcore.
Has lots of stones and bricks in it.

 

[stuart45]

Looking at the photos of the ground I think I would have gone a bit deeper with the dig. Older properties often had shallow footings, but they were built lime mortar and usually had thicker walls.

 

[John D v2.0]

The depth is needed to get down to solid ground out of the influence of moisture changes etc, the width is needed to spread the load. So your 3 storey house would need a wider foundation not a deeper one.

 

[Adam68]

Looking at the photos of the ground I think I would have gone a bit deeper with the dig. Older properties often had shallow footings, but they were built lime mortar and usually had thicker walls.

Actually he dug around 50cm with some areas less. The concrete is is around 200cm plus. I've not measured but from my estimation 30cm is left to ground level or less. Blockwork will therefore start below ground level.

 

[Adam68]

Actually he dug around 50cm with some areas less. The concrete is is around 200cm plus. I've not measured but from my estimation 30cm is left to ground level or less. Blockwork will therefore start below ground level.

The depth is needed to get down to solid ground out of the influence of moisture changes etc, the width is needed to spread the load. So your 3 storey house would need a wider foundation not a deeper one.

We have a 300cm wide footing which is 45-50cm deep. This will support a single brick so load will be less than double leaf.

 

[tomfe]

Adam68 are you actually build this yourself?
Is that a stepped foundation in your second picture?

 

[Adam68]

Adam68 are you actually build this yourself?
Is that a stepped foundation in your second picture?

No I'm a novice to this. I know what one is but building anything is not my cup of tea.
I must be as it's on slope.
Checked sizes and tge width is 300mm with depth of at least 6 inches but 20cm deeper areas as it's on a slope.

 

[^woody^]

From those images it looks like you are still building on top soil, and if so it makes no difference how thick the hardcore or slab is it will still move

 

[Adam68]

From those images it looks like you are still building on top soil, and if so it makes no difference how thick the hardcore or slab is it will still move

Any deeper would have made no difference it would have been top soil again. So if when you do slab for floor you just use 100mm hardcore and 150mm concrete then why would that not sink when u put a car on it. You don't dig 50cm down for floor.

 

[Adam68]

Foundation wall has started with blocks on side with motor underneath.

 

[Adam68]

What I don't get is when you have a sectional garage installed they don't use a foundation wall. They put concrete blocks on top of a base same thickness as one you build. Why does that not sink or move and yet we think blocks on foundation wall and thicker concrete strip will fail.

 

[Adam68]

My sectional garage installer was going to have just 4-6 inches of concrete with hardcore and then drop sectional pieces on top.
The weight would have been similar or probably more.

 

[^woody^]

My sectional garage installer was going to have just 4-6 inches of concrete with hardcore and then drop sectional pieces on top.
The weight would have been similar or probably more.

Could your sectional garage installer be wrong and just want to do a quick job?

The weight is not the main factor. The potential for soils to move over the seasons, change bearing capacity relative to ground moisture, and support vegitation is more important.

Top soils should not be built on

 

[noseall]

What I don't get is when you have a sectional garage installed they don't use a foundation wall. They put concrete blocks on top of a base same thickness as one you build. Why does that not sink or move and yet we think blocks on foundation wall and thicker concrete strip will fail.

They are fitted to a one-pour concrete slab. Any small movement will be irrelevant as the whole slab is likely to move and so the whole garage.

Yours is point loaded onto a dedicated strip footing. Any movement with yours and the walls will crack.

 

[Adam68]

They are fitted to a one-pour concrete slab. Any small movement will be irrelevant as the whole slab is likely to move and so the whole garage.

Yours is point loaded onto a dedicated strip footing. Any movement with yours and the walls will crack.

I understood that if you have a base already in situ they just install the sectional pieces on top of that and even if it's made new it's the same. The build however will have the floor concrete spanning the walls so will adhere to them.