What factors affect the depth of foundations?

[JAMES SHEKHDAR]

What factors affect the depth of foundations?

[Ian Stirling]

Whatever building regulations are in force. The nature of the soil and building. Expected seismic and other events that may occur. Cost.

[Christian McArdle]

Usually just the depth of the hole that the concrete was poured into.

Christian.

[Hugo Nebula]

On Fri, 04 Aug 2006 14:08:49 GMT, a particular chimpanzee named "JAMES SHEKHDAR" randomly hit the keyboard and produced:

The load-bearing capacity of the ground and the loads on the foundation; whether there are trees in the vicinity, especially in clay soils; frost protection; the proximity and depth of any drains and sewers.

[ironer]

plus the physical shape of strip foundations affects their strength, that is the ratio of width of a strip foundation to its thickness.

Unless things have changed since my last encounter with new foundations, normal requirement (at least in these parts) is:

the top of the cconcrete strip should be a minimum 1m below ground level to provide adequate frost protection;

then imposed load -weight to be supported - determines how strong a concrete strip is needed,

finally that determines the thickness of the strip and hence depth of the bottom of the trench.

Above is minimum - local conditions might require more excavation.

There used to be a relevant table in the building regs, maybe it's still there?

[woodglass]

I thought so ! :-)))

[The Natural Philosopher]

Weight of building above Soil quality

That's it mainly.

Soil quality breaks down into many tings like localised tree roots,type of soil,likelihood of flooding etc, etc, plus the depth of anything sturdy like bedrock in a peat bog.

The aim of the foundations is to spread the load of the building over as wide an ear as possible onto a layer of sunsoil that is as stable as possible..so the house sort of 'floats' in the ground.

If there happens to be a lump of rock there, you can build straight off that. If its a peat bog, you may have to go down t5 meters to find something solid - pipes is the answer there.

[Dave Fawthrop]

|JAMES SHEKHDAR wrote: |> What factors affect the depth of foundations? |> |> |Weight of building above |Soil quality | |That's it mainly. | |Soil quality breaks down into many tings like localised tree roots,type |of soil,likelihood of flooding etc, etc, plus the depth of anything |sturdy like bedrock in a peat bog. | |The aim of the foundations is to spread the load of the building over as |wide an ear as possible onto a layer of sunsoil that is as stable as |possible..so the house sort of 'floats' in the ground. | |If there happens to be a lump of rock there, you can build straight off |that. If its a peat bog, you may have to go down t5 meters to find |something solid - pipes is the answer there.

The problem is more difficult than that on made up ground, of which there is a lot on the West Riding. I watched some houses being built near us, and some were on reinforced rafts with 12 inch dia concrete piles. Another was on a four ft deep block of solid concrete. My house is on a reinforced raft.

[dennis]

Mine is on a six foot thick reinforced raft.. more steel in it than a bridge I saw. The house next door is on four foot deep strip foundations.

There is no difference to the soil.. apparently the builder had purchased some foundations in bulk and was using these rafts whatever the soil conditions.

[Dave Fawthrop]

|> The problem is more difficult than that on made up ground, of which there |> is a lot on the West Riding. I watched some houses being built near us, |> and some were on reinforced rafts with 12 inch dia concrete piles. Another |> was on a four ft deep block of solid concrete. My house is on a |> reinforced |> raft. | |Mine is on a six foot thick reinforced raft.. more steel in it than a bridge |I saw. |The house next door is on four foot deep strip foundations. | |There is no difference to the soil.. apparently the builder had purchased |some foundations in bulk and was using these rafts whatever the soil |conditions.

Mine **needed** the concrete raft. I put up an extension and one day found a building inspector in the bottom of the foundations digging out shale as if it were granulated sugar. He said "reinforced concrete raft or go down to original ground level", which could have been another 20-30 ft. I put in a reinforced concrete raft.

[Hugo Nebula]

On Sat, 05 Aug 2006 21:18:24 +0100, a particular chimpanzee named Dave Fawthrop randomly hit the keyboard and produced:

You'll have to put down some traps.

[Brian Sharrock]

That's what _he_ said; it's probably Jimmy Hoffa!

[Cordless Crazy]

1m below ground level??

Where did you get that from?

Normal depth is 450mm, which, even in Scotland is the requirement

-- Cordless Crazy