foundation depth in clay
- Thread starter dexterdo
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If high volume change potential you need to be 2.5m down...
Depends on the size of the extension.. consider removing the tree first as this may reduce depth required (only if tree is less than 10m current height)
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Its my neighbours tree and has been lopped to about 7m but wont be removed. Extension is to be 7m x 4.5m at its widest.
Ideally you would have a soil sample tested.
Also, as you get further from the tree you may be able to reduce the depth of the foundations
Shame as 7m removed tree would only require standard depth footings.. consider tipping your neighbour a few notes and pay for the tree removal..
How you tell its Plasticity Index, well one way is send a few samples off to a site investigation company for testing..
Local BC may know what PI you have in the area so can advise..
There is a kinda simple way of testing what you have (involving mulching the soil about) but its not something easy to describe unless youve done it before..
How you tell its Plasticity Index, well one way is send a few samples off to a site investigation company for testing..
Local BC may know what PI you have in the area so can advise..
There is a kinda simple way of testing what you have (involving mulching the soil about) but its not something easy to describe unless youve done it before..
Just looking in BRE Digest 240 and according to Table 2, the volume change potential of Gault clay is either high, or very high.
If very high, NHBC doesn't give guidance so you will be looking at an engineered foundation such as piles.
If high, your contractor might still prefer to implement standard footings, rather than have an engineered solution which will need to be both designed and sub-contracted out.
Where in the UK are you? Foundation depths can be reduced the further from London you get.
If very high, NHBC doesn't give guidance so you will be looking at an engineered foundation such as piles.
If high, your contractor might still prefer to implement standard footings, rather than have an engineered solution which will need to be both designed and sub-contracted out.
Where in the UK are you? Foundation depths can be reduced the further from London you get.
Sorry for late reply-we are 10 miles south of guildford
To give you some idea of the direction Static is heading you in, have thrown together a few quick figures for your consideration.
We would quote you, for the sizes given and a 2.5m dig depth as Ronny Raygun has stated by 600mm wide.
To dig and cart to tip of site. Trench fill with concrete 2.1m deep. For the sum of £5006.00 VAT inclusive. This quotation would only be given, providing that access of 1.6m would be available for 4 tonne 360 machine.
To dig by hand same size 1 metre deep and trench fill with concrete 750mm deep for the sum of £2858.00 VAT inclusive.
We would not consider to dig by hand 2.5 deep.
oldun
To give you some idea of the direction Static is heading you in, have thrown together a few quick figures for your consideration.
We would quote you, for the sizes given and a 2.5m dig depth as Ronny Raygun has stated by 600mm wide.
To dig and cart to tip of site. Trench fill with concrete 2.1m deep. For the sum of £5006.00 VAT inclusive. This quotation would only be given, providing that access of 1.6m would be available for 4 tonne 360 machine.
To dig by hand same size 1 metre deep and trench fill with concrete 750mm deep for the sum of £2858.00 VAT inclusive.
Thank you. We have been quoted for piling at a couple of thousand more than that. There is just about 1.6m clearance (assuming you need 3.2m for 360 degrees) but its very tight. So it sounds like we should go with piling doesnt it, which is an expense I wasnt expecting when we put in the planning app-do you think we should go for building regs approval or just on site inspections? I think I know the answer to that question but I`m just interested in a second opinion. Thanks to everyone for helping so far.
We would not consider to dig by hand 2.5 deep.
oldun
By the way, if we could get our neighbour to agree to removing the closest tree, we still have a 10m long row of leyandii and a silver birch at 13m away from the nearest point of the extension, all the way along our back fence(they belong to another neighbour who definately wont remove them as he likes them for privacy). Would we still need pling then?
To give you some idea of the direction Static is heading you in, have thrown together a few quick figures for your consideration.
We would quote you, for the sizes given and a 2.5m dig depth as Ronny Raygun has stated by 600mm wide.
To dig and cart to tip of site. Trench fill with concrete 2.1m deep. For the sum of £5006.00 VAT inclusive. This quotation would only be given, providing that access of 1.6m would be available for 4 tonne 360 machine.
To dig by hand same size 1 metre deep and trench fill with concrete 750mm deep for the sum of £2858.00 VAT inclusive.
Thank you. We have been quoted for piling at a couple of thousand more than that. There is just about 1.6m clearance (assuming you need 3.2m for 360 degrees) but its very tight. So it sounds like we should go with piling doesnt it, which is an expense I wasnt expecting when we put in the planning app-do you think we should go for building regs approval or just on site inspections? I think I know the answer to that question but I`m just interested in a second opinion. Thanks to everyone for helping so far.
We would not consider to dig by hand 2.5 deep.
oldun
13m is far enough away for conifers for their roots to not affect the foundations. The roots of conifers go deep but don't spread anywhere near as far as deciduous trees.
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