Footings and Cavitys Querie

staningrimsby · 30 Mar 2008

Hi everyone, hope everyone is well,

I have been a plumber for the last 6 years and a plasterer for the last 2 but after receiving 3 very over priced quotes for building my small extension i have decided to have a go myself.

My previous building experience goes a far as building a new garden wall which i must say i am very proud of it looks fantastic, so the brick laying side of things does not bother me, my questions are as follows;

1 When my footings are in place how far below ground level do i start with the engineering bricks ???

2. I am planning on a 50mm cavity, as i said this is a small extension so space is at a premium, or is there a minimum size for the cavity ???

My footings are going 1mr down as i am in close proximity to an anglian water sewer pipe so have to go down lower than that.

Any advice you could provide me with will be greatly appreciated,

noseall · 30 Mar 2008

[quote="staningrimsby";p="868474"

1 When my footings are in place how far below ground level do i start with the engineering bricks ???

whatever masonry will be visible once soil/grass/patio is reinstated. if the ground level deviates, then account for this with the brickwork.

2. I am planning on a 50mm cavity, as i said this is a small extension so space is at a premium, or is there a minimum size for the cavity ???

we are now using 100mm cavities with full fill dritherm cavity batts. you may be able to make the cavity smaller by using a rigid board insulation but don't count on it.

My footings are going 1mr down as i am in close proximity to an anglian water sewer pipe so have to go down lower than that.

generally a 1m dig is satisfactory. however, foundations that are in close proximity to drainage pipes do need to be lower than the drain invert.
Any advice you could provide me with will be greatly appreciated,

[/quote]

staningrimsby · 31 Mar 2008

The sewer pipe is 500mm down in my garden, i have been 5 houses down the road where the manhole is and at that point it is 1.2m deep.

^woody^ · 31 Mar 2008

If you have masonry construction with a 50mm cavity, you will have to have a thicker internal block or dry-line with insulated board - so there is no advantage - the wall is going to be 300mm thick whatever. Set the extension out based on the internal space requirement.

Alternatively, have a timber frame construction and your wall can be just under 150mm thick.

You need a building over permission from the water authority if you arre building over their sewer.

Are you sure its a sewer or is it a private drain?

Engineers usually start 225 (3 course) below ground to give a frost cover.

noseall · 31 Mar 2008

^woody^ said:
Engineers usually start 225

225?

this must be months old and not years.

what age do surveyors start at?

staningrimsby · 31 Mar 2008

Cheers Woody,

I spoke to the council and they looked on a program called "DigDat"

and said it defo a sewr pipe, im not building over it but will be only

650 mm away from it.

^woody^ · 31 Mar 2008

noseall said:
[225?

this must be months old and not years.

what age do surveyors start at?

225 BC - they are stuck in the past. Won't listen to any modern ideas

^woody^ · 31 Mar 2008

staningrimsby said:
Cheers Woody,

I spoke to the council and they looked on a program called "DigDat"

and said it defo a sewr pipe, im not building over it but will be only

650 mm away from it.

Building within 3m of a public sewer will generally require permission from the water authority - plus their fees and obligatory camera survey.

£500 later you get permission

Shytalkz · 1 Apr 2008

^woody^ said:
225 BC - they are stuck in the past. Won't listen to any modern ideas

**** **** you ******* ****

Shytalkz · 1 Apr 2008

Oh, was that about surveyors?

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Footings and Cavitys Querie

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