Fotings

[bookahandyman]

Just a quick one. How deep do my footings need to be on single story extension 7x3mt 2.5 high. First foot down is soil then clay? Cheers chaps.
Also how wide. Cavity wall block inside brick out. I've got 500 wide and 1200 deep in my mind but just checkin

 

[^woody^]

The correct answer is ...... what the plans or BCO says

Normally minimum 900 deep and width depends on the wall thickness

 

[bookahandyman]

It was six yrs ago since I last did one. Then I got away with 800 and 500. Wall is 275 thick unless cavity rules have changed since then.
No plans as I am building then designing
I have put in for building regs today. But trying to dig out this w/e as I have a digger til Monday for £90. Bargain. Then will get BI to have a butchers.

 

[^woody^]

A 275 cavity is sooo 2004

Walls are normally 300mm now unless you have some special insulation method

Go for 1000 x 600 while you have the digger

 

[bookahandyman]

Thought it might have changed. They seem to every five minutes. Would I get away with 500 with a 300 wall on them 100mm either side.?
Reason is I spent all day grinding a 500mm channels out of the back patio which is concrete?

 

[^woody^]

Yes 500 should be OK, but the danger is that the BCO might be fresh faced or have a little black moustache, and then you have the problem of widening the trench 50mm on each side

 

[theoldun]

Providing no trees. 1050 deep, 750 trench fill.
Width, guess total load 30 to 40 KN/lin metre. Take worst case say 50KN/lin metre. Gravel or sand 500 wide.. Stiff clay, stiff sandy clay 500 wide. Firm clay, firm sandy clay. 600 wide.
Then again, you may get some ar**hole of BC who will want it 19m wide.
Rattle it round at 500 if he won’t pass it go back round and trim the banks by 50mm each side under where you have sawn out.
oldun

 

[bookahandyman]

BI came out today and passed footings at 500 wide and 1000 deep. so happy days , concrete in tommorrow. thanks all.
Whilst i'm on here , whats the reccommended depth for celotex under wet UFH i'm thinking 120mm, going to block and beam the floor.
Also he said cavity is 85mm full fill. Going for the Big 4.2m doors across back now so gotta work out me steels? or does any reckon a catnick http://www.catnic.com/lintels/CX70-100.aspx would do, only a flat roof going on top with 195x47 timbers 4m long 400 centres poss 600

 

[ChapiTheBricky]

sorry to hijack this post but why are all the spec's for founds down south so deep? Usually in scotland 200mm deep concrete, 200mm scarcement each side and 250mm frost cover is standard

 

[bookahandyman]

I know what you mean. My brother is a civil engIneer in Dubai. He is buildin a six story building on sand with 700mm deep footings 400mm wide. He reckons my single story extension would be fine on 200mm max.

 

[freddiemercurystwin]

edit

 

[noseall]

600mm wide digger bucket at 1m deep - simples.

I'm not even sure whether a 500mm digger bucket is available.

Mass filling with concrete is far simpler and cheaper than laying blocks deep below ground.