Extension footings.

[Screech20]

Hey guys!

We finally started digging out our footings for our single storey extension today. (Full planning and building regs approval)
I applied the ‘measure twice, cut once’ rule, but unfortunately somewhere along the line we went a bit out!

Footings are to be 1000mm down, 600mm wide.
We’ve ended up going out 250mm too far, so will have to pull that out tomorrow.
That will then make the trench 850mm wide. Can we shutter off to form the 600mm and then back fill behind it without causing issues?

Thanks!

 

[John D v2.0]

apparently for domestic loadings the trench doesn't have to be that accurate. That was according to our SE, as the builder was quite wonky on the trench.

 

[Screech20]

I understand the dimensions are minimum so I could just fill them at the extra width, but over the whole trench will be about 2meters if concrete. So hoping to shutter it to avoid using too much concrete if allowable.

Cheers.

 

[John D v2.0]

if you're worried, there's lots of info online about eccentric (edge loaded) foundations, e.g. https://www.blsurveyors.com/eccentric-or-concentric/

 

[Alastairreid]

The answer to your question is yes you can square the footing of with a shutter.

 

[Screech20]

The answer to your question is yes you can square the footing of with a shutter.

Thank you.

 

[noseall]

The answer to your question is yes you can square the footing of with a shutter.

But don't underestimate the push of the concrete.

 

[Screech20]

But don't underestimate the push of the concrete.

Thanks noseall. Plenty of stakes and backfill it before the pour then?!

Cheers.

 

[noseall]

Thanks noseall. Plenty of stakes and backfill it before the pour then?

We usually manage the trench in equilibrium - i.e. back fill behind the shutter as the conc' goes in.

 

[nickjb]

Just build it 250mm bigger. Will anyone notice? I doubt the council would enforce

 

[Screech20]

It’s something that we did discuss last night.
I have already gone a little bit more than I should have, which has taken it to the max span for the flat roof joists that have been specified. So would need the calcs done again to satisfy BC if I was to leave it where it is.

Question: how close the the edge of the footing can the brickwork go?

Another question: we obviously found the house footings, these taper out as the trench goes down, do we need to cut these flush so that the new brickwork up to damp can go up to the wall?

Thanks.

 

[Alastairreid]

Question: how close the the edge of the footing can the brickwork go?



Another question: we obviously found the house footings, these taper out as the trench goes down, do we need to cut these flush so that the new brickwork up to damp can go up to the wall?

150mm.

Either step the new founds under or connect using rebar.