Distance of openings from wall

[tony1851]

I dont think Ive come across any builder doing strip footings for extensions of any size

Eh?

 

[Notch7]

Eh?

By strip footing, I mean a strip of concrete in the bottom of the trench and building up in blockwork.

Builders seem to mass fill the trench leaving only a block and brick course below ground level.

 

[tony1851]

By strip footing, I mean a strip of concrete in the bottom of the trench and building up in blockwork.

Builders seem to mass fill the trench leaving only a block and brick course below ground level.

A perfectly valid way, but up here (beyond the pale to southerners!) builders prefer just a 150-200 thick concrete strip and then trench blocks to just below ground level. Suppose it's down to cost/speed etc.

 

[Leofric]

Builders seem to mass fill the trench leaving only a block and brick course below ground level.

Deep trench fill concrete foundations aren't the norm around here in Yorkshire either, 600 x 225mm concrete strip foundations would always be specified for external cavity walls unless the engineer specified otherwise to suit ground conditions. 450mm wide ok for internal 100mm thick blockwork walls , but a housebuilder I worked for didn't even want to reduce the width for internal walls because they said it wasn't worth changing the bucket on the JCB when digging the trenches !

 

[noseall]

A perfectly valid way, but up here (beyond the pale to southerners!) builders prefer just a 150-200 thick concrete strip and then trench blocks to just below ground level. Suppose it's down to cost/speed etc.

Do they excavate with a steam shovel and bring the concrete on a cart?

I can't see any financial or practical reason not to mass fill. It is only the presence of drains at certain levels that would prevent otherwise. Even then it would have to be an extreme case.

 

[Notch7]

A perfectly valid way, but up here (beyond the pale to southerners!) builders prefer just a 150-200 thick concrete strip and then trench blocks to just below ground level. Suppose it's down to cost/speed etc.

That does surprise me, Ive honestly only seen strip footings in a textbook!

Also the ground is pretty variable in the South East, it has lots of areas with shrinkable clay. Ive known footings dug down to 3metres -sometimes building inspectors will allow it, and provided there is access for a bigger digger and ground doesnt collapse, trench footings can be dug from above and mass filled.

More and more builders use concrete pumps -combined with mass filled trench foundations means much less labour and saving on time so allowing getting out of the ground faster -

 

[Leofric]

That does surprise me, Ive honestly only seen strip footings in a textbook!

that surprises me even more. what about extra cost of concrete with trench filled foundations

Do they excavate with a steam shovel and bring the concrete on a cart?

not since Fred Dibnah died

 

[noseall]

what about extra cost of concrete with trench filled foundations

V's buying the blocks, sand, cement, lugging them around a slippery trench, clambering round with a level and a trowel in mud and muck and often rain and the hours of back breaking expensive labour....


...when all you need is a few extra seconds with the pump truck and a couple of hundred quid. We haven't used strip footings for decades. They became obsolete when concrete pumps and volumetric mixer lorries became widely available.

 

[^woody^]

V's buying the blocks, sand, cement, lugging them around a slippery trench, clambering round with a level and a trowel in mud and muck and often rain and the hours of back breaking expensive labour....

Pussy. Get in there and get your head down.

 

[noseall]

Pussy. Get in there and get your head down

Now you're talking Woods.

 

[Notch7]

V's buying the blocks, sand, cement, lugging them around a slippery trench, clambering round with a level and a trowel in mud and muck and often rain and the hours of back breaking expensive labour....


...when all you need is a few extra seconds with the pump truck and a couple of hundred quid. We haven't used strip footings for decades. They became obsolete when concrete pumps and volumetric mixer lorries became widely available.

Thats what I thought.

Im amazed that up in Yorkshire they do strip foundations.

Ive literally never seen a builder do one down here.

Mind you, I bet once builders try getting a concrete pump for a job they dont go back to barrows. The only frustrating thing is always having to do foundations, and concrete slab as separate pours needing 2 pump hires.

 

[noseall]

The only frustrating thing is always having to do foundations, and concrete slab as separate pours needing 2 pump hires.

And you still need a bit of gear to fill the cavities to within 225mm of DPC.

We weigh up whether to get ballast and mix it ourselves for the slab as you still need some lean mix for the cav's.

 

[Leofric]

Im amazed that up in Yorkshire they do strip foundations.

Well, as you know we're all thick up here . I'm amazed anybody is amazed about using strip foundations, it really is the normal specification around here for foundations unless ground conditions dictate otherwise.

 

[John D v2.0]

Strip would have slightly better thermal performance as a massive lump of concrete is a good thermal conductor. Although if it's concrete block with lean mix infill that would surely be so marginal it wouldn't make a big difference.