Concrete Foundation Shuttering

[Steevo]

A challenge for @RWG Contracts and others...


Looking to build some shuttering 1.2m x 1m x 7.5m long.

By my reckonings that's about 9 cube of concrete, which I think is about 20t or so. Some serious forces!

Due to the area involved, I can't just dig a hole that size because a larger area is already excavated so it means building up some shuttering that can take the forces.

How would others go about it and what would you use please?

 

[S J H]

4x2s and ply @Steevo if it's a one off.

 

[Steevo]

4x2s and ply @Steevo if it's a one off.

It most certainly is...or at least I hope it will be! I'd rather not have to do it again!

Picked up some 18mm thick ply sheets to start off with which look strong but that weight of concrete it quite a bit to hold back, even though the base will carry some of it there's a lot of sideways force and if it escapes...! One big mess!

 

[Forever Fendt]

It most certainly is...or at least I hope it will be! I'd rather not have to do it again!

Picked up some 18mm thick ply sheets to start off with which look strong but that weight of concrete it quite a bit to hold back, even though the base will carry some of it there's a lot of sideways force and if it escapes...! One big mess!

and then factor in pokering it

 

[Steevo]

and then factor in pokering it

Ah! Never thought about that!! Will it need a poker then?

 

[Hilly]

Keeping it down wil be the problem, you will need rebar to keep it together. Wil l need poker, that will test shuttering to the max !

 

[RWG Contracts]

A challenge for @RWG Contracts and others...


Looking to build some shuttering 1.2m x 1m x 7.5m long.

By my reckonings that's about 9 cube of concrete, which I think is about 20t or so. Some serious forces!

Due to the area involved, I can't just dig a hole that size because a larger area is already excavated so it means building up some shuttering that can take the forces.

How would others go about it and what would you use please?

A load of 18mm plywood and a shitload of 4x2's. Can you bolt through or is it going to have to be braced?

This is one we did, obviously nowhere near as much concrete involved, we only braced every 4' and propped every 8'. You'll need a lot more than that

 

[Steevo]

Keeping it down wil be the problem, you will need rebar to keep it together. Wil l need poker, that will test shuttering to the max !

Keeping it down?

A load of 18mm plywood and a shitload of 4x2's. Can you bolt through or is it going to have to be braced?

This is one we did, obviously nowhere near as much concrete involved, we only braced every 4' and propped every 8'. You'll need a lot more than that

View attachment 492374

Thanks Rob. That's most helpful. Bolting through shouldn't be a problem. I was planning on going overkill with it....but wanted to make sure I went the right level of overkill. I really wish I could be doing it into fresh ground that's for sure..!

 

[Morph]

The force is only the depth of the concrete. A 200mm wall 1200 high will exert the same force on the shuttering as a wall 10m thick.
A cheep way is too build the shuttering pegged into the ground like a fence, wire the 2 sides together through the ply and cut the wire to remove the shuttering. iyswim.

 

[Stock]

Can you not hire some pan for the job, acrow used to design the shutter if you were hiring them for tanks and stuff.................
Definitely need a poker for over 6" of concrete and you need to pin them down .................

Put a couple of inches of lean mix in first in to the trench as it will give you a work platform that you can drill to pin the shutters too.......................

 

[milkloss]

I'm not a concreting man by any means but that's some construction @RWG Contracts has got above!

Could you not support it inside and heap some ground up against the outside to help?

 

[RWG Contracts]

The force is only the depth of the concrete. A 200mm wall 1200 high will exert the same force on the shuttering as a wall 10m thick.
A cheep way is too build the shuttering pegged into the ground like a fence, wire the 2 sides together through the ply and cut the wire to remove the shuttering. iyswim.

Not sure I agree with that

 

[RWG Contracts]

I'm not a concreting man by any means but that's some construction @RWG Contracts has got above!

Could you not support it inside and heap some ground up against the outside to help?

It's to late when if moves better to be safe than sorry

 

[Hilly]

Keeping it down?



Thanks Rob. That's most helpful. Bolting through shouldn't be a problem. I was planning on going overkill with it....but wanted to make sure I went the right level of overkill. I really wish I could be doing it into fresh ground that's for sure..!

Whe you pur the concrete in the shuttering will want to come up and let concrete out the bottom, keeping it down will be hard if you not already on concrete and can hilit the shuttering to the ground.

 

[mar]

The force is only the depth of the concrete. A 200mm wall 1200 high will exert the same force on the shuttering as a wall 10m thick.
A cheep way is too build the shuttering pegged into the ground like a fence, wire the 2 sides together through the ply and cut the wire to remove the shuttering. iyswim.

I don't agree with it either

 

[milkloss]

could tou build two walls out of concrete block laid on thier sides? Probably an expensive way of doing things if it worked though.

 

[Hilly]

I did a similar job years ago, had to cut lenghts of angle iron bang them into the ground on an angle and tie the shuttering down with fence wire, was a bit worrying when 3 loads of concrete turned up but fortunately it all held together, i could see the shuttering wanting to lift tho and the tie down wires were very tight.

 

[Morph]

The pressure does not change as its calculation is height x density (about 2.5 tonnes/cubic m). Force is pressure x area.(the face of the shutter) The thickness of the wall is not considered in either calculation.
Edit : although a big pour at depth always is more worrying than a small pour at the same depth

 

[Hilly]

The pressure does not change as its calculation is height x density (about 2.5 tonnes/cubic m). Force is pressure x area.(the face of the shutter) The thickness of the wall is not considered in either calculation.
Edit : although a big pour at depth always is more worrying than a small pour at the same depth

Well i aint no mathematician but the wider you go the more concrete required, the more concrete the more pressure ?

 

[Morph]

If you poured a 6 inch slap 40 feet wide would you need stronger road forms than one 4 foot wide?