Shuttering for foundations

[tommyl18]

Hi,

Im currently building a single storey apex extension.

We have had to get a build over agreement from severn trent water because there is a shared drain 200mm away from where the footings will be that runs the full length of the footings.

We have dug down 1350mm deep which would give us 1m of footings and then 6 courses upto damp.

The top of the footings would be approximatly 200mm above the pipe.

the problem is this morning ive turned upto site and with the heavy rain all the sides have caved in exposing the pipe.

How can I shutter this without effecting the foundations or the drain or is there any other way round this?

 

[pinenot]

I surprised your local water board didn't advise that the footing be dug down to the level of the base of the drain minimum (that could be answered in the building regs section better though) When you say a build over agreement, what does that say?...pinenot

 

[fmck]

I surprised your local water board didn't advise that the footing be dug down to the level of the base of the drain minimum

The base of the footing 800mm below the pipe? In the past if you can't sleeve the pipe it would be wrapped in some expandable material so no movement in the concrete footing effects it. That's what we do here.

 

[pinenot]

The OP states in the first post top of footing (strip foundation ?) "200mm above pipe" I had assumed that meant top of pipe and footings being normally 150 > 200mm thick, would mean at best the strip foundation would be level with the top of the drain. Hove I got it wrong??...pinenot

 

[^woody^]

I don't understand any of it

 

[pinenot]

OK Tommy, it's over to you to explain all...pinenot

 

[tommyl18]

The pipe is very shallow to ground level its only aprox 450mm deep

I have dug the trench to accomodate 1m deep footings and 4 course of bricks below ground level then 2 course above ground level upto damp course

the problem im going to have is that the finished level of the footings is going to be higher than the pipe so i need to prevent the concrete when it is poured from going over the pipe because it is now exposed.

i have been advised to lay 700mm of concrete and then do the rest in trench blocks which would mean i wouldnt have to do any shuttering does this sound ok?

 

[pinenot]

Could you provide a sketch...pinenot

 

[noseall]

Ply shuttering will be ideal as a barrier betwixt your concrete and the drain pipe. See if you can jam the odd bit of polystyrene in there as well to allow for a bit of shear movement.

 

[tommyl18]

Untitled

• tommyl18
• 7 Sep 2013
• 1

 

[pinenot]

Thanks for that tommy.

Now that I can visualize things, first off you could make up open bottomed ply shutters (just like trench boxes) fitted into your trench, down just below the depth of the drainpipe (if it' 200mm down from ground level, as you have said, and I assume 100mm dia, that would make your shutter about 350mm deep in the ground) so say you rip up some 400mm strips of 3/4" shuttering ply use this to line the top 300mm of your trench, like this - View media item 66097 this should allow you to both clear the ground collapse and support the pipe until you have poured your founds, then you can excavate around the pipe and back fill with pea gravel, topped with soil as shown.

Hope this helps...pinenot

 

[tommyl18]

Thanks for that