Conservatory Footings

[andrewjames]

Hi all,

I've Just had 600x600 footings dug for a conservatory cavity dwarf wall sat on clay at the rear of my property

Due to the removal of part of concrete slabs what used to be my patio some of the trench walls have collapsed, should i just clear them out and pour the footings or add some shuttering and back fill with clay or mot?

Regarding the footings, how deep should the concrete be when building on wet clay, i understand 225mm is a general recommendation for a strip footing then around 5 courses of brickwork (375mm) below ground level and a further 2 courses above ground up to DPM to match with the house - Or do i need to trench fill to within 150mm of the ground with shuttering for wet clay?

Additionally i have 3 surface drain covers running along the rear of the house, i will have no need for any of these, can i cap them below ground or do they need to be presented as manhole covers for rodding access, as i mentioned i will not be using these drains within my garden

There is also a land drain around 6" down that appears to be blocked somewhere under where my base will be, as i'm building over the top should i repair and replace or can i cap it off

There is also a 4" clay pipe complete with knuckles which is 600mm down, i will need to protect these with lintels and back fill with shingle

Thanks

Andrew

Untitled

• andrewjames
• 17 Nov 2014
• 1

Untitled

• andrewjames
• 17 Nov 2014
• 1

 

[freddiemercurystwin]

I think you may have won the 2014 award for DIYnot Most Untidy Trenches!

 

[andrewjames]

I think you may have won the 2014 award for DIYnot Most Untidy Trenches!

i know, will do my best to tidy them up by hand, its how they were left

 

[andrewjames]

Any help would be great, thanks

 

[Deltamale]

Keep the trench as clean as possible with the bottom even and level and sides as straight as possible. Consistent concrete thickness is important for overall performance of the found without weak spots that could result in cracking later. (though not so likely in in a light structure like a conservatory.

Remember the more the trench walls break down widening the trench the more concrete you will end up having to order to make up the gap.

If the walls keep breaking down you may have to resort to making some formwork using plywood to keep the concrete where you want it and keep quantities down.

 

[jeds]

An over wide trench is bad news. Width changes the nature of the forces on the concrete and can lead to cracking - even with fairly lightweight structures. Shutter back to 600mm wide and backfill to prevent the shutters from deflecting too much.