foundation trench... height of concrete....Photo's

6 Oct 2004
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United Kingdom

600 wide foundation trench, 900 deep, three sided for extension.

I want to mark 300mm from the base of the trench, to set the height for the concrete. I have tried driving in 50 x 50 wooden stakes but the ground is to hard.

Any advice welcome

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I'm using treated timber stakes made for the job and they just keep splitting or the end mashes up. It's very stony ground.
Use some bits or rebar, 12 or 16mm. Being steel, and a lot thinner they should drive in easily.
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mark the inside of the trench with marker paint to give you a level to work to. it should be accurate enough for concrete pouring
thanks for the responses.

I like the rebar idea, spraying the walls of the trench sounds like a good fail-safe too, I could put some batten at the height I want and spray under it so the concrete just covers it.

Good call KEV, but after busting my balls with a pic-axe and a barrow for the past five (half) days, for the sake of saving myself £360 weekend hire charge for a digger and a skip loader, I'll leave the plant option to them that want an easy life.

I'll take and bore you with some pics tomorrow when the (spot mix) concrete is poured.
I bought some 12mm rebar and cut it up into 600mm lengths. The depth of the concrete is 300mm. I drove in the rebar stakes about 1m apart using a level and it seems to have done the job.

I suppose now a host of builders will come forward to tell me why having rebar embedded in your foundation is disastrous.

brumylad said:
600 wide foundation trench,
That's a very wide footing, 450mm wide is the norm. Has the building inspector seen the footing dug out before concrete in?
Just a thought Brumylad,did you check all depths against any nearby trees,it could cause you concern with ground movement if you have any reasonable sized trees in the garden.

SD Carps

I've decided to go for a partial fill cavity. Prescot wants 50mm of insulation and I want nice round figures to work to, so I've gone for a 50mm residual cavity, that means obviously a 100mm cavity. Therefore it's a 300mm thick wall. Footings are required to be minimum 150mm each side of the wall so 600mm wide trench.

I dug it by hand so its more like 700 in places but it is symetrical about the midline of the wall.

All the trees within 15m are fairly small species, more shrubs really. The ground is dense gravel rather than clay anyway.

The building inspector came the day before and gave the all clear.

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