Groundwork & Foundations

Foundation Trench Support - leaving in place after pour.

Anonymous user 28/02/2024 - 3.16 PM

Hi, I've just started a 'self build' project. I'm an architect so understand a lot about how buildings are designed, but would be grateful for some advice on the practical elements of actually building an extension. Currently digging out the trenches for the footings. Had a soil survey done, which showed good soil at 1.5m down x 450 wide, so have dug down to this and found the hard soil, so think that’s fine. Very hard work - new appreciation for the guys on site. My question is about formwork/ trench support. I have put in some fairly robust trench support as I’m doing it a bit more slowly and the top layers of soil are not that stable. Currently I've put in 18mm OSB supported with 40x60mm cross struts at approx. 400 centres (horizontally & vertically.) I’m going to get redimix pumped in after the BCO has been and signed off. Can the OSB forming the walls of the trench be left in place – I hope so as some of the banks behind it have already collapsed, so getting the OSB out is going to be difficult. I would also like to leave the struts in place (screwed to OSB walls), as I’m worried if I take them out the OSB will start be warp under the pressure from the soil. Any advice about leaving trench support in place after pouring the foundations gratefully received. Cheers Tim