Foundations

[Lawrence Zarb]

when laying foundations for an extension, for example, MUST it be laid in "one slab", or can it be layed in sections or layers?

[Phil L]

It's at it's strongest when cast in one. No it cannot go in layers. If it goes in sections, steel bars must be hammered into the soil where it will stop and concreted in, then dug around for the next section, so that the two are joined by steel, the BCO will inform you of steel diameters and how much he wants - they are usually 'not happy' about it being done this way but if it's not possible to do it in one, then there's no option, if it's possible to do it in one then that's what they (usually) insist on.

FWIW, it's better (I'm talking about strip footings here and not a raft) to mass fill the footing, EG: the one I'm half way through is sat on a 2ft wide and 2ft-6 deep strip of concrete, the plans asked for 9 inch, but it's often cheaper and quicker to fill the lot with concrete rather than lay blocks / bricks down a hole - the extra cubic metres of concrete get cheaper the more you order.