Structure

What happens as your extension walls go up, from DPC to plate height. Covers cavity wall construction, block types, wall ties, cavity closers, scaffolding, weather risks, and the quality checks you need to do at each payment milestone.

What structural steels do, who specifies them, how to verify your order, and why extension steelwork routinely exceeds initial quotes. Covers cantilevers, cavity width problems, and the ordering failures that delay builds by months.

How the timber roof frame goes onto your extension: wall plate, rafters, ridge, and warm roof insulation. Covers cut roofs vs trusses, the ridge beam vs ridge board distinction that catches builders out, warm roof construction, and what building control inspects before you cover anything up.

What goes on top of your extension roof structure: tiles, flat roof membranes, lead flashing, dry ridge systems, fascia, soffits, and guttering. Covers the lead flashing failures that cause 90% of extension roof leaks, the roofer-window coordination problem, and a pre-payment inspection checklist no other guide gives you.

How to specify, order, and install extension windows. Covers frame materials, glazing specs, the 8-12 week lead time trap, installation day checks, and the sealing details everyone misses.

What the BCO checks at the structural stage of your extension: steels, wall ties, cavity barriers, roof timbers, and the pre-plasterboard inspection that catches problems before they're hidden forever.

How to choose between bifold and sliding doors for your extension, protect your money from supplier failure, and get the installation right. Aluminium bifolds from £3,150–7,200.