Blog
Answers to the questions that come up before a kit is ordered and while it is going up.
Build over agreement: building an extension near a sewer
A build over agreement is the water company's consent to build over, or within 3 m of, a public sewer. Many rear extensions need one, because shared drains behind terraced and semi-detached houses became public sewers in 2011. Apply once the drawings are fixed and before any digging. Building control will not sign the extension off without it where it is needed.
Building notice vs full plans: which should you use?
With full plans, building control checks your drawings and approves them before you build. With a building notice, you tell them you are starting and they check the work on site as it goes. Fees are similar. For an extension built from a kit, full plans is the better route, because the drawings and calculations exist anyway and the kit cannot be altered once it is made.
What foundations does a timber frame extension need?
Usually the same concrete strip footings as a brick extension. A timber frame is lighter, which can allow a narrower footing, but depth is set by the ground and not by the weight above it. Expect at least 750 mm in clay, often 1 m, and more near trees. The part that is different is accuracy, because the frame is cut to the drawing before the base exists.
Lawful development certificate: do you need one for an extension?
A lawful development certificate is the council's written confirmation that a project is permitted development and needs no planning application. It is optional. For an extension it costs half the householder planning fee and is usually decided within eight weeks. If your kit will be made to drawings that rely on permitted development, get the certificate before you pay for the kit.
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