Phase 3 · Groundwork · Task 02 of 10
Setting Out: Marking Your Extension Footprint
Setting out transfers the approved drawings onto the ground before the dig. A near-free half-day that decides whether your foundations land in the right place.
The cheapest mistake on your whole build and the most expensive are the same mistake, separated only by whether the concrete has gone in yet. A footprint marked 100mm too wide costs nothing to fix with a tape measure on a Tuesday morning. The same 100mm, discovered after the pour, means the foundations, blockwork, slab, and roof are all in the wrong place, the steel ordered to a drawing dimension may not fit, and the offset to your neighbour's boundary might now breach your planning consent.
That half-day of marking the ground is called setting out. It is the first thing that happens on site once your builder arrives, it is almost always bundled into the groundworker's price, and most homeowners have never heard it named. Your job is not to do it. Your job is to understand it well enough to walk the marked footprint and check it before you say "go."
Do this first
Setting out is the first physical task on site, but several things must already be settled. You need the approved planning and building-control drawings in hand, and you need to confirm you are working from the approved revision, not an early draft. Your builder or groundworker should be on site with the site cleared. An LSBUD search must be done so you know where underground services run before anyone knocks a peg in. And if you are building close to a boundary, your party wall agreement should be settled first, because the offset you mark on the ground is the offset that award assumes. Everything downstream depends on this: the foundations and footings trench is dug straight to the lines you set out here.
What this guide covers
- 01What Setting Out Actually Is
- 02Who Does It (And Who Checks It)
- 03The Drawings You Set Out From
- 04The Method, Step by Step
- 05The 3-4-5 Method, Explained Plainly
- 06Equal Diagonals: The Catch Nobody Mentions
- 07Profile Boards Beat Corner Pegs
- 08Checking Against the Boundary
- 09The Datum: Getting Levels Right
- 10How Square Is Square Enough
- 11Your Pre-Dig Checklist
- 12What an Error Costs
- 13Setting Out and Building Control
- 14Resources
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