Extension Snagging Checklist: How to Inspect Your Builder's Work

The final payment to your builder is the most valuable thing you have. Once it's gone, your ability to get defects fixed goes with it. Builders who call back promptly when there's money outstanding have a habit of becoming hard to reach the week after final payment clears.

Snagging is how you protect that position. It's the systematic inspection of your completed extension before you sign off financially: a room-by-room, trade-by-trade assessment of every surface, fitting, socket, and structural element. Done properly, it tells you exactly what needs fixing, gives you a documented basis for withholding payment, and gives your builder a clear list of what they owe you.

Done badly (or done after you've paid), it's just a list of things that annoy you with no mechanism to get them fixed.

What Snagging Actually Means

The formal definition of a snagging item is work that should be completed before the project can be considered finished. In government and commercial contracts, snagging items are explicitly those things required before sign-off. In practice, on a domestic extension, the concept is the same: your builder's job isn't done until the snags are resolved.

Snagging is separate from the building control final inspection. The BCO checks that your extension complies with building regulations. They don't inspect the quality of your plastering, the level of your kitchen units, or whether your downlights all work. That's your job. The two processes run in parallel: the building control sign-off covers statutory compliance, your snagging inspection covers quality and completeness.

When to Do It, and Why Timing Matters

The right time to snag is after the builder considers the work substantially complete but before you make the final payment. That sequence is non-negotiable.

Across community forums, the pattern repeats relentlessly: homeowners who pay in full before snagging is resolved find themselves sending unanswered emails and chasing a builder who suddenly has other priorities. One account from a LegalAdviceUK thread put it bluntly: "We paid the invoices that night even though we weren't 100% happy with the works. We absorbed the snagging costs ourselves. It wasn't worth arguing over." They had already lost their ability to compel action.

Your contract should specify that final payment is conditional on satisfactory completion of snagging. If it doesn't say that, write it into any payment correspondence now. Even without explicit contract terms, you are entitled to withhold payment for unresolved defects, and a documented snagging list is the evidence that justifies it.