Snagging list for an extension: what to check

Snagging a house extension is not the same as snagging a new build. On a new build everything is new and the finish is judged on its own. On an extension, new work is married to an existing house, and the snags gather exactly where the two meet: the roof tie-in, the wall junction, the floor level at the threshold, the making-good around the opening. Find those before the client does and the job finishes clean. This guide covers what belongs on an extension snag list, the order to work in, a worked example, and how to run it from your phone so nothing gets lost between finding it and fixing it.

What an extension snag list needs to capture

Every snag needs enough detail that a trade can find it, own it and close it without a phone call. That is true on any job, but on an extension the location often has to name the junction, not just the room. Every item needs:

• Location. The room or area and the exact spot, naming the junction where relevant. "Rear extension, threshold to existing kitchen, floor level step" not "kitchen"
• Description. What is wrong, in plain terms a trade can act on. "Plaster cracked along new to existing wall junction" not "wall marked"
• Photo. A clear image of the defect, close enough to show it and wide enough to place it
• Owner. The trade responsible for the fix, so it goes to the right person first time
• Status. Open, in progress, fixed, verified, closed. Status is what turns a list into a process
• Date raised and date closed. So you can prove when it was found and when it was put right
• Verified by. Who checked the fix, so a snag is not just marked done by the person who caused it

The order to snag an extension

Work a consistent route, but give the junctions between new and old their own pass, because that is where an extension is most likely to disappoint:

1. Exterior and the tie-in. New brick or render against existing, the roof tie-in and flashings, rainwater goods, and how the new wall meets the old
2. The junctions inside. The knock-through or opening, the steel or lintel and its making-good, the floor level where new meets existing, and plaster at every new to old junction
3. The new room, top to bottom. Ceiling, walls then floor, left to right from the door, so nothing is skipped
4. Kitchen or bathroom in detail. Where the extension includes one, these generate the most snags: units, worktops, tiling, sanitaryware and seals
5. Doors, windows and services on test. Operation and finish of new doors and windows, and sockets, switches, lighting, heating and taps checked working, including anything added to the existing system
6. Making-good to the existing house. Decoration and finishes anywhere the existing house was disturbed to form the extension

A worked extension snag example

Here is what a handful of well-formed snags look like on a single-storey rear extension. It is illustrative only, but it shows the level that closes out cleanly.

Rear extension pre-completion snag. Item 1: Roof tie-in to existing, lead flashing to left abutment lifting at the top edge. Owner: roofer. Status: open. Photo attached. Item 2: Rear elevation, new facing brick a visible shade lighter than the existing at the junction. Owner: bricklayer. Status: open. Photo attached. Item 3: Threshold to existing kitchen, floor level step of approx 8mm between new and existing. Owner: floor layer. Status: open. Photo attached. Item 4: Opening to existing lounge, plaster cracked along the new to existing wall junction above the beam. Owner: plasterer. Status: open. Photo attached. Item 5: New bifold doors, right leaf drags on the track when closing. Owner: door fitter. Status: open. Photo attached.

Every item names the spot, the fault, the trade and a photo. When each trade comes back, they know exactly what and where without a phone call.

Why a spreadsheet fails on an extension

Most snagging still runs on a spreadsheet and a separate camera roll, and it falls apart for the same reasons every time. The photos are not linked to the rows, so matching image to item is guesswork. There is no reliable status, so nobody knows what is still open. Versions get emailed around and the person on site is never sure they have the latest one. On an extension there is the added problem that the client often lives in the house, so a half-finished snag list that drags on is felt every day.

A snag list you run from your phone fixes the mechanics. The photo attaches to the snag as you raise it, the status moves from open to closed in front of you, and the report is generated from the live list rather than typed up later. On a site with no signal it saves offline and syncs when you leave. The point of snagging is to close items out, and you cannot close what you cannot track.

Frequently asked questions

What is different about snagging an extension?

The snags on an extension cluster where the new work meets the existing house: the roof tie-in, the wall junction, the floor level at the threshold, the making-good around a knock-through, and matching brick, render and plaster to what was already there. On a new build everything is new, so on an extension the junctions are where you look hardest.

When should I snag a house extension?

Run a thorough snag before the final payment and before the client considers it finished, with enough time for the trades to return and close items out. Anything disturbed in the existing house, such as decoration where an opening was formed, is snagged and made good in the same list.

Who is responsible for fixing extension snags?

Each snag is assigned to the trade responsible: the roofer for a tie-in, the bricklayer for a brick match, the plasterer for a junction crack, the carpenter for a door that catches, and so on. Giving each item an owner is what gets it closed rather than argued over.

How does FORGE Command help with extension snagging?

FORGE Command lets you raise each snag on your phone with a photo, location, owner and status, track it through to closed, and export a branded PDF snag report. Every record is stamped with GPS, weather and time, and it works offline. It is a one payment of £39.99 with no subscription.

Related: snagging list for a new build, site diary for a house extension, site inspection checklist.