Snagging Guide: How to Inspect Your New Build or Extension

The builder says "all done." You walk through the extension and it looks great. You pay the final invoice. Two weeks later you notice a crack above the bedroom door, a kitchen drawer that doesn't close properly, and a cold draught from the patio doors. The builder's already on his next job.

In short: Snagging is your opportunity to catch defects, poor finishes, and incomplete work before you accept the build and release final payment. Do it methodically, room by room, with a camera and a checklist. Once you've signed off and paid in full, getting a builder back is significantly harder.

This is the inspection that separates a satisfactory handover from months of frustration chasing corrections.

When to snag

The right moment is at practical completion - the point where the builder considers the work substantially finished. "Substantially" is the key word. Minor items can be outstanding, but the building should be usable for its intended purpose.

Timing matters:

• Before you make the final payment - your retention or final-stage payment is your leverage. Once the money's gone, so is your bargaining position.
• Before you move furniture in - you need to see walls, floors, skirting boards, and windowsills clearly. Once a room is furnished, half the snags become invisible.
• During daylight - natural light shows up imperfections that artificial light hides. Paint inconsistencies, uneven plaster, and surface blemishes are much easier to spot in daylight.
• Allow 2–3 hours - don't rush it. A thorough snagging inspection of a two-bedroom extension takes at least two hours. A whole new-build house can take half a day.

Tell the builder in advance that you'll be doing a snagging inspection. This is completely normal and expected in construction. Any decent builder will welcome it - it's a chance to fix small issues before they become complaints.

What you'll need

Keep it simple:

• Notepad and pen - or a phone/tablet with a notes app
• Camera or phone - photograph every snag. Include a wider shot showing the location and a close-up of the defect
• Torch - for checking under units, inside cupboards, and in loft spaces
• Spirit level - a small one (600mm) for checking walls, worktops, and shelves are level
• Socket tester - a £5 plug-in device that checks whether sockets are wired correctly
• Sticky notes or masking tape - mark snags physically so the builder can find them

The room-by-room checklist

Work through every room systematically. Don't jump around. Start at the front door and work your way through the building.

External

Start outside. Stand back and look at the whole building before you go in.

• Brickwork - are courses level and consistent? Any cracked or chipped bricks? Is the pointing neat and complete? See our guide on checking brickwork quality for what to look for
• Render - any cracks, bubbles, or uneven patches? Render should be smooth and consistent in colour
• Roofing - are tiles evenly laid with no visible gaps? Ridge tiles bedded properly? Flashing sealed at junctions? Our roofing inspection guide covers this in detail
• Windows and doors - do they open, close, and lock smoothly? Are seals intact? Any gaps between frame and wall?
• Guttering and downpipes - properly aligned and securely fixed? Joints sealed? Downpipes connected to drainage?
• Drainage - gullies clear and correctly positioned? Ground levels sloping away from the building?
• Landscaping - paths level? Fencing secure? Any damage to existing garden areas?

Walls and ceilings (every room)

Check these in every room:

• Plaster finish - run your hand over walls. They should feel smooth and flat. Look for bumps, hollows, trowel marks, or cracks. See our plastering quality guide for standards
• Paint finish - consistent colour, no runs, drips, or brush marks. Check where walls meet ceilings - cutting in should be clean and straight
• Cracks - hairline settlement cracks are normal in new plaster. Anything wider than 1mm, or cracks above door frames or at wall-ceiling junctions, should be flagged
• Coving and cornices - joints tight with no gaps? Mitres neat at corners?
• Ceiling roses and light fittings - flush against the ceiling? No gaps?

Floors

• Carpet - smooth with no wrinkles or bumps? Properly secured at grippers? No gaps at skirting?
• Tiles - flat with consistent grout lines? No hollow-sounding tiles (tap them gently)? Grout fully filled with no missing sections?
• Laminate or engineered wood - level with no bouncing or creaking? Expansion gaps at edges hidden by skirting?
• Concrete/screed - level and crack-free? Floor tiles sitting flat?

Doors and windows

• Opening and closing - every door and window should open, close, and latch without catching, sticking, or scraping
• Locks - all working with keys provided?
• Hinges - secure with no squeaks or loose screws?
• Handles - level and firmly attached?
• Seals and draught-proofing - close the door or window and check for daylight gaps around the edges
• Glass - no scratches, chips, or blown double-glazing units (look for misting between panes)
• Paint on frames - clean finish with no runs or missed areas?
• Window sills - level, properly sealed, no gaps at joints?

For a detailed window and door checklist, see our windows and doors inspection guide.

Kitchen

• Units - doors and drawers aligned, opening and closing smoothly? Soft-close mechanisms working?
• Worktops - level with no chips or scratches? Joints tight and sealed? Upstands flush against walls?
• Splashback - tiles evenly spaced with consistent grout? No chips or cracks?
• Sink and taps - no leaks underneath? Hot and cold correct? Drain flows freely?
• Appliances - all fitted level and working? Oven heats up? Hob ignites? Extractor functions?
• Sealant - silicone bead at worktop-wall junction neat and continuous?

Bathroom

• Tiles - level, consistent grout, no hollow tiles? Corners mitred or finished with trim?
• Bath and shower - no chips or scratches? Taps work correctly (hot on left)? Water drains without pooling?
• Toilet - securely fixed, doesn't rock? Flushes properly? No leaks at the base?
• Sealant - silicone around bath, shower tray, and basin should be neat, continuous, and firmly adhered. This is one of the most commonly snagged items
• Towel rails and accessories - securely fixed and level?
• Extractor fan - working? Ducted to outside (not just into the loft)?
• Waterproofing - if it's a wet room, check that water doesn't escape the tanked area

For a comprehensive bathroom inspection, see our bathroom fitter checklist.

Electrics

• Sockets and switches - all working? Level and flush with the wall? Cover plates secure with no gaps?
• Socket tester - plug in a socket tester in every socket. It will flag reversed polarity, missing earth, and other wiring faults
• Light switches - all working? Dimmer switches functioning correctly?
• Consumer unit - labelled clearly so you know which circuit is which?
• Certificates - has the electrician provided an Electrical Installation Certificate (EIC) or Minor Works Certificate? This is a legal requirement for notifiable work

See our electrics inspection guide for the full checklist.

Plumbing and heating

• Radiators - all heating up evenly? No cold spots (which indicate trapped air)? Valves not leaking?
• Boiler - commissioned and working? Gas Safe certificate provided?
• Hot water - running to all taps? Adequate pressure?
• Pipes - no visible leaks at joints? Pipes properly clipped and insulated where required?
• Overflow pipes - not dripping? (A constant drip suggests a faulty valve)

Our plumbing and drainage guide covers this area in detail.

Loft and roof space

If the work involved roof alterations or a loft conversion:

• Insulation - correctly installed to the required depth (270mm for loft insulation)? No gaps?
• Ventilation - eaves vents or tile vents present? Condensation risk increases without proper ventilation
• Structural timbers - no cuts or notches to joists or rafters that weren't in the structural engineer's design?
• Fire barriers - party wall fire stopping intact?

How to present your snagging list

A well-organised snagging list gets results. A vague email saying "there are some issues" doesn't.

Format each item clearly:

Send the list in writing - email is fine. Keep a copy. Give the builder a reasonable timeframe to complete the repairs (typically 2–4 weeks, depending on the number of items).

What's a snag and what isn't?

Not everything on your list will be a legitimate snag:

Legitimate snags:

• Defective work (cracks, leaks, things that don't work)
• Incomplete work (missing socket covers, unpainted areas)
• Poor-quality finishes (uneven plaster, messy sealant, paint runs)
• Items not matching the specification (wrong colour tiles, different handles)

Not snags:

• Things you've changed your mind about (you now want a different tap)
• Wear and tear after you've been living in the space
• Items not in the original specification
• Minor imperfections that are within normal construction tolerances

Construction isn't furniture-making. Walls won't be laser-straight. Plaster won't be glass-smooth. There are industry-accepted tolerances - typically ±3mm over 2 metres for wall flatness. If you hold a spirit level to a wall and there's a 2mm gap underneath, that's within tolerance.

Builder's obligation to fix snags

Under the Consumer Rights Act 2015, building services must be performed with "reasonable care and skill." If work falls below that standard, the builder is legally obliged to put it right at their own cost.

If you have a formal building contract (JCT, FMB, or similar), there will be a defined defects liability period - usually 6 months after practical completion. During this time, the builder must return and fix any defects that emerge, whether or not they were on the original snagging list.

Your practical leverage is the final payment. Most construction contracts hold back 2.5–5% as retention, released after the defects period ends. This gives the builder a financial incentive to come back and sort things out.

If the builder refuses to fix legitimate snags, see our guide on your consumer rights when building work goes wrong.

Professional snagging vs doing it yourself

DIY snagging

Pros: Free. You know the space and will use it daily, so you'll notice things a professional might not.

Cons: You might miss technical defects. You might not know what's within tolerance and what isn't. Builders sometimes push back harder on homeowner snag lists.

Best for: Extensions, renovations, and smaller projects where you have a good relationship with the builder.

Professional snagging inspection

Pros: Thorough, independent, and backed by expertise. Professional snaggers typically find 50–100+ items on a new-build house. Their report carries more weight with the builder or developer.

Cons: Costs £300–£600 for a standard house. Not always necessary for smaller projects.

Best for: New-build houses (where developers are notorious for poor finishes), large extensions, and situations where you don't feel confident inspecting the work yourself.

A professional inspection can pay for itself many times over. If a snagger identifies a poorly installed DPC, an incorrectly fitted window, or missing fire stopping in the loft, the cost of fixing those later would dwarf the inspection fee. See our DPC inspection guide for why this particular item matters.

After the snagging inspection

1. Send the list - email the completed snagging list with photos to the builder. Keep a copy.
2. Agree a timeline - most builders will want 2–4 weeks to work through the list. That's reasonable unless the items are urgent (e.g., a leak).
3. Re-inspect - once the builder says the snags are fixed, go round again. Check every item. Some will be fixed properly. Some won't. Create an updated list if needed.
4. Release payment - once you're satisfied that all snags are resolved, release the final payment or retention. Not before.
5. Keep records - photos, emails, and the snagging list should be filed away. If issues emerge during the defects period, you'll have a documented baseline.

The golden rule

Snag before you pay. Not after. Once the final payment is made and the builder has moved on, your leverage drops to near zero. A professional builder will expect a snagging inspection and won't take it personally. If they do - that tells you something.

Not sure what you're looking at?

If you've got a quote for building work and you're not sure whether the specification is detailed enough to snag against later, upload it to MyBuildAlly. We'll flag vague descriptions, missing specifications, and items that will be hard to hold a builder to account on.

Sources

• Consumer Rights Act 2015 - your rights when building services fall below standard
• NHBC Standards - industry-accepted tolerances for new-build construction
• Citizens Advice: Problems with building work - what to do if a builder won't fix defects
• RICS Home Surveys - professional snagging and inspection services