15 Most Common New Build Defects (and How to Spot Them)

New build properties are not built by a single team from start to finish. They are built by dozens of subcontractors — bricklayers, plasterers, plumbers, electricians, tilers, painters — each working under time pressure across multiple plots simultaneously. Quality control varies. Snagging lists of 50–100 defects on a brand-new property are not unusual; they are normal.

The good news: most common new build defects follow predictable patterns. Once you know what to look for, you can inspect your property systematically and catch problems before they become costly to fix.

This guide covers the 15 defects that appear most frequently in new build snagging inspections, with practical advice on how to spot each one and what to do about it. For a full room-by-room approach, see our complete new build snagging checklist.

Why Do New Build Defects Happen?

Three factors drive the majority of defects in new build properties:

• Time pressure. Developers work to completion deadlines. When build programmes slip, finishing trades get squeezed — and that is when corners get cut.
• Skills shortages. The construction industry has well-documented labour gaps. Less experienced tradespeople produce more defects.
• Subcontractor chains. The plasterer does not care about the painter's job. The tiler is not checking the plumber's work. Each trade finishes and moves on, often to the next plot on the same site. Defects that fall between trades go unnoticed.

None of this means your developer is negligent. But it does mean you should expect to find defects — and you should inspect thoroughly.

The 15 Most Common New Build Defects

1. Paint Runs and Poor Finishing

Drips, runs, roller marks, missed patches, and paint on surfaces where it should not be — window glass, door furniture, skirting boards. Check behind doors and inside cupboards where access was awkward. Minor touch-up marks are expected; visible runs or missed areas on main wall surfaces are not. Paint defects are cosmetic, but they signal the overall standard — if the paintwork is poor, look harder at everything else.

2. Plaster Cracks

Hairline cracks along ceiling lines, above door frames, and at wall junctions. Check ceiling-to-wall junctions and stud wall lines especially. Shrinkage cracks under 1 mm are generally within tolerance — developers will often ask you to wait until the property has been through a full heating cycle. Cracks wider than 2 mm, diagonal cracks, or cracks that reappear after repair may indicate structural movement. Photograph with a measurement for reference, and escalate anything over 2 mm.

3. Poorly Fitted Doors

Doors that stick, scrape on carpet, swing open or closed on their own, or do not latch properly. Open and close every internal door and check the gap between the door and the frame on all four sides — it should be even at roughly 2–3 mm. A door that swings by itself usually means the frame is not plumb. Check that handles are secure and latches engage smoothly. These are straightforward fixes but they will not happen unless you report them.

4. Window Seal Failures and Draughts

Run your hand slowly around the edges of every closed window and feel for cold air. Check external mastic sealant is continuous and properly adhered to both the frame and the wall. Look for condensation between double-glazed panes — this indicates a failed sealed unit that cannot be repaired and must be replaced entirely. Test every handle and locking mechanism too. Draughts and failed sealed units are never within tolerance. Report immediately with photos.

5. Uneven Flooring

Rocking tiles, squeaky floorboards, lifting laminate, and poorly fitted carpet edges. Walk slowly across every floor and feel for movement. Use a spirit level on tiled surfaces — building regulations permit 5 mm deviation over 2 metres. Anything worse than that, or squeaky boards and lifting joins, should be reported now. Squeaks under carpet need the carpet lifted to fix, so catch them before you move in.

6. Bad Grouting and Tiling

Cracked or missing grout, cracked tiles, and hollow-sounding tiles. Tap each tile gently with a knuckle — a solid sound means it is properly bedded; hollow means it may not be fully adhered. Focus on wet areas: kitchens, bathrooms, and en-suites. Hollow tiles in shower enclosures are particularly serious as they can allow water ingress behind the surface.

7. Plumbing Leaks

Damp patches under sinks, drips at pipe connections, and slow drains. Run every tap for at least 60 seconds, flush every toilet, and check under every sink while water is flowing. Any leak, however small, is a defect. Place tissue paper around pipe joints — it reveals slow drips your eye will miss. Prioritise plumbing defects; even a slow drip causes cumulative damage.

8. Missing or Defective Sealant

Gaps in mastic sealant around baths, shower trays, worktops, and window frames. Run your finger along every sealant line — it should be smooth, continuous, and adhered on both sides. Missing sealant is always a defect. In wet areas it is a serious one — water will penetrate behind baths and showers, causing hidden damage that becomes expensive to fix.

9. Faulty Electrics

Dead sockets, non-functional light switches, buzzing dimmers, and sockets that fail a plug-in tester. Test every socket with a plug-in socket tester (around £10 from any hardware shop) and flick every light switch. Test dimmer switches at all levels and check that extractor fans operate correctly. Electrical faults are never within tolerance. A socket with reversed polarity, missing earth, or no power may have a wiring fault that poses a genuine safety risk. These are safety-critical defects that must be fixed before you move in.

10. Poor Brickwork and Pointing

Cracked mortar joints, mortar smears on brick faces, inconsistent pointing, and weep holes blocked with mortar. Walk the full perimeter and check especially around windows and doors. Blocked weep holes are a priority — these small gaps at the base of cavity walls are essential for drainage and must not be filled. Hairline mortar cracks as mortar cures are normal; blocked weep holes and misaligned bricks are not.

11. Roof Tile Issues

Slipped or cracked tiles, uneven ridge tiles, gaps in lead flashing around chimneys or roof junctions, and missing dry verge caps. Stand back from the property and examine the roof line from each side — use binoculars if available. Check the ridge line is straight and consistent. Any tile that appears to have slipped or sits at a different angle to its neighbours needs attention. Slipped tiles and gaps in flashing will let water in and are never acceptable. Photograph from ground level and request a roof inspection for any visible damage.

12. Drainage Problems

Standing water near foundations, disconnected downpipes, loose gutter joints, blocked drainage gullies, and surface water pooling on paths or driveways. Walk the perimeter after rainfall if possible. Check that downpipes are securely connected to gutters above and drainage channels below. Look for water pooling against the building — this can indicate ground levels that are too high or missing drainage. Standing water against foundations is a serious defect that causes long-term damp and structural damage. Report as high priority.

13. Incomplete External Works

Missing or broken paving slabs, unfinished fencing, no turf laid, incomplete paths, and garden boundaries that do not match the site plan. Compare every external area against the property specification and the original site plan. Check that all fencing, paving, turfing, and boundary treatments are complete and match what was promised. Developers sometimes defer external works to save time before completion — do not accept "it will be done after you move in" without a written commitment and deadline.

14. Fire Door Compliance Failures

Fire doors (typically kitchen-to-hallway and garage-to-house) that do not self-close, have missing or damaged intumescent strips, or gaps exceeding 3 mm around the frame. Identify fire doors by the label on the top edge or a certification plug. Open each one and release — it must close fully under its own weight without catching or sticking. Check that the intumescent strip (the strip around the door edge that swells in heat to seal the gap) is intact and continuous. Fire door defects are safety-critical under Building Regulations Approved Document B and must be reported as high priority. These are life-safety items, not cosmetic issues.

15. Loft Insulation Issues

Missing insulation, uneven coverage, insulation blocking eaves ventilation, and debris left in the loft space by tradespeople. Access the loft via the hatch with a torch and measure the depth of insulation in several locations — mineral wool should typically be 270 mm in new builds, as specified in the property's SAP calculation. Insulation must stop short of the eaves to allow airflow; blocked ventilation causes condensation and damp in the roof space. Report with measurements so the developer knows exactly what to correct.

When Is a Defect Serious Enough to Escalate?

Most snagging items are cosmetic — paint, plaster, minor finishing issues. These should all be reported and fixed, but they are not urgent. The developer's aftercare team will typically schedule cosmetic repairs in batches.

Functional and safety defects are different. These require immediate attention and should be flagged as high priority in your snagging report:

• Electrical faults — any socket or circuit that fails testing
• Plumbing leaks — even slow drips cause cumulative damage
• Fire door failures — life-safety compliance under Building Regulations
• Window seal failures — draughts and failed double-glazed units
• Drainage issues — standing water against foundations
• Structural cracks — anything over 2 mm or diagonal in pattern

If a developer dismisses a functional defect as "within tolerance," you are not obliged to accept their assessment. Refer to your NHBC Buildmark warranty (or equivalent provider such as Premier Guarantee or LABC Warranty). You have the right to escalate unresolved defects directly to your warranty provider for independent assessment.

Spot Every Defect — Without Missing a Thing

Knowing what to look for is half the battle. The other half is documenting every defect clearly enough that the developer has to act on it.

Snaggit guides you through a structured, room-by-room snagging process. Log defects with annotated photos, rate severity, and generate a professional snagging report in one tap — ready to send to your developer.