What to look for when viewing a house: a practical guide for UK buyers

Why most buyers miss the expensive problems

Property viewings are emotionally charged. You're imagining your furniture in the living room, not inspecting the pointing on the chimney stack. Estate agents know this - the viewing is designed to sell you a feeling, not give you a condition report.

The result: around 30% of UK property transactions fall through after the survey reveals problems that were visible at the viewing stage. Buyers lose an average of £3,337 in wasted fees each time a purchase collapses. The problems were there - they just weren't on anyone's checklist.

A structured approach to viewing changes this. You don't need to be a surveyor. You need to know what to look at, what the warning signs mean, and roughly what they cost to fix. That's what this guide covers.

Start outside: what to check before you walk through the front door

Before you go inside, spend five minutes walking around the property from the outside. This is where you'll spot the most expensive problems - and the ones most buyers completely ignore.

Roof

Stand across the street and look at the roofline. Is the ridge straight or sagging? A sagging ridge suggests failed timbers - a major structural repair. Look for missing, slipped, or cracked tiles. Check flat roof sections (common on rear extensions) for ponding, blistering, or patches.

Cost if missed: A full roof replacement on a 3-bed semi costs £8,000–£15,000. Flat roof replacement runs £1,500–£4,000 per section. Even re-ridging costs £800–£1,500.

Brickwork and external walls

Look for cracks. Hairline cracks in render are usually cosmetic. Stepped diagonal cracks following the mortar lines in brickwork are more serious - they suggest differential settlement or subsidence. Horizontal cracks at DPC level can indicate lateral movement.

Check for spalling (crumbling) bricks, particularly on older properties. Look at the pointing - is it consistent or has it been patched in places? Re-pointing a full elevation costs £1,500–£3,500.

Gutters, downpipes, and drainage

Overflowing or missing gutters cause penetrating damp - one of the most common and expensive problems in UK homes. Look for green staining below gutters, detached downpipes, or water pooling at the base of external walls. Check that gullies at ground level are clear and not blocked.

Cost if missed: Repairing penetrating damp caused by failed guttering can cost £2,000–£5,000 once internal replastering is included.

Windows and doors

Check whether the property is double-glazed throughout - single-glazed rooms are common in older properties and replacing all windows costs £4,000–£8,000 for a 3-bed house. Look for misted units (a white fog between the panes), which indicate failed seals. Check timber frames for rot, particularly at the base of sills.

Signs of damp, mould, and poor ventilation

Damp is the single most common issue found in UK property surveys. It comes in three forms - and each has different causes, costs, and severity.

Rising damp

Tide marks up to about one metre on ground-floor walls, salt deposits (efflorescence), peeling wallpaper at skirting level. Often worse on solid-walled properties without a functioning damp-proof course. Remediation costs £2,000–£8,000 depending on the extent.

Penetrating damp

Localised damp patches on walls or ceilings, often corresponding to a defect on the outside - a cracked render, leaking gutter, or failed pointing. Fix the external cause and the damp stops. But if left, it damages plaster, timbers, and decoration. Repair costs depend entirely on the external defect.

Condensation damp and mould

Black mould on window reveals, in corners, behind furniture. Usually caused by poor ventilation, inadequate heating, or thermal bridging. Common in bathrooms, kitchens, and bedrooms with single-aspect windows. Often cosmetic but can indicate deeper insulation or ventilation problems. Surface treatment is cheap (£100–£300), but solving the underlying ventilation issue may require extraction fans, trickle vents, or even a whole-house ventilation system (£2,000–£5,000).

What to do at the viewing: Check behind furniture if possible. Run a finger along window sills. Look at ceiling corners in every room. Smell the air in closed rooms - musty odours suggest hidden damp. Check whether extractor fans exist in the kitchen and bathroom.

Kitchens and bathrooms: where neglect shows first

Kitchens and bathrooms reveal maintenance culture. They're the most expensive rooms to refit and the most likely to show signs of water damage, poor DIY, and deferred maintenance.

• Silicone and grouting - black mould in sealant around baths, showers, and sinks indicates persistent moisture exposure and possible water ingress behind tiles
• Under-sink condition - open the cupboard doors beneath kitchen and bathroom sinks; look for water staining, warped boards, or active drips
• Tiling - hollow-sounding tiles (tap them) suggest poor adhesion; cracked tiles near corners may indicate movement
• Boiler - note the make, model, and year. Boilers over 10 years old are approaching end-of-life. Replacement costs £2,500–£4,500 installed
• Water pressure - turn on a tap (ask the agent if unsure). Low pressure can indicate ageing pipework, a failing pump, or supply issues

Electrics: the consumer unit tells the story

You don't need to be an electrician to spot warning signs. Find the consumer unit (fuse board) - it's usually under the stairs or in a utility cupboard.

• Modern consumer unit with RCD protection and MCBs (small switches) - this suggests the electrics have been updated, likely within the last 15–20 years
• Old-style fuse box with rewirable fuses or cartridge fuses - the electrics are likely 30+ years old and may need full rewiring
• Mix of cable types visible in the loft or at sockets - some circuits may have been updated while others remain on original wiring

Cost if missed: A full rewire of a 3-bed house costs £4,000–£7,000. A consumer unit upgrade alone costs £300–£600.

Structural movement: cracks, doors, and floors

Not all cracks are serious. But some are. Understanding the difference saves you from either panicking unnecessarily or ignoring a £30,000 problem.

• Hairline cracks in plaster - usually thermal movement or settlement; rarely a concern
• Diagonal stepped cracks following mortar joints - potentially subsidence or differential settlement; needs investigation
• Cracks above windows or doors - may indicate lintel failure, especially in older properties
• Doors that won't close properly - if multiple doors stick or have been shaved to fit, the building may have moved
• Sloping floors - place a marble or ball on the floor; if it rolls noticeably, there may be structural settlement

Cost if missed: Subsidence investigation alone costs £1,000–£3,000. Underpinning, if required, costs £10,000–£50,000+ depending on the extent. See our full repair cost guide for more detail.

What to photograph and note during the viewing

Your memory is unreliable - especially after viewing multiple properties. Build a habit of documenting every viewing:

• The consumer unit (photo of the board with the door open)
• The boiler (photo of the label showing make, model, year)
• Any cracks - with a coin or key for scale
• Gutters, downpipes, and the roofline from across the street
• Any damp patches, staining, or mould
• Bathroom and kitchen sealant condition
• The loft space (if accessible - ask the agent)
• Any extensions or alterations - look for building control completion certificates

These photos aren't just for your own records. If you decide to make an offer, they become evidence for negotiation. If you spot a cracked ridge tile and the vendor claims the roof is fine, you have the photo.

When to escalate to a survey or specialist inspection

A viewing-stage check isn't a substitute for a professional survey. But it tells you whether you need one, and what type. Escalation triggers include:

• Diagonal cracks in external brickwork - commission a structural engineer's report (£400–£800)
• Persistent damp on multiple walls - commission a damp survey (£200–£400)
• Old electrics with no RCD protection - budget for an EICR (£150–£300) and possible rewire
• Visible roof damage - get a roofer's inspection (£100–£200, often free if they quote for repair)
• Japanese knotweed, significant tree proximity, or subsidence history - commission a specialist assessment

The key insight: don't wait until after you've offered and paid for legal work to discover these. Catch them at the viewing, and you negotiate from strength - or walk away before it costs you anything. Read our guide on when to walk away from a property purchase if you're unsure.

How KeyWise helps at this stage

KeyWise turns this guide into a structured, guided process you use live at the viewing. Instead of trying to remember what to check, KeyWise walks you through each room with prompts, photo guidance, and condition flags. At the end, you get a risk summary with estimated repair costs - before you've committed a penny.

It's the difference between hoping you noticed everything and knowing you checked everything.

Frequently asked questions

How long should a house viewing take?

A thorough viewing should take at least 30–45 minutes. Most buyers rush through in 15 minutes, which is not enough time to check external walls, drainage, the loft, and every room properly. If the agent is hurrying you, ask for a second viewing at your own pace.

Should I get a survey before making an offer?

Not necessarily - but you should do a structured assessment at the viewing stage first. A pre-offer property check helps you identify red flags early. If you spot anything concerning, you can then commission a targeted survey or specialist report before committing.

What are the most expensive problems to miss at a viewing?

Structural movement (subsidence) can cost £10,000–£50,000+ to underpin. A full roof replacement runs £8,000–£20,000. Rewiring a 3-bed house costs £4,000–£7,000. Rising damp remediation runs £2,000–£8,000. These are all issues that show visible signs during a viewing if you know what to look for.

Can I take photos during a house viewing?

Yes. Taking photos is normal buyer behaviour. Focus on anything that concerns you - cracks, staining, boiler labels, consumer units, roof lines, and drainage. These photos become evidence if you need to negotiate or instruct a specialist later.

About the author

Jag Singh is a Senior Quantity Surveyor with 18 years of experience across residential and commercial property. He founded KeyWise to help UK buyers spot the issues surveyors and estate agents won't always flag.