The complete checklist of things to check before buying a house

1. Environmental risks

The ground under the house and the climate around it determine your insurance premium, your mortgage rate, and your resale ceiling. None of this changes after completion. All of it is in free public datasets.

Flood risk is the single biggest unpriced risk most buyers miss. Check river and sea, surface water, and reservoir flooding separately, and pay particular attention to surface water. It is the form of flooding most often left out of seller disclosures. Read the dedicated flood risk guide for buyer-specific thresholds. In estuary markets, use local context too: Southampton surface-water and tidal flood checks are a useful example of why both layers matter.

Subsidence follows clay geology. The British Geological Survey publishes shrink-swell maps that flag the underlying risk; combine that with insurance claim history and visible signs on the building. The subsidence guide covers what different crack patterns usually mean.

Radon matters mostly in the South West, parts of the East Midlands, and Scotland. Mitigation is cheap (£500-£2,000) but only if you know to ask. Contaminated landshows up under former petrol stations, dry cleaners, gasworks, and landfill sites. The local council's environmental health team will tell you whether the postcode sits on a register; lenders sometimes refuse without an environmental search.

2. Property condition

The survey covers condition, but only after you've already committed to one address. Three desk-research checks before that point save thousands.

EPC rating is on the public register and tells you the running cost band, the insulation profile, and any recommended improvements. Below D, expect higher bills now and a possible regulatory upgrade requirement on the horizon if MEES extends to owner-occupiers.

Building era drives defect probability. Pre-1919 housing stock means solid walls, lath-and-plaster, and lime mortar. 1920s-30s means cavity walls without insulation. 1960s-70s means concrete-frame and large-panel risk. Modern stock means cavity-wall ties and timber-frame to verify.

Construction typeis the killer. Non-standard construction (PRC, Wimpey No-Fines, Airey, BISF, certain timber-frame, single-skin extensions) can be unmortgageable with mainstream lenders, uninsurable without specialist cover, or both. Ask the seller's agent before viewing twice.

Roof covering is the largest single repair item on most surveys. Spray foam in the loft is a modern dealbreaker. Many lenders refuse, and removal plus new felt runs £8,000-£18,000. Ask before offering, not after the survey.

3. Legal and title

Most legal issues are knowable before you exchange, and most buyers don't look until the solicitor raises them. Three checks cover the majority.

Tenure: freehold, leasehold, or share of freehold. Leases under 80 years cross the marriage-value threshold and double the cost of extension. Ground rents above £250 outside London (£1,000 in London) can change the legal nature of the tenancy. Service charges on flats vary from £800 to £6,000+ a year.

Planning historyis on the local authority's public planning portal. Look for extensions, loft conversions, change-of-use, and any enforcement actions. Works done without permission, or without sign-off on building regulations, become your legal liability on completion. Indemnity insurance helps but doesn't cover everything.

Listed status and conservation area: listed buildings (Grade I, II*, II) require listed building consent for most repairs. Conservation areas restrict windows, doors, and external works. Both load insurance premiums and maintenance costs.

4. Local area

The building is fixable. The street isn't. Four area checks before you offer.

Crime: Police.uk publishes recorded crime by category at street level. The trend matters. A high baseline that's falling beats a low one that's climbing. Look at the last three years, not the last month.

Schools: Ofsted ratings, but check the catchment data too. Catchment areas shrink in popular schools, so last year's in-catchment address may not be in catchment this admissions round. The premium for a Good or Outstanding catchment runs 5-15% in many areas.

Broadband: check the actual address, not the postcode, on Openreach's availability checker. Rural spots, old conversions, and some new-build estates can max out below 30Mbps. Full-fibre availability changes resale value materially.

Transport and noise: train, road, and flight-path noise rarely show on a single viewing. Visit at peak commute times, on a weekend evening, and at night if you can. DEFRA's noise maps catch the obvious cases but miss intermittent sources like helicopter corridors.

5. Price and value

The asking price is a starting position, not a fact. Three pieces of evidence beat any argument an estate agent will make.

Sold comparables: HM Land Registry publishes every transaction. Filter to the same street, same property type, same number of bedrooms, same tenure, and the last 12-24 months. The median of that set is your anchor.

Listing history: a property that's been listed three times in two years, with two price drops and a fall-through, is telling you something. Rightmove keeps a public history. So does the Land Registry for any sales that did complete.

% above or below local median: anchor the asking price to the postcode median for the same property type. More than 15% above without an obvious reason (extension, premium condition, exceptional plot) deserves a sharper question to the agent.

6. Survey decision

The survey is the last large pre-completion check. Choose the right level the first time so you don't pay twice.

Level 2 (HomeBuyer Report) works for modern stock (post-1980) in obvious good order. Level 3 (Building Survey) is the right call for anything pre-1930, anything extended without clear sign-off, anything with visible defects, and any non-standard construction. Read the full comparison at Level 2 vs Level 3 survey before booking.

When the report arrives, run the wording through the Survey Decoder before reacting. Surveyors hedge for indemnity reasons; the wording usually reads worse than the underlying defect.

What to look for when viewing the house

The desk checks above tell you what the data says. The viewing is where you catch what it doesn't. Go round twice, once in daylight, and take photos of anything you flag — a surveyor can comment on them later. What to look for, room by room and outside:

• Damp. Musty smell, tide marks low on walls, peeling or bubbling paint, fresh paint on a single patch or wall, black mould around windows and in corners.
• Cracks and movement. Stepped diagonal cracks wider than 3mm, especially around bay windows, extensions, and where old meets new; doors and windows that stick or sit out of square.
• Roof and outside. Sagging or uneven roof line, slipped or missing tiles, bowing walls, cracked render, blocked or leaking gutters, and the condition of any flat roofs.
• Loft. Ask to see it. Spray foam on the underside of the roof is a mortgage red flag; also look for daylight, water staining, and the state of any insulation.
• Water and heating. Run taps to check pressure, flush the loo while a tap runs, find the boiler and note its age and last service, check radiators heat up.
• Electrics. Look at the consumer unit (fuse board): an old rewireable or fuse-wire board usually means a full rewire is due, often £3,000-£6,000.
• Garden and boundaries. Japanese knotweed (and in neighbouring plots), Japanese knotweed-style bamboo, drainage gullies, fence ownership, and how far trees sit from the building on clay soils.
• The street. Parking, mobile signal inside the house, noise at the time you visit, and the state of neighbouring properties.

Anything you spot here is worth flagging to your surveyor before they attend. The Survey Decoder explains what each of these signs usually means once a survey puts a label on it.

Questions to ask the estate agent and seller

The right questions surface problems before you spend money on searches and a survey. Ask the agent at the viewing; the seller answers most of the rest formally on the TA6 Property Information Form once you're under offer.

Ask the estate agent

• Why is the seller moving, and how long has it been on the market?
• Is there a chain, and what's the seller's position in it?
• Have there been previous offers or fall-throughs, and why?
• Has the price been reduced, and how negotiable is the seller?

Ask the seller (TA6 / via the agent)

• Has the property ever flooded, and is there a history of subsidence or insurance claims?
• Have building works, extensions or a loft conversion been done — with planning permission and building-regs sign-off?
• Are there boundary disputes, party-wall agreements, restrictive covenants, or rights of way?
• Any known Japanese knotweed, and what's included in the sale (appliances, fittings)?

If it's a flat or leasehold

• How many years are left on the lease, and what are the ground rent and service charge?
• Are there any major works planned or recently billed, and is an EWS1 form in place where cladding applies?