Common house survey problems explained

House surveys regularly flag the same set of problems across UK properties, regardless of age or location. Knowing what to expect before your report arrives helps you respond calmly and make informed decisions about whether to proceed, renegotiate, or walk away from a purchase.

The 10 most common house survey problems are:

• Damp: Rising damp, penetrating damp, or condensation affecting walls, floors, or ceilings.
• Structural movement or subsidence: Cracking in walls caused by ground movement or foundation failure.
• Roof defects: Missing or slipped tiles, sagging ridgelines, or failing flat-roof coverings.
• Japanese knotweed: Invasive plant growth within 7 metres of the property that can damage foundations and drains.
• Asbestos-containing materials: Found in properties built or refurbished before 2000, typically in roofing, insulation, or floor tiles.
• Electrical faults: Outdated wiring, missing earthing, or a consumer unit that does not meet current regulations.
• Woodworm and timber decay: Beetle infestation or wet rot and dry rot in structural timbers, floor joists, or roof trusses.
• Guttering and drainage issues: Blocked, cracked, or missing gutters and downpipes leading to water ingress.
• Poor insulation: Inadequate loft insulation, no cavity wall insulation, or single-glazed windows increasing energy costs.
• Missing certificates or unapproved alterations: Building work carried out without Building Regulations sign-off or planning consent.

Each of these issues carries a different level of severity and cost. Some are quick fixes costing a few hundred pounds, while others can run into tens of thousands and may affect your ability to secure a mortgage on the property.

Understanding what each survey problem actually means, and how serious it is, helps you separate the issues that require immediate action from those that are routine maintenance items. Surveyors use condition ratings (1 for good, 2 for moderate concern, 3 for serious) to classify findings, but the descriptions below give you a practical sense of what each problem involves and what it could cost you.

Damp (Moderate): Surveyors identify three types: rising damp, where moisture travels upward through walls due to a failed or absent damp-proof course; penetrating damp, where water enters through external walls, roofs, or windows; and condensation, caused by poor ventilation rather than structural failure. Rising damp repairs typically require a new chemical damp-proof course at £2,000 to £6,000 for a terraced house. Penetrating damp repairs vary widely depending on the entry point, but £1,500 to £10,000 covers most cases. Condensation is usually the cheapest to resolve through improved ventilation and may cost under £500.

Structural movement and subsidence (Serious): Cracking in walls is one of the most alarming findings in any survey report. Not all cracks indicate subsidence. Hairline cracks under 1mm wide are common in properties of all ages and are usually cosmetic. Diagonal cracks wider than 5mm, especially near windows or doors, suggest active movement that needs investigation by a structural engineer. Subsidence repairs involving underpinning typically cost £10,000 to £50,000, and you may struggle to get buildings insurance on the property in the future. Any history of subsidence must be disclosed to future buyers.

Roof defects (Moderate to Serious): Problems range from a few slipped tiles, which a roofer can fix for £200 to £500, to a full roof replacement costing £5,000 to £15,000 or more. Surveyors also check for sagging ridgelines, which can indicate failing timbers beneath the covering. Flat-roof coverings, common on extensions and garages, have a typical lifespan of 15 to 20 years and are a frequent source of condition rating 3 findings.

Japanese knotweed (Serious): This invasive plant can grow through concrete, damage foundations, and block drainage. If knotweed is found within 7 metres of the property boundary, most lenders will require a professional treatment plan, costing £5,000 to £15,000 over several years, before they will lend. A specialist survey and management plan from a Property Care Association (PCA) accredited contractor is essential before proceeding with the purchase.

Asbestos (Moderate to Serious): Asbestos-containing materials are common in properties built or refurbished before 2000. Typical locations include artex ceilings, floor tiles, roof sheets, pipe lagging, and soffit boards. If the material is in good condition and undisturbed, it is usually safe to leave in place with a management plan. Removal costs range from £1,000 for a small area to £5,000 or more for extensive work, and must be carried out by a licensed contractor.

Electrical faults (Moderate): Outdated wiring, particularly the old rubber-insulated or lead-sheathed wiring found in pre-1960s homes, is a common survey finding. A full rewire of a three-bedroom house typically costs £3,000 to £5,000. Even if a full rewire is not needed, an Electrical Installation Condition Report (EICR) costing around £200 to £300 will tell you exactly what needs attention.

Woodworm and timber decay (Moderate): Woodworm (wood-boring beetle) infestation is identified by small flight holes in timber. Active infestation is treated with insecticide spray at £1,000 to £3,000 depending on the area affected. Wet rot and dry rot in structural timbers are more serious, particularly dry rot, which spreads through masonry and can cost £5,000 or more to treat if left unchecked. Your surveyor will recommend a specialist timber report if they suspect active decay.

Guttering and drainage (Minor to Moderate): Blocked or broken gutters and downpipes are among the most common survey findings and also one of the cheapest to fix. Replacing guttering on a typical semi-detached house costs £400 to £900. However, long-term neglect of gutters causes penetrating damp and can lead to much more expensive water damage to internal walls and timbers, so these findings should not be ignored.

Poor insulation (Minor): Inadequate loft insulation, missing cavity wall insulation, and single-glazed windows are noted in surveys as energy efficiency concerns rather than structural defects. While they do not usually affect your mortgage offer, they increase running costs. Loft insulation costs £300 to £600, cavity wall insulation £500 to £1,500, and double glazing £4,000 to £8,000 for a full house.

Missing certificates and unapproved alterations (Moderate): If previous owners have carried out building work, such as loft conversions, extensions, or the removal of load-bearing walls, without obtaining Building Regulations completion certificates, your solicitor will need to address this before exchange. Options include obtaining a regularisation certificate from the local authority (£400 to £800) or taking out indemnity insurance (£100 to £300). Unapproved work can also affect the property's value and your ability to sell in the future.

The table below summarises the severity, typical repair cost, and mortgage impact for each of the most common survey problems. Use it as a quick reference when reviewing your survey report, but remember that actual costs depend on the property's size, location, and the extent of the problem. A surveyor's condition rating gives you a headline assessment, but you should always get at least two specialist quotes before committing to any repair work.

Repair costs in the table reflect 2026 averages for England and Wales. London and the South East tend to run 15 to 25 per cent higher than the national average, while Scotland and the North of England are often at the lower end of each range. If your survey flags multiple problems, the combined cost can significantly affect whether the property represents good value at the agreed purchase price. For a full breakdown of what surveys themselves cost, and how fees vary by property value, see our guide to house survey costs.

Receiving a survey report with condition rating 2 or 3 findings does not automatically mean you should walk away from a purchase. Most properties, especially older ones, will have some issues flagged. The key is knowing how to respond methodically so you make decisions based on facts and costs rather than panic.

Start by identifying which findings are condition rating 3 (serious) and which are condition rating 2 (moderate). Focus your attention on the CR3 items first, as these are the ones that could affect the property's safety, structural integrity, or your ability to get a mortgage.

• Get specialist quotes: For every CR3 finding, commission a report from a relevant specialist: a structural engineer for subsidence, a damp specialist for rising or penetrating damp, a roofer for roof defects. Ask for a written quote that includes the scope of work and a timeline. Get at least two quotes for each issue so you can benchmark costs.
• Assess the total repair bill: Add up the specialist quotes to get a realistic picture of the total cost of putting things right. If the combined figure is £5,000 or less, most buyers absorb this as part of the purchase. If it runs into tens of thousands, you have a strong case for renegotiation.
• Decide your next step: You have three options: ask the seller to reduce the price by the estimated repair cost, ask the seller to carry out the repairs before completion (less common and harder to enforce), or withdraw from the purchase entirely if the problems are too severe or expensive to justify proceeding.

For detailed guidance on the negotiation process, including how to frame your request and what sellers typically agree to, read our guide on negotiating after a survey.

Yes, certain survey problems can directly affect your mortgage offer. While your survey and your lender's mortgage valuation are separate processes, they are closely connected. If the lender's valuer identifies serious defects, or if you share your survey findings with them, the lender may take one of several actions that change the terms of your borrowing or block the mortgage entirely.

• Mortgage retention: The lender withholds a portion of the loan, typically the estimated cost of repairs, until the work is completed and re-inspected. For example, if your property needs £8,000 of roof repairs, the lender might release the full mortgage amount minus £8,000, which you would need to fund yourself until the repairs are done and verified. This is common for roof defects, damp, and structural issues.
• Down-valuation: If the valuer believes the property is worth less than the agreed purchase price because of defects, the lender will only lend against the lower figure. This means you need a larger deposit or must renegotiate the price with the seller to close the gap.
• Declined mortgage offer: For the most serious problems, such as active subsidence, significant Japanese knotweed infestation, or severe structural timber decay, some lenders will decline to lend altogether until the issue is resolved. This effectively blocks the purchase unless you can buy with cash or find a specialist lender willing to take on the risk.

It is worth noting that the lender's mortgage valuation is a much less detailed inspection than a Level 2 or Level 3 survey. The valuation focuses on whether the property is adequate security for the loan, not on giving you a comprehensive list of defects. For a full comparison of what each process covers, see our guide on mortgage valuation versus survey.

Survey findings do not exist in isolation. They feed directly into your conveyancing process, and your solicitor will need to address certain issues before exchange of contracts can take place. Understanding how survey problems interact with the legal side of your purchase helps you avoid unexpected delays.

• Indemnity insurance: If the survey reveals unapproved building work or missing completion certificates, your solicitor will usually arrange indemnity insurance to protect you and your lender against the risk of enforcement action by the local authority. This is a one-off payment, typically £100 to £300, and is standard practice. However, indemnity insurance is not a substitute for having the work properly inspected, and it does not cover the cost of putting defective work right.
• Additional searches: Certain survey findings trigger extra conveyancing searches. For example, if the surveyor notes potential flood risk, your solicitor may order a detailed flood search. If Japanese knotweed is suspected, an environmental search or specialist survey may be needed. Mining subsidence concerns in areas like South Wales or Nottinghamshire require a coal mining search. Each additional search costs £30 to £100 and adds 5 to 10 working days to the timeline.
• Delayed exchange: If your survey reveals problems that require specialist reports, price renegotiation, or additional legal work, the time between your offer being accepted and exchange of contracts will stretch. A straightforward purchase might exchange in 8 to 12 weeks, but survey complications can extend this to 16 weeks or more. Keep your solicitor and mortgage broker informed throughout so they can manage the process efficiently.

For a step-by-step overview of how all these elements fit together, from offer acceptance through to completion and getting your keys, read our guide to the conveyancing process.

Not all survey types are equally effective at detecting problems. The level of survey you choose determines how thoroughly the property is inspected, which in turn affects whether certain defects are identified or missed entirely.

A Level 2 Home Survey is a visual, non-intrusive inspection that covers all accessible areas of the property. It will identify visible signs of damp, structural cracking, roof defects, woodworm, guttering issues, poor insulation, and missing certificates. However, because the surveyor cannot move furniture, lift floorboards, or open up walls, some defects may be hidden from view. If the surveyor suspects a hidden problem, they will recommend further investigation in the report.

A Level 3 Building Survey goes deeper. The surveyor can carry out more intrusive checks, inspect areas that a Level 2 would note as inaccessible, and provide detailed commentary on construction methods and defects. For properties built before 1900, those with non-standard construction, or any building showing visible signs of significant problems, a Level 3 survey is the better choice because it is more likely to uncover issues behind surfaces and within the building's fabric.

As a general rule, if you are buying a standard post-1930s property in reasonable condition, a Level 2 survey will catch the majority of common problems listed in this guide. If the property is older, heavily altered, listed, or shows any signs of structural distress, invest in a Level 3 survey. The additional cost of £200 to £500 is small compared to the risk of missing a serious defect. For a detailed side-by-side comparison, see our guide to Level 2 vs Level 3 surveys.