Why repair costs matter before you offer
When you view a property, you're not just buying bricks and mortar at the listed price. You're buying everything that needs fixing, updating, or replacing - and you're paying for it on top of the asking price unless you negotiate it down.
New homeowners in the UK spend an average of £5,750 on repairs in the first year. For properties with significant deferred maintenance, that figure can reach £15,000–£30,000. The buyers who fare best are the ones who estimate these costs before offering - and either adjust their offer accordingly or walk away. See our guide on what to look for when viewing a house for how to spot these issues.
Damp proofing costs
Damp is the most common defect in UK properties and comes in several forms, each with different treatment costs.
| Issue | Typical cost |
|---|---|
| Rising damp - DPC injection + replaster (per wall) | £500–£2,000 |
| Rising damp - whole ground floor | £2,000–£8,000 |
| Penetrating damp - fix external cause + internal repair | £1,000–£5,000 |
| Condensation / mould treatment (surface) | £100–£300 |
| Ventilation system installation (MVHR or extract fans) | £2,000–£5,000 |
Important: many "damp specialists" diagnose rising damp when the actual cause is condensation or penetrating damp. Get an independent assessment rather than relying on a company that profits from selling a DPC injection. An independent damp survey costs £200–£400.
Roof repair and replacement costs
The roof is the most expensive single element of a house to replace. Even minor failures - a few slipped tiles - can cause water ingress that damages timbers, ceilings, and electrics below.
| Repair | Typical cost |
|---|---|
| Replace slipped/broken tiles (localised) | £150–£400 |
| Re-ridge a roof | £800–£1,500 |
| Flat roof replacement (single section) | £1,500–£4,000 |
| Full pitched roof replacement (3-bed semi) | £8,000–£15,000 |
| Full pitched roof replacement (4-bed detached) | £12,000–£20,000 |
| Chimney repointing / rebuild | £800–£3,000 |
Roof age matters: a concrete tile roof typically lasts 40–60 years. A slate roof can last 80–100 years if maintained. If the property was built in the 1960s–80s and still has the original roof, expect it to need replacement within the next 10–15 years.
Rewiring costs
Outdated electrics are a safety risk and a significant cost. If the consumer unit still has rewirable fuses or there's no RCD protection, the wiring is likely 30+ years old.
| Work | Typical cost |
|---|---|
| Consumer unit upgrade only | £300–£600 |
| Partial rewire (e.g. ground floor circuits) | £1,500–£3,000 |
| Full rewire - 2-bed flat | £2,500–£4,500 |
| Full rewire - 3-bed semi | £4,000–£7,000 |
| Full rewire - 4-bed detached | £6,000–£10,000 |
A rewire is disruptive - it involves lifting floorboards, chasing into walls, and significant making-good afterwards. Factor in £500–£1,500 for redecorating after a rewire.
Boiler and heating system costs
| Work | Typical cost |
|---|---|
| Boiler service | £60–£120 |
| Boiler repair (common faults) | £150–£500 |
| New combi boiler installed | £2,500–£4,500 |
| Full central heating system (boiler + radiators + pipework) | £4,000–£8,000 |
| Powerflush (existing system) | £300–£600 |
Boilers typically last 10–15 years. If the boiler is over 10 years old, factor in replacement within the next 3–5 years. Note the make and model at the viewing - some manufacturers have much better reliability records than others.
Windows and doors
| Work | Typical cost |
|---|---|
| Replace single failed double-glazed unit | £75–£200 |
| Full window replacement - 3-bed semi (uPVC) | £4,000–£7,000 |
| Full window replacement - 3-bed semi (timber) | £8,000–£15,000 |
| New front door (composite) | £800–£2,000 |
Structural repairs
Structural problems are the most expensive category of repair - and the most likely to kill a purchase if discovered late.
| Issue | Typical cost |
|---|---|
| Structural engineer's report | £400–£800 |
| Crack stitching / resin injection (localised) | £1,000–£3,000 |
| Underpinning (partial, one corner) | £10,000–£20,000 |
| Underpinning (full perimeter) | £30,000–£50,000+ |
| Lintel replacement (single window/door) | £500–£1,200 |
| Wall tie replacement (cavity wall, full elevation) | £1,500–£3,500 |
What changes the final cost?
The ranges in this guide are indicative. Several factors shift actual costs significantly:
- Location - labour costs in London and the South East are typically 20–40% higher than the Midlands or North
- Access - scaffolding adds £500–£2,000+ to any roof, chimney, or upper-storey external repair
- Listed buildings - heritage requirements can double or triple costs due to specified materials and methods
- Scope creep - opening up a wall to fix a crack often reveals more work behind it; budget a 15–25% contingency
- Timing - tradespeople are busiest in spring and summer; booking in autumn or winter can reduce costs and wait times
How to use repair costs in negotiation
Repair costs are your strongest negotiation tool - but only if you present them properly. Read our full guide on how to negotiate house price after a survey for detailed scripts and strategy. Key principles:
- Itemise each defect with a cost range - don't just ask for "£10,000 off"
- Use mid-range estimates, not worst-case - vendors reject inflated numbers
- Distinguish between urgent repairs (must be done before/shortly after moving in) and medium-term maintenance
- Be prepared to show your evidence: photos from the viewing, specialist quotes, or your pre-offer property check report
When rough estimates are enough vs when you need quotes
For negotiation purposes, the indicative ranges in this guide are sufficient for items under £2,000. For anything over £2,000, get at least two written quotes from local tradespeople before relying on the figure in your offer. This costs time but strengthens your position enormously - a vendor is far more likely to accept a reduction backed by a real quote than a range from the internet.
How KeyWise helps buyers quantify risk earlier
KeyWise's pre-offer property check process guides you through capturing condition data at the viewing - and then estimates likely repair costs based on what you've found. Instead of waiting for a survey to discover a £7,000 rewiring need, you flag the old consumer unit at the viewing and see the estimated cost immediately.
This means you can adjust your offer on the spot, ask the right questions of the agent, or decide to walk away before you've spent anything on solicitors or mortgage applications.
Don't guess. Know before you offer.
KeyWise gives you a structured framework to investigate properties at the viewing - so you can make an evidence-based offer.
Start a Viewing Risk Check →Built by a Quantity Surveyor. Used by serious buyers.
Frequently asked questions
How much does it cost to fix damp in a UK house?
Rising damp remediation typically costs £2,000–£8,000 depending on extent. Penetrating damp repairs depend on the external cause - gutter repairs cost £200–£600, but if internal replastering is needed, total costs can reach £2,000–£5,000. Condensation damp treatment ranges from £100–£300 for surface treatment to £2,000–£5,000 for ventilation system installation.
How much does a new roof cost in the UK?
A full roof replacement on a typical 3-bed semi-detached house costs £8,000–£15,000 for a pitched tile roof. Flat roof sections cost £1,500–£4,000 each. Localised repairs such as replacing slipped tiles or re-ridging cost £300–£1,500.
Should I reduce my offer based on repair costs?
Yes - if your viewing or survey identifies issues that will cost money to fix, those costs are legitimate grounds for negotiation. Present the vendor with specific, documented repair items and realistic cost estimates rather than a vague request for a discount.
How accurate are online repair cost estimates?
Online estimates including those in this guide give useful indicative ranges for planning and negotiation. However, actual costs vary by region, property specifics, and market conditions. For any item over £2,000, get at least two written quotes before relying on the figure in negotiation.
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.