Survey Found Subsidence: A Seller's Guide to Next Steps
What to do when the buyer's survey flags subsidence. Covers historical vs active subsidence, structural engineer reports, insurance, underpinning, TA6 disclosure, and impact on the sale.
What you need to know
Subsidence is one of the most serious findings a buyer's survey can produce, and it can have a significant impact on your sale. But the picture is rarely as bleak as it first appears. This guide explains the critical difference between historical and active subsidence, what a Certificate of Structural Adequacy is and why you need one, how insurance and underpinning work, your TA6 disclosure obligations, and realistic cost expectations.
- The distinction between historical and active subsidence is critical — historical subsidence with proper documentation is manageable, while active subsidence requires resolution before most sales can proceed.
- A Certificate of Structural Adequacy from a chartered structural engineer is the key document that enables a buyer to obtain a mortgage on a property with a subsidence history.
- Most buildings insurance policies cover subsidence with a standard excess of £1,000, but claiming can affect future premiums and buyer insurability.
- Subsidence repair costs range from £5,000 for resin injection to £50,000+ for extensive underpinning — many claims are covered by insurance.
- Honest, thorough disclosure on the TA6 is non-negotiable — failure to disclose known subsidence is misrepresentation.
Pine handles the legal prep so you don't have to.
Check your sale readinessLearning that the buyer's survey has flagged subsidence is one of the most alarming moments in a property sale — it is among the most serious of the common issues found in property surveys. Subsidence — the downward movement of the ground beneath a building's foundations — can affect structural integrity and is taken very seriously by mortgage lenders, insurers, and buyers.
However, not all subsidence is equal. The distinction between historical and active subsidence is crucial, and your response as a seller depends entirely on which you are dealing with. For an overview of the survey process, see our seller's guide to property surveys. This guide walks you through the next steps.
Historical versus active subsidence
The first thing to establish is whether the subsidence is historical (has occurred in the past and stabilised) or active (is ongoing).
| Factor | Historical subsidence | Active subsidence |
|---|---|---|
| Ground movement | Has stopped; property is stable | Ongoing; property may still be moving |
| Cracks | Old, filled, stable | New, widening, or reopening |
| Doors and windows | Functioning normally | Sticking or becoming misaligned |
| Documentation | CSA or engineer's report confirming stability | Monitoring may be in progress |
| Mortgageability | Most lenders will lend with documentation | Most lenders will not lend until resolved |
| Impact on sale price | 10 – 20% below comparable properties | 25%+ below, or may not be saleable on open market |
What causes subsidence
Understanding the cause helps you and your structural engineer determine the best course of action.
- Clay shrinkage (most common). Clay soils expand when wet and shrink when dry. Prolonged dry spells cause the clay to contract, pulling support away from foundations. This is particularly prevalent in London, the South East, the Midlands, and parts of the South West.
- Tree roots. Trees near a property extract moisture from the soil, exacerbating clay shrinkage. Willows, oaks, poplars, and ash trees are the most common culprits due to their extensive root systems and high water demand.
- Leaking drains. Persistent drainage leaks can wash away or soften the subsoil beneath foundations, causing localised subsidence. A CCTV drainage survey can identify this.
- Mining activity. Properties in former mining areas can be affected by the collapse of underground workings. A mining search identifies this risk.
- Inadequate foundations. Older properties (particularly those built before 1950) may have shallow foundations that are more susceptible to ground movement.
Your action plan
Step 1: Commission a structural engineer's report
Appoint an independent chartered structural engineer (look for members of the Institution of Structural Engineers, IStructE, or the Institution of Civil Engineers, ICE). The engineer will:
- Inspect the property and assess the cracking pattern
- Determine whether the movement is historical or active
- Identify the likely cause
- Recommend next steps (monitoring, remediation, or confirmation of stability)
A structural engineer's inspection and report typically costs £500 to £1,500 depending on the property and the complexity of the assessment. See our guide on structural survey costs for more detail on pricing.
Step 2: If subsidence is historical
If the engineer confirms that the subsidence is historical and the property is stable, ask them to issue a Certificate of Structural Adequacy (CSA). This is the document that most mortgage lenders require to proceed with lending on a property with a subsidence history.
With a CSA in hand, you can present this to the buyer and their solicitor, along with any documentation of previous remedial work. This evidence puts you in a strong position to negotiate, as it demonstrates that the issue has been identified, investigated, and resolved.
Step 3: If subsidence is active
If the engineer identifies active subsidence, the situation is more complex and will take longer to resolve. The typical process is:
- Monitoring (12 months). The engineer installs monitoring points and takes regular measurements over a full seasonal cycle to track the movement pattern.
- Cause investigation. Identify and address the root cause — this might involve tree pruning or removal, drain repairs, or soil investigation.
- Remedial work. If addressing the cause does not stabilise the property, structural remediation (typically underpinning) may be needed.
- Post-remediation monitoring. Further monitoring to confirm stability.
- CSA or engineer's report. Once stability is confirmed, the engineer issues documentation.
This process can take 18 months to three years from start to finish. If you are mid-sale, you will need to have a realistic conversation with the buyer about timelines. Our guide on when to fix versus reduce the price can help you weigh the options. Some sales pause while monitoring takes place; others proceed with an agreed price reduction to reflect the ongoing work.
Insurance implications
Most standard buildings insurance policies cover subsidence, subject to a standard excess of £1,000. However, there are several important considerations.
Making a claim
If you have not yet made an insurance claim for the subsidence, consider doing so. Your insurer will appoint a loss adjuster and structural engineer to investigate. If the claim is accepted, the insurer will fund the monitoring, investigation, and remedial work (minus the excess). This can save you tens of thousands of pounds.
However, making a claim creates a claims history that you must disclose on the TA6 and that will affect the buyer's ability to obtain affordable buildings insurance. The buyer's lender may also impose a mortgage retention until remediation is confirmed. Discuss the pros and cons with your insurer and solicitor before deciding.
Impact on the buyer's insurance
Properties with a subsidence history are more expensive to insure. The buyer may need to use a specialist insurer, and premiums can be significantly higher than for a comparable property without subsidence. Some standard insurers will cover properties with historical subsidence if they have a CSA and no claims in the past five to ten years.
Underpinning explained
Underpinning is the process of strengthening and stabilising a property's foundations. There are three main methods used in the UK.
| Method | How it works | Typical cost |
|---|---|---|
| Mass concrete underpinning | Excavating beneath existing foundations and pouring new concrete in sections | £10,000 – £30,000 |
| Mini-piled underpinning | Driving piles through the foundations to a stable stratum and connecting with a beam | £15,000 – £50,000+ |
| Resin injection | Injecting expanding resin into the ground to stabilise soil and fill voids | £5,000 – £15,000 |
Resin injection is the least invasive and most affordable option, but it is not suitable for all situations. Your structural engineer will recommend the appropriate method based on the soil conditions, the depth of foundations, and the nature of the movement. For more detail on underpinning and its effect on resale, see our guide on selling an underpinned house.
TA6 disclosure
You must disclose subsidence — whether historical or active — on the TA6 Property Information Form. The relevant sections cover structural alterations and damage, insurance claims, and any ongoing monitoring or remedial work.
Specifically, you should disclose:
- Any history of subsidence or ground movement
- Any insurance claims related to subsidence
- Any monitoring, investigation, or remedial work
- Any underpinning or structural repairs
- Any tree removal or management related to subsidence
- Copies of the CSA, engineer's reports, and insurance documentation
Failure to disclose known subsidence is misrepresentation. This is one of the most litigated areas of property disclosure, and buyers who discover undisclosed subsidence after completion regularly pursue legal claims successfully.
Impact on your sale price
Subsidence does affect property values, but the extent depends on whether the subsidence is historical or active.
- Historical subsidence with CSA: Properties typically sell for 10 to 20 per cent below comparable properties without a subsidence history. The discount reflects the stigma, higher insurance costs, and reduced buyer pool.
- Active subsidence: The discount can be 25 per cent or more, reflecting the uncertainty and the cost of remediation. Some sellers in this situation choose to resolve the subsidence before remarketing.
- Underpinned properties: Properties that have been underpinned and have a CSA typically attract a similar discount to historical subsidence — 10 to 20 per cent below comparable properties.
See our guide on average price reductions after survey for broader context on post-survey negotiation.
Selling options if subsidence is active
If the subsidence is active and you need to sell, you have several options.
- Wait and resolve. Complete the monitoring, remediation, and obtain a CSA before remarketing. This takes time but achieves the best price.
- Sell at a discount. Sell to the current buyer or a new buyer at a price that reflects the cost and risk of the ongoing subsidence. Cash buyers are more likely to proceed because they do not need mortgage approval.
- Sell at auction. Properties with active subsidence can attract investor buyers at auction who specialise in distressed properties. The price will be discounted but the sale is certain.
- Sell to a property buying company. Quick-sale companies will buy properties with subsidence, typically at 70 to 80 per cent of market value. This should be a last resort.
Key points to remember
- Not all cracking is subsidence — settlement, thermal movement, and lintel failure can produce similar signs
- A chartered structural engineer is the only professional who can definitively diagnose subsidence and issue a CSA
- Historical subsidence with proper documentation is manageable and most sales proceed
- Active subsidence requires resolution before most mortgage-funded sales can complete
- Buildings insurance may cover the cost of investigation and remediation
- Full, honest disclosure on the TA6 protects you legally and maintains buyer trust
Frequently asked questions
Can I sell a house with subsidence?
Yes, but it will be more challenging than a standard sale. If the subsidence is historical (has occurred in the past and been resolved), you can sell with appropriate documentation — a Certificate of Structural Adequacy or a structural engineer's report confirming the property is stable. If the subsidence is active and ongoing, you will need to address it before most buyers can obtain a mortgage. In both cases, honest disclosure on the TA6 is essential. Some sellers choose to sell at auction or to cash buyers to avoid mortgage-related complications.
What is the difference between historical and active subsidence?
Historical subsidence means the ground movement occurred in the past and has since stabilised. There may be evidence of previous movement such as repaired cracks, underpinning, or monitoring records, but the property is currently stable. Active subsidence means the ground movement is ongoing. Signs include new or worsening cracks, doors and windows becoming difficult to open, and monitoring data showing continued movement. The distinction is critical because historical subsidence with appropriate documentation is far less likely to prevent a sale than active subsidence.
What is a Certificate of Structural Adequacy?
A Certificate of Structural Adequacy (CSA) is a formal certificate issued by a chartered structural engineer confirming that a property is structurally sound despite having experienced subsidence. The certificate typically records the history of the subsidence, what remedial work was carried out, and confirms that the property is now stable and suitable for mortgage lending. Most mortgage lenders accept a CSA as sufficient evidence that historical subsidence has been resolved. Getting a CSA typically costs between 500 and 1,500 pounds.
Will subsidence stop the buyer getting a mortgage?
Active subsidence will prevent most mainstream mortgage lenders from lending. Historical subsidence with a Certificate of Structural Adequacy or structural engineer's report confirming stability is accepted by most lenders, although some may require a specialist valuation. Properties that have been underpinned can also be mortgaged, though some lenders are more restrictive. Specialist subsidence mortgage brokers can help buyers find appropriate lenders. The key document lenders need is professional evidence that the property is currently stable.
How much does subsidence repair cost?
Costs vary enormously depending on the cause and severity. Monitoring (typically 12 months) costs 2,000 to 5,000 pounds. Root management (tree pruning or removal) costs 500 to 5,000 pounds. Traditional mass concrete underpinning costs 10,000 to 30,000 pounds. Mini-piled underpinning costs 15,000 to 50,000 pounds or more. Resin injection stabilisation costs 5,000 to 15,000 pounds. Repairing cosmetic damage (cracks, redecoration) adds 2,000 to 10,000 pounds on top. Many subsidence claims are covered by buildings insurance, which can significantly reduce the seller's out-of-pocket cost.
Does buildings insurance cover subsidence?
Most standard buildings insurance policies cover subsidence, but there is typically an excess of 1,000 pounds (the standard subsidence excess set by the Association of British Insurers). If you have a subsidence claim history, your future premiums will be higher. Making a claim can complicate the sale because you must disclose the claim history on the TA6 and the buyer's insurer may charge higher premiums or impose specific conditions. If you have not yet claimed, discuss the options with your insurer before making a decision.
Do I have to disclose subsidence on the TA6?
Yes. The TA6 Property Information Form asks specifically about structural alterations and damage, including subsidence. You must disclose any subsidence you are aware of — whether historical or current — including any insurance claims, monitoring, remedial work, and underpinning. You should also disclose if you have had a buildings insurance claim related to subsidence declined. Failure to disclose known subsidence is misrepresentation and could result in a legal claim after completion.
What causes subsidence in UK properties?
The most common cause of subsidence in the UK is clay shrinkage — where clay soils dry out and shrink during hot, dry weather, causing the foundations to move. Tree roots can exacerbate this by extracting moisture from the soil. Other causes include washout (water eroding sandy or gravelly subsoils), mining activity, leaking drains undermining foundations, and inadequate foundations (particularly in older properties built with shallow foundations). Clay soils are concentrated in London and the South East, the Midlands, and parts of the South West.
What is underpinning and does it affect property value?
Underpinning is a structural engineering solution that strengthens and stabilises a property's foundations. The most common methods are mass concrete underpinning (excavating beneath existing foundations and pouring new concrete), mini-piled underpinning (driving piles to a stable stratum), and resin injection (injecting expanding resin into the ground to stabilise the soil). Underpinning does affect property value — underpinned properties typically sell for 10 to 20 per cent less than comparable properties without a subsidence history, though this varies by location and market conditions.
How long does subsidence monitoring take?
Subsidence monitoring typically lasts 12 months to capture a full seasonal cycle (clay soils shrink in summer and swell in winter). The structural engineer installs monitoring points on the property and takes regular measurements to determine whether the movement is ongoing or has stabilised. If monitoring shows the movement has stopped, the engineer can confirm stability and issue a report. If movement continues, further investigation and remedial work will be needed. The 12-month monitoring period can feel frustrating during a sale, but it is necessary to provide reliable evidence.
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