Selling a House with Foundation Issues: A Seller's Guide

Foundation problems are among the most serious structural issues a property can face, and they are one of the first concerns buyers raise when they see signs of ground movement. As a seller, learning that your home has a foundation issue can feel overwhelming. But foundation problems are more common than many people realise, and properties with a history of foundation work are sold successfully every year across England and Wales.

This guide covers the full range of foundation issues beyond the well-known topic of subsidence, including heave, settlement, shrinkage, and problems arising from poor original foundation design. It explains how each type affects your sale, what remediation options exist, and how to prepare your documentation so that your buyer, their solicitor, and their mortgage lender can proceed with confidence.

Types of foundation problems

Not all foundation issues are the same, and the type of problem your property has will determine the remediation needed, the cost involved, and how buyers and lenders respond. The main categories are:

Subsidence

Subsidence is the downward movement of the ground beneath a building, causing part of the structure to sink unevenly. It is the most widely recognised foundation problem and the one most commonly covered by buildings insurance. According to the Association of British Insurers, clay shrinkage caused by tree root activity accounts for approximately 75% of domestic subsidence claims. Our detailed guide on selling a house with subsidence covers this topic in full.

Heave

Heave is the upward movement of the ground beneath a building. It is essentially the opposite of subsidence and is most commonly caused by clay soils absorbing water and expanding. Heave often occurs after a large tree near the property has been removed, allowing the soil to rehydrate and swell. It can also result from broken drains saturating the ground or from frost action in shallow foundations. Heave damage can be just as serious as subsidence, and it must be disclosed on the TA6 form under Section 7.4 alongside subsidence and landslip.

Settlement

Settlement is the natural, gradual compression of soil under the weight of a building. It is most noticeable in newly constructed properties during the first five to ten years and usually stabilises without intervention. Settlement is generally considered less serious than subsidence because it is a one-off process rather than an ongoing risk. However, if settlement is uneven or more severe than expected, it can cause significant structural cracking and may require investigation by a structural engineer.

Shrinkage

Shrinkage cracking occurs when building materials such as concrete, morite render, or blockwork lose moisture and contract. In foundations, concrete shrinkage can create hairline cracks that are generally cosmetic but may allow water ingress over time. In clay soils, seasonal shrinkage and swelling of the ground itself creates cyclical movement that can stress foundations designed for more stable conditions. The British Geological Survey estimates that around 43% of the land area in England and Wales is underlain by soils with shrink-swell potential.

Poor original foundation design

Older properties, particularly those built before modern building regulations, may have foundations that are simply too shallow or inadequately designed for the ground conditions. Victorian and Edwardian houses, for example, often have strip foundations only 450mm to 600mm deep, whereas current Building Regulations (Approved Document A) typically require foundations to be at least 1 metre deep in clay soils. Properties built on filled ground, sloping sites, or in areas with variable geology may also have foundations that were not designed to cope with the actual conditions encountered.

Signs of foundation failure

Recognising the signs of foundation problems early allows you to investigate and address the issue before it worsens or surprises your buyer during their survey. Common indicators include:

• Diagonal or stepped cracks in external brickwork, particularly around windows and doors, wider at the top than the bottom
• Horizontal cracks along the damp-proof course line, which may indicate heave pushing the structure upward
• Doors and windows sticking or no longer closing properly due to the frame distorting as the structure moves
• Uneven or sloping floors, which can indicate differential settlement or subsidence beneath part of the building
• Gaps between walls and ceilings or between walls and floors, suggesting that parts of the structure are moving independently
• Cracks in internal plaster that grow wider over time, particularly if they correspond to external cracking in the same location
• Bulging or leaning walls, which may indicate lateral movement of the foundations or failure of wall ties

If you notice any of these signs, commission a report from a chartered structural engineer before marketing the property. The BRE Digest 251 classification system, which grades crack damage from Category 0 (negligible) to Category 5 (very severe), is the standard reference used by surveyors and engineers across England and Wales to assess the severity of structural movement.

Structural engineer reports

A report from a chartered structural engineer is the cornerstone of selling a property with foundation issues. It provides an independent, professional assessment that buyers, solicitors, and mortgage lenders will rely upon when deciding whether to proceed.

Look for an engineer who is a Chartered Member or Fellow of the Institution of Structural Engineers (IStructE) or the Institution of Civil Engineers (ICE). Their chartered status and professional indemnity insurance give the report credibility that all parties will accept.

A typical structural engineer's report for foundation issues will include:

• A description and classification of all visible cracking using the BRE Digest 251 categories
• An assessment of the likely cause of foundation movement, supported by a review of the property's construction, ground conditions, and surrounding environment
• A recommendation on whether monitoring is needed and for how long (the BRE recommends a minimum of 12 months covering at least one full seasonal cycle)
• Recommended remedial works, including underpinning if necessary, with an indication of urgency and approximate costs
• A conclusion on whether the building is structurally sound in its current condition

A structural engineer's inspection and report for a standard residential property typically costs between \u00a3400 and \u00a3800. If monitoring is recommended, ongoing costs for installing and reading crack monitors over a 12-month period may add a further \u00a3500 to \u00a31,500. These costs are a worthwhile investment because the report will be essential for your sale.

Underpinning methods

If the structural engineer determines that the foundations need strengthening, underpinning is the principal remediation method. There are several approaches, each suited to different circumstances:

Mass concrete underpinning

The traditional and most widely used method. Sections of the existing foundation are excavated in sequence and new, deeper concrete foundations are poured beneath them. Each section is completed before the next is started, ensuring the building remains supported throughout. Mass concrete underpinning is effective for most domestic properties and is well understood by mortgage lenders and insurers. Typical costs range from \u00a310,000 to \u00a330,000 depending on the extent of work required.

Mini-piled underpinning

Where ground conditions are particularly challenging \u2014 for example, where stable strata are very deep or where access is restricted \u2014 mini-piled underpinning may be used. Small-diameter piles are drilled down to stable ground and connected to the existing foundations via a reinforced concrete beam. This method is more expensive than mass concrete, typically costing \u00a320,000 to \u00a350,000 or more, but it can reach depths that mass concrete cannot and causes less disruption to the surrounding ground.

Beam and base underpinning

This method involves constructing a reinforced concrete beam beneath or alongside the existing foundations, supported on a series of concrete bases or pads. It distributes the building's load more evenly and is often used where the existing foundations are too shallow across a wide area rather than failing at a single point. Costs are typically in the \u00a315,000 to \u00a340,000 range.

Resin injection

A modern, less invasive alternative where expanding resin is injected into the ground beneath the foundations to stabilise and compact the soil. Resin injection is quicker and less disruptive than traditional underpinning, typically taking 1 to 2 days on site. It is increasingly accepted by mortgage lenders, though some remain cautious. Costs typically range from \u00a35,000 to \u00a315,000. The NHBC Foundation has published research on geopolymer stabilisation techniques and their suitability for different soil types.

Underpinning costs at a glance

Insurance claims for foundation damage

Standard buildings insurance policies in England and Wales cover damage caused by subsidence, heave, and landslip. If your foundation problem falls within one of these categories, you should make a claim through your insurer before committing to privately funded repairs. The standard subsidence excess is typically \u00a31,000.

When you make a claim, your insurer will appoint a loss adjuster to manage the case and a structural engineer to investigate the cause and recommend remediation. The insurer covers the cost of investigation, monitoring, and any remedial work required to stabilise the building. This can save you tens of thousands of pounds compared to funding the work yourself.

However, insurance does not cover all types of foundation problems. Damage caused by poor original foundation design, general wear and tear, or settlement of a new building is typically excluded. If your foundation problem falls outside the insured perils, you will need to fund the investigation and repairs privately.

Whether or not a claim has been made, you must disclose the insurance history to the buyer's solicitor. Claims records follow the property, not the policyholder, and the buyer's solicitor will ask about them as part of the TA6 form and conveyancing enquiries.

Disclosure on the TA6 form

When selling a property in England and Wales, you must complete the TA6 Property Information Form. Section 7.4 asks directly whether the property has been affected by subsidence, landslip, or ground heave. If your property has any history of foundation problems \u2014 whether current or historic, resolved or ongoing \u2014 you must answer this section honestly and in detail.

Our guide on what to disclose when selling covers your broader obligations. In summary, you should provide dates, details of the cause, a description of any remedial work carried out, and cross-references to the supporting documentation you have gathered. Thorough disclosure here prevents delays later and builds trust with the buyer.

Deliberately concealing foundation problems is not just unethical \u2014 it is legally risky. If the buyer discovers undisclosed issues after completion, they could pursue a claim for misrepresentation under the Misrepresentation Act 1967. Even if the problem was resolved years ago, if you knew about it, you are required to declare it.

Impact on surveys and valuations

Foundation issues will receive close scrutiny during the buyer's survey. If there is any history of ground movement or visible signs of structural distress, the surveyor is likely to recommend a Level 3 Building Survey rather than a Level 2 HomeBuyer Report. The survey will examine the property for signs of ongoing movement and will reference any documentation you have provided.

The mortgage lender's valuation is a separate assessment. The valuer will consider the foundation history when determining the property's market value and suitability as security for the loan. Possible outcomes include:

• Valuation at or near the asking price if the issue is fully resolved with comprehensive documentation including a certificate of structural adequacy
• A reduced valuation reflecting the cost of outstanding repairs or the perceived risk, which may trigger a renegotiation after survey
• A retention where the lender withholds part of the mortgage advance until specified repairs are completed
• A decline if the issue is active or unresolved and the lender considers the property too high-risk

Having a structural engineer's report already available can help the valuer make a more informed assessment and may prevent unnecessary delays or down-valuations.

Lender attitudes to foundation issues

Mortgage lenders assess each property as security for their loan, and foundation issues receive particularly careful scrutiny. The UK Finance Mortgage Lenders' Handbook sets out each lender's individual requirements for properties affected by structural problems.

The RICS guidance on valuation of properties affected by foundation movement advises surveyors to assess each property on its individual merits rather than applying blanket rules. In practice, however, some lenders have restrictive policies, particularly regarding underpinned properties or those with ongoing claims. Buyers may need to use a mortgage broker to find a lender willing to proceed.

NHBC Foundation guidance

The NHBC Foundation has published extensive research on foundation design, ground conditions, and remediation techniques for residential properties. Their publications are a valuable reference for understanding current best practice and are widely cited by structural engineers and surveyors.

Key NHBC Foundation publications relevant to sellers include guidance on foundations in clay soils, the effects of trees on foundations, and the performance of different underpinning methods. If your property was built by an NHBC-registered builder and is still within the 10-year NHBC Buildmark warranty period, foundation defects arising from non-compliance with NHBC standards may be covered under the warranty. Check your NHBC documentation or contact NHBC directly to establish whether your property is eligible.

Practical steps before listing

If you are selling a property with foundation issues, the following preparation will put you in the strongest possible position:

1. Commission a structural engineer's report. Have the issue professionally assessed and documented. This is the single most important step.
2. Gather all documentation. Collect monitoring reports, insurance claim records, underpinning certificates and guarantees, tree reports, drainage surveys, and any certificates of structural adequacy. Organise them chronologically.
3. Complete your TA6 form thoroughly. Answer Section 7.4 in full, providing dates, causes, and cross-references to the supporting documentation you have gathered.
4. Confirm your buildings insurance. Check that your current policy includes subsidence cover and obtain a copy of your claims history from your insurer. The buyer's solicitor will ask for this.
5. Consider obtaining a fresh report. If your certificate of structural adequacy is more than 5 to 10 years old, a fresh inspection can reassure buyers that no new movement has occurred.
6. Instruct your solicitor early. Brief them on the foundation history before accepting an offer so they can prepare responses to the enquiries that will inevitably follow.

Sources and further reading

• Royal Institution of Chartered Surveyors (RICS) — Guidance on the assessment and valuation of properties affected by foundation movement: rics.org
• Building Research Establishment (BRE) — BRE Digest 251: Assessment of damage in low-rise buildings with particular reference to progressive foundation movement
• Institution of Civil Engineers (ICE) — Guidance on ground investigation and foundation design for residential buildings: ice.org.uk
• Institution of Structural Engineers (IStructE) — Guidance on certificates of structural adequacy and assessment of subsidence in low-rise buildings: istructe.org
• NHBC Foundation — Research publications on foundation design, ground conditions, and tree-related subsidence: nhbcfoundation.org
• British Geological Survey (BGS) — Shrink-swell hazard mapping and GeoSure ground stability data: bgs.ac.uk
• Association of British Insurers (ABI) — Guidance on domestic subsidence claims and insurance: abi.org.uk
• HM Government — Building Regulations Approved Document A: Structure, covering foundation design requirements: gov.uk
• Law Society — TA6 Property Information Form guidance notes: lawsociety.org.uk

Frequently asked questions