Can a property with mould and a defective roof be treated as not suitable for use as a dwelling for SDLT?

Introduction

Buyers sometimes discover serious defects only after moving into a property. A common question is whether those defects mean the property was not suitable for use as a dwelling at the effective date of purchase, so that Stamp Duty Land Tax (SDLT) should be charged on a different basis.

This issue often arises where there is mould, water ingress, structural decay, or a need for major replacement works. The legal test, however, is strict. A property is not treated as unsuitable for use as a dwelling just because it needs repair, even expensive repair. The question is whether, at the relevant date, it was truly not suitable for residential use.

The Question

A buyer purchased a residential property and only after completion discovered severe black mould beneath a flat roof. Roofing contractors then reported that parts of the roof structure were rotting and that a full roof replacement was needed. The buyer wanted to know whether these defects could mean the property was unsuitable for use as a dwelling for SDLT purposes.

Nick’s Explanation

Nick’s view was that, on the facts described, it would be difficult to argue that the property was unsuitable for residential use.

In anonymised form, his key points were:

• the defect was discovered only after the purchase;
• the sales particulars suggested the property presented as a dwelling rather than as a building incapable of occupation;
• the legal standard for showing that a property is unsuitable for use as a dwelling is now much stricter than many buyers expect;
• the property would usually need defects of a very serious kind, going beyond ordinary disrepair or even major repair liability.

Nick also noted that the threshold has become significantly harder to satisfy. That point is now reinforced by later authority.

The Law

For SDLT, the starting point is the charge under the Finance Act 2003. Whether property is “residential property” depends in part on whether it is used or suitable for use as a dwelling, or is in the process of being constructed or adapted for such use.

The key statutory provision is Schedule 4ZA to the Finance Act 2003, read with the wider SDLT code, including the definition of residential property in section 116 Finance Act 2003.

In practice, disputes usually focus on whether the building was “suitable for use as a dwelling” at the effective date of the transaction. That is a factual and legal question. The test is not whether the property was ideal, modern, mortgageable, or free from defect. It is whether it was suitable for residential use in the real world at that date.

The courts have made clear that substantial disrepair does not automatically prevent a building from being a dwelling. The modern approach is demanding. In an uninhabitable or not suitable for use case, the condition thresholds are now relatively high following Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799.

Analysis

The issue can be analysed in stages.

1. Identify the relevant date

   The condition of the property is assessed at the effective date of the purchase, usually completion. Later deterioration is not enough, and later discovery of an existing defect does not by itself prove the property was legally unsuitable as a dwelling.

2. Ask whether the property was still capable of residential occupation

   Mould, damp, leaks, timber decay, and the need for a new roof are all serious matters. But many properties with those problems are still legally treated as dwellings for SDLT. The question is whether the defects made the building genuinely unsuitable for living in, not merely unpleasant, unhealthy, or expensive to repair.

3. Consider whether the defect was reparable

   If the problem can be remedied by repair or replacement works, even major works, that often points against the property being unsuitable for use as a dwelling. Nick’s summary reflected this point: the fact that a full roof replacement was needed does not necessarily mean the building ceased to be a dwelling.

4. Look at the overall presentation and use of the property

   Sales particulars, photographs, layout, utilities, kitchen and bathroom facilities, and whether the property was marketed and sold as a home can all matter. If the property looked and functioned as a dwelling, that usually makes an SDLT unsuitability argument harder.

5. Distinguish hidden defects from legal unsuitability

   A hidden defect discovered after moving in may support a private law claim against a seller or surveyor in some circumstances, but it does not automatically change the SDLT classification. SDLT asks a different question.

6. Apply the higher threshold confirmed by recent case law

   Following Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799, the threshold in “not suitable for use as a dwelling” cases is relatively high. The courts are unlikely to accept that a building falls outside residential treatment merely because it has serious defects, health concerns, or a major repair bill. The defects generally need to go much further and show that the property was truly not suitable for residential use at the relevant date.

On the facts described here, severe mould and a rotting flat roof are plainly serious. But if the property was bought as a home, had the normal characteristics of a dwelling, and the main issue was that substantial remedial works were required, the better view is usually that it remained suitable for use as a dwelling for SDLT purposes.

Outcome

The practical conclusion is that a buyer in this situation is unlikely to succeed in arguing that the property was not suitable for use as a dwelling for SDLT purposes solely because of mould, roof rot, and the need for a full roof replacement.

That is especially so where:

• the problem was only discovered after completion;
• the property was marketed and sold as a residence;
• the building still had the ordinary features of a home;
• the defect, although serious, was capable of being remedied by works.

Practical Steps

If you are assessing a similar SDLT position, it is sensible to gather evidence in a structured way:

• obtain the completion date and confirm the property’s condition at that date;
• collect survey reports, contractor reports, photographs, videos, and repair quotations;
• review the sales particulars and any pre-contract replies to see how the property was presented;
• consider whether the property had functioning basic living facilities at completion, such as kitchen, bathroom, water, electricity, and safe access;
• ask whether the problem was one of disrepair requiring works, or whether the building was truly incapable of residential use;
• compare the facts against current case law, especially Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799.

If the concern is wider than SDLT, separate advice may also be needed on survey negligence, misrepresentation, or other property law issues, because those are different legal questions.

Conclusion

Serious mould and a defective roof do not automatically mean a property was not suitable for use as a dwelling for SDLT. The legal threshold is now relatively high, and major but repairable defects will often not be enough. In most cases of this kind, the property will still be treated as residential property for SDLT purposes.

Legal References Used

• Finance Act 2003
• Finance Act 2003, section 116
• Finance Act 2003, Schedule 4ZA
• Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799

This page was last updated on 22 March 2026.

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