Can bad damp or poor insulation make a property non-residential for SDLT?

Introduction

People often ask whether serious defects in a home, such as damp, poor insulation or a very low EPC rating, mean the property was not suitable for use as a dwelling when they bought it. That question matters because, in some cases, a buyer may argue that the property should not have been taxed at residential Stamp Duty Land Tax rates.

The difficulty is that the legal test is strict. A property does not stop being a dwelling simply because it is in poor condition, needs repair, or is unpleasant to live in. The courts have made clear that the threshold for showing a property was not suitable for use as a dwelling is now relatively high, especially following Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799.

The Question

A buyer completed a condition questionnaire about a property. The issues identified were bad damp, old or poor insulation, and an EPC rating in the lower bands. The buyer wanted to know whether those defects could support an SDLT claim on the basis that the property was not suitable for use as a dwelling at the effective date of the transaction.

Nick’s Explanation

Nick’s explanation, put in general terms, was that these kinds of defects do not usually meet the legal threshold on their own. Bad damp, poor insulation and a weak EPC rating may show that a property is in poor condition, but they do not necessarily show that it has ceased to be a dwelling for SDLT purposes.

The key point is whether, at the effective date of the purchase, the building was objectively suitable for use as a dwelling. That is a higher bar than showing the property needed work, was uncomfortable, or fell below modern expectations.

In substance, Nick’s reasoning can be summarised this way: if the property still had the basic character of a home and could still be occupied as one, even if only after repair or despite serious defects, HMRC is likely to treat it as residential. Damp and poor energy efficiency are usually evidence of disrepair, not evidence that the building has stopped being a dwelling.

The Law

The starting point is the Finance Act 2003, which governs Stamp Duty Land Tax. Whether residential rates apply depends, in broad terms, on whether the subject matter of the transaction consists of residential property. That includes a building that is used or suitable for use as a dwelling, or is in the process of being constructed or adapted for such use.

The central SDLT question in these cases is whether the property was “suitable for use as a dwelling” at the effective date of the transaction. The test is applied objectively. It is not enough that the buyer did not want to live there, planned major renovation, or considered the condition unacceptable.

Case law has repeatedly shown that a property can remain suitable for use as a dwelling even where it has substantial defects, lacks modern standards, or requires extensive refurbishment. The courts look at the actual condition of the building and whether it still functions, in essence, as a home.

In uninhabitable or not suitable for use cases, the condition threshold is now relatively high following Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799. That authority reinforces that serious disrepair is not automatically enough. The issue is not whether the property was ideal, mortgageable, or attractive to occupy, but whether it had truly lost its character as a dwelling.

Analysis

Applying those rules step by step:

1. Identify the relevant date. The condition must be assessed at the effective date of the transaction, usually completion.

2. Consider the actual defects. Bad damp, old insulation and a poor EPC rating may indicate neglect, poor energy performance, and the need for works.

3. Ask whether those defects prevented the property from being used as a dwelling in any real sense. In many cases, the answer will be no. A cold, damp or inefficient house may still be a house.

4. Look for more fundamental failures. Cases are stronger where there is evidence of the absence of basic facilities, structural collapse, complete lack of sanitation, or conditions so severe that the building cannot realistically be occupied as a home.

5. Distinguish disrepair from non-dwelling status. The fact that a property needs renovation, has health hazards, or falls short of modern housing standards does not automatically take it outside the residential SDLT regime.

6. Apply the higher threshold confirmed by recent authority. Following Mudan, the courts are unlikely to accept that ordinary disrepair, even if serious, makes a property unsuitable for use as a dwelling unless the evidence shows something more extreme.

On those facts alone, bad damp and poor insulation are unlikely to be enough. An EPC rating in band F or G also does not decide the issue. EPC ratings measure energy efficiency, not whether a building legally remains a dwelling for SDLT.

Outcome

The practical conclusion is that bad damp, poor insulation and a low EPC rating will not usually be enough, by themselves, to show that a property was not suitable for use as a dwelling for SDLT purposes. A claim based only on those features is likely to be weak.

A stronger argument would usually require evidence that the property had gone beyond mere disrepair and had genuinely ceased to function as a dwelling at the relevant date.

Practical Steps

If you are assessing a possible SDLT position, it helps to gather evidence focused on the legal test rather than general dissatisfaction with the property’s condition. Useful steps include:

• Obtain the survey, valuation and any photographs showing the condition at completion.

• Check whether basic facilities existed and worked, such as kitchen, bathroom, water, electricity, heating and sanitation.

• Identify any structural issues or legal prohibitions on occupation that existed at the effective date.

• Separate evidence of disrepair from evidence that the building could not realistically be lived in as a home.

• Review the purchase file to see how the property was described in the contract, valuation and mortgage documents.

• Compare the facts carefully with the current case law, including Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799.

Conclusion

For SDLT, a property does not stop being residential simply because it has bad damp, poor insulation or a low EPC rating. The legal threshold for showing that a property was not suitable for use as a dwelling is now relatively high. In most cases, those defects point to disrepair, not to the loss of dwelling status.

Legal References Used

• Finance Act 2003

• 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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