Non-Standard Construction Mortgage FAQ
General information only. This is not financial advice.
Last reviewed: 2026-06-06
What counts as non-standard construction for a mortgage?
UK mortgage lenders broadly define non-standard construction as any property that is not built with a traditional brick or stone outer skin and a slate or tile roof. The most common categories that trigger lender scrutiny include: timber frame (including SIPS and cross-laminated timber); concrete construction (Laing, Reema, Cornish Type 1 and 2, Wimpey No-Fines, and other pre-cast concrete system builds); steel frame properties; prefabricated (prefab) homes; properties with thatched or flat roofs; and unusual hybrid structures combining modern methods with non-standard materials. Designation under the Defective Dwellings Act 1984 (applying to certain concrete system builds) is a further layer of restriction that some lenders will not lend on at all.
Can you get a mortgage on a timber frame house in the UK?
Yes — timber frame is generally the most accepted category of non-standard construction among UK lenders, and many mainstream lenders will consider it. Modern timber frame built to current building regulations is widely accepted. Older timber frame (particularly pre-1970s) can attract more scrutiny, and lenders may require a specialist structural surveyor's report confirming the frame is sound and free from damp, rot, or woodworm. Maximum LTV is often capped at 75–85% depending on the lender, and some will not lend on older timber frame without a HomeBuyer Report or full structural survey. As a complex income borrower, you may already be limited to a shorter lender panel, so checking which of your accessible lenders accepts the specific timber frame type before applying is important.
Why is it harder to get a mortgage on a concrete property?
Concrete system-build properties are harder to mortgage for two reasons. First, many pre-cast concrete systems from the 1950s–1970s (Laing Easiform, Reema, Cornish Unit, Wimpey No-Fines, and others) were designated as defective under the Housing Defects Act 1984, which means lenders must consider structural risk. These concrete types may have experienced carbonation (weakening of the concrete over time) or issues with the steel reinforcement rusting inside the structure. Second, even non-designated concrete properties are less liquid in resale — fewer buyers can obtain mortgages on them, which makes the lender's security harder to realise in a repossession scenario. As a result, many mainstream lenders simply decline concrete construction, and specialist lenders who do accept it typically cap LTV at 60–75% and require a full structural survey.
Which lenders will mortgage non-standard construction properties?
The lender panel that will accept non-standard construction is smaller than for standard brick-and-tile properties but is not negligible. Building societies with flexible manual underwriting are often more willing than high-street banks — names including Leeds Building Society, Skipton Building Society, and certain regional mutuals are known to consider non-standard construction on a case-by-case basis. Specialist lenders such as Precise Mortgages, Kensington Mortgages, and Aldermore also have appetite for certain non-standard types. The key variables are: construction type (timber frame vs concrete vs steel); age of the property; condition as evidenced by a surveyor; and your LTV. For complex income borrowers, the overlap between 'non-standard construction lenders' and 'complex income lenders' narrows the field further, making a specialist mortgage broker essential to avoid wasted applications.
What LTV can I get on a non-standard construction property?
Maximum LTV on non-standard construction is typically 75–85%, compared to 95% available on standard construction. For higher-risk construction types (designated concrete, certain prefabs, properties with flat roofs), the cap may be 60–70%. Thatched properties are often capped at 75% LTV, partly due to higher insurance costs. The practical consequence is that you need a larger deposit to purchase or remortgage a non-standard construction property. If you are buying and are also a complex income borrower, a 75% LTV (25% deposit) is a useful planning target because it unlocks most specialist lenders who will consider both your income type and the construction. Going in at 80–85% LTV narrows your options further.
What surveys does a lender require for non-standard construction?
Most lenders will require at minimum a full structural survey (Building Survey, Level 3 under the current RICS framework) rather than a basic valuation or HomeBuyer Report (Level 2) for non-standard construction. Some lenders — particularly for designated concrete types — may require a specialist structural engineer's report in addition to the standard survey. For timber frame properties with concerns, a damp and timber report may be required. The cost of these additional surveys falls on the borrower and can run to £800–£2,000 depending on property size and the specialist required. It is worth factoring this into your purchase budget. If the survey uncovers structural problems, the lender may retain funds (stage release) until remediation is completed, or decline the application.
Can I remortgage a non-standard construction property?
Yes — remortgaging is possible, and the same lender panel that writes new purchase mortgages on non-standard construction will also remortgage. One important consideration: if the property was previously mortgaged with a mainstream lender who accepted it historically, that does not guarantee a new lender will accept it at remortgage. Non-standard construction mortgage criteria have tightened at many lenders over the past decade. It is therefore important to research your remortgage options before your current deal expires, ideally 6–9 months in advance. If you are remortgaging to release equity, the LTV cap also applies — you cannot remortgage above the lender's maximum LTV for non-standard construction, so the amount you can borrow is constrained by the property's value and the applicable LTV ceiling.
Does non-standard construction affect my mortgage insurance or buildings cover?
Yes — non-standard construction typically means higher buildings insurance costs, and some standard home insurance providers will decline cover entirely. Thatched properties, for example, face a very limited insurance market due to fire risk, and premiums are substantially higher. Concrete properties may attract higher premiums due to structural risk. Lenders require buildings insurance to be in place as a condition of the mortgage, so you need to evidence that you can obtain adequate cover before completion. If insurance is difficult or expensive to obtain, factor this into your ongoing affordability assessment — it forms part of the stress test lenders apply. Specialist property insurers, including those who focus on listed buildings, thatched properties, or unusual construction, are the best route for non-standard construction homes.
Risk warning
Your home may be repossessed if you do not keep up repayments on your mortgage. Non-standard construction properties can be harder to sell or remortgage — consider this carefully before purchasing.
Explore further