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Harvey Sandhu
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Written by Harvey Sandhu, specialist mortgage adviser with over 40 years of experience. Berks & Bucks Finance . Updated 2026.
Can I remortgage a non-standard construction property?
Yes — you can. But some lenders specialise in certain construction types and others won’t touch them at all, which is why matching the right lender to your property matters more here than with a standard remortgage.
Non-standard construction includes buildings made from a variety of materials like concrete, timber, steel, thatch, or flat roofs, instead of traditional brick or block walls with tiled or slate pitched roofs. This covers a wide range of different building types.
Who this guide is for
- You have a non-standard construction property — concrete, PRC, steel frame, timber frame, thatch, or flat roof — and want to remortgage or switch rates
- Your current deal is ending and you're not sure whether to switch lender or stay
- You have a PRC certificate, or you're trying to find out whether you need one
- You want to know whether your specific construction type will be accepted by a new lender
Tell us your construction type and roughly how much equity you have, and we'll tell you which lenders are realistically open to your case.
No obligation. No jargon. I’ll tell you early if something isn’t possible
What You’ll Find on This Page
What is non-standard construction?
Non-standard construction is any property built from something other than the standard brick or block walls with a tiled or slate pitched roof that most lenders default to expecting. It covers a specific, named set of building methods; the following are some types of non-standard constructions.
Precast concrete (PRC) and in-situ concrete
Includes Airey, Reema, Unity, Cornish Unit, and Wimpey No-Fines, plus named bungalow variants such as Woolaway, Dorran, and Cornish Bungalow types built through the 1950s, 60s and 70s — Dorran is most associated with Scotland but is also found elsewhere in the UK. Most require a PRC certificate confirming approved structural repair before a lender will consider them.
Steel frame
Includes BISF (British Iron and Steel Federation) and Trusteel houses. Mortgageable, but the lender pool is restricted and condition matters more than age.
Timber frame
Modern timber frame built to current building regulations with a structural warranty is now largely treated as mainstream. Older timber frame, particularly pre-1980s, has a smaller lender pool.
Thatched roof
Accepted by a good number of lenders, but specialist buildings insurance is required, and the condition and age of the thatch affects both cover and lending.
Flat roof
A flat roof across the whole property — common on 1960s and 70s architect-designed homes — is classed as non-standard. A flat roof on a small extension usually isn’t.
Other types you may come across: ex-local authority high-rise and cladding-affected blocks, listed buildings, mundic properties (Cornwall and Devon), and rarer materials like cob or wattle and daub. These follow the same underlying logic — lender pool narrows, documentation matters — but are less commonly searched nationally.
Can I do a product transfer on a non-standard construction property?
Yes — a product transfer is available on a non-standard construction property, just as it is with any other mortgage.
The difference is how often it ends up being the outcome. If your current lender already holds your property as an accepted non-standard construction risk — a PRC certificate on file, for example — a product transfer usually goes through without a fresh valuation. Because the property is already secured with a lender who understands the construction type.
A new lender is still worth checking, particularly if their rate is better or they’ll lend more than your current lender will. It just means a new surveyor assessing the property fresh, so it’s worth confirming the new lender is genuinely comfortable with your construction type before you commit to an application.
Worked example — PRC/concrete property
Property type: Wimpey No-Fines semi-detached, PRC certificate on file
Current lender: aware of construction type, certificate on record
Product transfer: new rate secured, no fresh valuation required
New lender remortgage: fresh survey required — construction type may be re-assessed from scratch, regardless of the existing certificate
Either way, this is something we handle for you. We search the market first for a lender who can offer a better rate or more borrowing than your current deal. If nothing outperforms what you already have, we arrange the product transfer instead — so you get a proper comparison either way, without having to do the searching yourself.
Tell us your construction type and we’ll compare a product transfer against a full remortgage for you.
Can a new lender decline my non-standard construction property on remortgage?
Yes — this is one of the most common reasons a non-standard construction remortgage falls through. Every lender sets its own criteria for which construction types it will accept, and those criteria change over time.
A property that was acceptable to one lender 5 years ago may not meet a different lender’s current policy — or even that same lender’s policy today.
The decline usually happens at survey stage, after you’ve already committed time and, in some cases, a valuation fee. This is exactly why lender selection has to happen before an application is submitted, not after.
We check construction-type acceptance with the lender before you apply, not after — so you’re not the one finding out at survey stage.
Do I need a PRC certificate to remortgage a concrete or PRC property?
In most cases, yes. Precast reinforced concrete properties — including Airey, Reema, Unity, Cornish Unit, Woolaway, and Dorran — were built quickly after the Second World War, and many were later designated defective under the Housing Defects Act 1984.
A PRC certificate confirms the property has undergone an approved structural repair scheme. Without one, most mainstream lenders will not lend, and the specialist lenders who will typically require a much larger deposit and charge a higher rate.
Important
A PRC certificate is not a lender guarantee. It confirms an approved repair scheme was carried out, but each lender still applies its own criteria on top of that certificate.
If you have a PRC certificate, keep the original documentation ready — it’s often the single document that determines which lenders will even consider your case.
Can my non-standard construction property be down-valued when I remortgage?
Yes, and it’s a genuine risk specific to non-standard construction. A surveyor working for a new lender may value your property below your expectation, or below the value your existing lender currently applies.
This pushes your loan-to-value into a higher band, which narrows your lender choice and can increase your rate.
This risk sits alongside the product transfer question above — it’s one of the main reasons staying with a lender who already values your property comfortably can be the safer option.
Ask us to check indicative valuations with lenders who have recent experience of your specific construction type before you commit to an application.
Does spray foam insulation affect my remortgage?
Yes, potentially — this is a newer issue that has become more significant since 2023. Surveyors now routinely flag open-cell and closed-cell spray foam insulation in lofts.
Some lenders decline the case outright. Others will proceed, but only after a specialist report confirms the roof timbers haven’t been affected by trapped moisture.
If your non-standard construction property also has spray foam insulation, this can compound the number of lenders willing to consider the case.
Tell us upfront if spray foam insulation has been fitted — it changes which lenders we approach first.
Do I need a specialist survey to remortgage a non-standard construction property?
Usually, yes. A standard mortgage valuation is not the same as a full survey.
For non-standard construction, most lenders and brokers recommend a Level 3 building survey, which looks in detail at the construction method, condition, and any defects — well beyond what a valuation or a Level 2 HomeBuyer Report covers.
Budget for a Level 3 survey before you apply — it’s a cost worth incurring upfront rather than finding a problem at the point of application.
What are the most common mistakes people make?
Most problems in a non-standard construction remortgage come from assuming rather than checking. Both are avoidable.
- Assuming a new lender will accept the property because the current lender does
- Not knowing whether a PRC certificate exists, or where it is
- Applying to a new lender before checking construction-type acceptance
- Ignoring spray foam insulation when it’s been fitted
- Skipping a Level 3 survey to save cost, then finding a problem after committing to an application
Ready to check your non-standard construction remortgage options?
Whether the right route is a product transfer or a full remortgage, the decision comes down to your construction type, your certificate history, and your current lender.
We check the market for you, confirm which lenders realistically accept your construction type, and arrange the product transfer instead if nothing outperforms your current deal.
Tell us your construction type and we’ll tell you exactly what is available.
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Frequently Asked Questions About Remortgage for Non-standard Construction Remortgage
Does non-standard construction mean I need a bigger deposit or pay a higher rate?
Not all the time. Some non-standard construction properties may need a larger deposit than a standard brick-built home, and rates can be higher because fewer lenders compete for the business. The exact impact depends on the specific construction type and its condition.
Can I remortgage a thatched, flat roof, or timber frame property?
Yes. The lender choice is narrower than for standard construction. Thatched properties need specialist buildings insurance. Flat roof properties are assessed on the condition of the roof membrane. Modern timber frame is now widely accepted; older timber frame has a smaller lender pool.
What documents will I need to remortgage a non-standard construction property?
A PRC certificate if applicable, evidence of any structural repair or remediation work, recent survey or valuation reports if you have them, and details of the exact construction system if known — for example, Airey, Reema, or Dorran.
What is a Dorran, Woolaway, or Cornish Unit bungalow?
These are named precast concrete bungalow systems built mainly through the 1940s, 60s, and 70s. Dorran is most associated with Scotland but is also found elsewhere in the UK. All three can be designated defective without an approved repair certificate.
Can I remortgage an ex-council non-standard construction property?
Yes. Many ex-council properties from the 1960s and 70s use system-built construction methods that are treated as non-standard. The same rules on certification and lender acceptance apply as for any other non-standard construction property.
Return to the Remortgage Guide
For a full overview of remortgaging options and other common situations, see the main Remortgage Hub.
How Much Can I Borrow When Remortgaging — understanding equity, LTV, and affordability
Bad Credit Remortgages — options where your credit history is complicated
All mortgage products are subject to lender criteria, status, and affordability. Rates and product availability are subject to change. This page is for information only and does not constitute mortgage advice. Berks & Bucks Finance is FCA-regulated. Your home may be repossessed if you do not keep up repayments on your mortgage.