New build mortgages
New build purchases run on the developer's timetable, not yours. Short exchange deadlines and long build programmes pull in opposite directions, and the mortgage offer sits awkwardly between them. Getting the timing right matters more here than on any other type of purchase.
The problem nobody warns you about
A mortgage offer has a shelf life. A new build can take many months to complete after you exchange. Those two facts collide, and the result is the single most common problem on new build purchases: the offer expires before the property is finished, and the case has to be re-underwritten.
Re-underwriting is not a formality. Your circumstances are reassessed against criteria that may have changed, at rates that will certainly have changed. For a contractor, it also means your income gets read again — potentially by a process that reads it worse than the one that produced your original offer. Choosing a lender with a longer offer validity is therefore not a detail; on a new build it can be the most important criterion after the rate.
Exchange deadlines and what they really mean
Developers commonly require exchange within a short window of reserving — often around a month. That is a genuinely tight timetable for a full mortgage application, valuation and legal work, and it is where contractor cases stall if the paperwork is not ready.
The practical answer is preparation rather than speed. Have your documents assembled before you reserve, and get an Agreement in Principle from a lender that already understands contract income — not from whoever is quickest. Losing a reservation fee because an application went to the wrong lender is an expensive way to learn that.
Valuations, incentives and the price you actually paid
Developers often offer incentives — a deposit contribution, stamp duty paid, carpets and appliances included. Lenders treat these carefully, because an incentive effectively reduces the price you paid while the headline figure stays the same. Many will limit the total incentive as a proportion of the purchase price, and will lend against the net figure.
Separately, new build valuations sometimes come in below the asking price, because the premium a developer charges for a brand new property is not always recognised by a surveyor. That gap has to be covered in cash. Neither issue is a reason to avoid new build, but both should be understood before you commit rather than discovered at valuation.
Warranties and why lenders ask
Nearly all mainstream lenders require a recognised structural warranty on a new build — the well-known providers plus a small number of alternatives, typically covering ten years. Without one, the pool of lenders narrows sharply, and on a conversion or a small development that is worth confirming early.
It is a straightforward question to ask the developer at reservation stage: which warranty provider, and is it on lenders' accepted lists. A property with an unrecognised warranty is not unmortgageable, but it becomes a specialist case, which changes both the timetable and the pricing.
New build, answered
How long is a mortgage offer valid on a new build?+
It varies by lender and is one of the main reasons to choose carefully on a new build. Standard offers may not cover a long build programme, and some lenders offer extended validity specifically for new build purchases. Where the build will run beyond your offer, establish the extension process before you exchange rather than after.
What happens if my offer expires before completion?+
The lender re-underwrites the case, reassessing your circumstances against its current criteria and offering its current rates. That can go smoothly, but it is a genuine reassessment rather than a rubber stamp — which is why offer validity is worth weighing alongside the rate when choosing a lender for a new build.
Do developer incentives affect what I can borrow?+
They can. Lenders generally cap the total incentive as a percentage of the purchase price and may lend against the price net of incentives rather than the headline figure. Declare them all — incentives discovered later in the legal process cause delays at exactly the point a developer deadline is closing in.
Are new build valuations a problem?+
Sometimes. A surveyor values the property on comparable evidence, which on a new development can be limited, and the premium attached to a brand new home is not always fully reflected. Where the valuation comes in below the agreed price, the shortfall has to be covered in cash, so it is worth having some headroom in your budget.