New Build Mortgages: What You Need to Know Before You Buy

Why new build mortgages are different

Buying a new build property — whether a recently completed home or an off-plan purchase — involves a set of mortgage-specific challenges that simply do not exist with standard second-hand purchases. Lenders treat new builds differently: they apply more conservative valuations, restrict maximum loan-to-value ratios, and impose specific policies around builder incentives and mortgage offer validity.

Understanding these differences before you commit to a reservation or exchange is essential. We have seen buyers lose reservation deposits because they approached a mortgage too late, or find their offer expires during a lengthy construction delay. With the right preparation and broker, all of these risks are manageable — but only if you know about them in advance.

Mortgage offer expiry: the number one new build risk

Standard mortgage offers are valid for 6 months from the date of issue. For most second-hand property purchases this is ample time. For new build purchases — particularly off-plan developments — completion can be 12–24 months after exchange of contracts. This creates a critical mismatch.

When a mortgage offer expires before completion, you need to apply for an extension (most lenders offer at least one free 3-month extension) or, if the delay is significant, reapply for the mortgage entirely. Reapplying is not ideal — your circumstances may have changed, rates may have risen, and the process adds weeks of uncertainty to an already complex purchase.

The solution is two-fold: choose a lender with the longest possible offer validity from the outset (some specialist new build lenders offer 9–12 month initial validity), and work with a broker who monitors your completion timeline and requests extensions proactively — before the offer actually expires.

Builder incentives: what lenders allow and what they do not

Developers regularly offer cashback, stamp duty contributions, upgraded specifications, or discounted parking to attract buyers. These incentives are not free money — lenders require them to be disclosed and apply specific restrictions.

The standard lender policy is that builder incentives above 5% of the purchase price must be deducted from the valuation figure. So if a developer offers £20,000 cashback on a £400,000 property (5%), and the independent valuation already comes in at £400,000, the lender reduces the effective property value to £380,000 for LTV calculation purposes — meaning you need a larger deposit to maintain the same LTV.

Using builder incentives to artificially inflate your deposit (claiming them as your own funds) is mortgage fraud. All incentives must be disclosed on the mortgage application. We help you declare incentives correctly and identify which lenders apply the most favourable treatment within regulatory requirements.

Leasehold new builds: what to watch out for

New build flats are almost always leasehold. In recent years, the government and lenders have both clamped down on leasehold practices that make properties difficult to mortgage or sell — particularly onerous ground rent clauses.

Lenders will not offer mortgages on properties with ground rent that increases above the Retail Price Index, exceeds 0.1% of the property value per year, or is reviewed more frequently than every 25 years. Some lenders refuse to lend on any leasehold property with a ground rent above peppercorn (essentially zero). Always have your solicitor scrutinise the lease before you exchange.

Also check the lease length. For a new build, this is typically 125–250 years — well within mortgage requirements. However, it is worth confirming, as short leases (below 85 years) require specialist lenders and are difficult to resell.