Published 2026-07-10 · New Build Mortgage Guide · Written and reviewed by Phillip Wakeling-Smith (CeMAP)

New-build down-valuations: what happens when the surveyor disagrees with the price

Quick answer: A down-valuation is the lender's surveyor deciding the property is worth less than you agreed to pay. New builds attract them more than any other property type because of the new-build premium. The lender then lends against the valuation, not the price — so the shortfall lands on you, unless you negotiate it away.

Why new builds get down-valued so often

A new home carries a premium over an identical two-year-old one — partly genuine (warranties, energy efficiency, zero chain), partly marketing. A valuer's job is to ask what the property would sell for tomorrow on the open market, and comparable sales on the second-hand market often don't support the developer's price list. Add in incentives (which the valuer must be told about via the Disclosure of Incentives Form) and the assessed value can come in below the headline price.

What a down-valuation does to your numbers

Say you agree £300,000 with a 10% deposit, and the valuation comes back at £285,000:

Your lender now lends 90% of £285,000 = £256,500 (not £270,000).
To complete at the agreed price you must find £43,500 — your planned £30,000 deposit plus the £13,500 gap.
Any percentage-based builder incentive is also remeasured against the lower figure, so a "5% contribution" shrinks too.

The higher your intended LTV, the more brutal this is — at 95% there is no slack at all, which is why down-valuations kill more high-LTV new-build purchases than declined applications do.

Your options, in the order to try them

Renegotiate the price. The valuation is leverage. Developers protect their headline price list fiercely (it reprices the whole site), but they will often bridge a gap with incentives instead — deposit contribution, paid stamp duty, upgrades — which can achieve the same completion arithmetic for you.
Challenge the valuation. Possible but rarely successful; you'll need genuinely comparable new-build sales the valuer missed, not enthusiasm.
Try a different lender. Valuations aren't transferable. Another lender's surveyor may take a different view — though panel overlap means it's often the same firm. A broker will know which lenders use which panels locally.
Fund the gap or walk away. If the developer won't move and a second opinion agrees, believe the valuers: overpaying at day one on a property type that already carries a premium is how negative equity happens.

Protecting yourself before you reserve

Reserve with a long-stop mindset: know your maximum cash before you fall in love with a plot.
Research second-hand prices on the same and neighbouring developments — that's what the valuer will look at.
If you're using an incentive, understand how it behaves under a down-valuation (see builder deposit contributions).
Watch the interaction with your lender's new-build LTV cap — a down-valuation can push you over a cap threshold and reprice the whole mortgage.

This article is information, not financial advice. Valuation practices vary by lender and location — a whole-of-market broker sees the local patterns.