What is the cheapest way to borrow money for an extension?

For most homeowners a further advance from your existing mortgage lender is the cheapest secured route, because you avoid the costs and timing constraints of a full remortgage while borrowing against the same security. It usually undercuts a second-charge loan, which in turn undercuts a personal loan.

Can I remortgage to pay for an extension?

Yes. A remortgage capital raise moves your whole mortgage to a new, larger product and releases the difference as cash for the build. It makes most sense when your existing deal is ending soon or when rates have fallen enough to outweigh any early repayment charge.

Should I use a personal loan or a secured loan for an extension?

Personal loans are unsecured and fast but cap out at around the low-five-figure mark, so they suit finishes and tail-end work rather than a whole build. Larger scopes are usually cheaper on a secured route against the house, such as a further advance or remortgage.

Is bridging finance a good way to fund an extension?

No. Bridging and development finance are short-term, high-cost products designed for property traders, not homeowners extending the house they live in. If a broker steers you towards bridging for a standard extension, walk away.

What is Section 75 protection and how does it help with an extension?

Section 75 makes a credit card provider jointly liable when you pay for goods or services on the card, covering deposits if a supplier fails to deliver. Paying deposits by card and settling the balance in full each month gives you that protection at no interest cost.

How long does it take to get extension financing in place?

A full remortgage typically runs around one to two months end to end, while a second-charge loan is faster and cash is immediate. Lenders run a full affordability stress test on secured borrowing, so the route should be arranged in parallel with your build planning, not the week before work starts.

Back to Kitchen Extension

Phase 1 · Planning & Permissions · Task 15 of 17

Financing Your Extension: The Real Options for Homeowners

How to pay for a UK extension. Further advance vs remortgage vs second-charge vs personal loan, MCOB stress test, Section 75 deposit protection, and the products to avoid.

20 min readUpdated 2026Free with email

Process infographic comparing the five main UK extension funding routes across speed to draw down, indicative rate band, secured vs unsecured, FCA protections, and the build size each route suits best

Prerequisites

Complete these first

The expensive mistake is choosing the route before you know the number. People spend weeks comparing 0.2 percentage points on personal loans before they've added up what the build actually costs, then discover halfway through groundwork that the personal loan they took maxes out at £25,000 and the steelwork alone is going to swallow most of it.

Get the contingency-inclusive total first. That sits in Budgeting for Your Extension, and applying the 15-20% rule there is not optional. Once you've got a real number, choose a route to fit it. Not the other way around.

What this guide covers

01The Five Routes That Actually Work
02Products to Avoid
03The FCA Stress Test (And Why It Matters to You)
04Comparing Total Cost, Not Just Rate
05Section 75: The Deposit Insurance You Almost Get For Free
06What Lenders Want To See
07The Completion Certificate Trap
08Green Mortgages: Read the Small Print
09VAT and Capital Gains
10The Risk-Stacking Trap
11Decision Summary

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