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Guide

Does a garage conversion add value?

Usually, yes. Here is what it can add where you live, exactly how we worked it out, and when it adds less.

Published October 2026 · Researched and checked by Ben Criddle

The short answer

Usually, yes.

Turning a single garage into a signed-off room you live in can add about £28,000 to £39,000 to a typical semi-detached house in Solihull. That is roughly 8% to 11% of its value.

It adds most when the new room becomes an extra bedroom. To count with buyers and lenders, it needs a building control completion certificate.

What a garage conversion can add near you

Our estimates for a single garage turned into a signed-off room, by area and type of house.

Can add about, for a signed-off extra room in a single garage. Estimates from August 2026 house prices (UK House Price Index, published 21 October 2026). Not measured sale prices. The method is below.

How we worked it out

No published study measures the sale prices of converted garages. So we built an estimate from official data in two ways, and show the range between them.

Way 1: the extra bedroom

Nationwide studied what adds value to a home. A fourth bedroom on a three-bedroom house added 10% to a terraced house, 11% to a semi and 12% to a detached house. Most semis near us have three bedrooms, so a garage bedroom often makes a fourth.

For a Solihull semi, at an average £346,414, that is about £38,100. We do not use this way for detached homes, as most already have four bedrooms or more.

Way 2: the extra space

A single garage is about 15 square metres. A typical Solihull semi has 88 square metres, from energy certificate records, so the garage adds about 17% more space. We count half of that as value, about £29,500.

That halving comes from Nationwide too: its newer figures show that 10% more floor space adds about 5% to a price.

The range

The figures we show run from the lower of the two ways, rounded down, to the higher, rounded up. For a Solihull semi that is £28,000 to £39,000.

The limits. These are estimates, not sale prices of converted homes. They assume a proper, signed-off room, apply national percentages to local average prices, and do not count any effect of losing the garage itself. Average prices are updated monthly and move a little each time.

When does a garage conversion add less?

No completion certificate. Buyers and lenders see a room without sign-off as a risk and mark it down.
Streets where parking is hard to find. Which? notes that losing all covered parking can affect a home's appeal in some areas. Councils near us almost never see it as a problem: losing parking was the reason in 1 of 141 refusal letters we read.
A room that still feels like a garage. A step down, a cold floor or a blocked-up door that does not match the house all take value off.
Bigger detached homes. The room is a smaller part of the house, so it adds a smaller share, about 6%, though still a large sum.

What other studies say

Figures quoted online vary widely. Here is what the better-known ones are based on.

Nationwide, 202513%An extra double bedroom on a two-bedroom house. Measured from its own lending.
Nationwide, 20255%What 10% more floor space adds to a price. Measured from its own lending.
Checkatrade, 202510% to 20%What a well-done garage conversion could add. An estimate, no method given.
Estate agent, 202310%On a standard three-bed semi, an agent quoted by OnTheMarket. An opinion.

Our figures sit at the careful end of these: 6% to 11% of value, depending on the house.

Does a garage conversion add value? Your questions

Does a garage conversion devalue a house?

Rarely, when it is done well and signed off. It can put some buyers off on streets where parking is hard to find, or if the room still feels like a garage. A proper room with a completion certificate usually adds value.

Is a garage conversion worth it?

For most families, yes. You gain a room without moving house or building into the garden. A signed-off garage room can also add about 6% to 11% of a home's value near us. Whether it is worth it for you also depends on how much you will use the room.

Does a garage conversion add more value than an extension?

An extension usually adds more space, so it can add more value, but it costs more, takes longer and needs planning permission more often. A garage conversion uses walls and a roof you already have.

Do I need a completion certificate for the value to count?

Yes. Buyers and lenders treat a room without building control sign-off as a risk and mark it down. Our figures assume the room is signed off. Building regulations explained.

Does converting a double garage add more value?

Our figures are for a single garage, about 15 square metres. A double garage gives more room, often enough for two rooms, so it can add more. Tell us about yours and we will talk it through.

How much does a garage conversion cost?

Prices for every room and garage type are on our cost page, including VAT, with a calculator for your own garage. Garage conversion prices.