Builders in Horsham
Many Horsham homeowners reach the point where the house needs more room but moving is not the answer. We can put you in touch with up to 3 checked local builders for free, no obligation quotes on extensions, lofts, garage conversions and renovations.
Choosing the right project for your Horsham home
Horsham combines an old market town centre with Victorian and Edwardian streets, inter-war and post-war semi detached houses and large modern estates on its edges. That variety means there is rarely one obvious answer to the question of how to add space. A family semi with a long garden may suit a single storey rear extension, while a detached house on a wider plot could take a two storey side or rear addition.
A loft conversion keeps the garden intact and can add a bedroom and bathroom, provided there is enough head height under the roof. A garage conversion is usually the smallest project of the four and can create a study, playroom or extra bedroom. It is worth asking a builder or designer to look at more than one option before you settle on a scheme, because the best choice depends on the house as much as the budget.
Single and two storey extension costs
No source gives prices for Horsham specifically, but Less.co.uk publishes a South East figure for a mid range single storey extension of £1,900 to £2,900 per m², which excludes VAT, professional fees and interior fit out. For two storey work, the Federation of Master Builders says costs typically range from £1,000 to £2,500 per square metre. MyJobQuote gives the following totals for two storey extensions of different sizes.
| Size | Average cost | Source |
|---|---|---|
| Small, 20m² total | £35,000 | MyJobQuote |
| Medium, 40m² total | £56,000 | MyJobQuote |
| Large, 70m² total | £82,000 | MyJobQuote |
MyJobQuote says a two storey extension costs 50% to 75% more than a single storey extension of the same size, and that South East prices run 10% to 25% above the UK average. These are national guide figures and quotes vary with the design, ground conditions and finish. Our two storey extension cost guide goes into more detail.
Planning rules for two storey extensions
Two storey extensions face tighter permitted development limits than single storey ones. The Planning Portal says an extension of more than one storey must not extend beyond the rear wall of the original house by more than three metres, nor be within seven metres of any boundary opposite the rear wall. It also says all side extensions of more than one storey require householder planning permission.
GOV.UK sets the householder planning fee for a single dwellinghouse at £548 from 1 April 2026. Parts of Horsham's town centre are conservation areas, and some older buildings in the town and surrounding villages are listed, so check with Horsham District Council before you plan any work to an older property. Permitted development rights do not apply to flats or maisonettes, and the council may have removed them on some estates through a planning condition or an Article 4 Direction.
Party wall notices for semis and terraces
If your extension involves work to a shared wall or digging foundations close to a neighbour's house, the Party Wall etc. Act 1996 is likely to apply. GOV.UK says notice must be given at least two months before work to an existing party wall and at least one month before excavating near neighbouring buildings. A notice is only valid for a year, so serve it neither too early nor too late.
The Act is separate from planning and building regulations, and having either approval does not remove the need to follow it. Homebuilding and Renovating puts party wall agreements at £1,500 to £3,000 per neighbour. Talking to your neighbours early usually makes the formal process smoother.
Building control in Horsham
Extensions and loft conversions need building regulations approval, which you can get from the council or from a private registered building control approver. Charges vary by council, so check the building control page of Horsham District Council for current figures, or ask a private approver for its own fee. GOV.UK says you will usually get a completion certificate within eight weeks of the work being finished, as long as it complies.
Questions to ask before you choose a builder
Comparing quotes is easier when every builder is pricing the same thing. Ask each one to work from the same drawings and specification, and use the questions below to understand the differences between them.
- Which items are included, and which are left for you to arrange, such as the kitchen, flooring or decoration?
- Who will deal with building control and arrange inspections?
- How will the work be programmed, and what happens if the ground conditions turn out to be worse than expected?
- How are payments staged, and what contingency do they suggest you hold back?
To get started, fill in the contact form or call 01273 115520. We will pass your details to up to 3 checked builders who cover Horsham, and there is no charge and no obligation.
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Frequently asked questions
How much does a two storey extension cost in Horsham?+
No source gives Horsham prices, but MyJobQuote puts the average two storey extension at £60,000 in the UK and says South East prices run 10% to 25% above the UK average. Your own cost will depend on size, design and finish, so compare several quotes.
Can I build a two storey extension without planning permission?+
Some rear extensions of more than one storey can be permitted development, within a three metre depth limit and seven metres from the rear boundary, according to the Planning Portal. All side extensions of more than one storey need householder planning permission. Check with Horsham District Council before you start.
Do I need a party wall agreement for my extension?+
If the work affects a shared wall or involves excavation near a neighbour's foundations, you must serve notice under the Party Wall etc. Act 1996. GOV.UK says the notice period is at least two months for work to a party wall and at least one month for excavation.
How long does a two storey extension take to build?+
MyJobQuote says a two storey extension can take up to 14 weeks, with larger schemes taking longest. Planning, design and building control approval add time before work starts, so allow for those stages in your plans.
Sources for the prices on this page
Prices are published UK averages and include labour. Every job is different, so the quotes you receive will reflect your own property, access and materials.
- Less.co.uk: House extension cost per m² in 2026, checked October 2026
- FMB: Two-storey extension costs, checked October 2026
- MyJobQuote: Double storey extension cost guide, checked October 2026
- Homebuilding and Renovating: How much does an extension cost in 2026?, checked October 2026
- GOV.UK: Fees for planning applications in England from 1 April 2026, checked October 2026
- Planning Portal: Extensions planning permission, checked October 2026
- GOV.UK: The Party Wall etc Act 1996 explanatory booklet, checked October 2026
- GOV.UK: Building regulations approval, checked October 2026
Compare up to 3 free quotes
Tell us about the job and up to 3 checked local builders will be in touch with quotes. There is no charge and no obligation. Or call 01273 115520.