Extend your PO20 with an extension

A flat roof extension is a great way to add extra space to your home without splashing out on the costs of a pitched roof extension. Often exempt from planning permission rules, you can build a flat roof extension up to 3 metres in height as long as it's not visible from a road. But how much do they cost in PO20?

Build a flat roof extension cost in PO20 - Sort by rates or availability

Main Construction

From £22,440

(last active 01/10/26)

Location

Worthing, BN12

Need to find an Extension Builder near you for all your extension buildering work?

Main Construction provides a local, trusted extension bu...

Whites Carpentry & Building

From £22,008

(last active 01/10/26)

Location

Chichester, PO19

Whites Carpentry & Building prides in delivering an excellent extension buildering service and value for money in PO20 and the surrounding areas. ...

R&B Property Improvements

From £23,096

(last active 01/10/26)

Location

Havant, PO9

We are a Small Family run business with over 30 years experience in the building trade, Carpentry is my main trade, with NVQ Level 2.

SBS Building Services

From £22,144

(last active 28/09/26)

Location

Gosport, PO12

We are a small family run business with over 20 years experience in brickwork, bathroom/kitchen fitting, roofing, landscaping, fencing, tiling and ...

H P Building Services Sussex

From £21,992

Member since August 2026

Location

Lancing, BN15

H P Building Services Sussex is a one-stop solution for all your extension buildering needs. Establish over 10 years ago and covering 20 miles arou...

Futureways Design and Build

From £22,112

(last active 19/09/26)

Location

, BN18

Futureways Design and Build are here to help customers who need an Extension Builder in PO20. We offer a competitive rate to complete all your exte...

Park Building Services Ltd

From £21,752

(last active 19/09/26)

Location

Havant, PO9

Park Building Services Ltd is a trusted extension builder serving customers in PO20 and the surrounding area. Contact us to today to get a competit...

Alan Pacy Builder

From £22,200

(last active 18/09/26)

Location

Worth, BN12

Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...

GD Project Management Ltd

From £22,376

(last active 18/09/26)

Location

West Sussex, GU29

Giles Dixon is an experienced Project Manager with over 30 years experience, having worked from the ground up starting in 1984 as an apprentice ele...

Regent Property Holdings Ltd

From £22,128

(last active 18/09/26)

Location

West Sussex, PO21

Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...

Flat roof extension cost in PO20

Estimates for build a flat roof extension near PO20

A flat roof extension ranges from the cheapest of £21,752 (Park Building Services Ltd based in PO9) to the dearest of £23,096 (R&B Property Improvements based in PO9), but these are just estimates. While they give you an idea of who will be better value, the best way to compare costs is to get real quotes. 

Find out how much your flat roof extension will cost in PO20 by posting a job with HaMuch. We'll send it to extension builders in PO20.


Get extension builder rates instantly

Get extension builder rates instantly (excluding VAT or callout charges)
Location in UKHourly RateDaily Rate
Build A Flat Roof Extension near Chichester£34£242
Build A Flat Roof Extension near Bognor Regis£35£247
Build A Flat Roof Extension near Arun£35£241
Build A Flat Roof Extension near Havant & Waterloo£35£248
Build A Flat Roof Extension near Havant£35£249
Build A Flat Roof Extension near Littlehampton£35£244
Build A Flat Roof Extension near Rustington£36£246
Build A Flat Roof Extension near Waterlooville£36£250
Build A Flat Roof Extension near Horndean£35£253
Build A Flat Roof Extension near Portsmouth£36£250

Estimates for common extension builder jobs in PO20;

Whether you’re looking to extend your kitchen with a side return extension or you want to convert your basement into a liveable space, read our cost guides to get an idea of how much each project costs before getting a more accurate quote from our database of reliable tradespeople.

Underpin a building

Underpin a building - £17,725

Two storey extension

Two storey extension - £88,337

Build a timber frame extension

Build a timber frame extension - £26,225

Build a swimming pool

Build a swimming pool - £81,225

Single storey extension

Single storey extension - £59,496

Side return extension

Side return extension - £44,029

Install an RSJ

Install an RSJ - £2,425

Outbuilding

Outbuilding - £10,225

Build a Mansard loft conversion

Build a Mansard loft conversion - £52,225

Loft conversion

Loft conversion - £35,858

Build a kitchen extension

Build a kitchen extension - £42,225

Hip to gable loft conversion

Hip to gable loft conversion - £42,225

Granny annexe

Granny annexe - £87,225

Garden office

Garden office - £10,225

Convert a Garage

Convert a Garage - £16,225

Garage

Garage - £18,725

Build a flat roof extension

Build a flat roof extension - £22,225

Build a dormer loft conversion

Build a dormer loft conversion - £42,225

Concrete foundations

Concrete foundations - £6,475

Convert a bungalow loft

Convert a bungalow loft - £29,225

Convert a basement

Convert a basement - £40,029

More extensions & conversions cost guides...