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House extensions

More space without moving house, built by one team from the foundations to the last coat of paint, for one fixed price.

Contract range
£60k – £250k
Typical programme
12 – 24 weeks
House extension image

In short

A house extension adds new floor space to an existing home, usually to the rear or side, as one or two storeys joined to the original building.


FF Construction builds rear, side and wraparound extensions across Oxfordshire and the Thames Valley, from £60,000 to £250,000. We check whether your extension falls under permitted development or needs planning. We handle building control and party wall notices, and we fix the price before any ground is broken.

Scope

What does an extension include?

Everything from the first measured survey to the end of the defects period, under one contract.

  • Measured survey and planning or permitted development drawings
  • Structural engineer's calculations and steel design
  • Building control submission and inspections
  • Party wall notices, served early so they don't hold up the start
  • Foundations, drainage diversions and groundworks
  • Opening up the existing house, with steels and knock-throughs
  • Roofing, glazing, rooflights and bi-fold or sliding doors
  • Electrics, heating, plastering and all internal finishes

Choosing

Single storey vs double storey

The difference is mostly cost per square metre. The foundations and roof are the expensive parts, so a second storey adds a lot of space for proportionally less money.

A single storey suits a bigger kitchen, dining or living space opening onto the garden. A double storey suits anyone who also needs another bedroom or bathroom, and it avoids having to extend again in a few years.

Option A

Single storey

  • Often possible under permitted development
  • Shorter programme, less disruption upstairs
  • Rooflights and lantern roofs bring in daylight
  • Lower total cost
  • Ideal for kitchen and living space

Option B

Double storey

  • Almost always needs full planning permission
  • Adds bedrooms and bathrooms as well as living space
  • Lower cost per square metre
  • Upstairs is opened up during the works
  • Longer programme, typically four to eight weeks more

Process

Five stages, one appointment

You only pay once you have a fixed price and decide to go ahead.

  1. Site visit and budget range

    Free, about an hour. We look at the house, the garden access and what you want the space to do, and we give you an honest budget range. Drawings and approvals. We produce the drawings, confirm whether you need planning, and submit to the council and building control. Party wall notices go out at the same time.

  2. Fixed price

    A written price against the approved drawings and an agreed specification. It doesn't move unless you change what you asked for.

  3. Build

    Groundworks, shell, roof and glazing, then the knock-through into the house once the new space is weathertight. A named site manager is on site throughout.

  4. Handover

    The building control completion certificate, electrical certificates and warranties on the day, and return visits at three and twelve months.

Related projects

More of our work

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FAQS

Extension questions

Anything not covered here, ask on the site visit.

Other services

Start your project

Get a price for your extension

Tell us what you have in mind. We'll walk the house, tell you whether it needs planning, and give you a budget range and a realistic start date.

Or call 07999 962212, Monday to Friday, 7am to 5pm; Saturday, By arrangement; Sunday, Closed.