Extensions and garden rooms
Quick facts
Built within 90 minutes of Abergavenny. 27 Google reviews, all five stars. Correct at October 2026.
Because the frame becomes the room. The posts, braces and roof stay open above you, with as much glass as the design allows, and the room opens straight into the house.
Foxtail Oak designs and builds oak frame extensions and garden rooms within 90 minutes of our workshop near Abergavenny, and supplies frames cut and numbered anywhere in the UK. A finished extension costs £2,500 to £5,000 per m² of external footprint including VAT, designed and built, with the design and approvals in the price.
Mostly glass, built onto the house and opening onto the garden. Priced as an extension.
A room that works all year. Keeping a sound base can save £15,000 to £25,000.
Supplied, or supplied and raised with the glazing, for your own builder to finish. Quoted per job.
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£2,500 to £5,000 per m² of footprint including VAT, designed and built, depending on size and the roof.
The smaller the room, the higher the rate, because the design, the junction with the house and the glazing detail cost about the same whatever the size. Under 20 m² and over 60 m² are quoted per job. Correct at October 2026.
A 6 × 5 m lean-to room (30 m²), glass to the ground, finished and heated: about £103,000 including VAT (£85,900 + VAT), with the design, the drawings and the engineer. Paid to the council on top: the planning fee (£585 in Wales) and building control (£880 + VAT in Monmouthshire for 10 to 60 m²). Opening up into the house is priced on survey.
Within a band, the price moves with how much of the room is glass, the span, the ground, the junction with the house and the finishes you choose. Opening up and joining to the house, with the steels, lintels and making good inside, is our work on a design-and-build job but is priced on top of the rate.
Every figure includes VAT at 20%, because an extension to a house you already live in is standard-rated. Some firms quote without it, so check before you compare.
Every way of buying, and what the bands come to for real room sizes: How much does an oak frame extension cost?
Often, yes. An attached extension has its own permitted development limits, on depth, height and how close it is to a boundary, and a garden room standing on its own is judged under the outbuilding rules instead.
Designated land, a listed house and earlier extensions all change the answer. The oak makes no difference: planning looks at size, position, height and designation. An oak frame open to the roof is taller than a flat-roofed room of the same footprint, so near a boundary the eaves height is the limit to check first.
Building regulations are a separate question. A heated extension opened up to the house needs building regulations approval. We will tell you plainly what applies to yours at the first visit, rather than after you have paid for drawings. On a design-and-build job we prepare the planning application and building regulations drawings; they are in the price, and the council's own fees are paid direct. Even where a room is permitted development, we advise getting a Lawful Development Certificate. More detail: Do you need planning permission for an oak frame extension or garden room?
Neither. We build heated rooms open to the house, insulated walls, roof and floor, with the oak on show inside and glass where you want the garden.
A conservatory is usually a glass room kept separate from the house by an outside door and left off the house's heating, which is how it avoids the insulation an extension needs. An orangery is a style, usually brick or stone piers with a flat roof and a glazed lantern. Built heated and open to the house, it is an extension too.
We have replaced conservatories with oak rooms, at Ty Fry near Crickhowell and at Pontypool. How it works, what it costs and when the old base can stay: replacing a conservatory with an oak room.
If what you want is a separate, unheated sun room, a conservatory company will build it for less, and we will say so.
Yes, if it is designed as a heated room from the first sketch. The oak frame gives no insulation; the walls, roof, glass and heating around it do.
We build every extension with the frame inside the insulation, wrapped in our own insulated timber frame panels, then clad or rendered. No post breaks the insulation, and the oak is on show inside and through the glass.
Our standard glass is double glazed, argon-filled, with a low-emissivity coating, face-glazed to the outside of the frame so the frame can move behind it. On a south or west face we recommend solar control glass, which has to be chosen before the units are ordered. Opening windows are designed in from the start, because adding one to a finished frame means altering the frame.
A glazed room has little wall for a radiator, so the heating is planned with the design: underfloor heating, radiators, a stove or a mix.
Yes. The price covers the room, with its heating, electrics and plumbing; the kitchen itself is not in the price.
A kitchen that is too small is one of the two reasons people ring us about an extension most often. The other is wanting the light and the garden, and an oak frame answers that one best. The kitchen units, landscaping, loose furniture and blinds are yours to choose and buy.
Yes. Supply only is our kit: the frame cut, numbered and delivered anywhere in the UK, quoted per job.
There are three ways to buy, and the frame is the same in each. A glazed extension needs supply and install at least, because we never supply face glazing loose.
Quoted per job. The oak frame, the cut roof structure, the eaves and verge boards and the cladding boards, loose and over length, with the pegs and structural fixings. Our consulting engineer checks the frame, and it comes with assembly drawings. You or your builder raise it, build the base, roof it, glaze it, knock through and fit it out.
Quoted per job. We make the frame and raise it, build the roof structure, and fit the glazing and doors. Your builder does the base, the roof covering and gutters, the knock-through, the heating and electrics, and the finishes.
The banded rates above, with design and approvals included. We do all of it: the design, the planning application, the engineer, the foundations, the frame, the roof, the glazing, the heating, electrics and plumbing, and the finishes, through to a finished room.
| Designed and built | Supplied and installed | Supply only
Design, drawings and engineer | us | us | us
Planning application | us | extra | you (we'll advise)
Foundations, on ordinary ground | us | your builder | your builder
Deeper or piled foundations | your builder | your builder | your builder
Oak frame | us | us | us
Raising the frame | us | us | your builder
Roof structure | us | us | supplied, cut
Eaves, verge and cladding boards | us | us | supplied loose, over length
Roof covering, flashing and gutters | us | your builder | your builder
Glazing and doors | us | us | not supplied
Opening up and joining to the house | extra | your builder | your builder
Heating, electrics and plumbing | us | your builder | your builder
Floor finishes and decoration | us | your builder | your builder
Diverting existing services | your builder | your builder | your builder
Planning and building control fees | you | you | you
More detail: Supply only, supply and install, or design and build: which is right for you?
Whatever the room needs to do. We publish rates from 20 to 60 m², and quote smaller and larger rooms per job.
Measured to the outside of the frame. The first is our first extension, at Abergavenny. Under 20 m² and over 60 m² we quote per job, because the rate moves too much at those sizes to publish one figure.
Two storeys are less common, but we build them. Near Brecon, a two-storey extension on an old barn has a first-floor porch and a reading space. A second storey brings a structural floor, a stair, fire safety and a harder planning test, and what it adds is quoted per job.
A finished room on ordinary ground, from the foundations to the decoration, with one firm responsible for all of it.
We assume a new soakaway on every extension, because we would rather give you the worst-case price than a lower one followed by a bill.
A few of the rooms we have built. Each one has its own page, with the photographs and the story of the job.
Oak frame extension at Crickhowell: Crickhowell, Powys, 2022. Two metal-framed conservatories came off and one oak frame went on, with a canted bay to hold the view down the Usk valley. Designed and built.
Oak frame extension at Pontypool: Pontypool, Monmouthshire, 2023. A cold conservatory replaced with a smaller garden room that works all year, and a covered outdoor living area built into the same design.
Oak frame shop extension at Ewyas Harold: Ewyas Harold, Herefordshire, 2024. An extension across the front of the village store, which stayed open throughout, on a stone flood wall that was not straight. Supplied and installed.
Oak frame barn extension near Brecon: near Brecon, Powys, 2023. A two-storey extension on the front of an old barn, with a first-floor porch and a reading space that doubles as a spare bedroom. Designed and built.
More of our work: see every project.
The frame is raised in two to four days, and the whole build at your home, with all the trades, typically takes 8 to 12 weeks for an extension, groundwork included. You can stay at home throughout.
The extension is built outside the house and made weathertight before the wall between is opened, so the house is open to the new room for only a day or two. Those weeks are time at your home. Before them comes the wait for a place in our diary, counted from your deposit: 6 to 8 weeks for supply only, 8 to 10 weeks for supply and install, and 12 weeks for design and build. Planning, where the job needs it, is separate.
For centuries, because the frame sits inside a weather envelope. Exposed oak that is well detailed lasts about 50 years or more, and oak inside a weather envelope lasts centuries.
It cracks along the grain as it dries. It looks dramatic and does not weaken the frame, which is designed to move, with the glazing detailed so nothing binds. If you would rather the oak stayed still, air-dried or reclaimed oak is the alternative, and it costs more.
Very little inside. Oak indoors needs no treatment and darkens slowly with the light. The roof, the glazing seals and the gutters need looking after like any building's.
Nobody can give you a percentage, and we won't. A valuer counts floor area and quality, and an extension helps a sale when it is consented, well built and usable.
That is one more reason to settle planning and building regulations properly, and to keep the Lawful Development Certificate or the approvals with the house's papers.
We design and build within 90 minutes of Abergavenny. We supply and install within two and a half hours of Abergavenny, and elsewhere in the UK case by case. We supply frames cut and numbered to anywhere in the UK.
Standard foundations on ordinary ground are in the designed-and-built rate. Where the ground needs deeper or piled foundations, those are priced separately. We look at the ground on the design visit, before we quote.
Not so far. Every extension we have built has been done in oak, without steel in the frame. Past a certain span the timbers get bigger or the engineering gets heavier.
Yes, though most of ours are single-storey. What a second storey adds is quoted per job.
Yes, and on larger jobs we prefer it. We can come in at concept stage or take drawings that are already through planning.
Extensions and garden rooms so far, within about 90 minutes of Abergavenny:
WHAT HAPPENS NEXT
Tell us what you have in mind and where it's going. The first step is a phone or video call with Josh, using your photos. If it looks right for both of us, we come to you for a design visit, and a detailed quotation follows.
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Choose the size and finish in our price calculator and see the range at each way of buying, including VAT.
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