A single-storey extension is a new ground-floor room built onto your house, usually at the rear or side, with its own foundations, walls and roof, creating a bigger kitchen, living space or bedroom without moving home.
In Gwynedd, we price a single-storey extension against our guide for Wales, £32,000–£69,000 including VAT, then adjust it once we have surveyed your home. We work across Bangor, Gwynedd, Llandudno, Holyhead and Caernarfon and the rest of the county or region. Planning and building control requirements follow the rules for Wales, and we look into your property's position before a written quote is sent.
- Guide price
- £32,000–£69,000 inc VAT
- Time on site
- 10–16 weeks on site
- Planning rules
- Wales
- Price level
- About 8% below the national guide
- Towns listed
- 4
- Survey
- Free, with a written quote
Single-storey extensions prices in Gwynedd
The costs listed here are typical for a single-storey extension around Gwynedd and include VAT. They reflect labour and material costs in Wales, about 8% below the national guide, giving a range of £32,000–£69,000. Exact pricing depends on your home, so we only fix it once a free site survey is done.
| Type of job | What it usually involves | Guide in Gwynedd |
|---|---|---|
| Small extension (8–12m²) | A modest rear or side extension, such as a utility room or a slightly larger kitchen. | £20,000–£37,000 |
| Typical rear extension (15–25m²) | A kitchen-diner or family room with bifold doors and a rooflight or lantern. | £32,000–£69,000 |
| Large or wrap-around (30m² plus) | A wrap-around or wide rear extension, often with structural steelwork into the house. | £64,000–£120,000 |
The main things that change the figure:
- Floor area, shape and number of corners
- Roof type, rooflights, lanterns and the amount of glazing
- Ground conditions, foundation depth and drains to divert
- Finishes, kitchen, flooring and heating specification
What do you get?
- Groundworks, foundations and below-ground drainage
- Flat or pitched roof, with rooflights or a lantern if specified
- Steel beams to open into the existing house
- Electrics and plumbing by qualified trades, with certificates
- Windows and external doors, including bifolds if chosen
- Plastering, screed floor and internal doors
Housing across Gwynedd
Slate defines much of Gwynedd, from quarrying villages such as Bethesda and Blaenau Ffestiniog with their stone terraces to slate roofs across the county. Bangor and Caernarfon have Victorian and Georgian streets, Anglesey has stone cottages and bungalows, and resorts such as Pwllheli and Barmouth have Victorian terraces and newer bungalows.
Stone and slate homes need breathable lime render and pointing, and slate roofs often need careful repair rather than replacement. Terraces suit loft conversions, and bungalows commonly take extensions and window upgrades.
Eryri (Snowdonia) is among the wettest areas in the UK, and exposed coasts take strong wind and salt, so render and roof details need to be robust.
Planning and building rules in Gwynedd
England, Wales, Scotland and Northern Ireland each handle planning a little differently. Gwynedd comes under Wales, covered below, and we raise any questions with the council before your quote is finalised.
In Wales, permitted development allows many single-storey rear extensions, with depth and height limits that depend on the type of house and how close the extension comes to your boundaries. Side extensions, listed buildings, conservation areas and flats usually need planning permission.
Building Regulations in Wales apply to extensions, from foundations to insulation and fire safety. The Party Wall etc. Act 1996 applies in Wales as it does in England.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
The four stages
A visit to your home
First, someone visits your home in Gwynedd to see the space, take measurements and note anything that could affect the work, such as access or the condition of what is there. There is no charge for this visit.
Quote in writing
You get the price in writing, itemised so you can see where the money goes. As long as the specification stays the same, that is the price you pay for a single-storey extension.
Dates and permissions
We handle the paperwork side: checking whether planning permission or building control approval is needed, submitting applications where they are, and scheduling the trades and materials around your dates.
The work itself
On site, the agreed plan is followed and any change is put in writing first. At completion we do a final clean, go through the snagging list with you and leave you with the relevant documents.
What you can expect from us
Questions about a single-storey extension in Gwynedd
How much will a single-storey extension cost in Gwynedd?
As a guide, expect to pay £32,000–£69,000 including VAT for a single-storey extension in Gwynedd. That range is adjusted for Wales, which runs about 8% below the national guide. Where your project lands depends on size, materials, access and the condition of what is already there. We confirm a fixed price in writing after a free survey of your home.
How long does a single-storey extension take to build?
A single-storey extension usually takes 10–16 weeks on site, from digging foundations to final plastering. Bad weather, deep foundations or a complex roof can add time. Before work starts, allow several weeks for drawings, structural calculations and building control approval, and longer if planning permission is needed. We give you a stage-by-stage programme with your quote so you know what happens each week.
How long will a single-storey extension take?
On a typical home, allow 10–16 weeks on site. Larger projects, older buildings and extra work found once things are opened up can extend that, while simpler jobs may be shorter. Your quote includes an estimate of time on site, and your point of contact keeps you updated on the programme as the work progresses.
What does a typical extension build look like week by week?
A typical single-storey extension follows the same order: clearing the site and digging foundations, building walls up to roof level, then fitting the roof and windows to make it weathertight. Electrics, plumbing, insulation and plastering follow. The last stage is opening into the house, laying the screed and fitting doors and finishes. Building control inspects at key stages, and we book those visits for you.
How much does a single-storey extension cost?
A typical single-storey rear extension of 15–25m² costs £32,000–£69,000, built to a plastered finish ready for your kitchen and decoration. As a guide, allow roughly £1,600–£2,800 per square metre plus fixed costs for groundworks, steelwork and fees. Smaller extensions cost more per square metre. The kitchen, flooring and large glazed doors are usually the biggest extras. We confirm a fixed price for the agreed specification after the survey.
Towns in Gwynedd
Find your town below. Every place listed in Gwynedd is covered for a single-storey extension, with the same survey, written quote and fixed-price process.