Extra bedroom and en-suite extensions in Caernarfon
We plan and build extra bedroom and en-suite extensions for homeowners in Caernarfon and nearby. Every project starts with a free visit and a design stage priced in writing before any work begins.
The basics for Caernarfon at a glance.
- Postcode districts
- LL54, LL55 and LL61
- County / area
- Gwynedd and Anglesey, Wales
- Price region
- Wales
- Guide price
- £51,500–£69,500 (£1,840–£2,480 per m²), plus £5,500–£11,000 for the en-suite
- Approval route
- It may be permitted development if the ground floor goes no more than 4 m and the first floor no more than 3 m beyond the original rear wall, with the first floor 10.5 m from the rear boundary.
- Nearest towns
- Menai Bridge (7.3 miles), Llangefni (8.1 miles), Bangor (Gwynedd and Anglesey) (8.3 miles)
- Distance to Bangor (Gwynedd and Anglesey)
- about 8.3 miles
- First visit
- Free, no obligation
About an extra bedroom and en-suite extension
This service suits you if you need another bedroom, or want a main bedroom with its own bathroom, without converting the loft or moving. You get a first-floor layout that connects well to your landing, an en-suite designed for plumbing and ventilation, a useful room downstairs, the approvals your nation needs and the build, managed by us and carried out by vetted teams working under S&K.
We cover postcode districts LL54, LL55 and LL61 in and around Caernarfon, along with neighbouring Menai Bridge, Llangefni and Bangor (Gwynedd and Anglesey).
What it costs in Caernarfon
In Wales, which includes Caernarfon, we'd expect an extra bedroom and en-suite extension to cost around £51,500–£69,500 (plus £5,500–£11,000 for the en-suite) for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space), or £1,840–£2,480 per m² including VAT. Keep a contingency of around 10% for things nobody can see until the ground is opened up.
| Spec | Per m² | A 4 m × 3.5 m footprint on two floors (28 m² of new floor space) |
|---|---|---|
| Essential | £1,690–£2,290 per m² | £47,500–£64,000 |
| Standard | £1,840–£2,480 per m² | £51,500–£69,500 |
| Premium | £2,210–£2,980 per m² | £62,000–£83,500 |
Planning and building regulations in Caernarfon
In Wales, an extra bedroom at the rear can be permitted development if the first floor goes no more than 3 m beyond the original rear wall and stays 10.5 m from the rear boundary. A two-storey side extension can also qualify if it is 10.5 m from the side boundary, set back 1 m and adds no more than 50% width. Otherwise the fee is £585.
Approval in Wales: Householder planning application: £585. Councils normally decide householder applications within 8 weeks.
Building regulations: Building regulations approval under the Welsh Approved Documents, which differ from England's in places (notably energy efficiency).
Design points for Caernarfon homes
Connecting to the landing
The new bedroom must be reached from the existing landing, usually through a new opening in the outside wall or by taking part of an existing bedroom as a corridor. We look at the stairs and landing first, because a poor connection can waste much of the new space.
Sound and privacy
Bedrooms above a kitchen or family room benefit from an insulated floor to reduce noise. Side-facing upstairs windows usually have to be obscure-glazed, so we place the main bedroom window to the rear and the en-suite window to the side where possible.
How we'd run your project
Free site visit
We visit your home in Caernarfon, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
Get it approved
Once you're happy with the design we submit it to the council for Caernarfon and deal with any questions from the planning officer.
Structure and building control
A structural engineer sizes the foundations and steels, and we get building regulations approval before work starts.
Finish and certify
Second fix, plastering and making good, then building control's final inspection and the completion paperwork.
Questions about extra bedroom and en-suite extensions in Caernarfon
Who handles building regulations for a project in Caernarfon?
We handle it as part of the project. What's needed in Wales: building regulations approval under the Welsh Approved Documents, which differ from England's in places (notably energy efficiency). We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.
Which postcodes do you cover around Caernarfon?
We cover Caernarfon (LL54, LL55 and LL61) and nearby places including Menai Bridge, Llangefni and Bangor (Gwynedd and Anglesey), plus the rest of Gwynedd and Anglesey. The first site visit is free.
How much does an extra bedroom and en-suite extension cost in Caernarfon?
Our guide for Wales, which covers Caernarfon, is £1,840–£2,480 per m² including VAT. A typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £51,500–£69,500 (plus £5,500–£11,000 for the en-suite). Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
How big should a new double bedroom be?
There is no legal minimum size for a bedroom in a house you own, so the test is whether it works. A comfortable double needs room for the bed with space to walk round it, wardrobes and a door that opens freely. We draw furniture on the plans so you can judge the space before anything is built.
Does an extra bedroom add value to my house?
It usually does, though not always by the full cost. Nationwide's 2025 research found that adding a double bedroom to a two-bed house was linked to about 13% higher value, and a double bedroom and bathroom on a three-bed, one-bathroom house up to 24%. Local ceiling prices still apply.
Nearby
The same service in neighbouring towns:
Other extensions in Caernarfon
All two-storey extension services in Caernarfon · Extra bedroom and en-suite extensions across Gwynedd and Anglesey
Book a free site visit in Caernarfon and we'll tell you what's possible, what approvals you need and what the design stage would cost.