Part single, part two-storey extensions in Blaenau Ffestiniog

The basics for Blaenau Ffestiniog at a glance.

Postcode districts: LL41, LL47, LL48 and LL49
County / area: Gwynedd and Anglesey, Wales
Price region: Wales
Guide price: £66,000–£91,000 (£1,840–£2,530 per m²)
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: Bethesda (13.9 miles), Caernarfon (17.1 miles), Bangor (Gwynedd and Anglesey) (18 miles)
Distance to Bangor (Gwynedd and Anglesey): about 18 miles
First visit: Free, no obligation

About a part single, part two-storey extension

A part single, part two-storey extension is an extension where the ground floor is wider or deeper than the floor above, so only part of it rises to two storeys. It usually gives a large kitchen or living area with roof lights below and one bedroom or bathroom above. It is often a good way to add space while limiting the effect on neighbours.

We cover postcode districts LL41, LL47, LL48 and LL49 in and around Blaenau Ffestiniog, along with neighbouring Bethesda, Caernarfon and Bangor (Gwynedd and Anglesey).

What it costs in Blaenau Ffestiniog

Most of the cost of a part single, part two-storey extension is set by its size and specification. For Blaenau Ffestiniog and the rest of Wales, our guide is £1,840–£2,530 per m² including VAT, so about £66,000–£91,000 for a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total). Design fees, structural calculations and approval fees are separate and listed on our prices page.

Spec	Per m²	A 6 m × 4 m ground floor and a first floor over half of it (36 m² in total)
Essential	£1,690–£2,330 per m²	£61,000–£84,000
Standard	£1,840–£2,530 per m²	£66,000–£91,000
Premium	£2,210–£3,040 per m²	£79,500–£109,500

Planning and building regulations in Blaenau Ffestiniog

In Wales, a part two-storey rear extension can be permitted development if the first floor goes no more than 3 m and the ground floor no more than 4 m beyond the original rear wall, with the first floor at least 10.5 m from the rear boundary. Conservation areas and other protected areas are excluded. If the design falls outside these limits, a householder application costs £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 Blaenau Ffestiniog homes

Structure at the step

The first-floor wall above often sits over the new open-plan space, so it needs a steel beam or frame to carry it. Loads come down at different points than in a full two-storey design, and the engineer sizes the foundations to suit each part.

The roof junction

Where the single-storey roof meets the two-storey wall you need a sound weathering detail, usually a lead or similar flashing, and enough height for roof lights or a lantern. We set the roof falls and the upstairs window sill heights together so they do not clash.

How we'd run your project

Measure and listen
A visit to Blaenau Ffestiniog to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Drawings, then consent
We draw the scheme, check it against the rules in Wales, and take it through the right consent with the council.
Fixed price in writing
With approved drawings and calculations, we give you a fixed build price and a programme you can plan around.
Finish and certify
Second fix, plastering and making good, then building control's final inspection and the completion paperwork.

Questions about part single, part two-storey extensions in Blaenau Ffestiniog

Which postcodes do you cover around Blaenau Ffestiniog?

We cover Blaenau Ffestiniog (LL41, LL47, LL48 and LL49) and nearby places including Bethesda, Caernarfon and Bangor (Gwynedd and Anglesey), plus the rest of Gwynedd and Anglesey. The first site visit is free.

How much does a part single, part two-storey extension cost in Blaenau Ffestiniog?

Our guide for Wales, which covers Blaenau Ffestiniog, is £1,840–£2,530 per m² including VAT. A typical project with a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total) comes to about £66,000–£91,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Who handles building regulations for a project in Blaenau Ffestiniog?

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.

Can the single-storey part be deeper than the two-storey part?

With planning permission, yes, and that is often the point of the design: the ground floor projects further into the garden while the first floor stays back from neighbours. Under permitted development, the depth limits for extensions of more than one storey can apply to the whole extension, so we confirm which route applies before drawings are finalised.

Which side should the two-storey part go on?

Usually the side furthest from the nearest neighbour's windows, so the single-storey part sits nearest them and keeps their light. Other factors are where the stairs land upstairs, which room needs the extra space and where drains run. We sketch options at the design stage and explain which is most likely to be approved.

Nearby

Close to Blaenau Ffestiniog? We work across the area, including:

Other extensions in Blaenau Ffestiniog

All two-storey extension services in Blaenau Ffestiniog · Part single, part two-storey extensions across Gwynedd and Anglesey

Want a figure first? Try our guide price tool, then book a free visit to firm it up.