Two-storey extensions for end-of-terrace houses in Gwynedd and Anglesey

Gwynedd and Anglesey at a glance

Nation: Wales
Price region: Wales
Postcode areas: LL
Towns covered: 10 listed below, plus surrounding villages
Approval route: Can be permitted development in Wales if it is 10.5 m from the side boundary, set back 1 m from the front and doesn't widen the house by more than half; otherwise planning permission.
Site visits: Free, no obligation

What a two-storey extension for an end-of-terrace house involves

This service suits you if you own an end-of-terrace house with land to the side or a reasonable rear garden.

Across Gwynedd and Anglesey we cover Bangor (Gwynedd and Anglesey) (LL57), Holyhead (LL64), Caernarfon (LL54), Llangefni (LL60), Bethesda (LL57) and Pwllheli (LL51), plus the smaller places around them.

Guide price in Wales

Expect a two-storey extension for an end-of-terrace house in Gwynedd and Anglesey to land somewhere around £79,000–£106,500 for a 3 m × 7 m footprint on two floors (42 m² of new floor space). Our Wales guide rate is £1,890–£2,530 per m², including VAT. Steelwork for wide openings is the item most likely to move the figure; we'll know once the engineer has designed it.

Spec	Per m²	Typical project
Essential	£1,740–£2,330 per m²	£73,000–£98,000
Standard	£1,890–£2,530 per m²	£79,000–£106,500
Premium	£2,260–£3,040 per m²	£95,000–£127,500

Rules in Wales

In Wales, a two-storey side extension on an end-of-terrace house can be permitted development if it is at least 10.5 m from the boundary opposite the side wall, set back at least 1 m from the front and adds no more than 50% to the house's width. Narrow side plots and corner sites rarely meet this, so a householder application costing £585 is common.

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).

The Party Wall etc. Act 1996 applies in Wales, so notices may be needed for work on or near a shared wall or boundary.

Getting the design right

Continuing the terrace roof

A side extension on an end-of-terrace house usually continues the roofline of the row, so the pitch, eaves height and tiles must match. A small step down in the ridge and a set-back at the front often help the extension read as an addition rather than an extra house.

Older walls and foundations

Many terraces are older, with shallow footings and solid walls. Tying a new two-storey extension into them needs a careful structural design and sometimes movement joints, and we check the gable wall and its foundations before the design is fixed.

How we work in Gwynedd and Anglesey

Visit and first ideas
One of our team visits your house in Gwynedd and Anglesey, checks the walls, roof and drains, and sketches out options with you.
Drawings, then consent
We draw the scheme, check it against the rules in Wales, and take it through the right consent with the council.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Towns we cover in Gwynedd and Anglesey

Two-storey extensions for end-of-terrace houses in Gwynedd and Anglesey: questions

How much does a two-storey extension for an end-of-terrace house cost in Gwynedd and Anglesey?

In Wales our guide is £1,890–£2,530 per m² including VAT, so about £79,000–£106,500 for a 3 m × 7 m footprint on two floors (42 m² of new floor space). Essential and Premium specs move that by roughly 8% down or 20% up.

Can I build a two-storey side extension on a corner plot?

Often, but it needs planning permission and careful design. Councils protect the openness of corners and the view along the road, so they usually expect a gap to the pavement, a set-back from the front and a side wall with windows rather than a blank wall. We check local guidance and nearby examples first.

Will my end-of-terrace extension look like a new house on the end?

It should not, if it is designed well. A slightly lower ridge, a set-back from the front wall and a different front door position help it read as an extension. Councils often ask for this to avoid an extension that looks like an extra terraced house.

Are old terrace foundations strong enough to extend next to?

Usually, but they need checking. Older terraces often have shallow brick footings, and a new two-storey extension sits on deeper, modern foundations alongside them. The structural engineer designs the junction so the two can move slightly without cracking, and we dig trial holes to see what is there before the design is fixed.

Will I need planning permission in Gwynedd and Anglesey?

Gwynedd and Anglesey is in Wales. Can be permitted development in Wales if it is 10.5 m from the side boundary, set back 1 m from the front and doesn't widen the house by more than half; otherwise planning permission.

Neighbouring areas

All extension services in Gwynedd and Anglesey · About two-storey extensions for end-of-terrace houses