First-floor extensions in Renfrewshire and Inverclyde

Renfrewshire and Inverclyde at a glance

Nation: Scotland
Price region: Scotland
Postcode areas: PA
Towns covered: 10 listed below, plus surrounding villages
Approval route: Planning permission is usually needed: Class 1B permitted development only applies if every part of the extension is at least 10 m from all boundaries. A building warrant is needed before work starts.
Site visits: Free, no obligation

What a first-floor extension involves

A first-floor extension suits you if your house already has a single-storey extension and you need more space upstairs. You get a structural check of the existing walls and foundations, a design that ties the new floor into the house, the approvals your nation needs, a building warrant and the build, managed by us and carried out by vetted teams working under S&K.

Across Renfrewshire and Inverclyde we cover Paisley (PA1), Greenock (PA15), Renfrew (PA4), Johnstone (PA5), Erskine (PA7) and Port Glasgow (PA14), plus the smaller places around them.

Guide price in Scotland

In Scotland, which includes Renfrewshire and Inverclyde, we'd expect a first-floor extension to cost around £23,500–£34,000 for 4 m × 3.5 m of new first-floor space (14 m²), or £1,690–£2,440 per m² including VAT. These are guides, not quotes. Ground conditions, steelwork and access can move the figure either way.

Spec	Per m²	Typical project
Essential	£1,560–£2,250 per m²	£22,000–£31,500
Standard	£1,690–£2,440 per m²	£23,500–£34,000
Premium	£2,030–£2,930 per m²	£28,500–£41,000

Rules in Scotland

In Scotland, permitted development for extensions of more than one storey (Class 1B) needs at least 10 m to every boundary and no part higher than the house. Most first-floor extensions cannot meet the 10 m test, so plan for a householder application (£371, decided within two months) and a building warrant before work starts.

Approval in Scotland: Householder planning application: £371. Councils have two months to decide a local planning application.

Building standards: A building warrant from the council's building standards service before work starts, and a completion certificate at the end. Scotland uses its own Technical Handbooks.

There is no Party Wall Act in Scotland. Shared walls and boundaries are governed by title deeds and common law, so we speak to neighbours early and record the condition of shared structures.

Getting the design right

Replacing the flat roof

The existing roof usually comes off and is replaced by a new first-floor structure. The room below is exposed for a short time, so we plan temporary weatherproofing and sequence the work to keep the kitchen or living room usable for as long as possible.

Tying into the house

The new floor and walls must line up with the existing first floor, often through a new opening in the rear wall above the old one. Floor levels, the position of upstairs windows and the existing roof all affect where the opening can go, so we survey both floors carefully.

How we work in Renfrewshire and Inverclyde

Look at the house
We start in Renfrewshire and Inverclyde with a free visit: measurements, photos, a look at the loft and drains, and a frank chat about budget.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in Scotland before drawing in detail.
Fixed price in writing
With approved drawings and calculations, we give you a fixed build price and a programme you can plan around.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

Towns we cover in Renfrewshire and Inverclyde

First-floor extensions in Renfrewshire and Inverclyde: questions

How much does a first-floor extension cost in Renfrewshire and Inverclyde?

In Scotland our guide is £1,690–£2,440 per m² including VAT, so about £23,500–£34,000 for 4 m × 3.5 m of new first-floor space (14 m²). Essential and Premium specs move that by roughly 8% down or 20% up.

Can I build on top of my existing single-storey extension?

Often yes, but only after the structure has been checked. Foundations, walls and lintels built for one storey may not carry two. We dig trial holes, look for the original a building warrant and ask the structural engineer to confirm what can stay, what needs strengthening and what must be rebuilt.

What happens to the room below while the first floor is built?

The old roof is removed, so the room below is exposed for a short period. We fit temporary weather protection, plan the work so the roof comes off only when the new structure is ready, and agree with you which rooms will be out of use and for roughly how long.

Will I need planning permission in Renfrewshire and Inverclyde?

Renfrewshire and Inverclyde is in Scotland. Planning permission is usually needed: Class 1B permitted development only applies if every part of the extension is at least 10 m from all boundaries. A building warrant is needed before work starts.

Neighbouring areas

All extension services in Renfrewshire and Inverclyde · About first-floor extensions