Johnstone, Glasgow and the Clyde
Semi-detached rear extension in Johnstone
Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in Johnstone and want to know what a semi-detached rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
We cover Johnstone (PA5) as part of our Glasgow and the Clyde work. Where a Johnstone semi already has a small lean-to at the back, we usually replace it rather than extend it.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
How much does a semi-detached rear extension cost in Johnstone?
A semi-detached rear extension in Johnstone is priced at £1,800–£2,940 per square metre including VAT as a guide, before kitchen fit-out and fees. Prices in Scotland sit a little below our West Midlands baseline; building warrant fees and drawings are budgeted separately.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £21,500–£35,500 |
| 4 m wide × 5 m deep (20 m²) | £36,000–£59,000 |
| 4 m wide × 6 m deep (24 m²) | £43,500–£70,500 |
We put a fixed price in writing once the design is agreed, and explain any provisional sums such as foundations.
Do you need planning permission for a semi-detached rear extension in Johnstone?
The planning route for a semi-detached rear extension in Johnstone is set by Scotland's householder rules and your council.
In Scotland a single-storey rear extension can be permitted development under Class 1A: eaves no higher than 3 metres and an overall height of 4 metres, and where any part is within 1 metre of a boundary it can project no more than 3 metres on a terraced house or 4 metres on other houses. The rights do not apply in conservation areas, and a building warrant is still needed before work starts.
In Scotland an extension of more than one storey is only permitted development (Class 1B) if no part is within 10 metres of any boundary and it is no higher than the existing house, so almost every two-storey rear extension needs planning permission and a building warrant.
Scotland has no larger-extension prior approval route; extensions beyond permitted development need a planning application.
Classes 1A and 1B do not apply in conservation areas, and listed buildings need listed building consent. Before any drawing we look up the property's history with the council, because earlier extensions and removed rights change the answer.
What are homes in Johnstone like to extend?
Post-war semis and terraces are common around Johnstone, and many have room for a single-storey rear extension within Class 1A limits.
How a semi-detached rear extension in Johnstone comes together
Survey visit
We visit free of charge, measure up, check access, drainage and neighbours' extensions, and note what you want the room to do.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
Planning and regulations
We take the design through the right planning route, then produce the construction drawings and engineer's calculations for the building warrant.
Build and sign-off
We build to the approved drawings with regular updates, then hand over the accepted completion certificate and any guarantees from suppliers.
Semi-detached rear extensions near Johnstone
Close by, we work in Paisley, about 3.2 miles away, and Barrhead, about 5.2 miles away.
- Semi-detached rear extension in Paisley
- Semi-detached rear extension in Barrhead
- Semi-detached rear extension in Erskine
- Semi-detached rear extension in Renfrew
- Semi-detached rear extension in Clydebank
Other work in Johnstone:
FAQ
Semi-detached rear extension questions in Johnstone
Can I live at home while the extension is built?
Usually yes. Most of the work is outside until the back wall is opened near the end, and that stage is screened off.
Do I need planning permission for a rear extension in Johnstone?
Many single-storey rear extensions are permitted development under Class 1A, but not in conservation areas; you always need a building warrant before work starts.
Single or two-storey on a semi?
Two-storey if you need bedrooms, single-storey if you need a bigger kitchen. Planning risk is lower for single-storey.
Can I get a price without a visit?
Our online guide-price tool gives a range in a couple of minutes. A written price needs a survey.
Is the site visit in Johnstone free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.
Do I need a party wall agreement?
Scotland has no Party Wall Act; we agree access and protection with your neighbour in writing instead.