How Much Does a House Extension Cost in Glasgow & Renfrewshire?
One of the first questions homeowners ask when considering extra space is “how much does a house extension actually cost?”
In Glasgow and Renfrewshire, extension costs can vary significantly depending on size, design, ground conditions and the level of finish you’re aiming for. Understanding these variables early helps you budget properly and avoid surprises once work begins.
This guide breaks down realistic house extension costs in Glasgow and Renfrewshire, explains what affects pricing, and helps you decide whether extending your home is the right move.
Average House Extension Costs in Glasgow & Renfrewshire
As a general guide, most house extensions in the Glasgow and Renfrewshire area fall into the following ranges:
Single-storey rear extension
£1,800 – £2,500 per m²
Typically used for kitchen extensions, open-plan living areas or family spaces. This is the most common option for Glasgow homes and is often the quickest to build with fewer structural changes required.
Double-storey extension
£2,000 – £2,800 per m²
Ideal for homeowners needing additional bedrooms or bathrooms upstairs while extending living space below. Although more expensive upfront, double-storey extensions often provide better long-term value per square metre.
Wraparound or larger extensions
£2,500+ per m²
Best suited to properties requiring significant layout changes or maximum additional space. These extensions involve more complex groundworks, structural steel and design work, which increases overall costs but delivers a major transformation.
For a typical 20–30m² single storey extension, homeowners often spend between £40,000 and £70,000, depending on specification. A double-storey extension of the same footprint will cost more upfront but can offer better long-term value by doubling the additional space.
These figures include construction costs only and can increase depending on design complexity, materials and internal finishes.
What Affects the Cost of a House Extension?
1
Size and Layout
The larger the extension, the higher the overall cost — but the cost per square metre often reduces slightly as size increases. Open-plan kitchen-diners, utility rooms and family spaces are common requests in Glasgow homes, especially in traditional properties.
2
Materials and Finish
Brick matching, roof tiles, windows, doors and internal finishes all affect final costs. Higher-end kitchens, bifold doors and underfloor heating can significantly increase budgets but also add long-term value.
2
Single vs Double Storey
Single-storey extensions are simpler structurally, while double-storey extensions require additional foundations, structural calculations and scaffolding. However, if you need a lot of space, building upwards can be more cost-effective than extending further into the garden.
3
Ground Conditions
Ground conditions vary across Glasgow and Renfrewshire. Poor soil, high water tables or sloping plots can increase groundwork costs, which is why site surveys are essential before finalising a budget.
o You Need Planning Permission?
In many cases, house extensions fall under permitted development, meaning planning permission may not be required. However, this depends on several factors, including the type of property, the size of the extension, its proximity to boundaries and whether the home is located within a conservation area. In parts of Renfrewshire and certain areas of Glasgow, additional planning controls can apply, so it’s important not to make assumptions early on.
Even where planning permission isn’t needed, building warrants and building control approval are always required to ensure the work meets current regulations. An experienced builder can advise from the outset whether planning permission is necessary, helping you avoid delays, redesigns or unexpected issues once the project is underway.
Extension Costs vs Moving House
With rising house prices and increasing moving costs, many homeowners now find that extending their existing property is more cost-effective than relocating. Stamp duty, legal fees, removal costs and higher mortgage repayments can quickly outweigh the cost of a well-planned house extension.
A professionally designed extension can increase property value, improve layout and functionality, and allow you to remain in an area you already enjoy without the disruption of moving. In popular Glasgow and Renfrewshire neighbourhoods, extensions are often viewed as a long-term investment that enhances both lifestyle and resale value rather than simply an expense.
Typical Timescales for a House Extension
Most single-storey house extensions take around 10 to 14 weeks from the start of construction, while double-storey extensions typically take between 16 and 20 weeks depending on complexity. This timeframe usually includes groundworks and foundations, the structural build, roofing and external finishes, followed by internal works and final handover.
It’s important to factor in additional time before construction begins for planning, design, approvals and surveys. These early stages can add several months to the overall timeline but are essential for ensuring the build runs smoothly once work starts on site.
Budgeting Tips for Homeowners
Setting a realistic budget early is one of the most important steps when planning a house extension. Including a contingency of around 10 to 15 per cent helps protect against unexpected costs that can arise during construction. Obtaining detailed, itemised quotes rather than rough estimates also gives a clearer picture of what’s included and avoids confusion later on.
Design changes once work is underway often increase costs and extend build times, so finalising layouts and finishes early is key. Choosing experienced builders who understand local regulations and construction requirements will help ensure the project stays on track. Clear communication, transparent pricing and proper planning are essential to keeping your extension within budget and delivering the result you expect.
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