Is a Home Extension Cheaper with SIPS Panels? (2026 UK)
Not usually on the headline shell price — a SIPS (structural insulated panel) extension often costs a little more to build than traditional brick and block in 2026. But that's only half the story. SIPS go up faster, need less labour on site and deliver far lower running costs thanks to high insulation and airtightness. Over the life of the extension, SIPS can come out cheaper — this guide explains where the money really goes.
SIPS vs Brick & Block (2026)
How the two build methods compare for a typical single-storey home extension.
Rule of thumb in 2026: SIPS and masonry land within a few percent of each other on total build cost. The real difference shows up in time on site and energy bills, not the headline quote.
The Hidden Costs and Savings
- Panels cost more, labour costs less. The SIPS shell itself is pricier than blockwork, but it's erected far faster with a smaller crew, clawing back much of that on labour and preliminaries.
- Faster to weathertight. A SIPS shell is up and watertight in days, so follow-on trades start sooner and you pay for fewer weeks of scaffolding, hire and site costs.
- Lower energy bills for life. High insulation and airtightness cut heating demand, which adds up year after year — the main reason SIPS can be cheaper overall.
- More usable floor area. SIPS walls achieve the same U-value as a thicker cavity wall, so you gain internal space for the same footprint.
- Design and detailing matter. SIPS reward early, accurate design; late changes are harder than in masonry. Penetrations, services and airtightness detailing must be planned upfront.
- Find an experienced installer. Fewer builders specialise in SIPS, so get quotes from firms with a genuine track record rather than treating it as a like-for-like swap.
Get Free Extension Quotes
BestBuilders matches you with up to 3 vetted UK extension builders — compare SIPS and traditional brick-and-block quotes side by side before you decide.