How Long Does a SIP Extension Take to Build?
One of the most common questions our clients often ask before committing to a project is how long does a (structural insulated panels) SIPs extension take? The answer depends on size and complexity of each project, but it’s generally around 6 to 12 weeks from set up to completion for our team at Smart Rooms UK.
Traditional brick builds typically run 12–24 weeks for the construction phase alone, before design or planning is even considered. SIPs we build consistently outperform on build speed, making them the leading choice for anyone that wants a home extension built efficiently, without compromising on quality or thermal efficiency.
Typical SIP Extension Timeline
Understanding the full SIP extension process helps you plan realistically and avoid surprises. Here is how a typical Smart Rooms project unfolds from initial design through to handover.
Design & Planning Stage (2–6 weeks)
One of our SIPs specialist team carries out a site survey, produces drawings, and completes structural calculations. We’ll produce a clear brief and accurate measurements ready for efficient application of your SIP extension.
Groundworks & Foundations (2–4 weeks)
Next, we’ll work on excavation, drainage, and, if needed, concrete foundations. The varied geology of Wiltshire includes clay-heavy ground across the area especially in parts of Chippenham and Trowbridge. This can occasionally extend this phase, but our initial survey will give us a good idea of the conditions prior.
SIP Extension Installation (1–3 weeks)
This is where a Smart Rooms SIP extensions set itself apart. As our panels are factory-manufactured off-site to precise dimensions, the structural shell can go up in days. A typical single-storey SIP extension can be watertight within a week.
External Works (2–4 weeks)
Then roofing, windows, doors, and external cladding are added, and any electrical/plumbing work can be completed at the same time. Our teams clear coordination avoids bottlenecks that eat into your budget.
Finishing (2–4 weeks)
Finally, the plastering, joinery, decorating, and final fit-out. The speed gained in the structural stages means you reach this point sooner, leaving more time and flexibility to focus on the interior finish you want.
Smart Rooms offer our SIP building services, SIP Garden Rooms and SIP Garden offices across Somerset, Wiltshire, including Bath, Trowbridge and Bradford on Avon
Why SIP Extensions Are Faster Than Traditional Builds
Speed is the defining practical advantage of SIPs, and it comes from multiple factors working together.
Off-site manufacturing. Panels are precision-cut in a factory environment. There is no waiting for materials to be mixed, laid, or cured on-site, so the structure arrives ready to be assembled by our team.
Reduced weather delays. The shell goes up so quickly that exposure to typical British weather is kept to a minimum. This is an advantage where autumn and winter weather can stall traditional builds for weeks.
Fewer trades required. The streamlined structural phase means fewer overlapping contractors, reducing any scheduling conflicts that costs traditional projects weeks.
No waiting time. Brick and block require mortar to set before the next course can be laid. SIPs arrive on-site structurally complete and require no waiting period at all.
Why SIP Extensions Are Faster Than Traditional Builds
Do SIP extensions need planning permission?
Not always. Many single-storey rear extensions fall within permitted development rights, subject to size and height limits. Extensions that exceed those limits, fall within conservation areas, or affect a party wall will require a full application to Wiltshire Council. We can advise on your specific situation.
Can SIPs be built in winter?
Yes. The SIP structural shell is erected regardless of season, and because the building is weathertight so rapidly, internal trades can start their work in conditions that would stall a traditional brick build for weeks.
How long before I can move back in?
For a rear extension with no major structural works to the existing dwelling, you may not need to move out at all.
Are SIPs faster than timber frame?
SIPs combine both the structure and insulation within a single factory-built panel, removing the need for a separate insulation-fitting step on-site. This typically makes SIP builds faster overall and delivers superior thermal efficiency, keeping the warmth in effectively.
Get a Quote for a SIP Extension in Wiltshire
At Smart Rooms we offer SIP construction services including conservatories, extensions and outbuildings across Somerset and Wiltshire, including Bath, Bradford-on-Avon, Calne, Corsham & Chippenham, Devizes, Lyneham, Melksham, Trowbridge, Warminster, and Westbury.
With the help of Smart Rooms, you can build your dream home extension or garden room with limited disruption and waste. Call now to get things moving on 01225 744744, mobile at 07973 40475 or email info@smartroomsuk.com.
