Create a warm, modern living space with a high-performance SIPs annex kit built for comfort, strength and long-lasting value — all fully compliant with UK building regulations.
SIPs (Structural Insulated Panels) create a highly insulated, airtight building envelope. That means a space that’s comfortable in winter and summer, with lower heating costs compared to many traditional build-ups.
Because SIPs are supplied as a precision-cut panel system, the structure goes up quickly and accurately.
This usually means:
Shorter on-site time typically means fewer deliveries, less waste, and less disturbance — ideal if you’re living at home while the annex is being built.
SIPs form a rigid structural shell that feels solid and permanent — not like a temporary outbuilding. The panels combine structure and insulation in one engineered system, creating a robust building envelope.
Panels are designed and cut specifically for your project, helping reduce offcuts and keeping the construction site tidier compared with many traditional building methods.
Annex costs vary depending on size, specification (basic shell vs fully finished), groundworks, and services such as water, drainage, and electrics.
As a rough guide:
For a 30 m² annex, the SIPs kit supply (panels/kit only) is typically £54,000–£90,000 + VAT, depending on openings and roof design. This excludes groundworks, doors/windows, finishes, services, and installation.
These figures are indicative. We’ll always quote the SIPs supply clearly, and we’re happy to talk through the wider build cost drivers so you can budget properly.
Running costs depend on how you heat the space, how it’s used, and your energy tariff. SIPs are designed to reduce heat loss, so the space is typically cheaper to keep comfortable than many traditional constructions.
As a broad rule of thumb:
If you share your annex size, intended use, and heating plan, we can help you estimate realistic running costs and recommend the best SIP panel specification.