The two dominant ways to build a garden room in the UK are insulated timber-frame construction and traditional stud-timber framing. They look similar from the outside once clad. Underneath, they are meaningfully different buildings.
How each method actually works
Timber frame
A skeleton of vertical timber studs at roughly 400 mm centres, sheathed on the outside, insulated between the studs (usually with mineral wool or PIR batts), then finished on the inside with plasterboard or ply.
timber-frame (Structural Insulated Panel)
A single engineered component: two structural OSB skins bonded either side of a rigid PIR insulation core. There are no studs — the panel itself is the structure AND the insulation.
Where insulated timber-frame builds genuinely win
1. Continuous insulation
In a timber frame, every stud is a thermal bridge — a strip of solid timber cutting straight through the insulation from outside to inside. Roughly 10–15% of the wall area is timber, and that timber conducts heat around three times faster than the insulation next to it. timber-frame walls have no studs bridging the panel plane, so heat has nowhere easy to escape.
2. Factory precision
insulated panels are CNC-cut in a controlled factory and arrive on site as a set of numbered components. Stud walls are cut and assembled on site, which introduces small tolerance errors that compound across a build.
3. Airtightness
The bonded factory panel is inherently airtight; a stud wall relies on the site team detailing tapes, membranes and seals correctly at hundreds of individual joints. Real-world air-leakage tests on insulated shells routinely outperform stud construction by a factor of 3–5.
4. Speed and dryness
A insulated shell can be erected in 1–2 days, so cladding and interior work start on a dry, weathertight box. A stud-frame shell typically takes 4–7 days and is exposed to weather for longer during construction.
Where timber frame is competitive
- Upfront cost — a stud-timber garden room can be 10–20% cheaper for the shell alone
- Repairability — swapping a single stud is easier than repairing a damaged timber-frame
- Availability — nearly every joiner in the UK can frame a stud wall; timber-frame requires a specialist supplier
The short version
Timber frame is a proven, cheaper way to build a shell. timber-frame is a more expensive, more precise way to build a warmer, tighter, longer-lasting one. Every Arden & Oak building is timber-frame, from the smallest Snug up to a full Pavilion.