Cladding a Garden Room
Full exterior cladding for a garden room, office pod or summerhouse — the whole stack: membrane, battens, cavity, cladding, trims and ventilation. The flagship version of an exterior cladding project.
What you'll need
Materials
- Cladding boards (feather-edge, shiplap, rainscreen or vertical), 38×25 or 25×50mm treated battens, breathable membrane (Tyvek, Solitex, Pro Clima), counter-battens for a true cavity, stainless A4 nails or screws, insect mesh, corner trims, head/sill flashings.
Tools
- Mitre and circular saw, table saw helpful, impact driver, level (long), chalk line, staple gun for membrane, snips for tape, sturdy ladder or low scaffold tower, hammer drill if anchoring trims.
Material complexity: High
Allow 15% on cladding boards — windows, door surrounds and ends create more cuts than a flat run. Buy battens to total length plus 12%.
Main risk: Missing or undersized ventilation cavity — the cladding stack fails from the back within years even when the visible face still looks perfect.
Tips & traps
- No ventilation cavity — the most expensive mistake. Rear of cladding fails within years even when the front looks fine.
- Single batten layer without counter-battens on horizontal cladding — restricts vertical airflow.
- Skipping membrane or using non-breathable.
- Bottom row touching the ground — wicks moisture upward into the whole wall.
- Corner detail an afterthought — looks like utility instead of architecture.
Planning & timber detail
Why build this?
Cladding a garden room is one of the most transformative DIY projects you can take on — it turns a shed-grade outbuilding into a genuine architectural feature. Done right with full cavity ventilation and quality timber, it lasts 25+ years. The skills carry directly into cladding a house extension if you ever take that on.
Where it works best
Any garden building that needs a step up from felt or basic cladding — and any new self-build that wants to look permanent and considered.
Planning notes
Permitted development covers most garden rooms under 2.5m height and within size limits — check your specifics. The cladding stack matters most: from wall outward, breathable membrane → vertical batten (cavity) → cladding. NEVER skip the membrane. For horizontal cladding, counter-batten (horizontal then vertical) for full continuous cavity ventilation.
Typical sizes
3×4m garden room: ~28-32m² cladding after windows/door deductions, ~80-100 linear metres of cladding board in 18×144mm, ~70-80 linear metres of battens. Order full lengths to minimise joints on visible faces.
Suitable timber options
Cedar — light, stable, no maintenance if left to silver. The gold standard for whole-building clads. Larch — strong, richer colour, more movement to manage, needs oiling to look its best. Thermowood — modern, stable, slightly brittle at fixings. Accoya — premium, exceptional stability, paint-friendly if you want a coloured finish.
Fixing and finishing
Stainless A4 for cedar and any coastal/oak work. A2 minimum elsewhere. Fix above the overlap (shiplap, feather-edge) so heads are hidden. Pre-drill thermowood and any hardwood always.
Plan the layout BEFORE first cut: where do boards meet at corners (mitre or trim), how do they finish around windows (proprietary trim or housed), and how do they meet the roof and ground (flashing and ventilation detail). The trims and details take longer than the cladding itself.
Maintenance
Annual walk-around: check the bottom edge for clear ventilation, look for any failed boards. Re-coat oil finish before it goes chalky. Check trims and flashings — they fail before the boards do.
First 12 months: re-check all fixings as boards settle. Trims and flashings are 80% of long-term maintenance. Have spare boards stored dry for individual replacement when needed in future.
Timber behaviour
Durability
UC3 battens minimum (UC4 if any chance of ground contact). Cladding species itself can be naturally durable (cedar, larch) and UC-free. Critical: keep cladding 150mm minimum off ground level, with continuous vented gap at the base protected by insect mesh.
Movement
Whole-building cladding has serious movement to manage. Single fixing per board per batten, 3–5mm expansion gaps at ends and openings, 8mm minimum gap at vertical butt joints. Plan for ~5mm of seasonal swing across each board width.
Go deeper
Get the Timber Buying Companion
An 8-page practical guide to choosing better boards, avoiding waste and spotting common timber problems before you buy.