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Redwood Thermowood Shiplap Cladding
MODEL RTSL
- Thermally modified (Thermo-D) for better stability and durability class 2 above ground
- Chemical free: modified with heat and water only
- Rich golden brown, weathering to a modern dark grey/charcoal
- Suitable for internal and external use. Optional end matching.
- Thermally modified to a low 4–7% moisture content
- Shiplap profile gives clean shadow lines along the building
Our Redwood Thermowood Shiplap Cladding is shiplap cladding in Redwood Thermowood.
About Redwood Thermowood
Redwood, thermally modified to 4–7% moisture content. Rich golden brown, weathering to dark grey/charcoal.
Scandinavian redwood. Thermal modification makes it more stable than standard softwood and gives durability class 2 above ground.
Can be treated with a clear UV protection to help it keep its colour. The colour depends on the species.
The thermal modification uses only heat and water, so the cladding is chemical free.
Profile and fitting
Usually fitted horizontally. The shiplap profile gives clean shadow lines along the length of the building.
Grades and options
- Character Grade: a mix of grades 1 to 4.
- End matching (tongue and groove on the board ends) lets you place joints where they fall rather than on a batten, which speeds up fitting and reduces wastage.
Sizes and pricing
- 142 x 20 mm (visible face 132 mm): from £32.49 per m² ex VAT
- Supplied in random lengths between 1200 mm and 3600 mm.
- Set lengths are available for an extra charge using Set lengths (Cladding): surcharge £8.00 per m² ex VAT up to 3500 mm, £12.00 per m² ex VAT above 3500 mm. Add the same number of m² of set lengths as cladding.
Specifications
| Species | Scandinavian redwood |
|---|---|
| Origin | Scandinavian |
| Profile | Shiplap |
| Use | Internal and external |
| Grade(s) | Character |
| Sizes | 142 x 20 mm |
| Lengths | Random 1200–3600 mm (set lengths extra: £8.00 per m² ex VAT up to 3500 mm, £12.00 per m² ex VAT above 3500 mm) |
| Moisture content | 4–7% (after thermal modification) |
| Treatment | Thermally modified (heat and water, chemical free) |
| Finish as supplied | Machined |
| Priced per | m², ex VAT |
Finishing and aftercare
No further treatment is needed. To keep the original colour for longer, see our cladding treatments.
Drawings and downloads

Tap the drawing to open it full size.
Good to know
- Natural timber varies: expect some differences in colour and grain from board to board and from the photos.
- Thermowood can split, so allow an extra 10% on top of your usual wastage. Knots may remain after planing; they don't affect durability.
- For a clearer, Prime grade alternative see our Radiata Pine Thermowood Cladding..
- Boards left exposed to changing weather before fitting are likely to cup, warp and split. We suggest fitting between October and April where possible, within 7–14 days of delivery.
- Sizes are nominal and can vary slightly with moisture content.
- Not sure? Order up to two cladding samples first.
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- Thermally modified (Thermo-D) for better stability and durability class 2 above ground
- Chemical free: modified with heat and water only
- Rich golden brown, weathering to a modern dark grey/charcoal
- Suitable for internal and external use. Optional end matching.
- Thermally modified to a low 4–7% moisture content
- Shiplap profile gives clean shadow lines along the building
