Thermally modified timber for indoor and outdoor
Timber, harvested and prepared for construction, is a durable material known for its strength and versatility. It serves as an architectural element in structural systems, framing, cladding, decking, and flooring. Although it possesses a warm and natural character that creates an aesthetic appeal, the inherent humidity of timber can cause wood deformation, leading to bending, mold, and rot once the moisture content reaches 23%. However, with the development of new products and production techniques, Thermowood – also known as Thermally Modified Timber – has emerged as a method for creating natural, chemical-free solutions made from certified raw materials.
By reducing moisture content, it does not rot or mold, it experiences no longitudinal shrinking, and ensures high dimensional stability, resulting in a minimum biological life span of 30 years. After analyzing how to apply these solutions in architecture and design, we will showcase indoor and outdoor spaces featuring House Land Holz’s Thermowood products.
Thermally modified wood conveys numerous benefits for outdoor spaces, including resistance to warping, expansion, contraction, and damage from temperature and humidity variations. Moreover, its low moisture content prevents the presence of organisms. These qualities make it suitable for outdoor applications such as decking, siding, and garden constructions.
Thermowood materials come in a wide range of sizes and cross-section profiles, making them adaptable to various building applications and architectural styles. Because of their thermal insulation properties, thermally modified claddings are highly durable in extreme weather conditions. As for their aesthetic purposes, they can be used as primary or complementary covers for different architectural applications. These claddings can be customized with diverse textures and colors, as well as being adapted to horizontal and vertical applications. Their unique profiles are designed to meet the thickness requirements of each project.
Other Thermowood Cladding Profiles
Wood type: | Whitewood (Pine) |
Treatment: | None |
Density: | 420 – 480kg/m³ when moisture content is 6-8% |
Lifespan: | Proven life expectancy of 25+ years |
Quality class: | A or AB (A and B mixed) |
Thermal properties: | 0,09 W/(m K) according EN ISO 13787 + EN 12667 |
Humidity: | Dried up to approx 6-8% (+/- 2%) |
Dimensional stability: | Thermal modification increases stability |
Leaching: | As no substances are added during the Thermowood process, no chemical leaching will occur. In addition, as the resin is removed during the process, the problem of resin leakage through the knots or pitch pockets is removed |
Working properties: | With the lower moisture content after Thermal Modification the timber can be more brittle than unmodified Redwood/ Whitewood |
Applications: | External and internal cladding and decking, industrial productions like joineries, window and door manufactures |
Other uses: | Decking, cladding, fencing, joinery, flooring, spa and sauna interiors |
Dimensions (mm): | 20 x 95 / 120 / 145 mm |
Available length: | From 2 to 5.1 m |
Appearance: | Medium/ Dark brown. |
Insect attack: | Without additional treatments Thermowood is not resistant to termites |
Treatability class: | Resistant |
Movement class: | Low (A 145mm board can vary 1mm over the year.) |
Impact resistance: | Medium |
Fixings: | Stainless steel fixings are always recommended |
How to fix: | Face fixation with stainless steel ring thigh nails. Pre-drilling is not needed when using our PFS+ stainless steel screws. |
Ecological and safe: | Thermowood is produced using high temperature and steam. Since no chemicals are added during the process Thermowood contains only renewable substances. Disposal of offcuts can be burned or given into the normal waste system. |
Thermowood is rated as class 2, which is durable. Life span for this product of around 30 years.
- 100% natural processing with no chemical additives, biodegradable and recyclable.
- Superior performance outdoors, indoors or in different weather conditions thanks to special thermal treatment.
- Possesses high dimensional stability, durability and decay resistance, has colour uniformity and reduced thermal conductivity.
- No resin leakage, easy to paint or apply surface treatments.
The natural durability of Thermowood means that no treatment of the wood is required and any coatings applied are for aesthetic purposes only. Hovewer, the wood is not resistant to termites. Additional treatments required to protect your boards from termites.
One of the benefits of this product is it’s stability, the thermal modification process reduces the moisture content in the board ensuring less movement.
Thermowood has a thermal conductivity of around 20% less than standard softwoods. The thermal conductivity is y10 to 0.099 W/(m K).
Thermowood has a lower density than unmodified wood. This is the consequence of wood losing some of its compounds during thermal modification. With the equilibrium moisture of 6% (+20’C, RH 85%), the density of our Thermowood ranges from 420 to 450 kg/m3, slightly varying from the structure of wood in a specific batch. The density values settle around 10% lower compared to the untreated northern pine.
Wood density has direct impact on screw holding strength. While nail holding strength appears to be the same to that of untreated wood, due to Thermowood’s lower density, the screw holding strength proves to be 10-20% lower than in regular wood. The results are much better when smaller.
Compared with standard timber, Thermowood causes a smaller fire load and its smoke production is lower. This is also due to lower density and smaller amounts of wood constituents and extractives.
According to the European classification standard, Thermowood is classified as D-s2-d0. When treated with fire retardants, the fire class can be brought up to Class B (B-s1-d0).
Our Thermowood cladding, battens, boards and other thermowood products are available in various lengths, from 2m up to 5.1m. The standard board dimension is approx. 95mm, as this is traditionally the most commonly produced width. However, we also offer a range of other widths: 45mm, 55mm, 70mm, 95mm, 120mm and 145mm. The narrower board widths offer a number of advantages, including a wider choice of design options and improved dimensional stability. As an added benefit, narrower board widths are generally rated well beyond their specification.
Thermowood boards are supplied in linear metres based on random stock lengths at the time of order picking. Other sizes may be available on request.
Thermowood timber quick tips
Sort your lengths. Make sure you’ve set them all up. We recommend ordering 10% more to cover waste material.
Thermowood is hard and dense wood. Use professional equipment for best results.
We recommend using only high quality stainless steel screws to avoid corrosion and stains on the wood.
OSMO wood protection offers effective multiple protection against UV rays and harsh environmental conditions.