ThermoWood & Modified Wood
Tools for thermally modified timber — payback, mass loss, dimensional stability and real service life, compared honestly against teak and tropical hardwoods.
Thermal modification heats timber to 180–230 °C in a low-oxygen kiln, which lowers its equilibrium moisture content and improves dimensional stability and decay resistance — at the cost of some strength and a darker colour. These calculators help you quantify those trade-offs before you specify a thermally modified timber: estimate the mass loss and durability class from treatment intensity, compare movement and service life against teak or ipé, and check whether the price premium pays back over the life of the project. Every figure is drawn from the same verified species data used across the site.
ThermoWood Mass Loss Calculator
Durability Classifier
Decking Gap Calculator
Cladding Coverage Calculator
Specifying modified timber
Thermally modified timber is bought for one property: it stops moving. Durability improves as well, but stability is the reason it is specified and priced.
The trade-off is mechanical. Heat treatment breaks down hemicelluloses — that is what removes the food source for decay fungi and what reduces the wood’s capacity to hold moisture — and it costs bending strength and toughness in the process. That makes it right for cladding, screening, decking and exterior joinery, and wrong for structural members and anything that must bend.
The mass loss calculator is the practical check: mass loss during treatment is the accepted proxy for treatment intensity, so it indicates both how much durability was gained and how much strength was given up. The kiln schedule finder covers the process side.
Treatment class matters more than species here. Thermo-D and Thermo-S are different products with different intended uses — see the ThermoWood species reference and the full explanation of the process. Never size structural work off the untreated species’ figures.