Grading and Classifications
Grading
In the ThermoWood industry, softwoods such as pine and spruce are graded based on their appearance, structural integrity, and suitability for various applications after undergoing thermal modification. The grading typically includes A-grade, AB-grade, B-grade, and C-grade, with each category representing different levels of visual defects and overall quality. Mostly we sell AB-graded products but we have also in stock A-graded products.
Classification
In the ThermoWood classification system, wood products are categorized into Thermo-D (Durability) and Thermo-S (Stability) classes based on the intensity of the heat treatment and the properties achieved.
Grading system
Grading system in a nutsell
ThermoWood, a thermally modified wood product, undergoes a specialized heat treatment that enhances its durability, stability, and resistance to environmental factors. The grading system used for ThermoWood, specifically in softwoods like pine and spruce, classifies the wood into different quality categories—A-grade, AB-grade, B-grade, and C-grade—each suited for specific applications based on the wood’s appearance and structural integrity.
A-Graded Softwoods
A-grade ThermoWood represents the highest quality and is typically used in projects that require a pristine appearance, such as terraces and facades or panels. This grade allows no knots or defects. Usually A-graded and Thermotreated softwood means ThermoRadiata (Pinus Radiata) which is imported in our case from New Zealand since Nordic Pine is hard to have knot- or defect free. The wood’s dimensional tolerances are strict, with a moisture content of 6% ± 2%, and deviations in width and thickness limited to ± 0.5 mm. This grade is prized for its smooth finish and stability, making it ideal for visually demanding applications.
A-Graded Hardwood
A-graded hardwood refers to the highest quality thermally modified hardwood, characterized by its minimal visible defects such as small, tight knots or the absence of significant cracks. This grade is prized for its smooth, uniform appearance, making it ideal for high-end applications like luxury flooring, exterior facades, and premium furniture. The thermal modification process enhances the hardwood’s durability, making it resistant to moisture, decay, and warping, while also ensuring superior dimensional stability.
AB-Graded Softwood
AB-grade ThermoWood is similar to A-grade in its intended uses, such as decking and facades, but it permits slightly more visible imperfections. Knots can be up to 50 mm, and there may be some surface irregularities, though broken or splintered boards are not allowed. The physical properties remain the same, and wood from this grade can sometimes be upgraded to A-grade by removing defects. The dimensional tolerances and moisture content are the same as for A-grade, ensuring stability and durability. AB-graded products are usually ThermoPine (Pinus Sylvestris) and ThermoSpruce (Picea Abies)
Browse our A and AB-graded ThermoWood® Products
Classification System
Thermo-D (Durability)
Thermo-D products are treated to enhance durability, making them suitable for both indoor and outdoor use. Durability and appearance are key attributes, with Thermo-D wood being darker than Thermo-S, especially in hardwood applications.
Thermo-D Softwood Applications:
- Cladding
- Outer doors
- Window shutters
- Outdoor structures
- Sauna and bathroom furnishings
- Flooring
- Garden furniture
Thermo-D Hardwood Applications:
- Darker color than Thermo-S hardwood
- Furnishings
- Fixtures
- Furniture
- Flooring
- Sauna structures
- Garden furniture
Thermo-S (Softwood applications)
Thermo-S products are designed for applications where stability is a key requirement, along with aesthetic qualities. This treatment is primarily suited for indoor use or dry conditions, where the wood’s stability is essential.
Thermo-S Softwood Applications:
- Building components
- Furnishings for dry environments
- Fixtures for dry environments
- Indoor furniture
- Garden furniture
- Sauna benches
- Doors and window components
Thermo-S Hardwood Applications:
- Furnishings
- Fixtures
- Indoor furniture
- Flooring
- Sauna structures
- Garden furnitures
HJT-Holz and ThermoWood®
Browse our certifications
Our AB-graded coniferious products is sourced from ecologically managed Finnish forests and meets the highest environmental and quality standards. Explore our certifications, including FSC and PEFC, to see our commitment to sustainability and product excellence.
Offices
Head Office
Manufacturing is entirely made in Mänttä-Vilppula.
Lahnajoentie 196
35700 Mänttä-Vilppula
Finland
