Understanding Hazard Classes


ON 11 June

By: admin

What are Hazard Classes?

In the context of timber, the “H Class” (or Hazard class) serves as a classification system used to indicate the level of treatment to safeguard timber from threats, like decay, termites and fungi. These classifications help in deciding the treatment for timber based on its intended use and the environment conditions it will face. The higher the number in H class, the higher the level of protection.

Hazard LevelExposureHazardEnvironmentExamples of regular use
H1Indoor use only, above groundMinimal. Protected from weather and dampnessWell ventilated environments, above ground, protected from rain and moistureFraming, flooring, interior joinery and furniture
H2Indoor, above groundBorers, termitesProtected from rain and moistureFraming and flooring
H3Outdoor, above ground, exposed to all weather conditionsModerate. Decay and insectsClear of ground, subject to periodic wettingDecking, fascia, pergola posts (above ground), weatherboard, window joinery, framing
H4Outdoor, contact with the ground or continually dampSevere. Decay, insects and sometimes marine borersSubject to severe wettingLandscaping material, fence posts, green houses, pergola posts
H5Outdoor, contact with the ground or freshwaterVery severe. High decay risk and insect attach (borers and termites)Subject to extreme wetting and leaching and where critical use requires a high degree of protectionRetaining walls, house stumps, building poles
H6Marine exposureExtremely severe. Marine borers, decayWhere extensive contact with salt water existsPiles, boat hulls, jetty post and cross bracing, landings

Each category indicates a level of risk necessitating effective protective treatments. The right category should be chosen based on the timbers surroundings to ensure its durability and structural strength.

21 Timbers has a large range of timber in stock, coupled with friendly service and advice, we welcome you to contact us and speak with one of our friendly team members on 07 3801 1122 or contact us online today.

Leave a Reply