In South Africa, timber is treated based on six distinct hazard class levels to provide protection against insects and fungal decay. Each level specifies the type of exposure and the appropriate use cases for treated timber:
- H2: Internal Use (Low Hazard)
Designed for interior applications, H2 treatment is recommended for structural timber components like roof trusses, laminated beams, ceiling boards, doors, cupboards, skirting, and window frames. The chemicals used in this treatment class include CCA, TBTNP, and Boron.
Typical examples include:
Laminated Beams | Roof Trusses Structural Timber | Ceiling Boards Flooring | Panelling | Doors | Cupboards | Skirting | Window frames | Plywood
- H3: Exterior, Above Ground (Moderate Hazard)
This treatment is used for outdoor, above-ground timber exposed to moderate weathering and insect risks. Common applications include outdoor decking, balustrades, garden furniture, cladding, and log homes. It is also used for components like cross arms and spacers on utility poles. Treatments usually involve CCA or Creosote.
Typical examples include:
Balustrades | Fencing bearers and slats | Outdoor decking and beams | Garden furniture | Laminated beams | Weather board | Fascia boards | Steps | Cladding | Stairs | Log Homes | Gates | Plywood | Droppers
- H4: Ground Contact (High Hazard)
For timber that will be in contact with the ground, H4 treatment protects against severe decay and termite damage. Suitable for agricultural posts, pergolas, carports, playground equipment, and poles for fencing or utilities, this class ensures durability in direct soil exposure.
Typical examples include:
Landscaping structures | Playground structures | Fencing | Pergolas | Carports | Flower boxes | Decking | Bridges | Stakes | Garden Edging | Transmission Poles
- H5: Freshwater & Heavy Wet Soils Exposure (High Hazard)
Timber treated to H5 standards is fit for use in freshwater environments or areas with frequent and prolonged wetting. Applications include jetties, retaining walls, drains, and slipways. This level ensures timber durability in wet soil and freshwater conditions.
Typical examples include:
Piling/foundation posts/poles | Agricultural & feedlot posts/poles | Retaining Walls | Slipways | Culverts | Groynes | Flood Gates | Jetties | Drains | Walkways
- H6: Marine Exposure (High Hazard)
H6 treatment is specialized for timber used in harsh marine environments. Only a combination of CCA and Creosote chemicals provides sufficient protection against marine borers. This treatment class is necessary for structures like jetties, retaining walls, and slipways situated in seawater.
Typical examples include:
Piling | Retaining Walls | Slipways | Groynes | Jetties | Walkways
