Overview
H3-treated beams are structural timber members that have been treated to Hazard Class H3, a standard in countries like Australia and New Zealand for protecting wood from fungal decay and insects in situations where it is exposed to the weather but not in contact with the ground.
H3 treated timber is protected against:
- Fungal decay (rot)
- Mould
- Borer and insect attack
- Moisture exposure from rain and humidity
Common uses include:
Outdoor structural framing
- Pergola beams
- Veranda or patio roof beams
- Carport beams
- Outdoor rafters (above-ground)
Decking structure (only above ground)
- Deck joists or beams not touching the ground
- Bearers that are on brackets or posts with clearance
Exterior joinery and trim
- Fascia boards
- Bargeboards
- Exterior window or door trim (if the grade is suitable)
General construction
- Exterior wall framing in certain building systems (depending on local code)
- Fence rails (but not fence posts—those need H4 or H5)
