Hazard Class Ratings for Structural, Landscaping & Outdoor Timber

Choosing the right treated pine is one of the most important decisions in outdoor construction. The correct hazard class determines how well timber performs, ensuring strength, compliance and durability over time. Porta supplies plantation-grown pine treated to H2, H3 and H4 grades, each designed for specific conditions and certified to meet AS/NZS 1604 standards.

Understanding Hazard Class Ratings

Treated pine is classified according to its resistance to biological threats such as termites, borers and fungal decay. Each hazard class reflects how much protection is needed for a particular environment:

• H2: For internal framing in termite-prone areas
• H3: For outdoor, above-ground use
• H4: For in-ground or high-moisture environments

Choosing correctly matters. Under-specifying treatment can lead to early timber failure, while over-specifying can add unnecessary cost. Selecting the right grade for the right environment ensures both performance and value.

H2 Treated Pine – Internal, Dry Applications

• Best for: Wall frames, trusses, bottom and top plates, noggings
• Protection: Termites and borers

H2 treated pine is designed for enclosed, dry structural framing where moisture exposure is minimal, but termite activity is a concern. Porta’s H2 MGP10 framing range is machine-graded for consistency and treated to Australian Standards, making it a reliable choice for dry, enclosed construction zones, particularly in areas such as New South Wales and Queensland where termite protection is essential.

H3 Treated Pine – Above-Ground Exterior Use

• Best for: Deck joists, pergolas, fascia, fence rails, cladding
• Protection: Termites, moderate fungal decay and weather exposure

H3 treated pine is ideal for outdoor structures that remain clear of the ground but are exposed to the elements. Porta’s H3 range is milled straight for smooth installation and treated for protection against moisture and decay. It is perfect for decks, pergolas and cladding where good ventilation helps extend the life of the timber.

H4 Treated Pine – Ground Contact Applications

• Best for: Fence posts, sleepers, retaining walls, garden edging.
• Protection: Termites, severe decay and fungal attack.

H4 is the minimum treatment grade for timber used in direct contact with soil or constantly damp environments. Porta’s H4 range includes structural sleepers and fence posts designed for maximum durability and resistance to wet conditions. It provides strength and reliability for landscaping and ground-contact construction.

Why Specification Matters

Specifying the correct hazard class is critical to meeting Australian Standards, ensuring long-term performance and reducing the risk of costly rectification. Porta’s treated pine products are fully certified, traceable and responsibly sourced to provide confidence in every application.

Pro Tips for Builders & Landscapers

• Always assess site conditions, drainage and ground clearance before specifying treatment levels.
• When unsure, step up a class especially for mixed-use or exposed projects.
• For environments beyond H4, such as marine or extreme humidity, consider H5 or H6 rated products.
• Apply end-seal treatments and maintain adequate ventilation to maximise timber lifespan.

Build Smarter with Porta

Porta’s range of H2, H3 and H4 treated pine is engineered for strength, compliance and durability. Whether you are framing, fencing or landscaping, Porta provides sustainable, long-lasting timber solutions backed by certification, responsible sourcing and over 90 years of industry experience.

Porta. Trusted by professionals. Built for Australian conditions.