thisplace.com.au - Classifications for Treated Timber

H1 Hazard Level: Exposure - inside above ground;
Conditions - completely protected from the weather, well ventilated and protected from termites;
Biological Hazard - insects other than termites (i.e. lyctid or anobiid);
Uses - framing, flooring, furniture, interior joinery.
H2 Hazard Level: Exposure - inside above ground;
Conditions - protected from wetting, nil leaching;
Biological Hazard - borers and termites;
Uses - framing, flooring etc. - used in dry conditions.

H3 Hazard Level: Exposure - outside above ground;
Conditions - subject to periodic moderate wetting and leaching;
Biological Hazard - moderate decay, borers and termites;
Uses - weatherboard, fascia, window joinery, framing and decking.
H4 Hazard Level: Exposure - outside in ground;
Conditions - subject to severe wetting and leaching;
Biological Hazard - severe decay, borers and termites;
Uses - fencing, greenhouses, pergolas and landscaping timber.
H5 Hazard Level: Exposure - outside in ground contact with or in fresh water;
Conditions - subject to extreme wetting and leaching and or where the the critical use requires a higher level of protection;
Biological Hazard - very severe decay, borers and termites;
Uses - retaining walls, house stumps, building poles.
H6 Hazard Level: Exposure - marine water;
Conditions - subject to prolonged immersion in sea water;
Biological Hazard - marine wood borers and decay;
Uses - boat hulls, marine piles, jetty cross bracing, landscaping steps etc.

F Rating

The F-Rating you see on timber is the measurement of strength in a piece of timber. The higher the F rating the stronger the piece of timber, e.g.. F4, F5, F8, F11. With each grading various colours are used for identification e.g.. F4 - red, F5 - black, F8 - green, F11 - purple etc.