Timber Ratings Decoded

If you have been looking at timber decking in Brisbane, you have probably seen a lot of numbers used as ratings. These ratings tell you how long you can reasonably expect your timber to last, how strong they are and how well-protected they are against insects.

Timber Ratings Decoded

Strength Ratings: F and MGP

These ratings tell you how strong your timber is when it is under stress. Since you, your family and your friends will probably be enjoying your deck, sometimes all at once, stronger timber is usually better. F ratings are for hardwood and softwood. They start at F1, which is the rating with the least strength. For decking, we recommend hardwood rated F7 or higher.

MGP is for Machine Graded Pine. This usually won’t be your floor, but it will often be used for joists and bearers. There are only three ratings available: MGP10, which is the same as F5, MGP12, which is equal to F8 and MGP15 which is the same as F11.

Durability Ratings

Durability ratings measure a timber’s natural resistance to factors that age it, such as insects and fungi. The ratings are applicable to the heartwood of the timber, due to the poor durability of sapwood for all species.

Species of hardwood are classified into four groups: Classes 1, 2, 3 and 4. Class 1 represents the most durability while Class 4 represents the least. Anything that touches the ground, such as posts or footings, should have a durability class of 1 or 2. Sapwood should be removed or treated to H5. Timber decking, pergolas and handrails should be hardwoods in class 1 or 2 with the sapwoods either treated to H3 or removed. They can also be made of softwood treated to H3.

H Level Treatments

The “H” represents hazards that affect the durability of timber, such as termites and fungal growth. H levels represent chemical treatment to timber to make it more resistant to hazards. H1 is the lowest treatment level and H6 the highest. Decking that doesn’t touch the ground can be H3 or higher. Parts that contact the ground should be H4 or higher. H5 is for fresh water contact and H6 is for marine water contact.

Call (07) 3888 1293 to learn more.

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Posted in Jack's Blog, Timber Decking Brisbane