Unfortunately, the name is confusing for many people, as the F rating actually refers to the strength of the timber, and not the type of treatment it has received to protect against termites or rot.
So what does “F7 treated pine” actually mean?
What is an F grade on timber?
F7 is a structural rating for timber. It means the timber has been approved for use in structural building applications.
To be F grade certified, timber needs to be tested and proven to be capable of bearing all the necessary stress and load placed on it in its specific application. This can include wall studs, floor joists, or roof trusses.
What is F7 treated pine?
The F7 rating only tells you that the timber is structurally graded.
Another grading system known as “H” or “Hazard” determines what level of treatment the timber has had to protect it from termites and decay.
The H-level ranges from H1 to H6.
For most treated F7 timbers, it will be one of the following:
- H2 treated pine – suitable for inside, above-ground use
- H3 treated pine – suitable for outside, above-ground use
- H4 treated pine – suitable for outside, in-ground use
These three are all resistant to termites but they offer different levels of protection against decay, so are suitable for different applications.
What is the difference between F5 and F7 timber?
There are two main differences between F7 and F5 timber.
- The first is the cost of each, with F7 being more expensive than F5.
- The second difference is that the higher grade F7 can be used in higher stress applications.
Is F7 timber treated?
F7 timber is a structural-grade timber, but just because it has this F rating doesn’t mean it is treated.
Check for a hazard rating (e.g. H3 or H4) to see if it has been treated with preservative chemicals that protect against rot and insect attack.
You can use untreated F7 timber for things like flooring if you want to preserve its natural appearance. This is fine for jobs that don’t require it to be exposed to the elements or in contact with the ground.
However, any exterior work will require treated F7 pine — this includes posts, beams and other applications where moisture may get into the wood.
Is F7 Pine structural?
F7 timber is structural, so it’s used in structural applications like roof trusses and decking.
Strength graded structural pine is subject to both tension/compression and bending stresses – unlike non-structural framing pine which is only subject to tension/compression stresses.
F7 vs MGP10 timber
MGP10, or Machine Graded Pine 10, is an Australian strength grading standard.
MGP10 are very similar types of timber.
While MGP10 is machine graded, F7 can be either machine or visually graded.
According to Timberlink Australia, “MGP10 has a higher stiffness grade while F7 has a slightly higher strength grade”.
Can F7 timber go in the ground?
The hazard rating of the timber will determine whether it can be used in the ground. Timbers rated H4 and above are suitable for in-ground use.