What H3 treated Pine to use for decking joists?

[DonPerf]

Good morning

I am trying to discover the most economical lengths of H3 treated pine to complete the next phase of my decking.

The length required is 7.5 metres

Based on 450 mm centres I require 12 runs of the above length of 90x45mm timber

For example do I use 4.8 and 3 in the same length ( Given the remaining 300 could be used at the join) or is there a more economical way of doing it

Thanks 

Don

[EricL]

Hello @DonPerf 

Welcome to the Bunnings Workshop community. It's splendid to have you join us and thanks for sharing your question about H3 treated pine.

After adding the numbers together, I believe your combination of the 4.8m + 3m is the one to get. You could technically get the 2.7m to get an exact measurement of 7.5m. But the odds of one of them being short by a few millimetres is too great. It's therefor safer to get the 3m length. In this manner you can cut it exactly to the length that you need. The offcuts can always be used for support.

I suppose you could explore the option of using 4.8 + 3.6 which will give you a total of 8.4m. When you take 7.5mm you are left with a 900mm off cut that you can cut into two and use as noggins. The issue becomes about size. Even if you were to cut the timber precisely there would still be a few millimetres of difference due to the thickness of the saw blade. 

The noggins would be loose between the joists, and you would force them to bend when anchoring the noggins in place.

If you have any other questions we can help with, please let us know.

Eric