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Structural timber rating confusion...

Adam_W
Experienced Contributor

Structural timber rating confusion...

Hi team,

We are finally about to embark on the next stage of our renovations & I need to order some F14 100x100mm hardwood posts. Fair enough…
What I ran across though has me somewhat perplexed… timber with a structural GL rating.

Now I know GL stands for glue laminated but I cannot find a comparative table that tells you what GL rating is equivalent to which F rating.
Anyone have any knowledge of this area?
I don’t have a problem with using GL timber, I just need to make sure it has the right structural rating.

Community Manager Jason
Community Manager

Re: Structural timber rating confusion...

@Branchy249 - do you have any knowledge in this area?

 

Jason

 

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Community Manager Jason
Community Manager

Re: Structural timber rating confusion...

@Adam_W,

 

Did you have any luck finding information on this? 

 

If not, let me try tagging @MitchellM for you who might be able to assist.

 

Jason

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MitchellM
Established Contributor

Re: Structural timber rating confusion...

@Adam_W It is my understading that there is no "equivilent" chart for matching a specific F grading to GL product, hence why you have found it hard to obtain. I believe depending on the type of GL beam (there are many varying species of timber,types of glue,laminating techniques) it will recieve its own F rating from testing at the supplier. I also understand this to be both a visual and mechanical test done in house.

I believe the supplier should be able to give you the F rating on the GL product, however there is too many variables to create a viable universal chart.

Let's say a 150x50mm GL beam from manufacture "A" is made to their specifics and recieves a F rating of 11, manufacturers "B" is made from an inferior timber and recieves a lesser F rating.

Where-as with timber apart from visual defects in it, it is easy to assign a value to a specific sized piece and will generally be the same in batches.

 

This is my understading, I'm happy to be corrected if I am wrong, as I haven't worked directly in the Timber yard for 14 years. GL beams were not as common then as they are now.

 

 

Adam_W
Experienced Contributor

Re: Structural timber rating confusion...

Thanks @MitchellM (and welcome!)
I had suspected that the explanation would be something like that. So basically it all comes down to variables due to the bits they glue together. Makes sense!

BIM_Engineer
Valued Contributor

Re: Structural timber rating confusion...

@Adam_W as posts are generally in compression it would not matter if you used square GL Beams as posts
@MitchellM  Basically GL Beams have been replaced by LVLs in bending
@JasonStructural Beams & Columns need to be specified by engineers according to AS 1720 Timber Engineering or alternatively proofs certified as an  engineered solution
BTW Bunnings Doesn't Sell Glue Laminated Timber Beams

here Laminated & Finger Jointed Posts hth

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