F5 instead of MGP10 in engineering plan

Hello Experts,

My builder has used F5 timber instead of MGP10 which was on the engineering plan. When this was picked up during a private inspection. The builders have not notified us of anything in writing along with the unchanged engineering plans. Is this legal for them to swap the timber as per their wish without the engineering approval? I've been advised on a different platform that it is probably ok to swap F5 to MGP10 but not the other way round. Frame stage is now complete with roof tiles on and bricks ready to go soon and I am super concerned not knowing the basics around it. Timber schedule from engineering attached for reference.

Greatly appreciate some adviseAttachment 503233

If you don’t get any bites here, try the renovators forum.
Your ultimate guide to decoding timber ratings | Narangba Timbers

don’t know if that helps or hinders it is QLD.
my quick googling didn’t come up with a definitive yes/no.
your engineering plans will have the name of the engineer you could maybe ring and ask?
cheers

What others tell you is really of no significance. Ask the designing engineer or get your builder to do so

Thank you wrongwayfirst. Great idea, will check if the plan has engineer's name

Thank you wrongwayfirst and Beardy. Great idea, will check if the plan has engineer's name. Asked the builder today to give me the engineers contact. Fingers crossed, he would be ok with that

You got your answers here already View topic - F5 instead of MGP10 • Home Renovation & Building Forum specifically this one:

Quote:

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The certified engineering details are for MGP10 ( a higher stress grade timber) , the builder will have to go back to their engineers to recertify the engineering for F5
Their Building surveyor is talking nonsense as they aren't licenced to change the original engineering Details without resubmitting new engineering

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The ONLY person who can pass any deviations from spec is the Design Authority, that being the engineer who signed off on the original drawings. End of story. Your builder has to either get it reapproved by the engineer or make the appropriate changes (which will also have to be specified by the engineer) to bring it back up to an acceptable standard.

F5 is a lower stress grade and inferior to MGP10. The quote was given on the plans supplied so they should work to the specification.
The Timber Framing Code AS1684 gives the allowable spans and spacings of members for their given stress grade.
If a different grade is used it would be credible to suspect that the framing does not now meet the Australian Standard.

You will have a Certifier that signs off on the construction and I would bring this discrepancy to his attention, secondly the person that designed the plans must have accessed the code to correctly size the components so you could also ask them for approval/disapproval of the changes and pass that on to the Carpenters? before payment.