Old Hardwood. How to tell the Stress (F) Rating?

[Draffa]

I'm about to order some hardwood from a recycling yard to use on my verandah, but I have no idea what stress rating it all is (and the bloke running the yard had his span tables 'borrowed').

The engineering drawings specify 175*75 HW bearers (no F rating), 2800mm typical between supports, 150*50 Joists (F17), 3000 between Bearers, and 150*50 Joists (F14), 2100-3000 between Bearers.
They also specify steel PFC beams 250*90 and 200*75, both spanning 5650, which I would like to substitute with Hardwood if possible.

...not sure where to go from here. I'd prefer to use recycled timber over newly cut, if for not other reason than it's already done all the shrinking/cracking/warping it's ever going to do. Any suggestions are appreciated.

86766

[ringtail]

Ratings are usually given following destructive and non - destructive testing. Recycled timber is a bit of a gamble but depending on the species it may not be a problem. Ironbark for instance will just about always exceed F17 when its green and only get stronger when seasoned. If there is no F rating on the bearers that solves that problem. If you can get ironbark joists that will solve that one. As for the steel / timber beams, you will need something around 300 x 75 to clearspan 5650 with a tin roof. Have you talked to the engineer about using second hand timber ?, it may change a few things on the sizings to cover his backside.

[Draffa]

Recycled timber is a bit of a gamble but depending on the species it may not be a problem.So it's somewhat species-based?


Have you talked to the engineer about using second hand timber ?I was going to call him yesterday, but Twitter sucked the remaining daylight hours away. :D Hopefully I can get hold of him this morning.

[ringtail]

In some cases yes. Ironbark is stronger and more durable than most species that are given the same F rating. For example a 150 x 50 ironbark joist is more durable and stronger than a spotty gum joist of the same size yet they are both sold as F14. The ironbark is DC1 and the spotty is DC 1 / 2. The spotty is excellent timber though. I have no idea what is available second hand but if its old timber it may have bows, splits, checks, holes etc... that may make it difficult to work with. Finding long usable lengths might be a problem too. The engineer might not allow it full stop but only one way to find out.

[Bloss]

As Ringtail says - not quite as hard as it seems. Queensland seasoned hardwoods which are the dimensions you seek will exceed the specs you have. Not always certain with cypress or other pines - the dimension would need to be the same, but I would want a visual check by someone who knows what they are seeing. Using recycled timber can be hard on tools, but can be a satisfying approach - just remember how hard it will be though. And if they are not true then they won't be made true by manipulation - only but adding packing or removing timber - even a relieving cut over a bearer or pier will often not cause the timber to move.

[stevoh741]

If you are trying to work some old ironbark or similar, you're stress rating will go up quite a bit I imagine!!!

[ringtail]

If you are trying to work some old ironbark or similar, you're stress rating will go up quite a bit I imagine!!!

Gold.

[Draffa]

Thanks blokes.

I spoke to the engineer on Saturday, and he had no trouble with me using 'ungraded' recycled timber, for similar reasons as you've listed above. He was a bit iffy about using timber to span the garage opening (7.3m), and suggested I stick with steel. Reckons some Engineered timber would do it, but would need regular maintainance because it's semi-exposed to the weather.

Unfortunately, no one was at the timber yard today, so I couldn't order anything.

[intertd6]

For hardwood timber visual grading the species must be known or the grading is knocked back to a lower "F" rating which changes from state to state, some of the older blokes in ther timber game who have been in it all their lives can tell the difference between species in their areas & even then they get it wrong on the odd occasion.
Timber from a recycling yard could honestly be from anywhere in the country or beyond.
regards inter

[Draffa]

Timber from a recycling yard could honestly be from anywhere in the country or beyond.Around here, I reckon it's more likely than not to be Blackbutt.

Does anyone know of any companies in Brisbane (preferably northside) who are able to put some wood through a stress test (to destruction, if necessary)?

[intertd6]

If your deadset keen to use recycled HWD of unknown species there is an easy way to test each member for strength. You will have to find an old engineer who has had experience with timber structures, bridges, etc. Line up the members ready to be test loaded with determined known weights, the engineer will simply measure the deflection once loaded & give a load carrying capacity of each member. Grading rules would still apply for defects, knots, notches, sloping grain, etc limiting the structural grade applied to the members.
regards inter

[Draffa]

Ta. I've basically settled on using recycled timber for the main structure (the bit without F ratings), and timber with a known rating for the Joists. Just waiting on some quotes now.

[Gaza]

Around here, I reckon it's more likely than not to be Blackbutt.

Does anyone know of any companies in Brisbane (preferably northside) who are able to put some wood through a stress test (to destruction, if necessary)?

i maybe wrong but i think that only pine is machine grade thus the MGP rating vs the F rating.

[Draffa]

After much consideration, I've ended up just stumping up for new-cut Joists, posts and beams (had to get new-cut posts anyway, as nobody had any in the lengths I needed) direct from a sawmill (Grants Timbers at Woodford). The remainder of the verendah is recycled wood.

The combined cost of the new-cut plus the recycled stuff still came in under the quote for posts, beams, and joists of a well-known local timberyard. :)

Cheers.