Joists and bearers - hardwood or treated pine?

[ob1]

Hi,

I'm a newb on this site so be gentle

Well I've gone through the 1500 or so posts in this forum but unfortunately haven't found the question/answer I'm after. I am about to put a back deck in (6x4m) and the two quotes I am deciding over have two big differences. One quote uses H3 treated LVL Pine for their joists & bearers, the other uses F14 Hardwood (both sitting on Duragal posts). The guy that uses the F14 Hardwood says he won't touch the pine, and the guy that uses the pine says it's a better product and will last as long as the hardwood... My wife and I are planning on staying at this house for many years to come, so for a deck we want to use over the next 30 years or so, which timber should we use (the decking will be spotted gum)? We would prefer to choose the tradie that uses the H4 LVL pine (his other materials seem much better quality), but I'm a little concerned about the H3 LVL pine after the other tradie said he won't touch it (he said it would fall apart within 10 years)? Does anyone have any recommendations? The H3 LVL pine says it comes with a 25 year guarantee, but who knows if this is just a marketing ploy...

[MatterHorn]

Well personally I'm using F7 treated pine for my bearers and joists. I don't think they'll fall apart in 10 years or anything.

[Bloss]

Pick the builder you want and do what he says.

The life of H3 treated pine and hardwood would be similar - if anything the hardwood is likely to rot out sooner where the boards are fixed to it if there is no treatment given too it before boards are put on. Even a single coat of oil over the top of the bearer before the decking is nailed on can extend their life significantly.

Often comments about longevity of TP comes from experiences of inappropriate use, for example, using the wrong grading directly in damp ground, or from the installer not following instructions for use such as cutting and not coating the ends or cut sections.

Plenty of info on the web about use of various timbers and comparisons between TP and hardwood etc from the manufacturers, timber associations and government agencies.

Eg: see - http://www.treatedpine.net.au/overview/overview.asp for the various ratings. In a really wet climate or local situation you might choose to go up a grade to H4 even though the structure is above ground.

Google is your friend . . .

[glock40sw]

Hardwood!
There is nothing that even comes close.
Being a manufacturer and supplier of decking to all areas of Australia, ask me how I know hardwood is best.

[pharmaboy2]

heh, Trevor, I live in a HW framed house - got eaten to nothing - does anyone provide gurantees that the house wont be eaten by termites like the treated pine people do?

And I've also replaced plenty of HW windows and surrounds too - rotted HW.

?//??????????

[Connollys]

Hardwood comes in treated too

Cheers

[glock40sw]

Hardwood comes in treated too

Cheers

There you go.....

[ausdesign]

External structural timber should be 'durability class 1 or 2 ' or 'H3 treated' timber.
It's pretty hard to order class 1 or 2 hardwood from your local timber merchant.

[pharmaboy2]

LOL craig!

Yep, I've heard about it, but never seen it.

Peter's on the money - scantling h/w is unspecified species - so to do a proper job with the resources that are easily available tends to mean,........ that the nails go in easier!

[glock40sw]

External structural timber should be 'durability class 1 or 2 ' or 'H3 treated' timber.
It's pretty hard to order class 1 or 2 hardwood from your local timber merchant.

G'day.
Not if you go to the mill.
Class 1= Grey Gum, Grey Ironbark, Red Iron Bark, Grey Box, Tallowood and Turp.
Class 2 = Blackbutt, Spotted Gum, Rde Mahogany, White Mahogany and The Stringybarks.

Now, If you are in a state that is not God's country (NSW) Then you are out of luck as the vic species are worth 2 cents.

QLD Sources a lot of hardwood from NSW, so is would be available there as well.

[ausdesign]

There you go !
And all this time I thought that NSW didn't have trees.
Next I'll be told that Sydney Harbour isn't the only thing in NSW.

[brynk]

my favourite subject

i dislike treated pine but it certainly has its place - it is easier on the tools and probably easier to work with if it is kiln-dried and laser-cut compared to unseasoned hardwood. it is made from monoculture forests that will probably render the land useless for growing anything else for the next hundred years. but hey? we can alway grow more pine because people need mcmansions. the cutting and pressure-treating resemble a huge amount of embodied energy & handling which result in more greenhouse gas emissions, if that is important to your consideration. cutting it exposes you to some nasty drift which you probably don't want to breathe, though if i were cutting any of the timbers in an enclosed environ where i couldn't hold my breath then walk away to fresh air then i would wear a good dust mask. you can't burn it for warmth because you don't want to be around when it goes up in smoke for the same reason! a splinter will give you an infection almost immediately if it is cca-treated - i read 'industry literature' that says the new method isn't as toxic ... i've not used it at all yet.

your hardwood quote - ask the bloke which species he intends using? i am told the mixed hardwood (in ssw nsw) is (currently?) consisting of a large portion of eucalyptus radiata (NSW messmate) - a class-3 timber. how does he intend to ensure its longevity?

it was mentioned treating the top of the joists before the boards go on. this is a good start. the top of the hardwood joist *will* split which allows for a nice little pond. freeze-thaw cycles (if you have them in your area) will open this split up. wet-rot will move in if it is damp (if you have damp in your area). you can put fancy joist protectors down before you lay the board or you can cut up a roll of damp proof course like we did on our deck which uses red ironbark for the sub-struture - yes, the tops of the joists have split, even though i pre-drilled every nail & dipped the nail in the woodguard treatment before i hammered it in ! there are also fixing options that don't involve drilling / nailing into the joist.

another consideration is - how far can the timber span? you might realise a saving by using hardwood because it will span further than t/p (ie, less footings, less disruption). if i were to build a similar deck again for a client i would use another ironbark bearer instead of the pine whaling plate along the wall, and would (begrudgingly) consider using a deeper treated pine joist instead of the ironbark ones - this is a more expensive option but it would have saved considerable time in the construction. i would even try to buy the t/p cut to length so i didn't have to do it myself . if i am still around when the deck needs to be refurbed (looks around for the 'touch wood' smiley) in 25-odd years then i will probably do this - i will also have some bloody nice well-seasoned red ironbark sticks ready to go for finishing and then on sale to fund my retirement because nobody can grow ironbark anymore and aspiring weekend-warriors of the day can gaze in wonder at what the ironbark does to their fancy-arsed neutrino-powered tools of the future. i rant...

here is a doco on the in-ground durability of aussie timbers which will give you an idea of species & their expected life-times. you will note that the cca t/p is on the top of the list

http://www.fwprdc.org.au/content/pdfs/PN04.1004.pdf

r's brynk

[ob1]

Hi everyone,

Thanks heaps for the valuable feedback. The tradie using the hardwood (who won't touch pine) will be using red ironbark. I think after all the feedback I will end up choosing the hardwood (can't remember if it was F15 or F17). Brynk, thanks for the big post. It was very informative especially as you've got ironbark in your deck. Are there any other types of hardwood which would suit better for the Joists to avoid the splitting which Brynk mentioned? The deck will be covered so hopefully there won't be too much moisture getting on top of the decking.

Cheers,
Greg

[brynk]

gday again

hehe red ironbark my favourite, my favourite. beautiful, dense. destroyer of tools! my only regret is that we didn't use it for the decking as well as the structure, but the yellow stringy goes well enough.

if it is unseasoned hardwood then you will not be able to avoid the split. the timber shrinks as it dries and because the nails / screws are all in one line (unless they are staggered, though some people don't like this look) then the split is propogated along the top of the joist.

the solution is to cover the top of the joist with a thicker plastic before the decking goes down. there are joist caps / protecters made that are extruded plastic that drain off to the edges but they are costly. we bought some plastic damp-proof course - one of the 300mm wide 30m rolls (about 15 dinars) and cut them into thirds with the cross-cut saw. then we had about 90 lineal metres which we rolled out over the tops of the joists and fixed with tack nails on the sides. this coupled with gravity has sagged the plastic to the sides of each joist nicely. you can just make them out in the attached.

r's brynk