Verandah extension

A friend of mine is getting their decking extended out the back of their house.
The builder has used treated pine for everything. Posts,joists,bearers. using Mirboo for the decking.
It just looks a rubbish product to me, but i was wondering what others think of it?? This is going to get a fair bit of weather so, even things like expansion and contraction with the rain how does it last over a period of time. I'm not talking about rotting but more working at the nailed joints working there way lose particulay as this is going to flex way more than the equivalent size OB would. I asked the builder why he didn't like OB and he simply said it's too heavy to work with. At least he is honest.
Sinjin

I hate working with the it, dulls the blades and always feel I'm ingesting nasty stuff.

I've just lost the varandah over the toolshed, but that's another story.

That's a pretty standard construction method up this way. Treated pine sub floor and hardwood decking. We have one out the back of our place - it's been there for over a year now and no problems to speak of.

What's Mirboo and OB????

It's merbau - a type of hardwood like Kwila (I believe). Dunno what OB stands for - some Victorian thing.

OB - ordinary builders hardwood - unseasoned and rough sawn. Usually oversize by a couple of mm compared to KD DAR sizes - e.g. 90x45mm KD DAR would be rough sawn 95-100x47-50mm as an OB.

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Originally Posted by Eastie

OB - ordinary builders hardwood

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You're kidding, right?

Is it some new species of tree?

Exposed timbers, as for decks, have been a contentious point for a long time and generally not enforced correctly by councils.
If your using 'OB', it should be protected from weathering by waterproofing, painting etc or by using durability class 1 or 2 timber - try ordering that from your local supplier & see how many blank faces you get.
Some builders use garden grade F4 or F5 treated pine whereas they should be using F8 H3 treated pine to cover their b'sides and provide a quality job.
Possibly the worst situation is where OB joists are run out continuously from under the house, making replacement down the track a big job.
Yes 'OB' must be a Vic thing, but then we are in the forefront in most things.

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Originally Posted by rod1949

You're kidding, right?

Is it some new species of tree?

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No - unless I was taught wrong on the green dock at the mill where I had my first paying job, and then again in their timber yard. It can be any number of eucalypt species that is cut and sold green+oversized to account for shrinkage - you could simply call it "unseasoned", but it's easier to say OB.

On the 12mx3m deck I've just put down the stumps are a mix of concrete stumps and brick piers, the bearers are cypress, the joists are KD F8 H3 pine and the decking is Kwilla finished with intergrain sealer & DWD. It all works well together.

I reckon the hardwood deck wont outlast the pine. i've never seen treated pine rot (except for h3 in ground - but thats just dumb), my parents house even has h4 logs that have been inground for 30 years in a termite infested and poorly drained area, and not a skerrick of damage - cant be said for the 400*400 turpentine beam in the same garden.

making the effort to paint or alcore the tops of the joists and the joins over bearers cant be bad thing though - for the effort its worth doing.

I'd be using what this link will take you to along with duagal steel joists etc

http://www.ds.com.au/index_files/Page665.htm

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Yes 'OB' must be a Vic thing, but then we are in the forefront in most things.

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Pffft :rolleyes:

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Originally Posted by ausdesign

Yes 'OB' must be a Vic thing, but then we are in the forefront in most things.

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Double Pfffft! :D

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Originally Posted by pharmaboy2

I reckon the hardwood deck wont outlast the pine. i've never seen treated pine rot (except for h3 in ground - but thats just dumb), my parents house even has h4 logs that have been inground for 30 years in a termite infested and poorly drained area, and not a skerrick of damage - cant be said for the 400*400 turpentine beam in the same garden. making the effort to paint or alcore the tops of the joists and the joins over bearers cant be bad thing though - for the effort its worth doing.

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I'm getting around to taking a couple of photo's of H4 treated rounds that I'm currently removing showing three posts completely rotted out at ground level (how not to use treated pine). In relation to termites - cca doesn't necessarily kill them, it just makes the timber taste bad. Ive seen treated posts hollowed out, leaving only the outer 10mm where the treatment was most concentrated.

....
And to our northern friends who speak with a plum in their mouth it's pronounced "Oh Bee" :D

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Originally Posted by Eastie

In relation to termites - cca doesn't necessarily kill them, it just makes the timber taste bad. Ive seen treated posts hollowed out, leaving only the outer 10mm where the treatment was most concentrated.

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Yep I've seen that too in some treated Kapur, the big buggers that reside in Darwin, they'll sacrafice a few to get to the good stuff.