Decking timber question....

**shanan** · 16th April 2013, 07:08 PM

Hi guys,

I know that decking - in particular discussions about the "best timber" to use - has been a long and ongoing discussion across many forums.

Aussie hardwoods are great looking and hard wearing, but as we all know - can be expensive.

Then we go to the imports - many to choose from - generally at a cost lower than the aussie hardwoods.

Given the large size of my deck and my budget - research is pushing me towards these final two...

1. Merbau 90x19 @ $4.35 per metre (from a reputable supplier of sustainable timber of course)
2. Mahogany (Fiji) 90x21 @ $3.95 per metre (also from sustainable forests)

Merbau is a safe bet. Hard wearing and low cost. Various prices around, but best I could find from reputable source was $4.35 l/m. This was from a place that guarantees it was taken from sustainably managed forests and also will replace any dodgy bits you may receive in your pack once it is broken down. No throw away junk in any of the lengths I might purchase. Nice to know.

Mahogany is the mystery bet out of the two. I got a great price at $3.95 l/m, from a supplier that has provided prompt replies and great service so far. The timber rates well for wear and is also attractive and long lasting.

I have been trying to find posts of people using it and have not had much luck. My biggest concern is that I have NEVER seen or visually eyeballed a mahogany deck. A few spotted gum, some other Aussie hardwoods around, but mostly Merbau.

I do love the colouring of Merbau - I am familiar with it. Which again makes it an easy pick.
As for mahogany, all the web images I have seen of Mahogany seem to vary to no end! Pinks, reds, browns - don't know if I am looking at stained, or maybe different mahogany types.

Anyone got experience with Fijian Mahogany? This is what I am leaning towards, but would love to get any feedback on it from local guys who may be familiar with it before making a purchase.

Good to work with? Is it a nice colour with some age on it? Any issues? Did you stain it? That sort of feedback would be great.

Can't see anything wrong with mahogany and the price is certainly right. Just wish I could find some real feedback on it.

Cheers,
Shanan

**timboz** · 17th April 2013, 08:39 PM

Hi Shannon,

I would definitely steer clear of mahogany unless the deck is totally enclosed as it only has a durability rating of 3 and possibly only 4. The rating will depend on whether the 'mahogany' is that of Victorian era commerce ie Sweitenia species (which is likely as the Fijian forestry department established large plantations of Sweitenia around 50 years ago). If it is, then durability class 3. If however it is Phillipines mahogany, then it is Shorea species and is durability class 4 (as bad as it gets). Meranti is a Shorea species. Further, the Shorea genus has been heavily overexploited and supply is now largely limited to Malaysian origin. As for Merbau (AKA Kwila) also heavily overexploited,, the durability rating is only 2. If you really want your deck to last and love rich reds, I'd be trying to get a good price on red ironbark (which you may find is easier than you think).

Hope this helps, Regards Timboz

**PrideMahoganyFj** · 18th April 2013, 10:25 AM

Timboz mate i feel its my responsibility to clarify that Fijian Mahogany has a durability rating of 2, according to Australian standarda as they are H3 treated and Kiln Dried with a low moisture content of 10-15% max.
Strength standards are S6 green.
Thanks

**timboz** · 18th April 2013, 03:15 PM

Originally Posted by PrideMahoganyFj

Timboz mate i feel its my responsibility to clarify that Fijian Mahogany has a durability rating of 2, according to Australian standarda as they are H3 treated and Kiln Dried with a low moisture content of 10-15% max.
Strength standards are S6 green.
Thanks

Not to start an argument PrideMahogany, but no mention of H3 treatment was evident in the thread opener. Additionally I'm unaware of a single medium or high density species that has any significant preservative penetration of heartwood and thus heartwood durability - even for treated material - is effectively equivalent to natural durability in service. In this case, class 3. Any penetrations of the timber- nailing, cut ends will form entry points for fungal spores and rotting will occur from inside out. Sapwood is the only real beneficiary of preservative treatment. The equilibrium moisture content of an installed exposed deck will be around 20% (trigger point for fungal decay) regardless of what the moisture content was 'out of the pack'. Locally, decking/joist interface moisture levels will be much higher and fungal activity also much higher. The timber advisory board suggests both class 1 & 2 durability timbers may be used, but for my money I'd always go for a responsibly managed class 1 Australian hardwood (please note Fijian plantation Mahogany IS responsibly managed as opposed to Shorea species - nearly all fsc labelling is rubber stamping!).

Regards, Timboz

**shedbound** · 18th April 2013, 05:04 PM

Is cypress deck an option?
regards
joel

**shanan** · 18th April 2013, 05:18 PM

Thanks for the responses.

Will take all comments on board.

Timboz - appreciate the detail. Sounds like you know your stuff.

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