HW decking over Treated Pine?

**Bleedin Thumb** · 25th Jan 2008, 03:50 PM

Hi folks,

Been asked to specify a boardwalk up on the Gold Coast and would like to specify TP for the bearers and joists for longevity but I loath TP as a decking material - I will specify 125 x 38 HW - F17 class 2 for the deck.

1. I was wondering is there any reason that you can't or shouldn't use HW over TP when building a deck?

2. Also am I better off specifying HW class 1 for the bearers and joists..IE will I get better life out of durability class 1 than TP?

3. Also what about Treated hardwood? I always thought it was a bit of a joke because the chemicals wont penetrated very far into the wood but now admit that it seems to last very well and I may have been wrong.

**Dirty Doogie** · 25th Jan 2008, 04:17 PM

BT, Most of the boardwalks (and they are everywhere) here use 38 mm or 50 mm hardwood on treated pine subframe. I would suggest the hardwood is durabilty 1, however I know that when they are laying the decking they hit the timber with heavy duty preservatives also. I have also noted that they use 150mm stainless batten screws to fix the decking down.

I was always under the belief that treated pine would outlast most class 1 timbers - at least last as long as hardwood. But then the treated pine I have seen used as subframing is special stuff treated to H5 level (special orders from timber processors like Hyne and son).

I think I would tend to specify H5 subframe and untreated hardwood clas 1 decking (but grease it up while laying it). my only experience of treated hardwood has been making sleeper walls where it hardly lasted 10 years before rotting. If you know the walk dimensions a timber supplier may be able to deliver hardwood decking pretreated or coated to your required lengths.

**glock40sw** · 25th Jan 2008, 06:21 PM

G'day Mr Thumbs.
Tanalith E treated Hardwood will outlast treated Pine buy 30 years or so in an above ground application.
For inground use CCA Hardwood is all I'd use.

CCA treated Spotted Gum treated to H4 level will Kill Treated Pine for lifetime.

For the decking, Treated HWD is the go.

**BustedThumbs** · 25th Jan 2008, 11:24 PM

After pre-drilling and nailing 15kg of nails into over 1000m of decking i can think of an excellent reason to use treated pine joists instead of hardwood.

I couldn't park a tank on my deck, but it's strong enough for most other uses.

**Bleedin Thumb** · 26th Jan 2008, 02:45 PM

Thanks for the responses so far guys.

Trevor, this job is refurbishing an existing boardwalk about 350m long and 1.8m wide.
the posts at the front and concrete bearer supports at the back are OK so it is all above ground - although the bearers are resting on concrete at the back.

Have you got any documentation to support your claim of lifespan of treated HW?

I know you used to get 40 years guarantee from CCA..is there a similar guarantee for TanE treated HW?

Cheers

PS Busted when you say 1000m is that linear metres or square...still a big deck!

**glock40sw** · 26th Jan 2008, 06:53 PM

Originally Posted by Bleedin Thumb

Have you got any documentation to support your claim of lifespan of treated HW?

I know you used to get 40 years guarantee from CCA..is there a similar guarantee for TanE treated HW?

G'day.
Arch Chemicals have MSDS and product data sheets on their website.
As well as product information sheets for Tan E. In this there is the reference to lifespan of the product.

Or you could ring the blokes at arch chemicals in Narangba. Tlak to Greg or Noel

Or Timber Queensland at Brunswick st. in the Valley.
Talk to Don.

**Bleedin Thumb** · 27th Jan 2008, 12:48 AM

Thanks Trevor, I'll follow that up.

**brynk** · 27th Jan 2008, 06:10 AM

gday bleedin thumb

here is some excellent info on building salt-water exposed decking / boardwalks in these articles/sites:

outdoor structures australia - http://www.outdoorstructures.com.au

boardwalk design guide

inground durability of aussie hardwoods at the fwprdc

commercial, industrial and marine decks by timber qld

timber design for durability by nafi

Timber Decks Commercial, Industrialand Marine Revised Edition 2004 by nafi (this one is a different doco than the timber qld one by the same name listed above)

far be it from me to be stuck on a rant, but i would use unseasoned ironbark for the structure & seasoned ironbark for the decking

r's brynk

**Bleedin Thumb** · 29th Jan 2008, 01:19 PM

Thanks for those links Brynk, It will take me a bit of time to get through all of that.

Also I seem to remember ( I think) reading about a deck fixing system that didn't require nails or screws through the deck board.........I've done a search and can't find anything...........Am I dreaming???

Does anyone know of such a system?

**HappyHammer** · 29th Jan 2008, 01:32 PM

Here you go....I looked into this a while ago.

http://www.nonaildecking.com/instructions
http://www.abc.net.au/tv/newinventors/txt/s1242476.htm
http://www.nonaildeck.com.au/store/index.asp

HH.

**Bleedin Thumb** · 29th Jan 2008, 02:43 PM

Cheers HH, has anyone used any of these systems?

The biscuit jointer system looks costly as far as time goes - I would also question if it had the strength ..its is only less than half a deck board thickness holding it against cupping forces IE 7.5mm.

Anyhow I don't think it would be the go on the 38mm deck boards I'm using on this job but for a domestic application it may be OK.

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HW decking over Treated Pine?

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