View Full Version : Seasoned or Unseasoned - Deck

24th February 2004, 02:23 PM
I am currently in the process of designing (this sounds like I know what I am doing) a deck and am wondering what timber to ultimately use. I have all the dimensions sorted ie bearer, joists, posts etc, but am wondering whether I should be considering seasoned or unseasoned timber. I dont like the idea of timber shrinking and perhaps warping so I expect I should only be looking at seasoned - any thoughts. Whats more common?


24th February 2004, 07:21 PM
I don't thing unseasoned timber would be a good idea.

the decking hardwoods seem to be the go, kwila, merbau.

stay away from the treated pine stuff if you want it to look good. it goes a dirty gray brown blerk colour after a while.

others may know better.

25th February 2004, 12:47 AM

Thanks for the response - I agree that hardwoods are the way to go for the actual tread timbers. My question is in relation to the posts, bearers and joists. I'm not sure it makes a great deal of difference, but I have read that unseasoned timbers are prone to shrinkage and warping - just trying to see if there are any informed opinions on the subject.


journeyman Mick
25th February 2004, 01:15 AM
There may be regional differences due to supply but up here green hardwood subfloor framing is still the norm. Once it's all bolted/screwed/nailed/trip-l-gripped together warpage/movement is not really an issue. Shrinkage due to seasoning is only a minor consideration. Timber only shrinks appreciably across the grain. Let's say you had 150mm joists sitting on 200mm bearers, this gives you 350mm of cross grain hardwood. If you had a 3% shrinkage rate your floor height would drop by 10.5mm. If your deck height needs to marry in to an existing floor height then this could be a problem and you would need to get shrinkage figures and do a moisture content check. In practise I've never seen any problems.


25th February 2004, 08:19 AM
1500k south of Mick the same goes for unseasoned timber framing.

Don't forget to prime the tops, ends and joints (an old hobbyhorse of mine!)

Pine decking has it's place and can look quite good if finished with a bleach or liming stain...giving it a mellow pre-weathered look. Works ok at the beach or in the bush.

My last house had unroofed decks of both hardwood and treated pine, both given one coat of grey stain when new. After 12 years we pressure cleaned them (we are fastidious about regular maintenance you see):D Pine looked just as awful as it did the day it was layed, Hardwood had some areas where the sapwood had rotted and would need attention within a few years.

Even though the timber will last much longer, I think if you can get 15 years out of an unroofed deck your doing OK in any case.

25th February 2004, 04:54 PM

I just built a deck - same kind of issues came up. I bought unseasoned softwood for the sub-structure (I think). I have had no problems with shrinkage/warping etc. Except for the one joist I left out in the sun one day. Nothing a bit of brute force and 100 nails couldn't fix.

Talk to your timberyard - they should be able to help.

As for the decking, look for recycled timber. I found some at about the same price as merbau etc. Looks great, it is well seasoned and you get a warm fuzzy feeling knowing that you didn't contribute to the destruction of tropical rainforests. [stepping off my soapbox now].

Good luck with the deck. Buy a good hammer and lots of nails!


26th February 2004, 09:23 AM
Thanks Trav,

Its always good to hear real life experiences - what type of hardwood did you decide on? I assume you are using oil to protect the timber - how is it coping?


26th February 2004, 09:30 AM

I went with spotted gum/blackbutt mix. It looks great. I've been using wattyl decking oil - seems to work OK.

One thing to watch out for - you need to clean the timber before oiling it. I had a whole stack of little back spots appear on my deck - I needed to scrub the whole thing down with deck cleaner and then re-oil. There's a weekend I will never get back!