Thermo Treated Decking Lumber Question

[Steveo]

I am aware of a few companies making thermo-treated lumber in the eastern to mid-western US (Cambriawood, Ecovantange, Purewood, Westwood, Keim) where lumber is modified under high heat in a controlled atmosphere to improve dimensional stability and decay resistance.  I have only seen a few posts on this forum regarding this treatment, and those only from a fellow overseas.

Does anyone have any experience with how this end product performs as an exterior decking material.   I understand that it has very high rot resistance, but at the same time it is recommended to have a periodic maintenance program with recoating every year or two.  I am also concerned with brittleness and suseptability to splintering.   For the significant price premium over PT SYP, and with a similar required maintenance - I would like to know that it will end up superior in looks, lifespan and performance.

Anybody have any experience or pros or cons to share.

Thanks
Steve

[Magicman]

I'm no help for your question but, Welcome to the Forestry Forum, Steveo.   

[tyb525]

Member Serg should be stopping by shortly

[Steveo]

Thanks magicman.
TMB525 - I have read Serg's posts and looked at his photos - very nice (though I do have a hard time understanding all, lol) 
I have some samples in hand from two suppliers, and it is very interesting stuff.
Color is richer and darker all of the way through the wood, I would love to give it a try and see some more green products get a footing (though it is a tough step to be the test-monkey).
If anyone else has any info on how it performs over time (looks, splinters, etc), let me know - otherwise, I will report back once I make my decision (between this and black locust)
Cheers.

[beenthere]

Curious, how thermo-treated wood is "green product" to you?

[Steveo]

Curious, how thermo-treated wood is "green product" to you?

I am certainly no expert, just an individual trying to educate myself and do something different.  I understand that the energy expended to superheat the thermo-treated products likely takes them out of the realm of a "green" product.   My thoughts are generally in comparison to the standard residential decking material in my area, which is PT SYP.  The PT takes some effort and poisons to create the end product.  PT does not last as long, which means there is a doubling or tripling of material needed over a lifetime (to be cut, treated, handled, etc).  Then, at the end of its useful life, I do not believe that the PT wood should be put into a landfill or burned and therefore, similar to the composites, - I am not sure what you should do with it. 

I like the idea that Thermo-treating is a process that can be performed on a wide variety of species - and opens up more sources than just older growth redwood, cedar and tropical rainforest woods (which may or may not be sustainably forested) to get a long lasting durable material.

Once again, I am just an average joe in the midst of a busy active forum of knowledgable foresters, sawyers, etc - so you can probably shoot holes right and left at my logic.  By I guess that is part of the process in getting myself a good education prior to picking my next decking material.  (btw - I am leaning toward Black Locust at the moment)

Thanks

[serg]

Dear Steveo!




I want to understand precisely your questions. For this purpose, please, send to me an interpretation of the term «PT SYP».

If I have correctly understood: You ask, what is more practical to use wood preservative treatment or Thermo-treating wood?

If I the usual consumer - I choose the Thermo-treating wood.

Why?
My experience and 5 years of supervision have yielded positive results:
1.   Stable humidity of Thermo-treating wood  indoors from 4,8 % to 6,0 %, in the street 8 - 10 %.
2.   Stable geometry of products.
3.   Biological stability
4.   Insects, bugs, larvae won't appear in wood never.
5.   Change the color of the entire depth of the Thermo-treating wood, scratches aren't visible on Thermo-treating wood.
6.   Of course, Thermo-treating wood burns, but the positive result consists that the Thermo-treating wood allocates carbonic monoxide less.
7.   Finished blanks, block finished product, kits for building houses, can stay for a long time in cold shops without heating, wait a long time of departure on the construction site for installation (today in Russia nobody can do it - all the blanks will be destroyed by shrinkage, mildew, blue, insects .) I think in America there is a same problem.
8.   Low thermal conductivity of  Thermo-treating wood.
9.   The weight of one cubic meter of Thermo-treating wood more low so and hence the pressure on the foundation of the house less as well.
10.    "Green" product, environmental friendliness, I do not use an inert gas, oil

See photos, 8 months of operation in natural atmospheric conditions.


I know that it is necessary to apply a natural product to protection against ultra-violet light: oil - wax with a pigment




I can send you results of the tests physical - mechanical properties of Thermo-treating wood  (with the my supporting tests done during the last 3 years at the Moscow Forest University) as compared to wood which has not been thermal modified - if it's interesting.



If you have any questions - please send me.







tthermo abachi

thermo acacia

thermo ash


Best  regards,
Serg

[Den Socling]

Hi Sergie,

PT SYP is Pressure Treated Southern Yellow Pine.

What about brittleness? How well does thermally treated wood take a screw or nail?

Den

[timbatrader]

I produce Thermowood in New Zealand it is important to remember it is a process that can be applied to many different species and at different temperatures
The higher the temperature the better the durability but at the expense of strength. Different species will give quite different end results. In New Zealand we (www.tunnicliffes.co.nz) are using Radiata Pine modified at 230 degrees Celsius the top end of the scale. Our Thermowood is brittle and losses about 20% of its strength. Tests have proved the Thermowood to be durable outside in exposed conditions above ground. But not do so well in below ground tests.
In my experience decking timber needs to be treated to a higher standard than other outdoor timber cladding and the like. Decking lying horizontal in close contact with the bearers  often traps dirt between palings and holds water this creates a situation bordering on the same as timber in ground.
Combine that with the brittleness and the 20% strength loss I do not recommend Thermowood for decking   

[Steveo]

I produce Thermowood in New Zealand it is important to remember it is a process that can be applied to many different species and at different temperatures
The higher the temperature the better the durability but at the expense of strength. Different species will give quite different end results. In New Zealand we (www.tunnicliffes.co.nz) are using Radiata Pine modified at 230 degrees Celsius the top end of the scale. Our Thermowood is brittle and losses about 20% of its strength. Tests have proved the Thermowood to be durable outside in exposed conditions above ground. But not do so well in below ground tests.
In my experience decking timber needs to be treated to a higher standard than other outdoor timber cladding and the like. Decking lying horizontal in close contact with the bearers  often traps dirt between palings and holds water this creates a situation bordering on the same as timber in ground.
Combine that with the brittleness and the 20% strength loss I do not recommend Thermowood for decking

Thanks for the input Timbatrader - hearing that thermo-treated lumber is NOT recommended for exterior decking was absolutely the LAST thing that I thought that I would hear from a thermo-treated lumber producer (the local suppliers around here say otherwise - I hope that they are not overselling beyond its capabilities just to make a sale).

I am not overly concerned about the loss of strength of 20-30%.  This is continuous decking on joists at 16 inches o.c., so it should have plenty of strength and stiffness even with a reduction.  I will not be using it for any more highly stressed structural members.   My deck is over 1 meter above the ground (so only the kicker plate of the first stair step will be close to the ground.  Of course, the decking will be in direct contact with the supporting joists though.  I am curious if you have witnessed deterioration of the bottom of the decking where it is contact with the joists or if you are just mentioning that it may be a possibility due to the potenital of trapped water.  I have heard some recommendations that I treat on all sides of the decking lumber before installation (maybe that is for additional protection at the interface).

Serg - Thanks for your note and all of the photos.  I really do not need the more technical data on physical and mechanical properties, strength reductions, etc.  I am mainly looking for input from people who have had experience with 5/4 decking for an exterior application for an extended period of time - so I can hear about first hand experience regarding how the thermo-treated lumber held up (looks, splintering, durability, etc.)

Cheers  -  Steve

[beenthere]

.......................  I have heard some recommendations that I treat on all sides of the decking lumber before installation (maybe that is for additional protection at the interface).
............

Steve
What does "treat" refer to here? thermo maybe? and if so, how to treat less than all four sides??

[Steveo]

.......................  I have heard some recommendations that I treat on all sides of the decking lumber before installation (maybe that is for additional protection at the interface).
............

Steve
What does "treat" refer to here? thermo maybe? and if so, how to treat less than all four sides??

Sorry for the poor choice of words.  I meant to say, "apply a protective coating" to the decking that had already been thermo-treated  (I have heard varying recommendations for boiled linseed oil, to acrylic base products, to other proprietary brands).   The thermo-treatment apparently affects the full thickness of the wood equally (all sides and the interior).  I have cut one of my samples and have found that the color is fairly uniform throughout (and darker than the typical untreated samples of the species).
I have seen interesting photos of the color change due to different treatment temperatures - see page 44 of the link below to the ThermoWood Handbook.              http://www.thermowood.fi/data.php/200312/795460200312311156_tw_handbook.pdf 
I have not read the whole thing yet, but there is alot of interesting stuff in it.

Steve 

[serg]

Hello colleagues!
Unfortunately we didn't do tests concerning nails and screw pulling, but we are planning it in future.
As for the ultraviolet resistance, we recommend to use some protective coating, to save the original color and use higher heat-treatment temperature to make the initial color darker (especially, for the exterior application).
You asked about brittleness, we are using four temperature regimes: 165, 175, 185 and 195 °C and can prevent it choosing the right temperature for each species of wood. For example, with pine, that you are interested in, it's better to use mild regimes. You can improve strength properties of wood, if you know how to choose regimes of heat-treatment
We also made some tests concerning water absorption and get good results with spruce, birch, oak and hornbeam. Untreated and heat-treated pine is taking water in the same way. As for the moisture absorption, heat-treated pine, spruce, birch, oak and hornbeam are taking less moisture then untreated wood.
Sergey

[timbatrader]

Be careful about coatings like boiled linseed oil it does improve the looks and water resistance. But Thermo wood works by burning off or denaturing all the sugar like chemicals in the timber leavening no food for bugs mold or fungi. Which is one of the ways the durability is improved. If you add boiled linseed oil you are adding a food source for some molds which once established can carry on to do harm

[Steveo]

Just a follow up for anyone interested. 

I am a structural engineer and the original poster to this thread who was looking for information about Black Locust and Thermo-treated lumber.  I ended up going with the Thermo-treated and thought someone might be interested in a photo.

Specs:  Framing: P.T.SYP#2, Decking: Thermo-treated Poplar, Rails and Posts: Clear Cedar (C or btr), Balusters: powder coated aluminum, Deck coating for UV protection:  Flood CWF-UV5, Deck Fasteners - DeckMaster (concealed, screwed from below).

Took a while to build but it was fun.  The three kids did most of the screwing of the decking from below, while I supervised, aligned and weighted down the deck.

Steveo

[Steveo]

Oops, forgot the photo.  Here it is.


 

[jueston]

it looks great, i really like the color of the decking with the stain. 

[Den Socling]

It does look great. Could you post a couple close up pictures to show detail?

[GeneWengert-WoodDoc]

Properly treated syp will last for a century.  The problem we hear about is when it is treated to refusal or is not certified.  One treater in GA used green colored water to treat guard rail posts.  So, bad treaters are out there.

The screw holding of thermally treated wood is much lower.

The wood is also very absorptive of water, so a coating is needed.  I expect that freezing of water in the wood without a coating will do damage and may even make the surface slippery.  This absorbency would also mean that it will absorb any coatings or stains.  As already mentioned, any coatings must not be attractive for molds or mildew fungi

When we make a deck, we often use 5/4 radius edge syp treated.  This is both an appearance product and a structural product.  With the 20% strength loss (or more) in thermal wood, I do wonder if it still meets the required strength for decking material...probably not.  So, I do believe it would be unacceptable in the building code that is used in most locations in the US.

I am curious on how the deck boards were screwed from underneath...screw length, per drilled pockets, depth of penetration, one screw per joist or two, etc.

[jueston]

Properly treated syp will last for a century.

I find this interesting, because I know there are different levels of treating, but I don't think i have met a pine deck which was not covered by some type of porch which lasted more then 30 years. Most builders say pt decks have a 15 to 20 year life span.

[GeneWengert-WoodDoc]

Any idea on why the deck fails?  Does it rot?

It would seem that the frame underneath would be much more likely to fail than the deck as the frame has much higher RH and potentially wood that gets wet and does not dry quickly after a rain.

There is  some pt wood on the market place that does not have adequate treatment, but is sold as pt.  One needs to find the appropriate sticker or stamp from the legitimate agency.

[GeneWengert-WoodDoc]

I cannot imagine putting up a deck that would only last for 15 years and then, I assume, it would fail.  The failure could create a hazard or harm for a human and so we would see insurance claims and maybe court cases.  This just does not happen for properly treated wood.  The frames last 50 plus years with properly treated wood.  Maybe the builder did not treat the freshly exposed ends or did not treat any holes.  There are certainly some requirements for pt wood, including the type of fasteners that must be used...no contact; glav. fasteners or stainless.  Because the wood moves (rain-sun-rain-sun, etc.), the wood deck needs to be fastened so that the members can move.  Note that properly treated py wood has a life time warranty.

The best deck surface will be using pt 5/4 radius edged decking (both structural and appearance requirements).  Using 2x6s, No.2 pt (structural concerns only) is not as good due to more defects, shelling, heartwood, etc.

[jueston]

well i should rephrase what i said, i said that builders will say the deck will last 15-20 and that is false, that i meant was, after 15 or 20 years deck builders will recommend replacing the decking. I verified with a google search, and found many contractors saying just that. they are of course in the business of replacing decks, so there advice is obviously a little biased.

but either way i shouldn't speak of all decks everywhere, just with my limited experience. which has been with low quality pt lumber from a certain big box store where you save you big money at... their store... and that experience was that after 1 year it looks like it was built by a drunkard because it has twisted every which way. [i'm only 25 so i can't say i have seen a deck go from beginning to end] but the deck which was installed in this house when i moved in was at ground level, which shortens the life of pt lumber i'm told, it was supported by those concrete blocks with groves made for building decks on top of. when i removed the decking, which looked aged but sound, i found rot on the bottom of some of them, especially where it was in contact with the joists. some of the joists were also rotting at ends. the neighbor said the former owner built it himself 10 or 12 years ago with lumber from that same big box store. the deck was not very well built, and i doubt that he took any special precautions to ensure longevity.

i am confident that a professionally framed deck made with high quality materials would last much longer.

[GeneWengert-WoodDoc]

The twisting should not occur with 5/4 radius edged decking material as it has tighter requirements on slope of grain and other characteristics than a No.2 or Construction grade 2x6.  Note that in most of the U.S. east of the Rockies, decking is pressure treated southern pine, which is prone to twisting, partly because twisted grain (or slope of grain, SOG) occurs as spiral grain in the tree for the first 15 years of growth.  Red pine is even more severe SOG in the early years.  SOG, in addition to twist, also weakens the wood piece tremendously, even just a little slope.

My experience:  I have a 21 year old deck with 5/4 radius edged decking, pressure treated syp.  It looks today (well actually today it looks white, but when it warms up) as bright and flat as the day it was installed.  I did have it screwed down but have not put any finish or stain on it.  I power wash it every two years (or so) to get the mold and green algae and mildew off.  The reason I do not use a deck product (like a stain or water repellant) is that after a rain or melting snow, with the repellant sometimes the water will sit on the boards and freeze, making a miniature skating rink in every piece.  Without a coating, the water soaks in and so is less slippery.

[Den Socling]

Nice to hear that yours is still good after 21 years, Gene. Mine is 15 or 20 years old. I never noticed any warp or decay. I put a finish on it only once and that was a long time ago. All this talk of replacing a deck every 15 or 20 years was getting me worried.