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Modified woods for decking

Thought about posting this in TC rather than a new post, but doing a search and not coming up with anything in the forums I thought it might be nice to have a separate thread for posterity. 

I'm a little out of my element on some decking materials for a residential project. Owner is trying to avoid plastic composites (i.e. Trex) and tropical hardwoods (i.e. ipe).

Regular old cedar decking seems possible, but having had to replace it on a previous home myself, I know it doesn't last all that long if the (in my case the previous) owners don't maintain it, especially if it is prone to collecting debris in the gaps between boards holding moisture against the wood. Owner's yard has some large evergreens shading the area that drop needles and other small debris (pollen cones for example) that could be a potential issue. Owner says they are ok refinishing cedar, but would prefer something with less maintenance.

Anyone have any experience with modified woods ... thermally modified like Thermory or Arbor Wood; or chemically modified like Kebony (furfurylation) or Accoya (acetylation)? Owner isn't too particular about keeping the wood from graying out either, which I understand all of these woods will gray out if not finished and maintained, but it is not a requirement to maintain a finish on these to keep warranty coverage if I'm not mistaken. Anyway, if anyone is willing to share insights from their experiences with any of these types of products for decking, I'm all ears.

 
Apr 7, 21 12:24 am
randomised

Considered bamboo? Haven't used it as outdoor decking myself, was an indoor application (corridors and walls) but remember the sales rep. also mentioning it was great for outdoor use as well, next to swimming pools even or in a coastal salty air environment: https://www.moso-bamboo.com/ap...

Apr 7, 21 3:48 am  · 
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benroberts

Keep in mind with Moso and Dasso, you have to maintain and seal the decking regularly to keep the warranty, where as with modified woods you can let them gray and keep the warranty, like you said. 

For decking, Kebony is your best bet because it is the most durable of the modified woods you mentioned. It's also the only MW that is both chemically and thermally modified, and looks the most like Ipe. I would check out www.kebony.us for more info. 

Full disclosure, I work for Kebony, so do your own research and see for yourself! 

Apr 7, 21 9:58 am  · 
2  · 

Thanks, I appreciate the disclosure.

Apr 7, 21 1:38 pm  · 
1  · 
archanonymous

Kebony and Accoya both work well but with all the shipping (New Zealand > Europe > North America) I'm not sure how good the net carbon footprint is. Thermory is produced in the US and use North American grown wood (White Ash) which makes them the best in my book. Unfortunately, the board lengths aren't super long. But it does look nice.

Apr 7, 21 10:06 am  · 
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benroberts

Thermory is produced in Estonia, not the US, so they are shipping from the US to Europe back to the US.

Apr 7, 21 2:52 pm  · 
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benroberts, curious if you have information on the embodied carbon of Kebony's products from cradle to gate? Like in an EPD for example.

Apr 7, 21 8:25 pm  · 
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benroberts

We have FSC-certification and ICC, I can look into carbon-related documents.

Apr 8, 21 9:11 am  · 
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thatsthat

I've worked with Accoya for a greenhouse project I did about 5 years back. At that time, the contractor could only source it from England, which meant paying extra for shipping and delays on the project waiting for the material to come through customs. According to the manufacturer, only certain paints ($$$) should be used with the wood, which sounds like is not an issue for the OP's owner currently, but if the owner decides to sell, it may be an issue. For the greenhouse project, we had to paint, so I'm not sure how it finishes when left natural. Otherwise, the wood cut and installed like dimensional lumber.  

Apr 7, 21 10:16 am  · 
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I've noticed some finish manufacturers indicating in their data sheets that it is not suitable for acetylated wood which caught my eye. I'll have to dig in more if they decide to go with that type of wood. Though I am finding more information that it isn't as good for decking applications as other options.

Apr 7, 21 1:30 pm  · 
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justavisual

You can find a nice grey stain to prestain the accoya to avoid it weathering unevenly. It looks good we are using it on a project now. Def recommend accoya as a product...

Apr 8, 21 3:06 pm  · 
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tduds

We're replacing a deck on our house this year... thanks for the thread, I'll be looking into these (...even if only to find out they're way above my budget)

Apr 7, 21 11:15 am  · 
1  · 

I'm anticipating the budget conversation at some point. Especially with wood prices being what they are.

Apr 7, 21 1:31 pm  · 
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tduds

Prices are insane right now. I just spent $500 on lumber for a few planter beds.

Apr 7, 21 3:02 pm  · 
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I would have thought Oregon of all places might might have been spared somewhat on the higher prices.

Apr 7, 21 8:15 pm  · 
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proto

It’s nuts...I get a new higher number each time I ask our gc’s how much plywood is

Apr 8, 21 11:04 am  · 
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joseffischer

I get that I'm about to suggest something that may not be possible... but it's always helpful to have the big picture conversation with the client if their requests don't line up with our expertise...

You want a deck but you don't like composites due to plastics and you don't like the woods you build a deck out of because "don't use exotic wood"... for our environmentally conscious clients, we recommend patios over decks.  We can raise the grade if desired or provide a simple step down and smaller landing (out of exotic wood) to a lower patio... either way, your material selection should be in the pavers/stones world, which will align with your sustainable sensibilities.


Apr 7, 21 11:57 am  · 
2  · 

It's a fair suggestion. We did talk a little bit about this because they already have a smaller concrete patio that could be extended or torn out and redone larger with different materials if desired. They prefer a deck because it won't have a step down from exterior doors, and with the type of tree debris, having it able to fall through the joints and be out of sight is also appealing to them. On a patio, it just collects and they'd end up dealing with it more often.

Apr 7, 21 1:35 pm  · 
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Also, just to clarify on the expertise and my earlier "out of my element" comment, because I suspect some may take it to mean something I never intended (not aimed at you specifically joseffishcer, I agree with your comment, I'm just taking the opportunity to clarify):

I do have some experience with residential decking and have installed my fair share of composite decking products back in the day when I was working in residential construction. Framing the deck itself is actually pretty straightforward in this instance as it will be under 18 inches high and completely freestanding from the house. No permit required, no ledger and flashing required, pier blocks would probably work though instead I'm leaning toward a poured footing just to anchor the whole thing better.

I don't have a lot of expertise in these decking materials because they don't usually come up as materials on the commercial projects I work on. Most of our clients are not interested in wood materials for maintenance reasons, and instead we are doing pedestal set pavers, or similar for their roof decks, etc.

Normally in a case like this, I'd just defer to someone who knows more than I do, but it seems like the times architects stretch themselves to areas outside of their comfort zone are for money or family. This case just happens to be the latter.

Apr 7, 21 3:01 pm  · 
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Wood Guy

I love doing freestanding decks, when they will work. Have you considered helical metal piers? They're great for decks.

Apr 8, 21 10:58 am  · 
1  · 

I hadn't considered them, no. There are some contractors in the area that do it according to the google machine, but I'll likely be doing a lot of the work myself with the owner (not only do I get to design for free, I get to build for free too!).

Are there DIY options for helical piers, or do I need to have a contractor with the right equipment place them for me? For additional context, 12 inches is the frost depth where the deck will be located. It's not that big of a deal for us to dig by hand and mix up some bags of concrete.

Apr 8, 21 4:18 pm  · 
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Wood Guy

I don't have first-hand experience with modified woods other than plain old pressure treated, which is an odd gap in what should be within my wheelhouse. I typically spec local white cedar decking, and design for easy replacement after 10-15 years. I have used boatloads of Ipe and other tropical hardwoods in the past but try to keep it local these days. If black locust is available to you, I know it can make a good deck surface, though I haven't used it yet myself. Like Joel, when possible I push for patios rather than decks. 

Apr 7, 21 12:26 pm  · 
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lol, I was hoping you'd have more experience with these materials. I almost just reached out to you individually. I'll have to check on black locust.

Apr 7, 21 1:37 pm  · 
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atelier nobody

I've had good experience with Black Locust, although I've also had it get "VE'd" in favor of Ipé (which is cheaper because Third World labor).

Apr 7, 21 2:09 pm  · 
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Wood Guy

Haha, I know, my screen name is embarrassed for me. I used to design a lot of decks (and before that, built many) but for some reason I haven't done many in recent years, overlapping with the rise of various modified wood products and my growing interest in low-carbon construction. The one product I spec'd was Eastman Kodak's Perennial Wood, an acetylated southern yellow pine, but that was discontinued. I'm designing a new house now with a big deck, 75' from the Maine coast, and I can't talk the owners out of plastic decking. It's going to hurt a little.

Apr 7, 21 2:31 pm  · 
2  · 
randomised

Plastic? Show the owners this thread maybe?

Apr 7, 21 3:02 pm  · 
1  · 
Wood Guy

Rando, thanks for the suggestion but they know my stance. I need to write an article about it--referring people to something published that I wrote has been surprisingly effective. I guess I'm not very convincing in person? LOL.

Apr 7, 21 3:27 pm  · 
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atelier nobody

I don't know enough about it to make a recommendation one way or the other, but you might look into silicate-treated wood.

Apr 7, 21 2:10 pm  · 
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Thanks, I learned something new. A quick google search turns up some older articles on green building websites for TimberSIL that are gushing over it for being non-toxic, etc. That's quickly followed by other articles about lawsuits against TimberSIL for some issues on Brad Pitt's houses in New Orleans where it was installed and didn't last.

Probably one I'll avoid for this.

Apr 7, 21 3:13 pm  · 
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mightyaa

Black locust. Very hard like IPE and durable. Harvested in the southern States. IMHO better option than cedar and like cedar, you can leave plain untreated, stain, or whatever. It got a bad rap a number of years ago because it takes special kilning to dry it... and if done wrong, it warps... and was done wrong for a couple major projects.

https://www.blacklocustlumber....


Apr 8, 21 10:21 am  · 
1  · 
Wood Guy

It grows in the north too--I planted a small grove here in Maine, though it's now considered invasive. My architect friend in Vermont uses it regularly; it grows bigger and straighter there, apparently, and/or there are mills that know how to properly KD it.

Apr 8, 21 10:31 am  · 
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Jaetten

We specify Accoya a lot. Never in a decking solution, but for cladding, windows and doors it has been excellent on all of our projects.
Works the same as timber, its pressure treated and cutting doesn't effect this, as the timbers capillary system allows the treatment to penetrate through.

Not sure on how it performs in a structural context, which I assume you'd also want to use it for.

Apr 8, 21 10:41 am  · 
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What types of finishes are you using on it when used as cladding in your projects?

I'd just be using it as the decking material. Joists and beams will be pressure-treated hem-fir lumber rated for ground contact.

Apr 8, 21 11:46 am  · 
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proto

It seems like the standard is a little unreasonable here...you aren’t allowed anything but perfection and that doesn’t really exist

Pick a direction that fits the project design best then understand the downsides. Personally, I love ipe decking for its long service life (and it is gorgeous), as a balance to its harvest profile. And it prices out cheaper than clear cedar afaict

I’ve only used accoya once so no long term experience...I’m not a huge fan of the colors/patterns, but it was appropriate to the look for a particular project so we used it

Apr 8, 21 11:11 am  · 
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I don't think the standards set are unreasonable, nor are they set for perfection. Really the only standards so far are that we want to avoid certain materials, and a desire for minimal maintenance (not zero maintenance).

That leaves us with a bunch of options ... none of them perfect. Of course neither are the materials we're avoiding. We understand there will be pros and cons to each. Part of the process is understanding what those are so we can make an educated decision, and as you say "understand the downsides" to what we've chosen.

Apr 8, 21 12:06 pm  · 
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justavisual

Check out Esthec terrace - really good non wood solution for decks

Apr 8, 21 3:08 pm  · 
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