[Greenbuilding] Alternatives to Pressure Treated Wood

dantonioli at earthlink.net dantonioli at earthlink.net
Wed Oct 17 21:51:46 EDT 2007


Tim,

"Strength" and "structural integrity" are abstract terms that need to be
clarified when looking at the specifics of materials. Plastic lumber might
have "strength" in certain ways, but "weakness" in others. Just like all
materials. 

Concrete has amazing compressive strength (vertical loads) and a lot less
"strength" when it's applied horizontally.

My experience of working with, say, Trex, is that if you use it according to
the manufactures guidelines it works great. But if you take a "2x6" and rip
it down for sleepers, or rip it down at all, you're "weakening" the
"structural integrity" of the material. Down all the way to where the thin
end cracks and crumbles. The material simply can't don't much structural
work when it's altered in that way. Let alone be a good material for
attaching to other materials with screws, nails, metal hardware. It won't
work. You could make it work for a few years but it will fail, and it
wouldn't be ethical to use it on a project that someone is paying you for,
expecting it to hold. Plus, if you're pulling permits and doing work on the
radar the materials have to have ratings for the ways they're used. 

You're a big advocate of plastic lumber, and this is a situation where you
should take a very close look at my question: use of materials for sleepers
and ripping material down to zero. If there's a plastic lumber product or
"green lumber" available that can perform in this way then I'd sure like to
know about it.

As for black locust, my limited experience with it tells me that it will
work just fine for small dimensional sleepers and would be an excellent
replacement for pressure treated wood. But it's not available commercially,
and least in any readily available form in the bay area. 

Dan Antonioli





It's simply not true that plastic lumber has poor strength. Folks
continually confuse plastic lumber with plastic composite materials. They're
not the same and ASTM has agreed.

True recycled plastic lumber is stronger than wood. More flexible, yes. But
stronger (if one is considering modulus of rupture).

tim keating

At 12:15 AM -0400 10/9/07, Keith Winston wrote:
>Dan, I think me and everyone else are stalling because there aren't 
>very good options ;-)
>
>Yes, you're right sleepers are used all the time. Plastic lumber 
>typically has very poor strength, so while it might be used for a 
>sleeper design (as long as it's "full contact"), I'm not sure I'd trust 
>it structurally, from what I've seen. I sort of like the concrete pier 
>ideas, except that everything has to be quite high to make space for 
>full-fledged structural lumber in that case. If you're using sleepers, 
>you should probably try to align them with the underlying framing 
>(unless they are across it), since if you've got 1/2" plywood 
>sheathing, it might not support the weight of your deck happily between
rafters.
>
>There is some borate & polymer treated wood that I've heard about but 
>haven't seen. It can be found here:
>
>http://www.eswoodtreatment.com/
>
>Probably won't be too easy to get locally.
>
>There is cedar or redwood or ironwood/Ipe or whatever else you might 
>find, none of which (well, maybe Ipe) could be considered sustainable 
>(the Ipe distributors say it's grown sustainably, rainforest activists 
>typically say there's no such thing as a sustainably grown rainforest 
>tree, last I heard...). Ipe is extremely hard, has to be drilled to be 
>nailed or screwed, and would be sort of painful to use. Oh, and it's 
>not available in 2x lumber I don't think. Although it's extraordinarily
strong.
>
>There's another option on the books for pressure treated wood, 
>acetylated wood. I believe it is only currently available in Europe. Go 
>on vacation and bring some home! Take a freighter and it might not be 
>too ungreen! You can find out more here:
>
>http://www.titanwood.com/
>
>I've heard of a possible silicone treatment of some type for 
>direct-contact wood, but I haven't seen anything develop for the last 
>couple years.
>
>Good luck. Keith
>
>
>dantonioli at earthlink.net wrote:
>>  Hi Keith,
>>
>>  People keep wanting information about the design, which is 
>> understandable  but which distracts from the question. The only real 
>> alternative here that  I'm familiar with is to use redwood or other 
>> rot resitant woods. Sleepers  tapering down to zero are used all the 
>> time quite successfully....it's only  one end of a tapered piece.
>>
>>  A typical "floating deck" on a roof has to account for slope. Even
"flat"
>>  roofs are sloped. The point is to make a level deck. If you have 
>> plenty of  room to work with, then you can cut 4x4 or 6x6 posts and 
>> create a shoulder  to fit under sections of girders, underneath a 
>> typical framed 2x6 joist  package. The posts sit on additional 
>> roofing material and there are no  penetrations. I've built several 
>> and they're holding up just fine after a  number of years, but I'm 
>> sick and tired of using pressure treated wood in  this way....all the 
>> extra ripping and treating with copper green is  non-green and toxic 
>> to work with. I'm old enough to remember when all we  used in 
>> California was redwood....but it's limited, politically incorrect,  
>> and third-growth material rots out after five years or so....it just
doesn't  hold up like old growth.
>>
>>  The only pitch for plastic lumber is coming from people who have no  
>> experience working with it!
>>
>>  Dan
>>
>>
>> 
>>
>>  -----Original Message-----
>>  From: Keith Winston [mailto:keith at earthsunenergy.com]
>>  Sent: Monday, October 08, 2007 3:10 PM
>>  To: dantonioli at earthlink.net
>>  Subject: Re: [Greenbuilding] Alternatives to Pressure Treated Wood
>>
>>  Is the corner drain under the new deck (when built)? If I understand 
>> your
>  > context, sounds tailor made for drain clogs. What type of roof?
>>  EPDM maybe? Wood won't be strong when ripped down to nothing, like  
>> everything else. You can hold the deck back from the edges, or, raise 
>> it a  bit, as others have suggested, and use larger framing material. 
>> Sounds like  a large deck, 20' x 40'? Or maybe I'm misinterpreting.
>>
>>  Keith
>>
>>
>>  dantonioli at earthlink.net wrote:
>>  
>>>  The roof deck is sloped from three directions down to a corner drain.
>>>  The difference in elevation is approximately a foot, spanning a  
>>> distance of twenty feet. You need a sturdy frame of joists to 
>>> support  an elevated deck, but as I mentioned in many areas the 
>>> clearance is  minimal and, thus, the need for sleepers.
>>>
>>>  I've yet to see plastic lumber that can be ripped from, say, zero 
>>> to  three-and-a-half inches and hold its structural integrity, let 
>>> alone  be attached to a frame to create a rigid platform. But maybe 
>>> there's a  product that someone on the list has actually used in this
capacity.
>>>  Always checking the possibilities.
>>>
>>>  Dan
>>>
>>> 
>>>
>>>  -----Original Message-----
>>>  From: greenbuilding-bounces at listserv.repp.org
>>>  [mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of 
>>> Speireag  Alden
>>>  Sent: Monday, October 08, 2007 9:00 AM
>>>  To: greenbuilding at listserv.repp.org
>>>  Subject: Re: [Greenbuilding] Alternatives to Pressure Treated Wood
>>>
>>>  Sgrìobh <dantonioli at earthlink.net>:
>>>
>>>  
>>>    
>>>>  I'm considering a roofdeck project where I'll have to use a lot of  
>>>> pressure treated wood as "sleepers." The surface is uneven and  
>>>> there's only a few inches of clearance between the bottom of the 
>>>> deck  boards and the roofdeck....which means a lot of long rips 
>>>> through  pressure treated wood, and a lot of copper green over all 
>>>> of the  exposed untreated surfaces. The last time I built a deck 
>>>> this way I  told myself that I wouldn't do it again because working 
>>>> with PT this  way is unhealthy--there's a ton of pt dust, too much 
>>>> copper green,  and I can feel the physical effects and it sucks. 
>>>> I'm most likely  going to turn the
>>>>    
>>>>      
>>>  job down but thought I'd look into options.
>>>  
>>>    
>>>>  The question is: is there a rot resitant, structurally sound 
>>>> material  that can be cut and tapered? FSC wood? Exciting new
composition lumber?
>>>>    
>>>>      
>>>       There are structural plastic lumbers out there.  You should be  
>>> able to find them via Google.
>>>
>>>       However, I'm confused about why you need them.  If the 
>>> clearance  is that small, I'm picturing a flat roof.  Why not use 
>>> decking as  sleepers, with shims to even things out?  Then you 
>>> wouldn't have to  cut anything at all, except for length.
>>>
>>>       What am I missing?
>>>
>>>  -Speireag.
>>>
>>>  --
>>>  Anger, if not restrained, is frequently more hurtful to us than the  
>>> injury that provokes it.
>>>  --Lucius Annaeus Seneca, philosopher (BCE 3-65 CE)
>>>
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