poplar for roof repair

[Newby2019]

Hi

I've read that some people are using poplar lumber for roof decking
and for structural elements instead of plywood and pine 2x4s

Would this really be OK? Would moisture be an issue if used in mansards
rather than roofing?

Thanks

[WV Sawmiller]

   Where are you located? Are you talking about Tulip poplar?

    I can't imagine using poplar for decking or any place where it would be likely to hold moisture. Tulip poplar is not very durable in such conditions. I would think it would be fine for roofing where it should be dry but I am no expert or such.

[Don P]

I've recently sawn an entire house out of tulip poplar, dimensional lumber and sheathing. Any untreated building material is going to fail if it holds moisture. We borated everything which would help with decay fungi but powderpost beetles was the real reason.

[Magicman]

You should be OK.  If there is moisture under the roof you have more problems other than the decking.  No decking should get wet regardless of the material.

[Newby2019]

You should be OK.  If there is moisture under the roof you have more problems other than the decking.  No decking should get wet regardless of the material.

We also have mansards that may need decking and structural elements like 2x4s We've always just called them "overhangs" because they are above the first floor windows like awnings with shingles on top and soffits beneath - do you think poplar would hold up there?

And I am talking about the Home Depot poplar sold in the NE (NYC)
I saw people Mentioning some other types of "poplar" not sure of the difference.
Thanks

[Newby2019]

I've recently sawn an entire house out of tulip poplar, dimensional lumber and sheathing. Any untreated building material is going to fail if it holds moisture. We borated everything which would help with decay fungi but powderpost beetles was the real reason.

Does the Borate help with moisture issues as well?
How does one get wood "borated"?

Thanks

[Newby2019]

  Where are you located? Are you talking about Tulip poplar?

   I can't imagine using poplar for decking or any place where it would be likely to hold moisture. Tulip poplar is not very durable in such conditions. I would think it would be fine for roofing where it should be dry but I am no expert or such.

Thanks for the reply.
I read a post awhile back about someone who used poplar to avoid plywood and the more "aromatic" woods because of asthma concerns. We have similar issues and wondered if it really was workable.

[Magicman]

And I am talking about the Home Depot poplar sold in the NE (NYC)

Now I have no idea.  Our Tulip Poplar is all that have any experience with and it is not a true Poplar. 

This is a good example/reason for adding your location to your profile and also giving as much information as possible when asking questions.  My statement still stands that no lumber, regardless of species, will last long if subjected to trapped moisture and it matters not whether it is leaked from above or condenses from below.

[btulloh]

It's really hard to understand this moisture thing from what you've told us. As already mentioned, roof decking should never be exposed to moisture. Leaks or improper vapor barrier design is undesirable for any material. Poplar was used extensively for roof decking prior to plywood. Log cabins used poplar logs and are still standing, as long as they were out of the elements. 

It sounds like you could use a builder or contractor to sort things out. Or maybe some pictures and information so we could understand your situation. 

[btulloh]

If asthma or chemical sensitivity issues are the main goal you really should seek out an local expert.  There are building products that are specifically manufactured to mitigate those issues, but it's complicated.  There are many materials in the living space that are more problematic than roof decking.  Carpet, carpet pad, glues, counter tops and cabinet materials, paint, and on and on.  Most architects are able to specify appropriate materials.  Perhaps there is a builder with specific knowledge of these.  

Best of luck with sorting this out.  It sounds like an important thing to get right.

[Don P]

Agreed.

The common name "poplar" mostly describes 2 different woods, tulip poplar and aspen. It really doesn't matter much here, they are both non resistant to decay on their own however that would apply to any framing or sheathing you see in the big box that isn't treated. None of the framing lumber there would be classed as aromatic so any of them would be fine. Decay is caused by high moisture levels, the solution is to build and flash properly and to vent so that any moisture can quickly dry. Magicman is correct.

For borate look up Timbor or Bora-care or info on borate here. It has very low mammalian toxicity but inhibits the growth of decay fungi and kills insects that consume wood containing it by disrupting their gut bacteria. You can apply it or have a pest control operator perform that service. Search "borate" on home depot's site and you'll get a couple of the products they carry. Nisus is probably the largest supplier to the market, lots of info on their website.