pressure treated ash shingles

[Josef]

Hello,

I know ash is relatively low on the list of suitable species for weather exposure but would it be suitable as a shingle (but end 3/4 inch tapered to 1/4 inch, 18 inch long and random width from 6 in to 12 in) if it were pressure treated. The treater has spec'd ACQ applied under pressure to "refusal", an application they certify as suitable for "direct ground contact" in larger cross section posts. Cost to treat seems pretty reasonable.

This has come into consideration as we have so much large ash dead due to the EAB. We build small structures for clients for sheds, cabins, cabanas, pavilions etc and it seems a nice niche for our products.

Normally we'd use white oak or cedar, but with so much ash to be salvaged it would be great to find another use for it.

Thanks for all the help in answers to my questions in the past and hopefully someday I'll be knowledgeable enough to answer questions for someone else.

Joe

[beenthere]

Might work, but wonder what pressure treatment you are thinking about?

And do you have a pressure treater nearby that would consider doing it?

I'd think there would be a real problem bundling up shingles in a form that when put in a retort and filled with treating solution, they wouldn't be floating around everywhere. But maybe there is a solution for doing that.

Think I'd give a shot to using them un-treated. Then spray coat the final product with a semi-transparent stain with mildewcide.  Should work as good as white pine shingles.

[Josef]

Yes, we have a treater about 40 miles from me. The treatment is ACQ, Alkaline copper quaternary. This treater does a lot of wedges, about half the size of these shingles, for the mobile home and mine industries, a cube 42" x 42" x 54" stacked with 1/4 inch spacers (stickers) between alternating layers and banded tight. Not sure of the pressure they use but the chemical solution is heated as well. At a starting point of 20% mc they claim almost 90% saturation penetration. This cube would yield about 2.6 sq of material coverage at 5" exposure.

Joe

[Josef]

They also pull a vacuum on the load before introducing the chemical mix, real neat process.

Joe

[beenthere]

That is good.. go for it.

[GeneWengert-WoodDoc]

Treated to refusal is a term used for treating wood and the amount of chemical is unknown but usually not deep enough and concentrated enough to meeting the standard specifications for above ground and ground contact.  In other words, it is an inferior treatment with no consistency or guarantee.  Of course, I do not know your greater or his specific situation, so I cannot comment about what he is actually doing.

Roof shingles perform best if they are from a low shrinkage species, so we use a wood like cedar and also quarter saw the wood.  Your ash, even if quartersawn, will move twice as much as quartersawn western red cedar.  If not QS, then it will move three times of QS WRC.  If not QS, it will also be prone to cupping.

You might also check with the insurance company to see if they have any restrictions or requirements. 

[Josef]

I see I have some more questions to ask the treater on monday. I'm scheduled to deliver to him one cube next month as a test run. I'll then apply them to a roof slope in the shop and put it out in the weather and watch it for a winter and spring. Interesting points about the movement of the ash vs wrc, never considered that aspect of the material, was primarily concerned with the "longevity" and how that was affected by the treating. Since my applications are primarily on "decorative" structures under 300 sq ft not my house I'm going to evaluate it more and see where this goes.

Now I need to find the relative movement of wrc so I can have a starting point for spacing of the shingles when applied.

Joe

[beenthere]

Keep the shingle width narrow and the shrinkage will not cause a lot of cracked shingles. Less than 8" width should lay out pretty well and look as good (or even better) than wider shingles. Just more layup work.
I'd be most concerned about splitting when nailing. Maybe stapling would work better.

[beenthere]

Josef

Now I need to find the relative movement of wrc so I can have a starting point for spacing of the shingles when applied.

Here is a chapter in a wood handbook of shrinkage values.. table 4-3

http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_04.pdf

[longtime lurker]

We use ACQ as a treatment solution: it's okay stuff. Standard ACQ is an approved H3 treatment here, double strength ACQ is a H4, and H4 with a month of drain time followed by another H4 application will hit the retention standards for H5... And it doesn't carry the CCA stigma.

It's not the best treatment solution in the world in all honesty but its the best of what's left that's not banned or getting bad PR, and we use it for everything from General framing through cross arms, poles and ties.

The issue ain't what you treat with though, it's how high the retention level of the active ingredients is that determines how effective it is.
If the guy mixes his chemical To the recommended strength ( most people do... Contracts for things like cross arms and ties get lost if you don't get it right) and he treats properly with ACQ, it's going to do a job for ya. Thing is that you need to understand what job it's doing.

Pressure treatment is going to fully penetrate all sapwood, and an envelope of most heart woods. It doesn't penetrate to the core of the timber, what it does is create a chemical barrier around the core. The strength and depth of treatment determine how long the barrier lasts before it eventually leaches away. We're talking decades here btw.
Thing is that when you breach the protective envelope then you expose untreated core wood. Cut a piece of treated timber in half and the exposed core wood is visible... And the integrity of the piece is now dependent on the natural durability of the core wood because decay fungi and pests can get at it.

I'd not be fretting too much about longlivity of a shingle properly treated with ACQ. But be aware that pressure treatment with anything is not a magic bullet that fixes all problems

[Josef]

I had hoped to use 1 inch crown 316 stainless staples if I could, since these are primarily small structures, a large roof slope might be about 10' x 20' and about 10 in 12 or 12 in 12 pitch. I see from the info in your link it appears the white ash has about the same shrinkage as white oak, but considerably more than the softwoods like cedar or pine. Wonder how long a pressure treated white pine shingle would last?

Perhaps for this test I should try several different species that I have here on the farm, on the same sample slope, at the same pitch and exposure ratios. Would be interesting to see which fared better in resisting cracking or curling.

Joe