Poplar Siding

      Advice on using locally sawn Poplar as siding for a house addition. February 14, 2010

Question
I am in the process of a major addition to my home in North Alabama. I will be continuing walls that are sided with smooth 5/8" x 6" beveled siding. I was planning on using cedar siding from a building supply company, but I have an opportunity to get poplar siding from a local mill for about a third the cost of the cedar.

The mill said they would air dry 5/4 x 6" boards for 30 days, then plane and cut them in half to get two beveled siding pieces with one smooth side each. Does this sound plausible? That sounds like a relatively short drying time, even for a product to be used outdoors. What kind of bottom thickness should I expect?

Forum Responses
(Sawing and Drying Forum)
From contributor S:
When we make lap siding, we plane first, saw into lap and kiln dry for 36 hours. If the wood is pine without kiln drying, you will have pine pitch still oozing out.



From contributor W:
I have poplar boards on my sawmill building here in PA. They aren't treated with any chemical or paint and have held up well. My roof does have a big overhang, though, and that helps keep some of the rain off the siding. In Alabama, I would think that insects would be an issue. I believe red cedar is less susceptible to insect damage than poplar.

I would look at the whole value of your project and then figure what percentage of the project you are saving by using the poplar instead of the cedar. On the subject of air drying, I would ask the mill what moisture content they are shooting for. I think it would be best to get the MC below 30%. Perhaps you could get the poplar boards kiln dried before they are split into the siding?



From contributor T:
That's a lot of waste going from 5/4 to 5/8, but if you're paying for 5/8, I guess it doesn't matter. I have used siding right off my mill and planed also and for the most part I prefer the rough-sawn for exterior and planed for interior. There are advantages and drawbacks to both rough and planed lumber used for the exterior, but that is species-specific maybe. The native specie here which is best suited for siding is eastern red cedar, and while planed has the advantage of taking a preservative much quicker during application, the rough-sawn holds a lot more of it and thus takes longer to begin graying. I don't know if poplar would react that way though. I also like the rough-sawn look better for exterior, but maybe you are getting your siding from a circle mill and you don't like the circle-sawn look. A well-tuned circle mill can have a very nice look too. Of course rough-sawn siding, especially circle rough, will hold dust and have to be washed more often.

In addition to what was pointed out regarding air dried lumber and the pitch in pine (don't know if that's true with poplar), some air dried species will be more prone to bugs unless kiln dried to bring down the moisture before being put into service, and also unless it gets the high-temp treatment to kill whatever eggs are already in it. Some species like ERC are exempt from that (except for the sap), but I do not know much about poplar. I assume it has little or no resistance to bugs.

One thing is certain, although it was done routinely with old growth from what I understand - putting any lumber into service green is an absolute last resort and you better know how to nail it if you do. Even then you'll have tons of movement and will have to replace some that cup/twist/split too dramatically. Drying first culls these boards automatically. You still have to nail air dried and kiln dried lumber properly when used for siding, and don't forget to orient the growth rings properly, especially if you are using it horizontally.



From Professor Gene Wengert, forum technical advisor:
Yellow poplar siding has been used for years. Like any wood product without natural decay or insect resistance, there is a risk of insects. As this wood will be used outside, its MC will be around 12%, which is high enough for several different insects. Kiln drying will not eliminate this risk. Y-P does not have resin or sap exudation.

If the wood is first air dried for a month and then resawn, the freshly sawn surface will be higher in MC than that outside surface. This will result in the freshly sawn surface drying and shrinking and will cup the pieces toward this newer surface. Further, there will be movement in width, overall. This movement can pull nails, so make sure that you install the bevel siding with nails only on the hidden edge. Yellow poplar can also warp (a few pieces), so it may be necessary to replace a piece or two, but this is not hard to do. Some pieces will not fit tightly (warp in place slightly) to the next lower piece, so there is a risk of bees or other insects getting in the gaps and nesting. Nevertheless, this siding has been used; it is just not as good a choice as cedar.

Incidentally, kiln dried SYP pine that is then treated and resawn makes a similar product with good service records, except for a few pieces that warp when wetted, dried, wetted, etc. To reduce wetting by using a water repellent finish is essential for best performance of yellow poplar, SYP and many other species.

The low shrinkage of redwood and western cedar, low risk of warp, and natural decay resistance make these species more suited for outside exposure. Even with these, a water repellent is best, unless a more rustic appearance is desired.

In most species, knots near the end or edge will create a spot where cracking, due to wetting and drying, can be a risk. Underneath the siding, you do need to have a weatherproof material (plywood sheathing for example). The siding is mostly decorative.

From the original questioner:
Thank you so much for the responses. My concerns about the newly milled poplar have been validated. In spite of the large cost differential for 7500 lf, we have decided to go with pre-primed cedar. The product we found matches the profile of the existing 78 year old siding almost perfectly and we'll be able to get it more easily if need be.

I should have mentioned that the siding will be painted. I was concerned about not being able to get the new siding back primed due to time constraints. This will not be an issue now. I will most likely re-prime the outside surface, as I've read about cases of pre-primed siding not holding paint well.



From contributor U:
I agree with contributor T - considering planing and saw kerf losses, rough cut 5/4 would be too thin to yield 5/8 siding. ~6/4 rough would be more like it.

You made the right choice in passing on this deal for the reasons Dr. Gene pointed out. Yellow poplar dries fast but it shrinks a lot and will go crazy if not held or nailed down. Traditionally, white oak and yellow poplar were the first and second choices of local species for siding barns. Local lore holds that termites don't like yellow poplar. I've never seen an insect problem with it.

It amazes me that a yellow poplar log or board will disintegrate within three years when lying on the ground. But nail a yellow poplar board to the side of a barn and with little maintenance it will be there 100 years later. I can usually tell from a distance if an old barn was sided with yellow poplar because the bottom 1-2' of the boards near the ground will be rotted off. If you ever use yellow poplar for siding you'll be pleased as to how easy it nails and holds paint.



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