Doug fir vs cedar

[Nealm66]

I was checking out these wide (12"?) 2nd growth 1" doug fir boards ( no bats)on a really old barn from the stage coach days in perfectly good condition. This is in the puget sound in the pnw on the south west side( incoming weather) so this is no small feat with our weather. Some very slight cupping is all. Some really old red paint here and there. I don't see second growth cedar at twice the cost lasting any longer in like conditions yet that's what sells for any type of wood siding/fence boards around here. I wished I would have taken some pictures 

[SawyerTed]

Here using western cedar would be cost prohibitive at $95 for one 5/4x12x12.  If Douglas Fir is cheaper, it's a good alternative.  

[moodnacreek]

A big part of boards for siding, even in cedar. is being able to select. Tight vertical grain and color . With color the darker the better and no light spots. Then the installation , well of the ground and no obstructions to fast drying. Very dry lumber is good to. Doug fir petrifies with age and I think this is what can save it.

[Nealm66]

Holy smokes. $95 for about 12 bd ft! That's crazy. There's a huge difference between old growth and second growth in the tannin. I wouldn't jump up and down and say old growth cedar will outlast Doug fir as I've seen both used as roofing shingles on very old cabins with equal deterioration. I've also seen a lot of leftover buckskin Doug fir logs in 3rd growth stands that were in very good condition inside. Never see any cedar logs as the shake rats gobbled them up years ago but definitely see pretty solid stumps from back in the misery whip days. Anyways, I guess I was just curious if anyone else had wondered why Doug fir hasn't found it's way into the exterior market like cedar

[DanielW]

Doug fir should last as good as most things on siding. A lot of people incorrectly assume wood that's good in ground contact and resistant to rot is also the best wood for siding/roofing. There's some little truth to that, but it's by no means a universal rule. When properly installed so siding/roofing can breath and dry out, the grain structure makes a much more significant difference, and rot isn't nearly as much of a concern. Lots of buildings in the East still have pine shingles keeping out the weather just fine after 100+ years. They might not be as pretty as cedar, and might fail a little sooner, but they'll still outlive the person who installed them by a substantial margin.

Similarly with oak: White oak is far better for rot/ground contact, but red oak is usually considered superior for shingles/siding. Locust lasts about 4X longer than cedar against rot, but makes pretty poor shingles. One of the problems is the ease with which it splits/cracks. Another (especially with White oak) is that it's so impermeable to water: The outer face absorbs water to only a very small depth, which dries out very fast and cups badly, whereas the red oak both sheds and absorbs water a little more uniformly and dries out more evenly without cupping/splitting. One sub-species or red oak is actually known as 'shingle oak'.

Cedar just happens to it the bill nicely, both for rot resistance and for siding/roofing use.

I cut a lot of shingles - mostly for siding. I do a lot of white pine, and have no reason to suspect that any siding done with it will ever have to be touched within my lifetime. I think some of the reasons cedar is so popular are:

a) That was always the best option back in the day when cedar was much more plentiful/cheaper, and that notion that's it's the best/only wood to use has carried on.

b) The incorrect assumption mentioned above that woods resistant to rot are the best choices for siding

c) Colour: Even though fir (and even white pine) siding can last for ages, it pretty quickly turns to a murky brown if not coated. White cedar fades to that nice silvery-grey folks associate with New England. Red cedar actually turns to an ugly brown as well, but it goes on very pretty, and some folks want to maintain that colour with a transparent stain.

I heard (but this might not be true) that companies like Maibec were still cutting their shingles from cedar, but they're now using fir and pine for many of their pre-stained siding products.

[Nealm66]

Dang! That's impressive knowledge. I'm just about done cutting a lot of Doug fir board and bat for a neighbor and have a couple large cedar trees to cut down and mill for his sister who did cedar board and bat and says they have to do battle with woodpeckers all the time where they don't seem to mess with the Doug fir. I'd hate to see the truth shatter the Doug fir market as logging 2nd growth cedar ranks highly on my sucks list but the higher pay makes up for it. Anyways, very interesting, thanks for that