Cypress or Spanish Cedar for Exterior Trim?

Woodworkers discuss the attributes that make a natural wood suitable for painted outdoor trim applications. April 20, 2008

We have a good bit of exterior trim to fabricate, which is part of a major residential restoration project... actually the president's house on a college campus. From my readings, cypress or Spanish cedar seem to be the front runners for exterior trim. From those that have been there, what is the preferred species? My source for cypress is air drying to 12% and it is half the cost of Spanish cedar.

Forum Responses
(Architectural Woodworking Forum)
From contributor J:
I have limited experience with cypress, and the one or two times I have worked with it, the MC was a lot higher than I would have liked it to be, so I really have no comment to properly dried cypress. In my experience with Spanish cedar, it mills nicely and takes paint very well. I do find that the dust is rather irritating on the nose and lungs, so breathing protection may be more of a necessity.

From contributor P:
I love cypress. It's easy to work, easy to finish, lightweight, and of course the weathering capabilities are wonderful.

From contributor K:
If you use the cypress, keep in mind that the sapwood has no decay resistance, so if it is going to be in the weather, you should be very selective. Most of the Spanish cedar is clearer heartwood, however I have seen a little of it that had some pitch that would bleed out of the pores. Maybe they just didn't get that batch hot enough to cook off the volatiles, though.

From contributor D:
Spanish cedar is great except that the resins eventually bleed through on a lot of the boards, even when dried properly. Cypress is also good for outdoor use, but when milling it sometimes you will get surface checks.

If money is not an object, and you're not concerned about the Amazon rainforest, probably the best material for exterior trim is genuine mahogany.

From the original questioner:
Thanks for all the input. Is there a suggested treatment to minimize bleed-through on Spanish cedar?

From contributor D:
Regarding treating Spanish cedar so it doesn't bleed through, I don't know how you can stop this. It occurs on some pieces and not others and seems to take months to appear. If the trim is up two stories it'll probably not be noticeable.

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
We can stop the bleeding of resin from softwoods, like pine. However with hardwoods, like Spanish cedar, the wood contains gum and this can not be treated in the kiln drying process to minimize the bleeding of the gum. The amount of gum bleeding is spotty from piece to piece, but when it happens, the complaints are justified and replacement is the only answer. The gum will bleed through paint.

So, the bottom line is to use cypress heartwood. I suggest using a reputable supplier who will have the correct material. However, even today's heartwood is not as good for natural decay resistance as the old stuff. The best material would be pressure treated pine (except not Southern pine). SYP will not hold paint well.

From contributor L:
My experience with pressure treated has been pretty negative due to the initial high moisture and the wild goings on as it dries out in place. We found we needed to wait some time before painting it due to the moisture levels causing peeling. We made the exterior trim for a huge old house about 10 years ago out of cypress, all went well, still looks good. Like most woods for exterior use, it is pretty soft.

From contributor Z:
Siding isn't all that demanding an application. Plenty of ventilation, and replacement isn't all that difficult. You might get away with second growth cypress but I wouldn't use it on an important house. I've been using Spanish cedar (Cedrillas odorata) for about seven years and have never had a problem with bleeding. You should be priming all that stuff before it goes in place so any bleeding should be detectable at that point. If you've got a lot of bleeding, you've got the wrong supplier.

Using mahogany as siding on someone's house borders on the obscene. I'd rather see you use teak.

To finish, let me add that we have never used Spanish cedar as siding per se; the dressing makes it too expensive. Plenty of cornice work, built in gutter, doors, windows, etc. Personally, I would spec all heart vertical grain western red cedar.

From contributor W:
If this is all paint grade, then I would look at synthetic materials. They will last forever and paint well. Ipe would also be a forever choice, but it is hard to machine and nail. Treated pine is good for trim if you get the right product. We have a supplier that takes clear treated pine and has it re-kiln dried. It is a little more expensive but is nice to work with.