Wood Choice for Paint Grade Historic Millwork

Woodworkers discuss the pros and cons of Spanish Cedar, Mahogany, Sapele, Black Locust, and recovered Heart Pine for a restoration and historic reproduction project. April 27, 2011

I am putting together a proposal for replacement sashes and specialty window fretwork on a Gothic style historic building. This will all be painted and direct exposure to the elements. Based on a combination of price, workability, paint-ability and longevity what would your choice be? We have worked with Spanish cedar a bunch and love it. Itís easy to machine and as far as I know good for long term exterior use. The builder on this project mentioned black locust so I am researching it as an option but we have never worked with it before. The building location is in NJ so a little bit of everything for weather.

Forum Responses
(Architectural Woodworking Forum)
From contributor J:
Stick with the cedar. Black locust is heavy, hard and difficult to machine, though great for fence posts.

From contributor B:
Use either Spanish cedar, mahogany, or recycled heart pine. The only thing black locust is used for are fence posts.

From contributor D:
We use Spanish cedar with great success, and it paints up nicely. We're not too far from you, we're in southern CT.

From the original questioner:
Other than this thread is there any documentation that I can print about it that would discuss its poor characteristics for smaller millwork pieces? I have a meeting tomorrow to review my proposal. You would think it wouldn't make a difference but to the builder it is like the word of the day, and is inserted repeatedly into every conversation.

From contributor J:
How about matching the materials used originally?

From the original questioner:
It's old growth pine. Too expensive to use NOS and new growth would rot in a couple of years. Design and depth of profile makes it very susceptible to water accumulation and breaking apart during freeze/thaw cycles. This plus the fact that original was run vertical makes the ends soak up moisture like a sponge. Paint-grade exterior we used to use mahogany till it became scarce and expensive then we switched to Spanish cedar. This entire conversation would be a non issue if the builder didn't keep mentioning it.

From contributor O:
I would think that black locust would be hard to source in kiln dried stock but I never tried. Is it even available in a grade suitable for mill work?

From contributor K:
Sorry, I can't point to published data on black locust but our experience cautions against it over Spanish cedar. Difficult if not impossible to source thoroughly dry and subject to considerable warpage, locust is highly rot resistant but difficult to mill and likely to check in service, also a significant skin irritant to some individuals. Spanish cedar is not the most pleasant wood to work (literally leaves a bad taste in your mouth) but seems a much better alternative to me for exterior millwork.

From contributor F:
Another factor to consider is movement. Denser woods typically expand and contract more than lighter ones, which is why cedars and redwood are more widely used for paint grade. The movement causes earlier failure of the paint I canít see black locust as a suitable paint grade material.

From contributor H:
Spanish cedar, African mahogany or sapele would be my suggestions. Of the three we put Spanish cedar at the bottom of the list due to the nasty smell and taste of the sawdust. I can't add anything to the Black locust discussion other than Black locust honey is the most incredible honey you'll ever taste!

From contributor A:
To contributor H: do you have any idea about the rot resistance of saepele?

From contributor H:
Everything I've been told indicates that sapele is equal to Spanish cedar and African mahogany. All three pretty much interchangeable in terms of endurance outdoors. It's more a matter of small differences in cost and workability. I too would like to know if someone knows this more specifically.

From contributor D:
In my experience, sapele, which is an African mahogany is easier to work with. Even though Spanish cedar is less dense, you often get into some stuff that fuzzes when machined. You can sometimes tell before you cut into it by feeling the surface fibers in the rough. They'll be cottony instead of brittle splinters. Spanish also bleeds sap after a few months if it was summer harvested, and seems to me to have more pitch pockets. Most sources won't know when it was harvested and it's caveat emptor.

From contributor T:
Black locust can be machined, but it is much harder; black locust is to oak, like oak is to Spanish cedar. Not aware of kiln dried sources. I have used it for turning 1"- 4" diam. exterior balusters, and they hold up very well, and hold paint well, not kiln dried.