Alder for Exterior Doors

Soft and unstable, Alder wood is not well suited for building entry doors. August 23, 2006

We have a customer that wants us to build an arch top exterior door out of alder. From what I have been reading in the Knowledge Base, it would be best to laminate the thickness instead of one thick piece. I have also seen a post on just using 1/2" pieces laminated onto a hollow type substrate. Is it a good idea to make an exterior door out of knotty alder? Which method would result in a better quality door? Thanks in advance for the help!

Forum Responses
(Architectural Woodworking Forum)
From contributor J:
I think alder is one of the worst choices for exterior doors. Here in Colorado, architects and homeowners spec it all the time for entry doors. It is unstable, not at all weather or rot resistant and bleaches out when exposed to sunlight. If you are forced to build with it, use 3 ply construction at the minimum.

From contributor D:
We no longer warranty any part of alder exterior doors, and will likely not warranty interior doors either, before long. It is one of the worst for exterior use. We had pairs of doors swelling to close a 7/16" gap, and twisting and bowing. By contrast, our H mahogany paired doors close 1/16" of a 1/4" gap in their first year out.

A sidebar on alder is that it was a weed species that Weyerhauser and others tried to eradicate from growing in their clear cuts/replants. When the sprays and techniques they used were deemed too toxic, they had to let it grow in. Turning their lemons into lumber, they first pulped it, then let it grow, and then marketed it as the cheapest thing that can be called lumber. Then they hire designers and fabricators and make kitchens, photograph it all, and get published in the consumer home magazines. Next thing you know, you and I are calling around trying to buy the stuff, and the price has risen considerably. All this has almost no effect whatsoever on the buyers, since they think they really, really want alder, and I'm the bad guy for not wanting to stand behind it.

Another sidebar is that Weyerhauser copied their strategy on alder from their own playbook of 50 years ago. During the war effort (this would be WW2), the government had most wood shops using clear Western pine - sugar and ponderosa - for crating items to ship overseas. This left huge piles of knotty pine at every mill in the West. After the war, with the housing boom in full bloom, Weyerhauser hired designers (a young Carleton Varney was one) and built rooms with knotty pine paneling in them, photographed the rooms, and then published it all in the consumer house magazines. Next thing you know, every house in the country was being paneled with knotty pine T&G, effectively dating every house built in the 1950's.

From contributor O:

We make alder entries. We do laminate. However, we will not place knotty alder on the exterior face. Only superior grade. Helps keep the moisture out.

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Red alder makes a lightweight door, as it is a lightweight wood. One issue to be considered is that it is very soft, so as a door, it will get many dents when kicked, bumped into, etc. The finish must be flexible to handle these dents or you will find that you will get finish fractures. I would encourage you to make sure that the customer is aware of this so he/she does not complain later to you about a finish failure. Note that alder has no natural decay resistance, so you must keep it dry. Because of its low strength, it is not the best choice for a security door.