Treated Cypress Options

A discussion of surface coatings, preservative treatments, and natural decay resistance of Cypress used for outdoor shutters. July 12, 2008

I am looking for a source for treated cypress. I am bidding a bunch of louvered shutters that have been spec'ed out of dip-treated cypress. I guess I could spray Bora-care on the material, but it is really more material than I care to do. Does anyone treat cypress?

Forum Responses
(Architectural Woodworking Forum)
From contributor D:
I had 5,000 feet custom pressure treated (like pine, in the pressure treatment cylinders). I was told that cypress was not pressure treatable, but it treated very well, especially the sapwood. The heartwood is naturally resistant anyway. I used it as siding on my house. 25 years later, it still looks great. Not sure if you can have any pressure treated this way anymore, but with the slowdown in building, I would think that the pressure treaters would be willing to do it.

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Usually thin shutter slats are dipped (not pressure treated) in a product such as Woodlife to provide water repellency and some surface decay resistance. This can be done at home. Borate products will leach out in an exterior exposure, so it would seem that they would not be appropriate in this situation.

From contributor W:
There is a lumber company in Metairie, Louisiana (a suburb of New Orleans) called Gueydan Lumber that has what you are looking for. They have pressure treated cypress and they re-kiln it after the treatment so the lumber is dry enough for windows, doors and shutters. Very cool stuff. It is a pleasure to work and lasts forever.

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Someone might wonder why cypress needs to be treated. The answer is that sapwood has very poor natural resistance to decay and even heartwood in today's trees has unacceptable decay resistance. Only old growth heartwood (not too common anymore as it has been used up) has good decay resistance.

From contributor W:
Of course if you call them you could always ask for sinker cypress, which is pulled from the bottom of Lake Ponchartrain and Maurepas. It is as old as old growth gets. I had a piece that had 200 rings inside of 6 inches.

From contributor S:
Borates are fine provided the timber is then coated to prevent excessive wetting. That said, borates will only leach to areas that are wetter than the timber, so they only really leach in contact with wet porous surfaces (concrete, soil, etc.).