I'm going to build a picket fence for installation in the spring. The fence is for our own historic school house shop property and the work will give us something else for the guys to do when things get a little slow. My experience with western red cedar in recent years is that the old growth lumber is gone and the new growth lumber does not hold up well outdoors. As such I'm thinking about using pressure treated 2x2's for the pickets. 1 1/2" picket, 1 1/2" space, 1 1/2" picket etc. This makes a very nice looking fence.
For the rails I can go with pressure treated 5/4 stock or use some 3/4" western red cedar resaw rippings I have on hand. I'm not nearly as concerned about the rails holding up over time as the pickets. I have found with picket fences that more often than not itís pickets that fail.
I'm wondering though if there might be some sort of negative interaction between the pressure treated pickets and the cedar rails. Does anyone have any experience with this?
(Architectural Woodworking Forum)
From contributor S:
I wouldn't use pressure-treated lumber for any purpose. Aside from toxicity, high cost, the inability to stay straight, lack of testing, no real-world experience, and marketing b-s, you'll need to use stainless and/or G-90 galvanized fasteners and hardware.
The difference between G-90 galvanizing and say, G-60, is the thickness of the galvanizing. "Flash galvanizing", which is what you might run through your nail gun, is the thinnest. In other words, the manufacturers want you to use the thickest galvanizing there is, because they know the chemicals in the (treated) lumber will attack the fastener. My guess is they (the manufacturers) are simply trying to stave-off lawsuits for as long as possible.
I think I'd try to find some thirsty, inexpensive, open-grained lumber and use a quality, polyurea coating. Properly coated, the lumber will be waterproof, UV-proof, and re-paintable in the future. The fence would likely outlast you.
Next, I'd use Spanish cedar, or white oak or cypress. They paint well, and are good in the weather. Old growth cypress or oak will be preferred. You do get five bonus points for not even mentioning the PVC plastic fence. I like to see woodworkers employed.
I have a close friend who owns one of the local lumber yards. He has a load of old stock (read: drier) 2x2 clean, clear and straight P/T balusters. I am well aware of potential problems with P/T (this gray hair didn't just happen on its own) and hope I have learned enough over the years to help cull out most of the potentially problematic sticks. With good planning on construction I can build this 125' fence so that any warped picket can be removed by taking out two screws (stainless or galvanized needs to be determined).
Just a point of interest here. I built a very long picket fence about 25 years ago. When it was taken down last year the wood was still sound but the fasteners (not galvanized or stainless) had failed. The rails were P/T but the pickets were re-sawn spruce 2x4ís. I had cut four 3/4" x 1 1/2" pickets out of 32" long 2x4s, and obviously three 32" blanks per 8' stud - a very economically built fence.
Another fence I put together about 15 years ago is in mixed condition. The rails were of pine and are a mess. A section with pine pickets is also a mess. However, a section built with the P/T rails and 3/4" x 2 1/2" furring strips for pickets is very sound. You never quite know what to expect I guess.
I vote for cedar and cypress. Even new growth is better than pt I believe. Maybe considering some diy treatment would be beneficial, such as a borax type treatment. I run into your dilemma all the time in selecting wood for exterior shutters. I use the best wood possible, and since we mostly paint our panels, I depend heavily on the best quality primers and paints to offset the effects of nature. Regardless of clear or painted finish, I double or triple prime or seal the end grains as much as possible.