Pressure treated furring strips - any effect ?

Guest User
6/26/2003
My contractor is installing typical painted metal sheets over an existing 5v metal roof by furring out with pressure treated 1x4's. One maker of a metal roofover system advised that the chemicals in the treated wood would "eat" the metal. What do you think? Is this method better than tearing off the old roof? (I asked the contractor to do it this way do to the "thermal break" created between the two roofs, I'm in Florida and need any extra possible insulation). Thanks, Fred
Todd Miller
Classic Products, Inc.
6/27/2003
The chemicals in the lumber could very well be corrossive when in contact with the metal. The coating on the back side of the metal will provude some protection but not forever. Inqiuire with the roofing manufacturer who knows more about the quality of their back coat and their metal substrate. Overall, though, I would suggest non-treated lumber or an underlayment between the lathe and the metal.
Allan Reid
Dura-Loc Roofing Systems, Inc.
6/27/2003
There is a reaction when there is moisture present and it is worse with galvalume. I must qualify it as the copper based pressure treatment. On the extreme other side of the coin, standard spruce or pine lumber will release acids when the become wet which will eat the metal away from the back. Unless you are in a termite prone area, use standard kiln dried lumbe. Better yet ventilate the air chamber along with the attic and you will be fine.
Guest User
7/3/2004
I have an old barn with a layer of old wood shingles then a layer of asphalt shingles on top of the wood shingles. Many of the asphalt shingles are missing. Can I apply furring strips over old roof and apply a new metal roof?
Todd Miller
Classic Products, Inc.
7/5/2004
It depends upon what type of metal roof you choose. Some vertical seam systems, as well as some of the shake and tile profiles, can be installed in this manner.
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