Bending plywood for roof
I'm installing new 7/16 plywood on the roof of a trailer. The framework in the roof is flat and then angles down a few degrees near the edge (as opposed to having a gradual curve all the way across). ...
Forum Discussion
Lantley wrote:
I have never seen exterior grade luan.I'm not saying it doesn't exist. But what I have seen in the big box stores is interior grade.
Do you THINK RV manufacturers use "moisture resistant" anything on RVs?
NOPE.
You do realize "EXTERIOR GRADE" plywood simply means it is another name for BC grade plywood? BC grade is very rough texture on both sides with one side being lightly sanded.
Exterior grade plywood glue is not moisture resistant, get it wet or damp and it WILL eventually come apart, to get moisture resistant glue you have to MARINE GRADE and that is not sold in big box stores.
The ONLY exception I have found is TREATED plywood (green color) which they must use water resistant glues since they must fully saturate the wood with WATER BASED PRESERVATIVES. That is not recommended for inside use or use where it may be exposed to inside or to fire and it is extremely heavy when new.
Exterior grade is meant to be COVERED and not seen, Luan on the other hand can be used exposed or covered. I have even substituted Luan for inside paneling in my trailer rebuild, just stained and hung it.. Much cheaper than paying twice the money for MDF paneling.
Luan on the other hand uses the SAME glue as exterior grade plywood but has one very smooth finegrain side and the sub layers have a finer wood grain than any plywood I have ever seen and with a bonus that they tend to use much higher quality sub plies which do not have voids.
1/4 luan is a lot nicer to work with than 1/4 plywood since it has finer wood grain and the sub layers do not have hidden voids and will be stronger because of that.
For a roof application Luan can be used, that is what I have done, works great and as long as you keep up with normal roof maintenance and keep the leaks at bay it will last as long as any other plywood.
Although if you are the scared person, then simply give the Luan a skim coat of polyester resin and boat cloth to seal it.. Many boat builders use Luan with fiberglass and resin and those last many years.
