How to Handle Oak Expansion Outdoors
#7
I am building two Little Free Libraries for a park. They will be similar to the attached picture except with a flat roof sloped front to back.
They want me to use white oak for aesthetic reasons.The sides will be approximately 18" wide and 24" tall. My concern is that being outside summer and winter will create significant expansion and contraction issues.
My first thought was to create the sides using three ship lap boards and use only one screw in each board  or maybe two screws with the heads in a short channel instead of a drilled hole.
Will this approach account for the expansion or is there a better way to keep the libraries from cracking? And how would you suggest joining the sides to the front, back and roof?
One more question: what finish would be most protective and relatively low maintenance?
Thanks for you thoughts and experience.

   
   
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#8
(03-19-2018, 04:19 PM)ron kanter Wrote: I am building two Little Free Libraries for a park. They will be similar to the attached picture except with a flat roof sloped front to back.
They want me to use white oak for aesthetic reasons.The sides will be approximately 18" wide and 24" tall. My concern is that being outside summer and winter will create significant expansion and contraction issues.
My first thought was to create the sides using three ship lap boards and use only one screw in each board  or maybe two screws with the heads in a short channel instead of a drilled hole.
Will this approach account for the expansion or is there a better way to keep the libraries from cracking? And how would you suggest joining the sides to the front, back and roof?
One more question: what finish would be most protective and relatively low maintenance?
Thanks for you thoughts and experience.

Glue up the sides with waterproof/resistant glue edge to edge.  Secure them only to the back.  The front is standard face frame, so no real problems with expansion, contraction, though it might lift the roof a bit.  Secure long grain to the sides' long grain.  Roof may be secured to the sides, floating over the back and front.  I would make a cap rail of a narrow piece with a ^ groove to keep the miter or overlap from wicking water in.  It's cross grain, so there float your broad head screws a quarter inch front and rear.  

Stainless, given the problems of tannic acid and oak.

Re-read and I see you don't like the roof as pictured. With a roof cross-grain to the sides, hang it from the back. I'd do as pictured, however.
Better to follow the leader than the pack. Less to step in.
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#9
West Systems has developed an epoxy formulation, G-Flex, which is both "waterproof" and elastic. It is today's gold standard for adhesive bonding of oak in the marine trades and has had a very good history of durable bonds despite the movement of the oak with moisture changes.

https://www.westsystem.com/specialty-epo...ned-epoxy/
https://www.westsystem.com/specialty-epo...ned-epoxy/

I don't think you can find a better adhesive for oak. leave the surface rough (band saw cut surface or 60-80 grit sand paper) to add surface tooth for strongest bond.

G-Flex isn't cheap, but in small packages it isn't too bad for your project. Follow directions closely, as with any two-part product. The West Systems site has lots of good epoxy information, including bonding oak.
Fair winds and following seas,
Jim Waldron
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#10
I'd also be concerned about that triangular piece on the face side: that's a lot of width.
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#11
Thanks for the responses.
MM - some important approaches to consider and I might have forgotten to go with stainless steel screws without your input.
Jim - good to know about the G-flex epoxy. Not sure it solves anything in this situation.
Bill - the piece over the door will not be nearly so wide because of the change in design.

Everyone, please add your thoughts. I don't want these libraries to crack or leak and ruin a bunch of nature books.
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#12
I hate plywood as much as the next guy, but in this situation it might be worth considering. It would indeed be a shame to damage book.
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