I hope to be joining the Dallas Makerspace here in a couple weeks, and am planning on constructing a small mailbox library mostly out of 3/4 inch ply. I have started to source my materials, but am getting hung up on the best type of plywood to use for the majority of the structure.
This will be outdoors and exposed to the elements, but will be completely roofed, painted and sealed. I don’t mind purchasing more expensive materials, but am having trouble determining what type of plywood is best for longevity and surface finish for painting.
Here is a sketch of the design! I appreciate any suggestions.
Thanks! This is helpful. Seems like anything “Marine grade” would do the trick, but the higher letter grade would mean less sanding and hole filling when it comes time to prep edges for paint.
You can’t buy marine grade at Home Depot. You might be able to buy smaller pieces at West Marine but you’ll pay for them.
I’d strongly consider cedar fencing or deck material rather than plywood but if properly sealed and painted you should get a couple or several years out of any plywood.
Because non-marine plywood uses glue between the plies that isn’t completely waterproof. It can swell and cause the plies to delaminate - then water gets between the layers and the process accelerates.
One other potential option is Hardie (aka cement fiber) board. it used for things like exterior home siding and trim and such. For the most part, it is impervious to weather. The downside is it is more of a pain to machine, e.g. you can’t use DMS wood shop tools on it. You’d need to use a circular saw (or another similar type of hand power tool) with a suitable blade.
Just an option to think about…whatever you built would pretty much last forever.
But I think if it were me I’d use some cedar fence slats as suggested above. With appropriate build, assembly, and maintenance (e.g. clean & re-stain every few years) it would last a long time…fences built and maintained like this last 20+ years.
What about using exterior plywood underlayment. This is what the second floor of a home is decked with. Many cities require that it be able to withstand standing water for a considerable time before it warps or delaminates.
I second using a rot resistant wood. Cedar, red wood, sycamore, teak, etc. There are many to choose from. If this really large or was meant for production, the math would change.
So…I’m more of a metal guy that tends to use wood shop to make table tops, stool seats, Etc so my immediate first thought was:
1x1 angle for the main body
12ga for floor, shelf and top
Plexi attached with clear silicone and rivets
1.5in schedule 40 sunk in a 1.5ft x 18in concrete pour
It would make it stable, waterproof and extremely durable.
And as an added bonus, swapping out the Plexi when it gets a little weathered would be pretty straightforward with a drill and razor blade.
AND…you might get it done for under $100. (No dimensions on the render, so hard to say for sure)
I’d go with 3/4” CDX plywood if that’s what you’re most comfortable with, paint it with exterior paint, then sheath the outside with cedar using a nail gun and brads.
This would give you protection from the elements with the ease of plywood construction. Consider using a Kreg jig for the panel box connection: butt joints with angled screws for a tight finish.
For the sheathing, you could do vertical slats (preferably tongue and groove) or shiplap the cedar boards and make horizontal siding. Use Thompsons Water Seal or similar to protect the cedar boards. 3-4” plain rough cut cedar fence pickets could be the source material: cheap and appropriate scale.
The ahiplap rabbet cuts can be done on the table saw. A dado set can cut them in one pass, or two setups and two passes with a regular blade. A straight-cutting router bit can also handle the rabbets.
Tongue and groove is easier with a router and matched T&G router bits.
This project has been my excuse to get a Kreg Jig and boatload of fasteners. Thats 100% what I’m planning on doing, and may look into sheathing the two non-windowed sides, thanks!
