Outdoor plywood (clear coated) sign.. how to finish?

Hi,

I'm looking at designing a sign and considering plywood backing or plywood letters. However, I'm not sure how to finish these signs for exterior. See link below for an example. Is this sign only going to look good a few years? How often would you need to replace it?

I do live in N. Utah (Ogden) and it's mostly a dry climate here, but very hot at times and sunny always during the summer.

https://www.tinkeringmonkey.com/port...exterior-sign/

Thanks and cheers,

There is an MDO (medium density overlay) made for outdoor use of this kind. Plywood, not so much.

Even MDO would not work,as the plys eventually split in weather. Only way to get the plywood weather proof is to coat in
with a thick liquid plastic. Or glue light canvas to all surfaces with Tite bond 2 ,or the like, then paint them. If you are
up for that ordinary plywood will work.

what kind of liquid plastic?

Think there is only one . Plasti Dyp or some such. I mention it only because it is the ONLY thing equal to the canvas
treatment. You will not be able to get it to look like wood. And if it's in the sun, I predict it will not last as long as the
painted canvas. It worked for couple hundred years plus, but sadly it's not advertised anymore. There is a guy on you
tube who has used it for a number of things. Be asured he is not in my employ.

Bearing in mind that his is from the folks that sell it . . .
"MDO, also known as Signboard, is an exterior-grade plywood with a high-quality fiber surface saturated with phenolic resin solids. The plywood below the fiber face is smooth, clear and free of patches, providing a smooth surface with minimal grain showing through. MDO plywood is water-proof and weather-resistant. This plywood is often used for exterior signs. MDO plywood can be sawn, nailed, routed, shaped and drilled. Although this product is designed for exterior use, it works well inside the home in areas that need to be smooth and hold up well to moisture. This product resists inclement weather areas well. It is often used for exterior signs and sub-board underneath laminates for countertops. "

So we can all agree that the link I sent is of a sign that will need to be replaced soon?

I saw the MDO option earlier, but from the photos I see of it, it looks more like melamine than wood grain

Most signmakers these days do not use wood...they use manufactured products like HDU (high density urethane board), pvc, etc., and paint to resemble wood where required. To your specific question, the sign in the link would require relatively frequent maintenance to retain its color and that would be made more challenging by the applied lettering. Even when wood like cedar is used, it's very common to paint it rather than try to use a clear finish because, well...wood turns grey in the sun and weather. Paint lasts a lot longer and is easily refreshed if need be.

BTW, MDO looks like cardboard...because it's paper applied to an exterior grade plywood. There are multiple grades of it, too, the best not telegraphing any wood grain, etc., through the paper surface. It's very popular for road signs. Like any plywood product, it must be painted including fully sealing the edges.

Thanks everyone. I'll keep this in mind.

I'll look into plastics and metal : )

PVC sheet is reasonably priced for external signs. The best material for exterior signs IMO is solid surface, lasts up to 50 years without any coating. This one is just a few feet from a salt water river, a rough service area for sure. I have some that I installed in 2004 that look just like the day I installed them, even the paint still looks great. Paint can be easily refreshed when the time comes, just spray and sand off the excess on the surface.

If you cut letters and graphics from solid surface material and use the appropriate adhesive your sign will be maintenance free for 50 years.