MDO question

[Jake Helmboldt]

I've never used MDO and am looking for some advice. Our pool has asked me to make new covers for the bathroom windows; they are essentially a plywood cover that is hinged at the top to open outward kind of like a hurricane shutter (propped/suspended open at the bottom).

They are very rudimentary, but my question is whether I need 1 or 2-sided MDO. The backside will largely be protected from the elements, facing the interior, but it is humid and there will be some minimal weather exposure.

Any advice is appreciated.

[Myk Rian]

2 sided, since both sides will be exposed to weather.

[Jamie Buxton]

Two sided, because the back side is visible. The back side of single-sided MDO is really low-grade material, full of knots and checks and such.

[Jake Helmboldt]

Thanks guys. Having not used it, I haven't even taken a look to see what it looks like.

One othe question; does it matter if I use a latex or oil primer (since it is waterproof I assume no issues with water-based primer as you would have with MDF)?

[Myk Rian]

Thanks guys. Having not used it, I haven't even taken a look to see what it looks like.

One othe question; does it matter if I use a latex or oil primer (since it is waterproof I assume no issues with water-based primer as you would have with MDF)?
Just be ready for 3+ coats. It really soaks the paint up.
I use MDO for making yard light houses.

[ken gibbs]

What is an MDO? Pleaee translate & thanks.

[Rich Engelhardt]

Medium Density Overlay

It's an engineered product - "plywood" with resin saturated paper facing.
Very flat, very stable and very water/weather proof.

I've only seen it offered around me at Menards.

[Howard Acheson]

One thing you should understand is that MDO is not any more water resistant than exterior rated plywood. In fact, MDO is just exterior rated plywood with one or both sides covered with a resin impregnated paper. The coating is to provide a nice surface for painted signs which is what MDO was developed for. The weakness in both is that water can get into the edges and cause the wood to swell and rot which can cause delamination in both panel types. Edges need to be effectively sealed to have the panels last as long as possible. We used to seal the edges with epoxy resin then use paint.

Unless you're looking for a perfectly flat surface, standard external rated plywood would work as well. Just paint it with a good exterior house paint front and back and you're done.

[Jason White]

If you plan to paint both sides, get double-sided. You can also get it pre-primed on one or both sides. I just bought a sheet that cost about $50 or so primed on both sides.

Jason



I've never used MDO and am looking for some advice. Our pool has asked me to make new covers for the bathroom windows; they are essentially a plywood cover that is hinged at the top to open outward kind of like a hurricane shutter (propped/suspended open at the bottom).

They are very rudimentary, but my question is whether I need 1 or 2-sided MDO. The backside will largely be protected from the elements, facing the interior, but it is humid and there will be some minimal weather exposure.

Any advice is appreciated.

[Jake Helmboldt]

One thing you should understand is that MDO is not any more water resistant than exterior rated plywood. In fact, MDO is just exterior rated plywood with one or both sides covered with a resin impregnated paper. The coating is to provide a nice surface for painted signs which is what MDO was developed for. The weakness in both is that water can get into the edges and cause the wood to swell and rot which can cause delamination in both panel types. Edges need to be effectively sealed to have the panels last as long as possible. We used to seal the edges with epoxy resin then use paint.

Unless you're looking for a perfectly flat surface, standard external rated plywood would work as well. Just paint it with a good exterior house paint front and back and you're done.

Howard, how did you apply the epoxy (and how heavy/thick)? I wasn't aware this was an issue, nor that exterior ply is as water resistant. Isn't the surface of exterior ply pretty rough?