What type of plywood do i need?

[BEN SHELTON]

I've got an outdoor project that I need some advice on.

I have a porch/patio behind my house and the "ceiling" surface is sheathed in some type of plywood. About 1/4" thick and painted.
I need to replace some of the sheets but I am not sure what type of plywood to use.

The local orange box has 5mm crap ply (sandeeply) and 1/4 plywood.
The 5mm stuff is awfully thin and not really stiff enough but it is smoooooth.
The 1/4 ply is stiffer but the surface is not as smooth. I feel like i'd have some undesired finish roughness if I tried to paint it.
I am not limited to the big box stores. I can shop elsewhere if I know what to look for.

So, what type of sheet good do I need to use to get a 1/4" thickness with a smooth, paintable surface that is also stiff and flat enough to not sag?

Thank you,
Ben

[Mike Cutler]

You can get unfinished 1/4" cabinet ply. It'll be a little $$$$ though.

[johnny means]

What is the issue that lead to the need for repairs?

[BEN SHELTON]

What is the issue that lead to the need for repairs?

Roof leaked, rotted the ply in places. Thanks to my friends we put on a new metal roof so that problem has been fixed. Now it is time to replace the ruined ceiling panels.

[Art Mann]

I had some areas of the soffit on my house rot due to gutter problems. I replaced it with 3/8" B-C grade SYP plywood and I like it much better than the original 1/4" material. I didn't buy it at Lowes or Home Depot because their quality was unacceptable. I went to a local lumber yard instead.

[Bill ThompsonNM]

I had some areas of the soffit on my house rot due to gutter problems. I replaced it with 3/8" B-C grade SYP plywood and I like it much better than the original 1/4" material. I didn't buy it at Lowes or Home Depot because their quality was unacceptable. I went to a local lumber yard instead.

+1 to that suggestion

[Mac McQuinn]

A 6mm Marine ply would do well IMO although be bit pricey. It should handle moisture very well and paint very nicely. I feel it would give you the smoothest finished surface overall.
Mac

[Jerry Miner]

Ask locally about 1/4" MDO (medium-density "overlay")--- this product is made for outdoor signs, has a smooth, easily painted surface (resin-impregnated paper) and is laid up with "exterior" glue---it is designed for outdoor use (unlike cabinet ply).

[Curt Harms]

Ask locally about 1/4" MDO (medium-density "overlay")--- this product is made for outdoor signs, has a smooth, easily painted surface (resin-impregnated paper) and is laid up with "exterior" glue---it is designed for outdoor use (unlike cabinet ply).

That sounds like a good idea. MDO is what is used for road signs I believe.

[Dimitrios Fradelakis]

[QUOTE="Curt Harms;2146966"]

That sounds like a good idea. MDO is what is used for road signs I believe.[/QUOTE

Correct.

MDO would be your best choice for your specific application.

[Mel Fulks]

Under your metal roof MDO isn't really needed but is an excellent product and will not have footballs or defects. I would
consider some type of nice moulding ,or even flat strips to cover joints.

[Howard Acheson]

Be sure to use a plywood or MDO rated for EXTERIOR use. Exterior plywood will be made with an exterior glue.

[Mac McQuinn]

In consideration of the MDO mentioned product, I must relent, it would be a better product for your use. I've used it in shelving and some other projects and it indeed machines well, doesn't chip out on edges(w/ sharp blades) and really does well with quality paint or varnish. I've edged it with oak and this gives it a nice contrast and finished edge.
Mac



A 6mm Marine ply would do well IMO although be bit pricey. It should handle moisture very well and paint very nicely. I feel it would give you the smoothest finished surface overall.
Mac

[Mark Bolton]

In consideration of the MDO mentioned product, I must relent, it would be a better product for your use. I've used it in shelving and some other projects and it indeed machines well, doesn't chip out on edges(w/ sharp blades) and really does well with quality paint or varnish. I've edged it with oak and this gives it a nice contrast and finished edge.
Mac

MDO edged with oak? Interesting. Why though? Did you want painted shelves with a natural finished edge? I guess it could be a neet look..

MDO would be best if the OP is looking for a smooth finish. In any exterior application, covered or not, it s the best option for paint grade as long as you don't want wood grain. I have had MDO scraps laying in a hayfield grown up in grass, mowed over with a bush hog, and when you pry them out of the mud both faces are smooth and little to no edge swell. I would use them in a heart beat (but they wound up in the fire). But be forewarned, sticker shock will be major. But if you want to do it right, and once, MDO is the answer.

Super nice would be appropriately sized square panels with a decorative trim, all painted. A mini coffer of sorts.

[Mac McQuinn]

Mark,
I needed a a storage cabinet for clamps, power hand tools, etc and thrifty as I am, I looked around for supplies and what I had in the material inventory. I came across some 3/4" MDO in 6' lengths @ $6.00 each although widths varied a bit. I wanted a nice shelf/side shadow line although needed a specific shelf depth to accommodate my tools. I added the red oak from cut-offs from another project to supply the width extensions. This covered the end grain of the ply and gave me the width needed. Shelves are adjustable using LV pins and collared holes. I felt this would allow the MDO to survive over the long term. Here's a basic picture of side/shelf junction. Everything received a couple coats of Shellac.
Mac
269173


MDO edged with oak? Interesting. Why though? Did you want painted shelves with a natural finished edge? I guess it could be a neet look..

MDO would be best if the OP is looking for a smooth finish. In any exterior application, covered or not, it s the best option for paint grade as long as you don't want wood grain. I have had MDO scraps laying in a hayfield grown up in grass, mowed over with a bush hog, and when you pry them out of the mud both faces are smooth and little to no edge swell. I would use them in a heart beat (but they wound up in the fire). But be forewarned, sticker shock will be major. But if you want to do it right, and once, MDO is the answer.

Super nice would be appropriately sized square panels with a decorative trim, all painted. A mini coffer of sorts.

[John TenEyck]

MDO is always rated for exterior use, as far as I know. Also, you can buy it with the impregnated paper on one or both faces, at least with the thicker grades, one face obviously being cheaper. I made some porch columns with 3/4" MDO last year and it is a pleasure to use (but the cut edges are very sharp so be careful) and paints beautifully.

John

[Myk Rian]

MDO. I use it for light houses and mail box posts.