MDF and outdoors

[Steve Hayes]

Can MDF be sealed to weather the outdoors? It's for decorations and will be hung and not touching soil.

[Frank Fusco]

Take a lot of seal. Stuff is already heavy. Not designed for getting wet. No matter what you do to it, I expect you would end up dissapointed and spending more money than on another product.

[Ian Barley]

There are exterior grades of MDF (Medite? is the brand name over here). It is however fiercely expensive compared to the normal stuff.

If standard mdf is well painted with an oil based paint you will get a few years in a light exposure location but I would recommend looking for a better alternative.

[Scott Thornton]

I don't think MDF and outdoors go hand in hand. If you are looking for a paint grade plywood for exterior use, I would suggest MDO, it takes a finish better than any other ply. You will want to seal it pretty well though.

Ideally, you should use an actual "exterior" grade plywood.

[Cliff Rohrabacher]

Yah but the $$ you wil pay for a proper sealer won't be cost effective.

You'd need a penetrating expoxy or catalzying urethane to get realistic all weather long term protection.

Whi not use a Cedar, IPE, plastic decking, or even the PVC white trim lumber that is getting popular.

There are so many very much better choices than mdf

[Steve Hayes]

I'm looking for something easy to cut and at least 12" wide. Cedar may be the choice. How does cedar plane? It needs to be 1/2 inch.

[Allen Bookout]

I don't know what kind of decorations that you are talking about but if they will have a flat surface and just be cut to shape something that will last for years is marine plywood or exterior plywood completely encapsulated with a two part epoxy like West System and then coated with either paint or clear that will withstand UV rays. If you need a real smooth surface you can flow coat it and sand it extremely smooth. When coated with a high quality "paint"you cannot tell it from fiberglass.

Actually you can even bend the plywood around frames if necessary.

I have built small boats using this system and they are extremely durable.

Allen

[Errol Wentworth]

MDF=NO

MDO (medium density overlay) is an exterior ply with resin overlay. It is commonly used to make exterior signs.

Extira is a composite material that is also suitable for exterior use. Google "extira" for more info.

MDO is likely to be less expensive and easier to work. Extira is HEAVY and the dust is awful.

Errol

[David Duke]

MDF=NO

MDO (medium density overlay) is an exterior ply with resin overlay. It is commonly used to make exterior signs.

Extira is a composite material that is also suitable for exterior use. Google "extira" for more info.

MDO is likely to be less expensive and easier to work. Extira is HEAVY and the dust is awful.

Errol

What Errol said.

[Howard Acheson]

>> There are exterior grades of MDF (Medite? is the brand name over here

Even the specs for that material say is it not suitable for direct exposure to outside elements. It is used UNDER a standard siding but not directly exposed.

I would avoid MDF. Instead, use an exterior rated plywood or MDO (Medium Density Overlay). MDO is an exterior rated plywood with a resin impregnated paper coating on one or both sides. It was designed for exterior signage in the interstate highways. The resin impregnated paper coating is specifically designed to be painted. However, like any exterior plywood, the edges must be sealed or water can cause delamination.

[Ben Grunow]

Steve- we are using PVC that is available in boards and sheets (1/2" too) like regular wood is sold. Imagine a PVC pipe but in board or sheet stock and slightly less dense, about the density of pine. THis stuff is white and can be worked just like wood and requires no paint and will last forever (lierally). Expensive but never rots andeasy to work and glue and even takes paint. Mfgr is Azek or Kleer. Google and see. Good luck

[Bruce Benjamin]

There are at least a couple of types of MDF that have some degree of water resistance. In addition to the Medite already mentioned there's Medex and another variety I can't recall right now. I have some Medex and I think it was about 50% more expensive than regular MDF. There's another brand, I can't recall the name now, and the manufacturer claims outdoor use is fine. Not for submerged usage but for use anywhere standard exterior grade plywood would be used. It's not easy to find in my area and the closest distributer is a couple hours away. When I called them they would only sell in larger quantities than I wanted to purchase. I wish I could remember the name but whatever it was it was supposed to be not just water resistant but water proof. It certainly might have some applications for some people.

Bruce