Weatherproofing MDF

[George Brown]

I have not been able to find a thread on sealing mdf for outdoor use.

I'm going to be making some plaques of mdf for the outside. I could seal it with polyurethane, or exterior 450 (from general finishes), but it has to stand up to wind, rain, sun, temperature changes etc for at least 10 years.

Anybody had any experiences with it?

[Jamie Buxton]

True MDF turns to oatmeal if water gets to it. However, there are MDF-like panels intended for use outside. Extira is one -- http://www.extira.com/

[George Brown]

True MDF turns to oatmeal if water gets to it. However, there are MDF-like panels intended for use outside. Extira is one -- http://www.extira.com/

Estira, I have read has paint adhesion problems and still needs to be sealed well. It is also quite a bit more expensive than mdf and is oily. I don't know how well extira holds detail when router carving.

[Nicholas Bukky]

George,
I use Extira for extrior signs a bit it is tuff stuff I laid a piece out side the shop on the ground for over 2 mos. and it did nothing and was raw!!!!

If you use a good primer coat(i use XIM from SW) and good exterior paint they will hold up fine!!!

Just my thoughts!!

Nick

[George Brown]

Nick,

How well does it hold 3 dimensional detail?

And how expensive is a sheet?

Thanks

[Nicholas Bukky]

It carves just like mdf only the dust is thicker and heavier probably from the adhesives in it.
It is $50 for .5 $60 for .75 and $70 for 1inch 4x8 sheets from the place I get it.

I have vcarved it and textured it and pocket cut it but have not done any 3d forms out of it yet but would not hesitate to try it if I need to.

I think JimMcG did some rotary turned balisters from some laminated extira.

Nick

[james mcgrew]

just do not breathe it (iritating) machines like mdf

[Sergio Arze]

You could seal the MDF with a tooling gealcoat or just a plain white gelcoat.

[George Brown]

You could seal the MDF with a tooling gealcoat or just a plain white gelcoat.

What do you mean by gelcoat?

[Steve knight]

myself I would soak it with coats of epoxy till it stays on the surface. that should seal it pretty well against water. then use a normal painting sealing routine.

[George Brown]

myself I would soak it with coats of epoxy till it stays on the surface. that should seal it pretty well against water. then use a normal painting sealing routine.

It would probably work but the epoxy gets expensive. Cost is an issue in this project. I hope to do many of them, and the engraving time is already hour and a half. Got to keep production time and costs low :(

[Joe Pelonio]

One-Shot makes both primers and topcoats that can be used both before and after the color paint on MDF and will seal it for 10-15 years. Unfortunately they will run about $50/quart. Worth the price but
runs up the sale price.

http://www.1shot.com/home.html

[George Brown]

One-Shot makes both primers and topcoats that can be used both before and after the color paint on MDF and will seal it for 10-15 years. Unfortunately they will run about $50/quart. Worth the price but
runs up the sale price.

http://www.1shot.com/home.html

Thanks for the info, will keep in mind for other projects.

[Nicholas Bukky]

Buy extira prime in with XIM primer and use a good exterior paint on it. No cost of epoxy etc.....

Nick

[George Brown]

Buy extira prime in with XIM primer and use a good exterior paint on it. No cost of epoxy etc.....

Nick

I'm having trouble finding extira in my area, still working on it though.

[Gerry Grzadzinski]

The Extira should hold up fine, as long as your paint does.
I used 15 sheets of it to build a storefront almost 10 years ago. It still looks good today. But I didn't paint it, so I'm not sure what type of paint was used.

[Nicholas Bukky]

George,
I get mine from a place that is based out of Pittsburgh called DSI
www.distributor-service.com (http://www.distributor-service.com) I don't know if they go East but there has got to be someone that carries that stuff near you.
www.cmicompany.com (http://www.cmicompany.com) is extira they might be able to lead you to a distributor in your area also or if you know of a large sheet goods place..

Nick

[George Brown]

Just as an update, I was able to find extira from my local Lowe's. Price was reasonable, about $66 a sheet, had to be special ordered, but they could get it. I will see how it works.

Thanks for all the recommendations.

[Tony Dietz]

With all the painting, priming and worry... why not just sign foam?

[james mcgrew]

tony is right if the expense can be worked in the sign foam is a cure all!!

[George Brown]

Waaaay too expensive. Sign foam is almost $300 a sheet. MDF is $25/sheet and Extira is $65/sheet. A long ways from $300 a sheet!!

[Nicholas Bukky]

How do you guys paint the sign foam????

nick

[George Brown]

Just an update, extira machines just like mdf, maybe a little better. Dust settles more quickly then mdf and is harder to clean up, but with a good dust collector, no problem. It, however, will NOT cut with a laser. Extremely difficult to do so.

[Brian Peters]

Just buy and use Extira. It's a superior product. If you don't like the way it machines you could always use HDU sign foam. Both are bullet proof in an exterior application. Messing with ways to seal it/epoxy it is both expensive and labor intensive and it isn't even guaranteed.