Using MDF on an enclosed porch?

My view is that your site would be considered exterior inasmuch as there’s no heat. It’s the edges of MDF that absorb moisture easily, and I have a hunch that in a few years you’d regret the decision.

Consider an exterior ply with a sanded face if you want to go to sheet goods.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

I agree with Lee. A few dollars saved now will leave you kicking yourself later.

-- Charlie M. "Woodworking - patience = firewood"

My first reaction would be a no on the MDF in an exterior application
but then I remembered it is sold as a profiled siding material and
has been for many years.

If I were you I’d research the durability of the siding and ask
yourself if you want to take a chance.

MDF does not tolerate moisture – it will swell and turn into mush….exterior ply or OSB would be a better choice….Another way to go is to use pine or Douglas Fir as it is cheap (or any other cheap wood would work as being painted can give it enough protection from the elements) and when painted can be fairly tolerant of the moisture ….White Oak, Redwood or Cedar are typically the go to outdoor woods.

-- Woodworking.....My small slice of heaven!

There is an exterior grade MDF that will work just fine. Look it up on the net. I have it on the exterior columns on my home. As long as it is not submerged…....
Bill

-- bill@magraphics.us

I had forgotten about the exterior MDF too, Loren. A friend put a hunk in water and it was there a couple weeks and did not even change shape. 3/4” thick.

And that’s all I know!

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

I have heard of an exterior grade MDF, but have only seen it made into siding (expensive yet looks cheap…and tacky) I imagine they would have a bonding agent that is waterproof….and hopefully UV proof also. I do not know the price of it….but I still think you would be better served by an exterior solid wood…like plywood or such….because even if the binding agent is waterproof…the wood particles are not…sooner or later it will break down….but that is more a personal preference….I am not a big fan of MDF…I pretty much only use it for jigs.

-- Woodworking.....My small slice of heaven!

MDF can take a good humid day or two before it goes to pieces , you are going to be fine.

Unless the porch has the same or similar humidity as an inside of a house (whether or not it’s got AC) it may be a mistake.

The glues used are ureformalhyde and they are pretty water proof but the swelling of all the little particles from, humidity swings will break the bonds . How much? Ask the manufacturer. I be they have engineering specs galore.

-- When the moderator chooses sides, his site sucks.