Painted MDF outdoors

[Aragorn]

Hi folks

I am making a blackboard which will spend most of its time outside. The board itself is an ellipse shape, so I'm looking to cut it from MDF or ply.

Question is, if MDF is painted (can be oil-based or acrylic), do you think it would stand up to the elements for a reasonable length of time?

Regardless of whether I use MDF, ply or MDO, I'm mostly worried about the edges as I don't much fancy having to edge an ellipse in hardwood to protect it better.

Suggestions most welcome!

 

[Gill]

Question is, if MDF is painted (can be oil-based or acrylic), do you think it would stand up to the elements for a reasonable length of time?

Mine didn't .

It was standard MDF that I'd used to make a sign, primed with an acrylic primer, painted with acrylic and given several coats of Holts car lacquer. It lasted about a year.

Gill

 

[Anonymous]

Hi,

I don't think I'd do it. But if you must, use a couple coats of premium oil-based primer.

Can you get MDO? It's a paper-topped stuff designed for outdoors signs. It might be called differently than here.

http://www.canply.org/english/products/ ... lywood.htm

 

[AndyBoyd]

Surely marine ply is the way to go

 

[Aragorn]

Hi Gill
Oh dear. Not good I'd like mine to last longer than a year. Thanks for the heads-up though. I wanted to use MDF coz I have a nice offcut just the right size... :roll:

Hi Trent
MDO is available here in some places. I'd still be concerned about the edges though. Presumably it's just like regular ply when cut?

Hi Andy
(homer) D'oh! I don't know why this didn't occur to my sieve-like brain... Will the edges be OK if I use marine ply?

 

[Waka]

Aragorn

Marine ply would be the best to use as Andy says, if you seal the edges it will last a longgggg time.

 

[RogerS]

Aragorn

The panels of our summerhouse are made from exterior grade MDF - according to the suppliers. These are then painted using paint from teknos www.teknos.com ...which are paints specific for the woodworking industry.

The summerhouse suppliers reckon that the building should last for many, many years. I recently saw an elderly summerhouse and couldn't see any signs of damp damage.

http://www.hspgardenbuildings.co.uk/summerhouses.htm for more details

Roger

 

[Aragorn]

Thanks all for your tips and advice.
I've settled on marine ply, and I'll look into those paints Roger.

I've just spent the last half hour setting up the Trend ellipse cutting jig and cutting my first ellipse with it. Quite nice. Leaves a good finish on the ply (as you'd expect from a router) and a nice even ellipse (as you'd expect from Trend).

 

[mahking51]

Aragorn
If using marine plywood consider using West Sytem Epoxy to seal the edges (and all over). itwill last for a very long time if painted. It is important to paint it well as the epoxy is not very UV resistant unless coated.
Have used this many times in a salt water environment and very pleased with its longevity.
Regards
Martin