advice needed

[megamoo]

I am a complete novice carpenter and I want to make a dog house, (its actually a cat house but just think dog kennel). I want to make it out of MDF which is cheap but it will be out in full sun and full rain and weather.
My question is can anyone recommend something I can paint on it to seal the MDF so it doesn't bubble and swell, or is this impossible and I should use some other material? I don't have a lot of money to spend on this.

[Wizened of Oz]

or is this impossible and I should use some other material?

Yes, and yes.

[Skew ChiDAMN!!]

Hehe. Not quite, but for all economic intents 'n purposes Wizened is right. It'd cost a small fortune to seal MDF well enough to resit weather... and then any scratching or chewing will undo all your efforts anyway.

IMHO, you're better off at looking at buying marine ply in the first place. You could cut costs by making a frame up from KDHW and using thin sheets of 6mm(ish) marine ply as cladding. Personally, I'd use 18mm sheets all the way. for sheer simplicity of build. ie. the same as you're probably planning with MDF.

It's more expensive then MDF, but will last much, much longer. Especially if you paint it.

[Wizened of Oz]

Giving some thought to your project, I think Weathertex might be the best sheet material for your project.
Signwriters commonly use it for outdoor signs, so this gives you some idea of its durability.

[munruben]

I'm with Skew, Marine ply is the way to go. False economy to use MDF although Wizened of Oz's suggestion is worth thinking about.

[megamoo]

Ok I'll have a go down the marine ply track then. Thanks for the respones. If I get any time to actually make the thing ill take a picture and post it.

[jatt]

May I recommend what I do, that is scrounge from construction sites or go down to the local secondhand timber yard.

Its surprising what u can get hold of if u ask. Timber offcuts, sheeting like blueboard etc.. a lotta perfectly good stuff gets chucked into the bin.