Using MDF for fascia boards - any problems?

Aug 21, 2009 14 Replies

I need about 100M of 25x250 fascia boards and they are working out quite expensive. What are the problems if I decides to cut fascia boards from



2400 x 1200mm sheets of 25mm MDF?

Also are there any advantages in using MDF primer as opposed to normal wood primer?



Thanks, Brian


MDF doesn't like water. A decent ply would be better. Or even PVC.

MDF is essentially thick cardboard. So umm what do you think will happen when it rains?

MDF is basically Wheatabix. Don't even think about it. uPVC.

Exterior MDF would last a while. Normal or MR would die pretty quickly

Didn't know they made that? Never seen it in the sheds.

All sorts of things exist that they don't sell in sheds. ;)

Click on MDF:

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isn't nearly as cheap though.
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If it's anything like exterior grade chipboard, I still wouldn't bother. ;-)

Quick deterioration of the MDF leading to early renewal - thus dramatically cutting any cost savings over tanalised or untreated timber [1].

None, the stuff will still rot or break down early.

[1] I have just finished painting my 30+ year old tanalised fascia boards and there was absolutely no sign of rot or decay in them - and that's a 'life' that you will *never* obtain with any type of MDF when used externally.

My advice is to 'bite the bullet' and pay the costs for some decent, treated timber and then decorate it correctly - or replace (or cover) the old stuff with plastic.

Cash

ISTR in Scandinavia an external grade MDF is used for road signs.

Permanent ones? I suppose if it was coated with some high tech stuff it could be ok - but house paint isn't high tech. ;-)

=A0 London SW

I don't know why you are quite so sceptical - I can understand some scepticism, but if they use a fully waterproof glue (and enough if it), why should it last any less well than WBP ply providing it isn't particularly stressed? They may well treat the sawdust with preservative (I know Medite are developing one with acetylised wood - dust equivalent of Accoya). They might even use durable hardwood dust, but I doubt it. It's a resin panel, with a cellulose filler is all. If the resin is right, and the quantity of it is right, and the filler is right, I see no reason there will necessarily be an issue. How much would you worry about leaving a sheet of compact grade laminate (commonly used for cladding - have a peek over at the new blue Royal Holloway!), or tufnol outside?

Would last longer than the ali ones round here -- no scrap value for the pikeys.

Experience of this sort of thing claiming to be waterproof? Of course a road sign is by nature well ventilated.

Maybe - but them they're likely more expensive to make than a decent marine ply - so rather pointless.

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