Best practice for butt joining MDF?

[tmurphy]

I am about to brave the madness that is B&Q on a Bank Holiday Monday, I have my crash helmet and stab-vest ready to go

I'm going to pick up two 2440x1220 sheets of 18mm MDF for my floating wall.

Does anyone have any tips for making the join where the two panels meet as invisible as possible?

Theoretically they should line up perfectly or is it wise to leave a few mm gap and use some sort of filler between?

Due to the width of the install and the location of the screen and spakers I'll be using the horizontally.

Regards

Tony

[velveteer]

Hi Tony,
I would butt the two pieces up as close and level as possible, don't leave a gap.
You will more than likely be able to see where the pieces join, so will probably need to use some sort of filler. one of the best fillers is isopon p38, which is sold as a car scratch filler. works on wood too though, easy to sand as well. Apply some and sand back- it may take a couple of attempts at filling and sanding to get the finish you want. Don't forget to get some mdf primer as well (you will need enough for at least two coats)
Hope this helps.

[Mike Spence]

In your opinion would it be worth running a bead of filler along the joints before butting them together so that a small amount is squeezed out? It could then be smoothed and sanded in the knowledge that there were no gaps.

[velveteer]

Originally Posted by Mike Spence

In your opinion would it be worth running a bead of filler along the joints before butting them together so that a small amount is squeezed out? It could then be smoothed and sanded in the knowledge that there were no gaps.

Not something I would do, but it all depends on the way you work. It's certainly worth a try- but to be honest, just butting them together and then filling/sanding several times, then finishing with paint, you shouldn't be able to see any gaps after that anyway.

[banners]

Plaster board tapers at the edges, so maybe a smallish chamfer on the edge to allow a decent gap for filler to work/bond?

Car body filler works a treat as it cures so fast. Time = Money!!

Steve

[tmurphy]

Thanks for the replies, I now have the MDF and tomorrows job will be to give it first fixing to the frame, hopefully by the end of the week I'll be at point of filling / sanding !

Tony

[nbaker]

Originally Posted by banners

Car body filler works a treat as it cures so fast. Time = Money!!

Steve

And also cracks as someone else here found out

[MarkP80]

Hi,

Try to make sure you get a batten behind the mdf for the full length of the join, and screw the sheets to this. This will ensure stability of the joint and minimise the possibility of the filler cracking. I simply used ployfilla, the type you mix yourself, as this is very eaasy to sand. Ready mixed is much harder, I find.

MarkP