Advice on tiling underlay on deck

[Bodgy]

I have a 3m x 10m wooden deck that is currently timber planked.

I wish to tile it. The timber has the usual gaps to allow drainage between planks.

My question is regarding the fibro sheet I'll put down over the timber before tiling.

Given the deck is stable and flat, I should be able to get away with less than the usual thickness of fibro as its not structural at all, just a flat surface for the tiles.

Any ideas what thickness will do the job?

[silentC]

I'm not sure that any of the underlay products would be suitable for external use. James Hardie has a product suitable for exterior use - HardiPanel. Thinnest it comes is 15mm.

Are you considering just putting something over the existing decking boards?

[Dirty Doogie]

Bodgy, if you intend to put down a waterproof membrane over the fibre cement sheet you could use 6 mm hardiflex nailed at 150 mm centres. If you dont use a waterproofing membrane then you'll have to go up to a 12 or 15 mm thick hardipanel.

You have to be very sure that your decking doesnt deflect when you walk on it though if you want to use the 6mm stuff.

[Bodgy]

Thanks guys.

I would have thought that the grouted tiles on top would be sufficient waterproofing?

There is a little flex in the deck, not much as the joist are 450mm centres and the planks @ 19mm thick.

I wish I could tile over decking, but I doubt the tiles would stay stuck down. The fibro will give it that little bit more rigidity.

[pawnhead]

I would have thought that the grouted tiles on top would be sufficient waterproofing?

No. It's all porous so your decking would end up rotting.

There is a little flex in the deck, not much as the joist are 450mm centres and the planks @ 19mm thick.

There's usually more flex in a deck than in a floor, who's interlocking tongue and grooves help with support. But even then you'd be wise to use a flexible tile adhesive. I don't know how it stacks up to weather though.

I wish I could tile over decking, but I doubt the tiles would stay stuck down. The fibro will give it that little bit more rigidity.

As a builder, I wouldn't guarantee anything less than ripping up the decking boards, giving the joists a fall to shed water, and then gluing and screwing down compressed FC with a waterproof membrane on top. If I did, then I might find myself constantly coming back to replace loose, drummy, or cracked tiles, or complaints about water ponding and mould build up.
It's up to you, and it may be alright, but guaranteeing a "Bodgy" job is not worth the grief that may ensue IMO.

[Bodgy]

Thanks for the advice. Another nightmare I was afraid of.