[jondoe]

I have a double deck - the bottom is 5' off the ground, the top one 8' above it (both 12x18'). I am redecking both, and screening in the lower deck. A few questions. We need to seal the top. I have finally decided to stay with 2x6's - with 30# tar paper barrier between the joists, sloping outwards away from the house. Risky? It seems like it will work. It's not like it's supporting anything, maybe some running water. Their will be a wooden ceiling below that, that the paper will not touch.

For the lower deck, we're going for tile. Also risky, as the joists are 24" apart. The floor will be screened from the elements, and will get wet at times - not that it rains much in Atlanta. Would 3/4" ply be enough? Pressure-treated? What kind of spacing is needed between pieces? I can't imagine it would warp much, but will it flex too much for the grout, with traffic?

Thanks for any advice...

 

[Ron6519]

I don't understand the 2x6 use. Are they joists? Decking?
Lower deck tiled? What joists are 24" on center? It doesn't sound like you have anywhere near the deflection rate for tile.

 

[jondoe]

Yes, the decking of the upper deck is 2x6. Both decks are currently 2x6 decking.
The tar paper is to keep the rain and mosquitoes out of the lower deck.

So, plywood wouldn't offer enough support for backerboard and tile?
(when the house was built, 30 years ago, 24"oc was the standard. I could change it to 16", but that would add a whole new dimension to the rebuild)
Any thoughts on other flooring for the lower deck?
Is plywood recommended at all? I've never seen one down here. I've only seen 2x6 decking.

 

[12penny]

...any pictures of current conditions?

 

[Ron6519]

Yes, the decking of the upper deck is 2x6. Both decks are currently 2x6 decking.
The tar paper is to keep the rain and mosquitoes out of the lower deck.

So, plywood wouldn't offer enough support for backerboard and tile?
(when the house was built, 30 years ago, 24"oc was the standard. I could change it to 16", but that would add a whole new dimension to the rebuild)
Any thoughts on other flooring for the lower deck?
Is plywood recommended at all? I've never seen one down here. I've only seen 2x6 decking.

The tar paper will trap moisture against the deck bottom, with all the seams, will leak and will deteriorate pretty rapidly.
Thet have corrugated plastic that you can use under the deck that will direct the water to the edge of the deck and the ground.
You didn't mention the joist sizes, but a single layer of ply wouldn't be enough. If the joists were small and spanned excessive distances, you couldn't install tile.