Tile over a sturdy wood deck post and beam

[David Hardy]

Can I install tile over a strong wood deck that has no deflection if I first lay down Wonderboard with thinset and screws and then Redgard or will this cause the wood to rot out quickly? I would use Flexbond thinset, porcelain tile and probably Prisims grout? The deck is stout and in good shape built of PT 2x6 decking and weathered well. One concern is slop for drainage cause its level flat now.I would maybe fir it to proper slope under the Wonderboard.

[dgbldr]

...I would maybe fir it to proper slope under the Wonderboard.

How exactly would you do that and how would you then install the cement board? Can you provide a drawing of your proposed method?