Tile on a deck?


Old 01-08-15, 01:12 PM
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Tile on a deck?

I've got a deck on a 70-year old house that's going to need to come out and get replaced (currently probably a 4:1 ratio of wood to rot in the surface boards, only marginally safe because it was originally surfaced with 2-by lumber for whatever reason). Currently the deck surface is maybe 14 in above grade, and I'm in southern CA so I'm not sure what sort of piers/footings may exist under the thing but my current plan includes pouring some concrete as necessary for the replacement.

There's a hot tub in a standing enclosure on the deck which needs to move for this operation, and I'm planning to relocate the tub and sink it partially into the new deck by incorporating a support structure (and probably a pergola covering the tub) into the deck but only lowering the tub bottom to grade level or slightly below, maybe pouring a slab to support this bottom which would be hidden under the construction when all is done.

I'd like to have the replacement surfaced with slate or some kind of weather-tolerant stone tile, would that require a sub-floor (ply or slats) under backer-board to mount the tiles, or would the concrete board have sufficient strength on its own if placed over 16-in spaced joists?

Since the existing deck is low, it could be replaced with a patio to simplify the use of stone surface and some steps to the house entry, but that would mean a dramatic rethinking of what to do with the tub.
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Old 01-08-15, 01:43 PM
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Need to look at how much room there is between the ground and the deck structure - there needs to be room for air flow or the wood will rot. Sound familiar?

It's looking like a patio will be the way to go.
Old 01-08-15, 02:37 PM
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If I go with a new deck, my plan was actually to dig out the area underneath at least 6" deep (plus digging piers for deck/pergola posts of 18-30 depending on code and which height post would be at any particular spot) and lay in a gravel bed with concrete piers a couple inches above that for mounting post brackets to ensure good drainage/circulation under the structure. Also, being in CA, redwood is readily available and fairly inexpensive around here which I'd plan on spraying with linseed oil before completing the top. I might even go with composite framing since the substructure will be difficult to maintain regardless.

I'm pretty sure the rot issues I'm looking at now are largely due to the deck likely being 30-40 years old plus the previous owner having a general aversion to decent maintenance (or workmanship, which is what convinces me the thing predates his ownership) as it's fundamentally decently built but was probably never re-finished or touched-up in the last 10-15 years
Old 01-08-15, 02:43 PM
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So you have an aversion to pouring a patio as mitch17 suggested? It would be more substantial, with no issues to holding the hot tub and you can tile on top of it, or have it cut and stained to replicate stone. That low to the ground, I would recommend a patio pour.
Old 01-08-15, 04:34 PM
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If I do a patio, I'd rather do pavers than pour concrete, except for where the pergola would then anchor where I'd still have piers. I'm not fully opposed to this, but it's definitely plan "B". Pouring/pumping a full concrete patio is a last resort that i can't imagine any need to resort to, there's already too much poured concrete around the property for my taste as it is (especially in earthquake country where slabs are prone to cracking), and I'd like to eventually tear up the existing driveway slab and put in pavers after taking care of a bunch of other higher-priority projects first.

I'd prefer the deck option if it's doable because the house is raised and also because it would allow for the hot tub to be sunken partially into the surrounding surface without having to form out a pit to sink it below ground (the current housing has a service hatch, which I can incorporate a functional equivalent for in a deck as opposed to maybe needing to get the whole works re-plumbed for a sunken installation). Plus it's easier to edge the grass around a deck and ignore loose trimmings that end up in the gravel bed than sweep up the edges of the patio every time I mow/edge.
Old 01-09-15, 04:39 AM
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IMO it's never a good idea to install tile over wood on the exterior! Between the hot tub and the tile you'd need an extra strong/stiff deck. Any flexing will pop the tile and that includes moisture changes in the wood.
Old 01-09-15, 11:02 AM
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My plan would have been to put hardie-backer over some slats or ply subfloor on the deck framing with the tile on the cement board, not sure if that would mitigate or prevent flexing problems. Do you know if there's an outdoor-usable version of subfloor adhesive?

I can live with a wood-surfaced deck, and might end up going that way since it's definitely more maintainable and ultimately less work to build, I just really like the look and idea of the semi-textured slate surface.
Old 01-09-15, 08:51 PM
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Installing hardie-backer on an exterior plywood surface is asking for trouble. Such as having to replace rotting/swelling plywood after a few years of moisture immersion, which will prove complex with all of the tile and grout being present.

If you insist on tile, go with a poured concrete base. Even though it may crack, it will never rot.

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