Ceramic, porcelain, and stone tile decks and patios, this section will detail these installations. For tiling patios on concrete slabs on grade, look in Floors Exterior.This section will deal with elevated tile patios and tile decks in an exterior environment such as a pool area.
Generally, ceramic, porcelain, or stone tile can be installed over suitable substrates, in elevated exterior locations, including mortar beds and in some cases backer board units.
Note: For a backer board unit installation, look further in this section for details.
These substrates must be structurally sound, meet deflection requirements, and meet on-plane requirements.
Whether the intended project is new construction or an existing remodel, the demands are the same. Certain demands, outlined in this section, need to be followed to help ensure a lasting tile installation in these locations. These demands include mandatory expansion joints, moisture considerations, and thermal demands.
The mandatory expansion joints relate directly with the thermal demands. Since exterior tile-work will be exposed to the elements, the tile-work will expand and contract more than interior protected tile-work. Therefore expansion joints are necessary every 8′-12′ in each direction in field and perimeter. These joints must proceed through the tile work.
Another thermal demand relates to the area of freeze thaw. In colder climates, the action of the freezing and thawing temperature can cause tile installations to fail. When excess moisture inside of a set tile freezes and then thaws, pressure builds to a point where tiles can spall and fracture. This situation relates directly to the water absorption rates for the tile selected.
Be sure to select a tile recommended for use in areas subject to freeze/thaw conditions. Tile with a high water absorption rate should not be selected in areas that have freeze/thaw conditions.
The moisture considerations also relate to the problem of efflorescence. Efflorescence is the stubborn powdery residue that commonly collects in grout joints when the surface dries. The powdery residues are soluble salts that are brought up through the tile work from the substrate below through hydration. The hydration is simply the evaporation of the water brought to the surface that deposits the salts.
Elevated patios and decks, finished in ceramic or stone tile, must be sloped to completely drain the surface of any surface water. The surface can slope to a drain or off the roof edge. The mandatory sloping will help reduce the problems of efflorescence.
In Figure A, we see tile installed over a mortar bed with a waterproof membrane under the tile elements. This waterproof membrane leads to a two-piece drain that includes weep holes. This system will also work without a drain if the edge of the tile work extends past the roof edge.
Note: Install bonded waterproof membrane on top of mortar bed to prevent moisture from entering system (new 2009).
This is a classic exterior elevated deck design. For this system to work, the waterproof membrane catches all the moisture that passes through the tile work, through the filter fabric, and then through the drainage layer. The moisture accumulates on the membrane and flows down the slope into the drain or off the roof.
Note: All elements of he roof deck must slope to the drain or roof edge.
The construction steps are as follows: The sub-floor is first pre-sloped, ¼ per foot, to the drain or roof edge. The continuous waterproof membrane is installed over the pre-sloped sub-floor and extends up any abutting vertical walls fastened to the wall-framing members. Ideally, the waterproof membrane should extend up the vertical wall 12″.
Note: In the following steps, the term siding refers to stucco, masonry, or any exterior wall siding material.
In the case of existing remodeling, the siding should be removed to allow this important step. A flashing should be installed to bridge the joint between the membrane and the existing siding membrane to form a continuous membrane.
The next step is to install the first layer of siding membrane, which laps over the waterproof membrane in shingle fashion. At this point, a drip edge flashing is installed over the first layer of siding membrane and waterproof membrane. The height of the flashing is dictated by the finished height of the tile surface. Ideally, the flashing should extend up the wall 6 or more inches.
The drip edge flashing allows any accumulated moisture that passes through the siding to flow out onto the deck tile surface.
In the case of remodeling or new construction, the wall siding could be completed after the deck is tiled to ease in the installation of the flashing detail. Next the siding membrane is installed in shingle fashion over the flashing.
A drainage layer is installed over the waterproof membrane. In Figure A, the drainage layer consists of ½ crushed stone at a minimum of 1 inch thick. This layer is topped with a filter fabric of burlap or closely woven cheesecloth. An alternative is a drainage mat system manufactured specifically for this purpose.
When installing the drainage layer, care should be taken to ensure that the membrane is not punctured. With stone this may be difficult, as the drainage layer needs to be compacted to avoid creating a deflection problem for the tile-work above.
If the floor includes a drain, crushed tile or stone should be placed over the weep holes to ensure the holes stay open for drainage.
A mortar bed is installed over the drainage layer at a minimum of 1 ¼” thick. Tile can be installed over a mortar bed that is still workable with Portland cement paste or with dry-set/latex Portland cement mortar over a cured bed.
For areas subject to freeze thaw conditions, the mortar bed, thin set, and grout should be as dense as possible. This means the addition of latex additives for the thin set and grout and a product such as anti hydro for the mortar.
An alternative method is to install a bonded sheet type waterproof membrane over a prepared mortar bed. The tile layer would be bonded directly to the waterproof membrane eliminating the need for the drainage layer. This method is particularly beneficial to areas subject to freeze thaw cycles.
It is possible to install certain backer-boards over suitable framing to replace the mortar bed method. This would involve the use of a backer-board recommended by the Manufacturer for this type of installation.
The backer-board should be installed and fastened over framing and exterior plywood recommended by the Manufacturer to meet deflection requirements. The bonded sheet type waterproof membrane would be installed over the backer-board and would be followed by the tile layer.
In this case the waterproof membrane would still need to extend up any abutting exterior walls and would still include the necessary flashing details.
In this photo, we see an exterior deck tiled with paver tiles over a mortar bed.
The Contractor installed the mandatory expansion joints that were detailed by the Architect.
These photos detail how the drainage off the roof edge was accomplished.
Note in this photo the drip edge design of the drainage flashing.
Note how the Architect and Contractor handled the roof edge detail in this installation with a double flashing.
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