How to Tile Outdoor or Exterior Walls
Ceramic, porcelain, or stone tile can create beautiful tiled exterior walls. Think building facades, tiled free-standing walls, tiled columns, and the like. In this section, we'll provide you with an overview of what to consider and prepare for.
Generally, ceramic, porcelain, or stone tile can be installed in exterior locations over suitable substrates such as masonry, concrete, mortar beds and in some cases certain types of backer board units. These substrates must be structurally sound, meet deflection requirements, and meet on-plane requirements.
As with any installtion done outdoors, exterior tile work has other demands that interior tile work does not always have. These demands include mandatory expansion joints, moisture considerations, and thermal demands.
Mandatory expansion joints relate directly to 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. These joints must proceed through the tile work.
(See Installing Tile Outdoors for visual examples of the types of installation issues you want to avoid.)
As always, follow the Manufacturers recommendations for all the products you plan to use in exterior tiling projects.
Installing Tile on Exterior Walls
To help illustrate how to install wall tile outdoors, we've included the diagram below.
Figure A and Figure B are typical examples of exterior wall tiling. Figure A represents tile installed over a mortar bed fastened to masonry or concrete while Figure B is tile bonded directly over masonry or concrete.
Certain backer board units can take the place of the mortar bed in Figure A. However, be sure to follow Manufacturer recommendations, Architects instructions, federal, state, and local building codes.
Tile installed over a mortar bed fastened to masonry or concrete
In Figure A, a membrane must be installed over the masonry or concrete followed by metal lath reinforcing wire (self furring lath is preferred). The metal lath should be securely fastened to the masonry or concrete using powder actuated nails and washers to grab multiple strands of the wire. The metal lath should be cut at all expansion joints and inside corners.
A scratch coat of wall mortar follows this step. The brown coat is then applied. The tile bond coat can be Portland cement paste on a mortar bed that is still workable or dry-set/latex modified thin set mortar on a cured bed.
Another step somewhat exclusive to exterior walls is the necessity to exclude water penetration under the tile-work from above. Therefore flashing should be installed to prevent future problems.
Note: Some Manufacturers provide trowel-applied membranes that can be applied directly to the cured mortar bed beneath the tile and bond coat that can take the place of the membrane.
Tile bonded directly over masonry or concrete
In Figure B, the tile bond coat is dry-set/latex modified thin set mortar directly on masonry or concrete wall.
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.