Tile How-To: >> Floors Exterior
Ceramic, porcelain, or stone tile in exterior patios, walkways, porches, this do it yourself or how to section answers these questions.
|
Dr's tip: As always, follow the Manufacturers recommendations for all the products you plan to use in exterior tiling projects. |
Generally, ceramic, porcelain, or stone tile can be installed over suitable substrates, in exterior locations, including mortar beds over concrete slabs and directly to concrete slabs. These substrates must be structurally sound, meet deflection requirements, and meet on-plane requirements.
In addition, 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.
This is an example of a job where these other demands were not carefully examined and accounted for.
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. 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. For example, certain tiles in the impervious water absorption class (less than .5% water absorption) may be suitable.
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.
Ideally, the concrete slab would be constructed in such a way to minimize the water absorption. This is accomplished in two ways. First the required slope to completely drain the surface water should be required. Then the slab should have the required drainage below. This is accomplished with a gravel base below the slab to facilitate drainage.
|
Dr's tip: These requirements need to comply with federal, state, and local building codes. |
Unfortunately, many exterior floor tiling takes place on slabs that already exist. In this case, certain precautions can be taken to minimize the affects of water absorption into the slab. For example, the edges of the slab can be treated with a waterproofing membrane below ground level. Also, sources of water like sprinklers can be repositioned to minimize surface water.
When a project is desired on existing concrete slabs such as patios and walkways, the suitability of the existing concrete is the issue. Tile should not be placed on existing concrete that is ed (structural defect), is not on-plane within ΒΌ" in 10 feet, is not sloped to provide complete surface drainage, and slabs that do not have the required expansion joints.
A word on expansion joints in existing concrete slabs: All expansion, control, construction, cold, and seismic joints should continue through the tile-work. This includes perimeter joints and where the floor meets vertical surfaces. Review the section on expansion joints.
If the existing concrete slab is not suitable for the installation of tile directly on its surface, another method must be chosen or the slab should be replaced to allow the project to proceed.
Here are some examples of successful exterior flooring projects:
There are walkways and entrances.
Here is a patio.
Here are two examples of fine slate tile exterior jobs.
Keep an eye on this section for step-by-step exterior floor tiling projects.
