The immediate temptation when tiling in cold weather is to keep on working until the mortar starts to freeze. Unfortunately, the mortar is uselss long before this point is reached, and it will fail, causing expensive repair work.

Problems start around 50F (10C) when the curing time of the mortar begins to slow down. The strongest mortars require a full week of curing at 50F. Below this point, the curing time becomes longer, and for proper strength and curing, it is vital that the work be protected from traffic and vibration. This may require stopping any other heavy work in that area. Although the curing time is extended, the mortar eventually will gain its full strength if left untouched.

At or below 35F, ice crystals start to form in the mortar. If the mortar has not had a chance to fully cure, the expanding crystals will destroy the bond from within the mortar. Although there may be no visible damage, the job is ruined and will never have a proper bond. If freezing occurs after the mortar has cured, there will be no damage.

A second problem, caused by slow curing times, involves grouting. At low temperatures (especially when below 50F) the motion and vibration caused by grouting will destroy a mortar bed which is still curing. To prevent this, wait an extra 2-4 days, until the mortar has cured sufficiently.

Many contractors assume that using portable heaters (salamanders) to keep up the temperature in the work area will help. Heaters do help, but can also be the cause of other problems. The dry out the winter air, which is already low in humidity. This delays and may even prevent curing in the heater's immediate area. They also give off carbon monoxide, a deadly poison, which requires thorough ventilation on the site.

In order to safely use portable heaters:
1. Raise them off the floor, and keep them far enough from the tile work to prevent the tile from becoming hot to the touch.
2. Use damp curing techniques to ensure adequate moisture will be present for at least three days.
3. Make sure there is adequate ventilation. Carbon monoxide vapors penetrate any crack or crevice, and can kill without warning. Follow the safety recommendations of the heater manufacturer, or local fire officials. Consider purchasing, and using, inexpensive carbon monoxide detectors or disposable detector patches. And where feasible, consider the use of electric heaters, which do not create carbon monoxide.

Epoxies, silicone rubber, and latex bonding agents also suffer in cold weather. The first question to ask is whether or not the material is freeze-thaw stable. If the material has frozen in shipping or storage, it may have separated or otherwise been damaged in less visible ways. If the product does not state that it is freeze-thaw stable, contact the manufacturer to be sure before using any.

Bring all products indoors for at least 12 hours before use, to allow them to warm up to a workable temperature. Products which are workable at 70F with an overnight curing time, will become stiff by 50F, with a curing time extending into 3-4 days. At 40F, they will generally be too stiff to use at all.

As a multi-part product becomes stiffer, it is also unlikely to mix properly. This will cause total failure in epoxy products. Again, this can be prevented by bringing the products up to working temperatures overnight. Since these temperatures must be maintained until the materials have cured, many contractors use heat lamps or electric blankets for small areas, and portable heaters for large areas, to warm the surrounding surfaces both before installation and during the curing time.

A last hazard is condensation. When humid air meets a cold surface, water will form on that surface. In a porous tile material, or a porous substrate, this moisture may interfere with proper bonding or rubber and epoxy type compounds. Whenever possible, the tile should be brought indoors overnight, allowing it to come up to room temperature. This eliminates one source of condensation. To dry out the substrate locally, use a cheesecloth or clean rag dampened with denatured alcohol (do not use any random petroleum distillate). Alcohol absorbs water and rapidly evaporates, taking the water along with it. Cleaning with alcohol also helps to ensure a clean surface, for a good bond under any conditions.

By following these simple precautions, you can be assured of a top-quality job every time. Moderate heat, moderate moisture, and getting your materials indoors, on-site before the work begins will prevent problems before they start. Remember, if you are not comfortable in the work area, it probably is not fit for good tile work, either.