What Is Considered Cold Weather Masonry?

Think About the Possibility of Using Bulk-Delivered Dry Mortar Ingredients

Caucasian Worker on Scaffolding

Don Mason / Blend Images / Getty Images

Masonry work requires special attention when working temperatures are below 40 degrees Fahrenheit. When the temperature drops below this point, masons should act promptly and follow special steps to keep masonry warm and workable. Masonry work in cold weather produces slower hydration in the mortar and when the water freezes it creates a destructive change in volume causing the mortar expansion. If the mortar contains more than 6 percent water, the expansion due to freezing will be great enough to crack the mortar.

If the masonry is rewetted, the architect or engineer should specify how the masonry should be wetted and how to test if the procedure worked. Wet or ice-covered unit surfaces prevent the development of a good bond between the mortar and unit.

How Would Cold Weather Affects Mortar?

Working under cold or freezing temperatures can cause severe problems if not addressed properly. Keeping mortar above 40 degrees Fahrenheit is important. And you should be able to do it following these 3 steps:

  1. Do not mix large amounts of mortar mix, so that way water will not be absorbed by the materials and will not frost.
  2. If temperatures are too low, mortar can be placed on heated surfaces such as metal mortarboards.
  3. Keep a close eye on mortar temperature to avoid mortar being dried due to excessive heat.

24 Masonry Cold Weather Tips

The following cold-weather procedures shall be implemented when either the ambient temperature or the temperature of masonry falls below 40ºF.

  1. It is recommended to use speed hydration by using high-early cement or by using an accelerator. Caution: Type III cement could change mortar color varying the required appearance.
  2. Analyze how admixture could affect cold weather construction and reactions.
  3. Place materials on planks and cover them with tarps.
  4. All masonry materials should be completely covered to prevent wetting by rain or snow.
  5. Use, when possible, bulk-delivered dry mortar ingredients
  6. Some masonry materials might need to be heated before use so that cement hydration can occur properly.
  1. Masonry units with high rates of absorption will accelerate stiffening.
  2. Calcium chloride (at a limit of 2 percent by weight of cement) is commonly used in concrete as an accelerator, but the Specification prohibits its use in mortar for Masonry Structures.
  3. Place masonry on unfrozen surfaces because ice reduces bond and when it melts the masonry could move.
  4. When temperatures are above 32 degrees Fahrenheit, cover walls with plastic to prevent water from entering masonry.
  5. When the temperature is between 32 and 20 degrees, use ½ inch insulation blanket to cover the walls to prevent or reduce rapid heat loss, or block water from entering masonry.
  1. When temperatures are between 20 and 0 degrees, the wall must be covered with a plastic insulation blanket, approximately one inch thick, or maintain a heated area to 40 degrees for two days following installation.
  2. Mortar shall be maintained above freezing until used.
  3. Sand or water shall be heated to produce mortar above 40 degrees Fahrenheit.
  4. Heat sources might be used on both sides of the masonry under construction.
  5. Windbreakers shall be installed if wind conditions are more than 15 miles per hour.
  1. Glass unit masonry shall not be laid during cold periods.
  2. Heated enclosures are recommended when the temperature drops below 20°F.
  3. Most commercially-available masonry ‘antifreeze’ admixtures are accelerators rather than freezing-point depressants. ASTM C1384 provides criteria for evaluating admixtures, including accelerators, for use in masonry mortars.
  4. It may be necessary to heat sand to thaw frozen lumps when temperatures fall below freezing.
  5. Heated water should be combined with cold sand in the mixer to avoid flash set,  before adding cement.
  1. Do not lay masonry units having either a temperature below 20°F or containing fro­zen moisture, visible ice, or snow on their surface.
  2. Contractors are recommended to use insulating blankets or heat lamps to retain the heat of cement reaction for a longer time.
  3. Masonry units should be kept dry, although very high absorption fired-clay brick may need to be wetted, not saturated, before use.