Quality Control All-Weather Construction

1) Cold Weather Construction
2) Hot Dry Weather Construction
3) Wet Weather Construction
4) Guide Specifications

1. Cold Weather Construction

The performance characteristics of masonry mortars and grout are influenced by temperatures below normal. The changes in the performance characteristics are predictable and quality masonry construction may proceed with only minor changes in mortar and grout preparation -- heating of materials. Heated mortars, which prolong the period before freezing, possess hardened properties equal to or more desirable than their unfrozen or early frozen counterparts.

All masonry units used during normal temperature masonry construction may be successfully used during below normal temperature masonry construction. No change or only a minor change will be required to produce quality masonry. Low absorption units may require additional or earlier protection from freezing. The effect on the unit is considered insignificant, however, if freezing occurs after the moisture within the mortar has been decreased sufficiently low to prevent expansion on freezing. Units with a higher initial rate of absorption (greater than 5 to 6 grams suction per minute per 30 square inches) are advantageous in some instances. Units with greater absorption characteristics remove more of the water from the mortar and reduce the possibility of damage by early freezing.

To summarize: No drastic change in mortar mixture or masonry unit is required for below normal temperature masonry construction. As the temperature decreases, Type III cement should be considered as a replacement for Type I cement and dry hydrated lime should be considered as a replacement for slaked quicklime. No change of masonry unit is recommended but, prior to commencing construction, masonry units with suction rates greater than 5 to 6 grams suction per minute per 30 square inches should be selected, especially if prolonged periods of below normal temperature construction are predicted.

Diagram

Freezing characteristics of mortar and mortar ingredients

1.1. UBC cold weather construction requirements:
(SEC. 2404(C))

General. All materials shall be delivered in a usable condition and stored to prevent wetting by capillary action, rain and snow.

The tops of all walls not enclosed or sheltered shall be covered with a strong weather-resistive material at the end of each day or shutdown.

Partially completed walls shall be covered at all times when work is not in progress. Covers shall be draped over the wall and extends minimum of 2 feet down both sides and shall be securely held in place, except when additional protection is required. (See 1.1.4.)

1.1.2. Execution-Preparation. If ice or snow has inadvertently formed on masonry bed, it shall be thawed by application of heat carefully applied until top surface of the masonry is dry to the touch.

A section of masonry deemed frozen and damaged shall be removed before continuing construction of that section.

1.1.3. Construction. Masonry units shall be dry. Wet or frozen masonry units shall not be laid.

Air temperature 40F. to 32F.: Sand or mixing water shall be heated to produce mortar temperatures between 40F. and 120F.

Air temperature 32F. to 25F.: Sand and mixing water shall be heated to produce mortar temperatures between 40F. and 120F. Maintain temperatures of mortar on boards above freezing.

Air temperature 25F. to 20F.: Sand and mixing water shall be heated to produce mortar temperatures between 40F. and 120F. Maintain mortar temperatures on boards above freezing. Salamanders or other sources of heat shall be used on both sides of walls under construction. Windbreaks shall be employed when wind is in excess of 15 mph.

Air temperature 20F. and below: Sand and mixing water shall be heated to provide mortar temperatures between 40F. and 120F. Enclosure and auxiliary heat shall be provided to maintain air temperature above 32F. Temperature of units when laid shall be not less than 20F.

Tarpaulins form a temporary enclosure

1.1.4. Protection. When the mean daily air tempertaure is 40F. to 32 F., masonry shall be protected from rain or snow for 24 hours by covering with weather-resistive membrane.

When the mean daily air temperature is 32F. to 25F., masonry shall be completely covered with weather-resistive membrane for 24 hours.

When the mean daily air temperature is 25F. to 20F., masonry shall be completely covered with insulating blankets or equally protected for 24 hours.

When the mean daily air temperature is 20F. and below, masonry temperature shall be maintained above 32F. for 24 hours by enclosure and supplementary heat, by electric heating blankets, infrared heat lamps or other approved methods.

Cover tops of walls at the end of each day

The NW Masonry Guide Table of Contents

Masonry Institute of Washington
Washington State Conference of Mason Contractors