Masons doing residential construction work occasionally use a torch during cold weather to speed up the drying or settling of the masonry. Besides some of the obvious problems, such as the potential for damaging vinyl siding and windows, does this procedure adversely affect the masonry itself?

Torching masonry walls to hasten the set should not be permitted. Rapid heating of walls during cold weather causes the mortar to dry out on the surface. This condition may damage the surface of the joints by interrupting proper hydration of the mortar. The surface may become soft and easily eroded.

Residential jobs should follow the cold weather procedures outlined in the Brick Industry Association’s “Technical Note 1” (BIA Tech Note 1) and the Specifications for Masonry Structures by the Masonry Standards Joint Committee (MSJC 1999, ACI. 530.1-99/ASCE 6-99/TMS 602-99). Both documents include similar requirements.

Normal temperatures are considered to be between 40° F and 90° F (4.4° C and 32.2° C). Cold temperatures are below 40° F or when the temperature of the units fall below 40° F. These procedures require heating the sand and mixing water to produce mortar temperatures between 40° F and 120° F (48.9° C) and maintaining the mortar temperature above freezing until placed in the wall.

At temperatures between 40° F and 25° F (-3.9° C), completed walls must be covered with a weather resistant membrane. This covering must remain on the wall for 24 hours, according to MSJC 1999, and for 48 hours, according to BIA Tech Note 1.

When temperatures are between 25° F and 20° F (-6.7° C), heat sources are required on both sides of the masonry under construction, and wind breaks are necessary when the velocity exceeds 15 mph. At these temperatures, the masonry must be covered with insulating blankets. The duration for which this covering must remain on the wall is given as 24 hours in MSJC 1999 and 48 hours in BIA Tech Note 1.

At temperatures below 20° F, the requirements are the same as for the previous category except that an enclosure or other method is required to maintain the temperature about 32° F (0° C). The covering must remain on the wall for 24 hours according to MSJC 1999 and 48 hours according to BIA Tech Note 1.