Cold Weather Construction: Cold Weather Construction

If you cover your materials, you can actually lay block with a temperature of as low as 20° F. Once snow or ice accumulates on the block they must be heated to above freezing. The same goes for brick.

It’s that time of year, when the GC’s start asking for you to submit your cold weather construction plan. Why do we care about protecting newly built masonry from the cold? Simply put, cold temperature slows down the strength gain of mortar and grout. The chemical reaction between cement and water slows down as it gets colder, and stops completely below temperatures of about 14° F. If you let wet mortar or grout freeze you can cause permanent damage.

Cold weather construction requirements are spelled out in the TMS 602 Specification for Masonry Structures. TMS 602 calls for special procedures any time the temperature falls below 40° F. There are 3 components to a proper cold weather construction plan.

1. As you prepare to build masonry. For example, if snow or ice exists on the top of foundations or previously built masonry, it’s not enough to just brush off the snow - you must heat surfaces to above freezing before continuing to build.


2. During masonry construction. Construction requirements are based on ambient air temperatures during construction. Different requirements are listed for temperatures between 32 and 40° F, 25 and 32° F, 20 and 25° F, and less than 20° F.


3. Protecting newly-built masonry. Protection requirements are based on the Mean Daily Temperature, or MDT. The MDT is simply the average of your favorite weather site’s prediction of the overnight low temperature and the expected daily high temperature. For example, if the weatherman says today it will be 40 degrees and the overnight low will be 24 degrees, the MDT is 40 + 24 or 64 degrees, divided by 2 = 32° F. Newly built masonry must be protected for 24 hours, and grouted walls must be protected for 48 hours after construction.

Heat sand and/or water to provide mortar and grout with a temperature of between 40 and 120° F. Since at least 2005 the Code has also required masonry grout to be at a temperature of 70 to 120° F at the time it is placed in the wall.

TMS 602 spells out exactly what must be done for cold weather protection, and some contractors simply copy right out of the 602 specification to develop their cold weather construction submittal. See Section 1.8 of the 2008 or 2013 TMS 602 Specifications for Masonry Structures, available at www.masonrysociety.org.

You can download a summary of TMS 602 requirements here and modify it for your project.

A few tips:

• Use Type III cement (high-early strength) in your grout in cold weather to reduce protection requirements for grouted walls from 48 to 24 hours.
• The Specification gives a wide range of allowable mortar and grout temperatures, between 40 and 120° F. The optimal range is between 60 and 80° F.
• Be careful not to scorch your sand! High temperatures from gas-fired torches can break down the sand and result in harsh mortar that is difficult to use.
• Mixing cement with water that is too hot can cause permanent damage due to a “flash set.” Make sure your mix water never exceeds 120° F.
• Don’t ever use ”antifreeze“ in your masonry materials. And think long and hard before using accelerating admixtures. Accelerators do help to speed up strength gain, but accelerated mortar and grout can still be damaged by freezing. Protection from freezing is still required.
• Build a heated enclosure around your mixing station to make it easier to keep mortar and grout at the right temperature.