By: Sean McPartland
Masonry Contractors typically experience a slow-down in work during the winter months. Once the spring arrives, Contractors have an opportunity to complete unfinished work from the prior construction season and get a fresh start in preparation for the construction season ahead.
Spring weather in NYC is unpredictable but is historically the wettest season of the year. We can experience large temperature swings in a short period of time; historical weather data indicates that temperatures have ranged between 12 degrees Fahrenheit and 97 degrees Fahrenheit. While we may not experience temperatures at these extremes during the spring, Contractors and Engineers should expect and be prepared to deal with hot and cold weather requirements for placement of masonry products with temperatures below 40AF and above 90AF.
Cold weather can have a negative impact on masonry systems and affect the overall performance, including the loss of strength and longevity of the system. These cold weather related issues can be prevented with proper planning. In preparation for placement, masonry units should be stored in a heated environment. Water used for mixing should also be at a sufficient temperature to produce a mortar that is ideally between 60AF and 80AF. Additionally, mortar should be mixed in small amounts to prevent the mixture from cooling to a temperature below 60A. Finished masonry products must be protected with weather-resistive protection for 24 hours and the curing temperature of the masonry system must remain at 40AF or above during the curing period. Although it may not be necessary for the spring, Contractors and Engineers must consider the use of enclosures, forced air heaters and/or heated blankets for additional protection when there is a potential for temperatures to dip below freezing during the curing period.
Similarly, hot weather can have a negative impact on masonry systems and their overall performance. Some issues that Contractors have faced with include reduced workability, reduced the setting time and masonry units absorbing more moisture from the mortar. Consequently, masons may find it more difficult to place mortar and masonry units, as heat may dry out the mortar, making it more difficult to spread. Proper planning will reduce the negative effects that hot weather can have on the finished masonry product. Some simple remedies include storing masonry products in the shade and away from direct sunlight, as well as scheduling brick installation during the morning hours when temperatures are cooler and using cool water for mixing mortar. Mortar will absorb heat from mixers, wheel barrows and other metal surfaces that may be used for mixing. To prevent the rapid evaporation of water, metal surfaces should be wet prior to the placement of mortar into the mixer. A mortar with insufficient water will result in reduced bond strength in the masonry system, causing premature failure.
As per the Farmeras Almanac, Spring 2017 will bring NYC an additional 1″ to 2″ of rain above average. In general, masonry work should not be performed during a rain event. In most cases, it is not cost effective, or practical, for Contractors to successfully protect masonry products and the work area from the elements without jeopardizing the overall quality and performance of the masonry system. Excess water in the masonry system can reduce the bond strength and cause mortar to wash out. While it may be simple to instruct Contractors not to plan work when rain is forecasted, it is not as easy to implement. Contractors typically make determinations on work for the following day in the afternoon. For example, if there is a 20% chance of precipitation between 12:00 p.m. and 4:00 p.m., should Contractors be expected to cancel work operations for the following day? As the timing of a rain event can be unpredictable, Contractors should have sufficient protective coverings on site, at all times. Contractors and Engineers should always work together to be prepared for such events.