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DESIGN TIPS—WEATHER CONSIDERATIONS AND TIPS

 

The following are design tips for Setting Practices throughout the various ranges of temperatures.

 

COLD WEATHER

 

Cold weather provides for many complications that can be avoided when the proper precautions are taken. One should never set stone in weather that is below 40°F, when a freeze is expected within 24 hours, without proper cover to prevent water from entering during the rain or in snowy conditions. One compromises the integrity of the entire project as joints and sealants will be unable to appropriately seal and future repercussions become inevitable.

 

Cold weather setting provides an array of complications as well as harsh considerations that must be maintained to try to preserve the integrity of the project. Please review the following so you can make an educated determination of when, if and how you will proceed in cold weather conditions.

 

Cold weather brings out the calcium chloride that causes efflorescence. While rain water is a natural way of washing the stone, it can also bring with it the complications of pulling the salts to the surface. (See our bulletin for further information on Efflorescence.) Additionally, water can penetrate the joints, if not properly covered, before they have been properly sealed.

 

Cast stone set in cold conditions has a tendency to expand in warmer weather thus cracking is expected to occur more so than cast stone set in warmer conditions, above 46°F.

 

To properly install cast stone material in cold conditions the material must be brought up to working temperatures thus water, sand, mortar and such will have to be heated on a continuous basis without scorching. Proper covering of the material in plastic or canvas, that is non-staining, must be done on a continuous basis. Should the need arise to install in very cold conditions, please review the recommendations below.

 

The International Masonry Industry All Weather Council recommends the following:

HOT WEATHER

 

Hot weather is considered anything that is 90°F and above. Special measures and precautions must be taken to ensure that the quality and integrity of the project are not compromised if installation in hot weather conditions is performed.

 

The primary concern with hot weather is the evaporation of water in the mortar and increased rate of hydration of the cement that makes the mortar less workable. Temperature of water, cement and sand can make a big difference, thus keeping them cooled is recommended.

 

Cast stone material should be drenched prior to setting thus sufficient water must be kept within reach. Although cast stone material is least affected by hot weather conditions, it is the evaporation of water from the mortar by the hot cast stone, and hot weather conditions, that can also affect the bonding of the mortar to the cast stone material. If too much evaporation takes place, the bond between mortar and the cast stone is compromised. Lower bond strength results without sufficient water.

 

Clay brick products continue to expand after their manufacturing. It is important to understand that if cast stone is set up against brick units, that they will also absorb the moisture from the mortar as well as their excessive heating will also result in evaporation of moisture within the mortar.

 

Admixtures (accelerators or modifiers) should be reviewed as their components and function may not be recommended for the hotter temperatures. See ASTM C 1384 – Standard Specifications for Admixtures for Masonry Mortars for compliance issues.

 

Mortar temperatures need to be controlled per the ambient air temperatures so mortar is workable and evaporation is minimized. It is important to understand that temperatures above 120°F may cause flash set of the cement. High temperatures affect mortar set times thus it must be kept moist and cooled. Adding cold water or ice will assist in controlling mortar temperatures. (Make sure the ice is melted in water prior to adding to mix.)

 

Keep in mind that warm winds throughout the day, even in days with lower temperatures, will also have a drying effect on the mortar, thus constant watch on moisture content of the mortar mix is essential.

 

The Masonry Industry Council suggests that mortar used in high temperatures be discarded after two hours. The Cast Stone Institute suggests that mortar be discarded after 90 minutes.

 

Many associations are concerned with the proper procedures, thus contacting the following Industry Associations will provide you with further recommendations: a.) Brick Industry Association (BIA), b.) Mason Contractors Association of America (MCAA), c.) National Concrete Masonry Association (NCMA), d.) Portland Cement Association (PCA), and e.) Cast Stone Institute (CSI).

 

American Concrete Institute Specification ACI 530.1 provides information on how the temperature of materials can be adjusted and specific construction methods to assist one while installing masonry material in hot weather.

 

The Masonry Industry Council Tables 1 & 2 provide requirements that the mason or contractor should follow for temperature control.

 

The following are suggestions for minimizing the effect of the hot weather on the masonry project:

DESIGN TIPS — WEATHER CONSIDERATIONS (PDF)

 

The information within this and all our bulletins has been provided as a guideline and based upon statistical data and prior uses. We always suggest that you consult with your engineer, architect or contractor for the best design and use of cast stone for your project. Our design team is always available to answer any of your questions. We do not accept any liability from damages resulting from your interpretation of the data contained within.