Choosing the Best Anchor for the Job: Anchoring Precast
The choices available to you when you use anchoring precast
Author’s note: We use anchoring and reinforcement on every project, whether in restoration or new construction. The types of anchors generally are based on which veneer we are anchoring, the weight of the veneer, the condition of the substrate and challenges present when installing the anchors. This blog will discuss the use of anchoring precast.
When anchoring precast, you will have a few choices, based on the size of the unit you are setting. Precast panels that weigh 30,000 pounds or more typically are anchored with a combination of expansion anchors and welded attachments. Once set into place, the bolted connections can be tightened, and the welded connections can be made. Welding is a big part of the process.
Today, arc welding is the only approved site welding technique, and it must be performed by a certified welder. A certified welder must complete a series of test welds that are x-rayed by an independent laboratory. A seasoned stone setter or pre-cast erector adds to the quality and complexity of the projects that can be installed by a contractor.
When welding larger precast that requires aerial access, many equipment rental companies offer the “suitcase welders” that plug directly into the work basket. This eliminates the need for the crew to run long lead lines, fueling welders through the day and providing multiple welding units for larger projects.
Smaller precast units, stone and cast stone units are usually dimensional units that allow for a more standard anchoring. Again, depending on weight of the unit and the anchor choice, the anchor location can be either in the top and bottom or on the sides of each unit. In many cases, the anchor is in four locations to support the corners and bottom of the unit evenly.
Anchors are usually set into a kerf that can be detailed and manufactured or field cut. Either way, it is important to fit the anchor so that it tightly supports the unit and will not hold water that could create spalls later. Split anchors made with 304 stainless steel in various forms and configurations are usually used for this application.
I have worked with many stone setters who prefer to use the Strapmaster by Krando. This tool is useful in creating the exact anchor that you need, when you need it. Simply mount the Strapmaster to a retired walk board; place it in your work area; and cut, bend, twist and punch the anchor that is needed for the spot required. This tool is not the choice tool for production veneer anchors, but is a useful tool for custom, random and dimensional stone and precast units in the field.
Anchors and reinforcement are not areas we spend a lot of time considering, but they are on every project. Getting them right is extremely important. When it is your choice, plan your submittals wisely.