Concrete Anchors That Should Be Used in Solid Concrete Applications

The terms "concrete anchor" and "concrete fastener" are generally used interchangeably although by definition, they are not the same. An anchor will work better in some applications while at other times; fasteners should be used to complete the job. Before starting any project, be certain to choice the one that will finish the job in the most effective and safe manner possible.
The term concrete anchor refers to a heavy duty type of anchor that is usually of a larger diameter. These diameters include 5/8", 3/4", 7/8", 1" and 1-1/4". A concrete fastener should be used in lighter duty applications and are available in diameters including 3/16", 1/4", 3/8" or 1/2". The distinction made here is just to explain the difference between the two. Throughout this article, the terms concrete anchors and concrete fasteners will be used interchangeably.
Anchors can be used in a base material of concrete, brick or block. Because many of these anchors can also be used in brick and block, they are sometimes described as masonry anchors or fasteners. There are three types of concrete fasteners that can only be used in solid concrete. These are the wedge , drop-in and the strike anchor. The wedge and strike anchor are both male type or stud anchors and the drop-in anchor is a female type. These concrete anchors will be the focus of this article.
The Concrete Wedge Anchor
Types of Wedge Anchors
Concrete wedge anchors are made from zinc-plated carbon steel, hot-dipped galvanized carbon steel, 303 stainless steel or 316 stainless steel. The choice of plating or type of steel is dependent upon the corrosive resistance required for each specific application. Zinc plated carbon steel offers some rust resistance, hot-dipped galvanized anchors are excellent rust resistors and the 303 and 316 stainless steel fasteners provide superior rust resistance.
Wedge Anchor Uses
Zinc plated anchors are for indoor use or applications where the anchor will not be subjected to the elements. The hot-dipped galvanized anchor is primarily used outdoors in mild climates where the anchor will be subjected to water. Stainless steel anchors are usually used in areas where the anchor will be submerged in water or exposed to other caustic materials.
Determining the Right Length of Wedge Anchors
The wedge anchor comes in 9 different diameters ranging from 1/4" to 1-1/4". The length of the anchor required is determined by the thickness of the material being fastened, plus the minimum embedment for the diameter anchor being used, plus the height of the nut and washer. The height of the nut and washer is roughly equal to the diameter of the anchor itself. For example, the nut and washer for a 5/8" wedge anchor is approximately 5/8" high. Below is a chart indicating the minimum embedment for each diameter:
Diameter 1/4" 5/16" 3/8" 1/2" 5/8" 3/4" 7/8" 1" 1-1/4"
Min. Embedment 1-1/8" 1-1/4" 1-1/2" 2-1/4" 2-3/4" 3-1/4" 3-7/8" 4-1/2" 5-1/2"
So with this information, to determine the length required for a 5/8" diameter wedge anchor, fastening a 2" thick fixture:
2" (thickness of material) + 2-3/4" (minimum embedment) + 5/8" (space for nut and washer) = 5-3/8" minimum anchor length
Based on available lengths of the 5/8" diameter wedge anchor, you would need a 5/8" x 6" wedge anchor.
Drilling a Hole for a Concrete Wedge Anchor
The diameter of the hole to be drilled in the concrete is the same diameter of the anchor being used. The hole should always be drilled using a hammer drill and a carbide-tipped drill bit. Always be careful when handling any power tools and wear the appropriate safety gear such as goggles. Before inserting the anchor into the hole, clear the hole of all debris. Carefully hammer the wedge anchor into the hole to the desired depth. To protect the threads of the wedge anchor, place the washer in the hole and thread the nut a couple of turns before hammering in the wedge anchor. Once in place, the anchor is set into the concrete by tightening the nut- this pulls the anchor up, wedging the clip between the steel of the wedge anchor and the concrete. It is recommended that the nut be tightened utilizing a torque wrench to assure it is tightened to the required torque value.
The Concrete Strike Anchor
Strike Anchor Types
The strike anchor is the only other male concrete fastener that is designed for use in solid concrete only. These anchors are manufactured from carbon steel with yellow zinc plating. Unlike concrete wedge anchors, the strike is not available hot-dipped galvanized or in stainless steel.
Sizing of Strike Anchors
Strike anchors are available in six different diameters ranging from 1/4" to 3/4". The length of the anchor required is determined by the thickness of the material being fastened, plus the minimum embedment for the diameter of anchor being used, plus the height of the nut and washer. The height of the nut and washer is roughly equal to the diameter of the nut itself. Below is a chart displaying the minimum embedment for each strike anchor:
Diameter 1/4 5/16 3/8" 1/2" 5/8" 3/4"
Min. Embedment 1" 1-1/4" 1-1/2" 2" 2-1/2" 3"
As an example, the length of strike anchor needed for attaching a 1-1/2" fixture, using a 1/2" concrete strike anchor:
1-1/2" (thickness of material) + 2" (minimum embedment) + 1/2" (space for nut and washer) = 4" minimum anchor length
Based on the available lengths of 1/2" diameter strike anchors, the correct size would need a 1/2" x 4-3/4" strike anchor.
Drilling Holes for Concrete Strike Anchors
The appropriate diameter of the hole to be drilled is the same diameter as the strike anchor being used. The hole should always be drilled using a hammer drill and a carbide-tipped drill bit. Before inserting the anchor into the hole, clear the hole of all debris. Then, with nut, washer and set-pin in place, insert the strike anchor into the hole. The strike anchor is set by driving the pin down through the hollowed-out center stud, thus spreading the anchor at the opposite end of the threads. Using a proper sized hammer, set the pin with several sharp and square strikes on the head until the pin is flush with the top of the anchor. The anchor is properly set when the head of the pin meets the stud.
Should I use a Wedge of Strike Anchor?
Determining whether to use a concrete wedge anchor or strike anchor is simply a matter of personal preference. Both anchors have essentially the same holding values. However, the wedge anchor's pull-out and shear values are a little better and more consistent than that of the strike anchor. The wedge is also more popular merely due to the availability of diameters, lengths and materials. The strike is preferred when the application requires all the anchors to protrude from the concrete in equal lengths, resulting in a clean and consistent finished look.
The Drop-In Anchor
Types of Concrete Drop-In Anchors
The drop-in anchor is the only female type anchor designed for use in solid concrete only. Drop-in anchors are manufactured from carbon steel that is zinc plated and are also available in 304 or 316 stainless steel. Making the choice between carbon zinc and stainless steel depends entirely upon the end use and the degree of rust resistance required. Zinc plated carbon steel offers some basic rust resistance, 304 stainless steel affords better rust resistance and 316 stainless steel provides superior rust resistance.
Drop-In Anchor Diameters
There are 5 diameters of drop-in anchors available - 1/4", 3/8", 1/2", 5/8" and 3/4". The diameter of the anchor refers to the inside diameter or the diameter of the bolt/threaded rod that is inserted into it. Each diameter is only available in one length and the minimum embedment for each anchor is equal to the anchor's length. The drop-in anchor is designed to sit flush with the base material and requires that a bolt or threaded rod be inserted into it. Before inserting the drop-in anchor into the hole, clear the hole of all debris. To set the anchor, simply drop the anchor into the predrilled hole and tap lightly with a hammer until the anchor is flush with the base material. Insert the proper sized setting tool into the drop-in anchor, and strike the setting tool until the lip of the anchor touches the lip of the setting tool. This will insure that the anchor is properly set.
Overview
Again, these three anchors are the only mechanical type anchors that are designed for use in solid concrete only. These concrete anchors cannot be used in brick or block based material. They provide the best, most consistent holding values among these types of fasteners. Determining which of these fasteners to use is dependent upon the application, the amount of rust resistance required desired finished look and personal preference.
Article Written By: Bob Carlisle, President of Concrete Fasteners
Concrete Fasteners, Inc has over 40 years experience selling concrete fasteners. We ship to all 50 states and many countries. We can ship out one box or a whole pallet of concrete anchors. Our products are of the highest quality, "your satisfaction is guaranteed." We ship all orders the same day order is received.
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