A number of steps must be taken before buying concrete anchors for your particular application. Many factors need to be considered including the type of base material, whether it is an indoor or outdoor application and whether it is a structural application, etc. The following guide will help determine which anchor to buy for your unique application.
The base material is the material that the item will be fastened to. When referring to concrete fasteners, base materials include concrete, brick or block. Some fasteners are specifically designed for concrete and will not work in brick or block, while other concrete anchors will work successfully in all three base materials.
Concrete: All anchors for concrete have to be embedded into the concrete a minimum distance. They must also be spaced apart from each other as well as be located a minimum distance from an unsupported edge of the concrete.
Brick: It is important to determine if the anchor will be inserted into the brick or in the mortar joint. Because some brick can be abrasive and porous, anchors like Tapcons may not work.
Block: It is important to determine if the type of block is solid or hollow where the anchor will be placed. The anchors can be placed in the mortar joint, but the holding values will depend on the quality and quantity of the mortar.
The environment that the anchors will be placed into will also determine the type of material they will need to be made of and the type of coating that the anchor has.
Indoor: The standard zinc plated concrete anchor will work well in outdoor applications in a dry environment which is not caustic. If the indoor environment has chemicals or other considerations, then the stainless steel or hot-dipped galvanized anchors should be used.
Outdoor: Zinc plated wedge anchors should not be used outdoors unless it is a perfectly dry environment because they will rust over a period of time. Hot-dipped galvanized anchors are well suited for use in moist environments. Stainless steel will not rust in an environment where water is present and can be used in certain areas where other chemicals may be present.
The thickness of the material to be fastened and the type of material being fastened will determine the type of fastener that needs to be used.
Type of material: Galvanized or stainless steel anchors must be used when the material is treated lumber. Different materials may react with each other and cause rust. For example, a concrete anchor made from stainless steel will react with aluminum in certain environments and may rust.
The thickness of material: The length of the anchor, or bolt inserted into a female concrete anchor, is partially determined by the thickness of the material being fastened to the base material. The embedment length of the anchor in the base material plus the thickness of the material being fastened plus the space for the nut and washer determines the length of the anchor or bolt.
In most cases, there is a relationship between the depths of the embedment of the anchor in the base material and the holding values. The larger the diameter, the higher the shear loads that the anchor will be able to withstand.
Embedment: Concrete anchors derive their holding values from the base material they are inserted into. In most cases, it is the base material that fails, not the concrete anchor. Each anchor has its own minimum embedment depth requirements, which means that each anchor needs to be embedded into the base material a certain distance in order for it to have any strength. Deeper embedment into the base material will result in better holding values.
Diameter: The diameter of the anchor is what determines the shear loading capacity of any type of concrete anchor. A shear load is a weight placed on the anchor perpendicularly.
There are a number of different concrete anchors that can be used to fasten to concrete, brick or block. The specific concrete anchor was chosen for any particular application is determined by personal preference or by the specific requirements of the application.
Wedge Anchors: Wedge anchors can only be used in concrete and should not be used in brick or block. These anchors are manufactured in zinc plated, hot-dipped galvanized and stainless steel. Wedge anchors are designed for light to heavy-duty fastening and come in diameters ranging from 1/4" to 1-1/4" and in standard lengths up to 12".
Sleeve Anchors: Sleeve anchors are versatile anchors that can be used in all three of the base materials- concrete, brick, and block. Sleeve anchors are manufactured in both the zinc plated and stainless steel materials. The sleeve anchor is designed for light to medium duty fastening applications and diameters range from 1/4" to 3/4" with lengths up to 6-1/4".
Concrete Screws: Concrete screws can be used in concrete, brick or block. They are made from carbon steel with a special rust-resistant coating and stainless steel. The standard concrete screws come in two diameters- 3/16" and 1/4" for light duty fastening. The large diameter concrete screws come in diameters of 3/8", 1/2", 5/8" and 3/4" for medium and heavy-duty fastening applications.
Drop in Anchors: The drop in the anchor is a female anchor, which means it is placed into the base material and a bolt or threaded rod is then inserted into it. Drop-in anchors are designed for use in concrete only and should not be used in brick or block. Drop-in anchors are available in stainless steel as well as zinc plated. They range in diameters from 1/4" to 3/4" for light to medium duty fastening jobs. See more information about drop-in anchors.
Concrete fasteners can be purchased at a local hardware or big box store when only a couple are needed. Because concrete anchors are individually packaged at these types of stores, customers pay a premium price for the convenience. The price at the stores will be 30% to 70% higher than prices found online. If larger quantities of anchors are needed, then the small amount of pre-planning that is needed for online purchasing will result in huge savings. All the necessary information to help you determine the correct fastener that you will need is all available online. Online purchases will also result in the convenience of having the concrete fasteners delivered to your doorstep at substantial savings!
As with any anchoring project, it is important to keep safety in mind and follow instructions carefully. Always remember to wear safety goggles, handle all tools with extra care and follow all technical specifications. This article is meant to serve only as a basic explanation of concrete fasteners. Always refer to manufacturer's instructions or consult a contracting expert during any anchoring project.