Fastening to concrete, brick or block is different than fastening to wood or sheet metal. Screws are used when fastening to wood or holding two pieces of metal together. Nut and bolt can also be used for these purposes. Concrete, brick or block are basically solid material that is very hard because only one surface is available- it is not 3-dimensional for fastener use. Fastening to concrete, brick or block must be done to the surface and the holding values are wholly dependent on the base material. Many different fasteners are available and are designed for fastening to concrete, brick or block. It is very important to remember that the holding values of the anchor chosen are entirely derived from the strength of the base material.If the anchor is installed correctly, the base material will fail first- not the anchor. The choice of the concrete fastener to use is dependent on the specific application and personal preference. Several concrete fasteners are designed to use only in concrete while others can be used in all 3 base materials (concrete, brick, and block).
Choosing the fastener is dependent on the base material, the weight of the object to be fastened, the head style required and whether the anchor will be indoors or outdoors. Concrete fasteners can be categorized into three categories: light duty (smaller diameter, shallow embedment), medium duty (deeper embedment) and heavy duty (larger diameter with deep embedment into the base material). All concrete fasteners have a minimum embedment depth at which they must be inserted into the base material in order to achieve holding values. This minimum embedment is dependent on the type of anchor being used and the anchor's diameter. Fasteners for concrete must also be spaced at least 10 anchor diameters from each other and no closer than 6 anchor diameters from an unsupported edge. Concrete fasteners are available in two basic types (male and female) and their uses are dependent upon the specific application at hand.
Wedge anchors are male type anchors for use in concrete only. They should no be used in brick or block. The loading capacity of wedge anchors ranges from light to heavy duty due to the large range of diameters that are available. Wedge anchors are available in zinc plating for indoor use and hot dipped galvanized and stainless steel for outdoor applications.
Strike anchors are only available in a male version and can only be used in solid concrete. Diameters range from 1/4" to 3/4" with lengths up to 6" for use in light to heavy duty applications. Strike anchors should not be used outdoors since they are only available with yellow zinc plating.
Drop-in anchors are female concrete anchors that are designed to accept machine threaded bolts or a threaded rod. These can only be used in concrete. The loading capacity of these anchors range from light to heavy duty and are available in a wide range of diameters. Each diameter is only available in one length. Stainless steel drop-in anchors can be used outdoors or indoors.
Tapcon® concrete screws are male anchors designed to tape threads into concrete, brick or block. The standard blue concrete screw would be considered a light duty anchor in diameters or 3/16" and 1/4" in lengths up to 6". The large diameter Tapcons can be used in medium duty applications. Both have a special coating that provides excellent rust resistance. These screws can be used outdoors where the anchor will be submerged in water. The stainless steel Tapcons can be used outdoors while the zinc plated screws should be used in indoor applications.
Sleeve anchors are male type anchors that can be used in concrete, brick or block. The loading capacity of this anchor ranges from light to heavy duty. These anchors can be used in both indoor and outdoor applications since they are available zinc plated and in stainless steel.
Metal hit or hammer drive anchors are male type anchors that are suitable for use in concrete, brick or block. They are not recommended for overhead use. Metal hit anchors are light duty anchors available in two diameters- 3/16" and 1/4". The body of the anchor is made from rust resistant material called zamac. The nail comes in zinc plating and are suitable for indoor use and should not be used outdoors.
Machine screw anchors are female anchors that can be used in concrete, brick or block. They are available in a range of diameters from 1/4" to 3/4" and should only be used for light to medium duty fastening applications since they don't allow for deep embedment into the base material. Machine screw anchors should only be used indoors.
Lag shields can be used in concrete, brick or block. They are also excellent for use in the suspect base material. They are available for light to medium duty with anchor diameters ranging from 1/4" to 3/4". Two lengths are available in each diameter- a short and long length. These anchors are made from rust resistant material and are suitable for indoor and outdoor use. They should not be submerged in water and should be used in conjunction with a stainless steel lag screw.
When using concrete anchors in your home and for home improvement projects, it is imperative that the correct fastener for the specific application be chosen to ensure that the project goes smoothly. If the application is outdoors, then it is necessary to purchase concrete anchors that can be used outdoors in terms of material and rust resistance. All of these considerations can make using concrete fasteners faster and easier.
Please remember with all fastening jobs to keep safety in mind. Always follow safety instructions on all tools, and refer to manufacturer's installation instructions when available and always remember to wear safety goggles!
Article written by: Bob Carlisle, President Concrete Fastening Systems, Inc