The many considerations for choosing the proper cement screw to use for any particular application are described in the following:
Standard cement screws come in two diameters of 3/16” and 1/4”. The measurement refers to the outside diameter of the screw, which allows the screw to be inserted through a hole in the fixture equal to the diameter of the cement screw being installed.
Each diameter of cement screw comes in different lengths from 1-1/4” long to 6”. The minimum length of cement screw used for any particular application is determined by adding the thickness of the material being fastened to the minimum embedment of 1”. The maximum length of cement screw to use is equal to the maximum embedment of 1-3/4” plus the thickness of the material being fastened.
The depth of the hole is critical because it must be deep enough to allow the cement screw to be embedded at least to the minimum embedment depth of 1”. Space must be left at the bottom of the hole to allow all the dust that is created during the tapping process to fall into and out of the way. It is suggested that the hole is drilled a minimum of 1/4”deeper than the cement screw will penetrate the base material.
The hole drilled in the base material is critical to allow the cement screw to obtain its minimum holding strength. The hole must be drilled using a carbide tipped bit that meets ANSI standards because ANSI standards will ensure proper hole to anchor tolerance. The 3/16” cement screw requires a 5/32” bit and the 1/4” diameter needs a 3/16” bit.
Cement screws are manufactured from two types of steel: low carbon plated and 410 stainless steel. The standard low carbon cement screw should be used in indoor dry applications. The 410 stainless steel can be used in applications where moisture may be present.
Two head styles are available: hex washer and flat countersunk. The hex washer head utilizes a nut driver for installation and the flat countersunk requires the use of a phillips drive. The length of the hex head cement screws are measured from underneath the head and the flat countersunk are measured as an overall length. The hex headed cement screws are used in applications where the head of the screw sits on top of the item being fastened. The flat countersunk cement screw is used in applications where the head of the screw is countersunk into the item being attached.
The cement screw can be used in solid concrete, hollow precast concrete, brick, CMU, block and mortar joints. The holding strength of the cement screw is dependent on the strength of the base material as well as on the quality of the installation.
Cement screws can be removed, but should not be reused in the same hole because holding values may be diminished or nonexistent. Using the cement screw in another hole can be done as long as the cutting edge of the screw is able to tap threads.
The most popular brand name for cement screws is Tapcon®. Tapcon screws are sold by Concrete Fastening Systems™, Inc., located in Cleveland, Ohio. The Tapcon brand cement screws are made in America and can be shipped anywhere in the United States with an arrival in two days. We also make and sell our own brand of masonry screws for cement applications - CONFAST® masonry screws. Our brand is comparable to Tapcon but sold at a lower price due to lack of a middleman distributor.
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.