Expansion anchors are fasteners designed for use in masonry base material that provides holding power through expansion. There are two kinds of expansion anchors; pre-expanded and un-expanded. The pre-expanded expansion anchor is inserted in a predrilled hole compress and then exerts force to create the holding power. The un-expanded expansion anchor requires the anchor to be set after it is installed into the predrilled hole in the masonry.
Each type of expansion anchors has base materials in which it works optimally. Some expansion anchors can be used only in solid concrete; others can be used in solid concrete, brick or block. The holding values of any expansion anchor are only as good as the quality and quantity of the base material into which it is placed. For example, if the base material is sandy and easily falls apart, then the holding values will be very low or nonexistent.
Pre-Expanded Expansion Anchors
Because these anchors do not require any secondary tightening and require less time to install, the in place fastening cost is decreased. Pre-expanded anchors only come in small diameters and only are suited for light-duty fastening applications. They have a head that prevents the anchor from being removed and are considered tamper-proof. As the anchor is driven into the hole, the pre-expanded part of the anchor continually pushes out against the walls of the hole, trying to regain their original shape. This continuous force provides the holding values for this type of anchor.
- Split Drive Anchor – come in only the 1/4” diameter, with two head styles of a round and flat countersunk. They come in lengths from 1-1/2” to 4” and can only be used in solid base material, such as concrete.
- Sike – is the brand name for Powers fasteners concrete anchor. The Spike is formed with an “s” shaped configuration at the working end of the shank. This anchor comes in four diameters of 3/16”, 1/4”, 3/8” and 1/2”. They are manufactured from both zinc plated carbon steel and stainless steel. The spike comes in five different head styles: mushroom, flat countersunk, pipe, tire-wire, and forming.
Un-Expanded Expansion Anchors
- Wedge Anchor – This anchor utilizes an expansion clip at the working end and provides excellent consistent holding values of any type of expansion anchor in solid concrete. It is manufactured in 9 different diameters and in many lengths to meet most concrete fastening requirements. They are available in zinc plated carbon steel, hot-dipped galvanized carbon steel, 303/304 stainless steel and 316 stainless steel. When purchased, they will be packaged with the correct number and size of nuts and washers.
- Strike Anchors – This anchor uses a hardened nail to expand the working end of the anchor and can only be used in solid concrete. They come in 6 diameters and in a number of different lengths for each diameter. They are made from carbon steel with a yellow zinc coating. They do not come in stainless steel. They are packaged with the nut and washer. They are easy to use because they require no special tools, and they can be set so that each anchor protrudes from the surface of the concrete the same distance.
- Drop-In Anchor – This is a female type anchor designed for use in solid concrete only. This anchor is designed for overhead use using threaded. Comes in four diameters: 1/4”, 3/8”, 1/2”, 5/8” and 3/4”, with each diameter coming in only one length. The anchor, once inserted into the concrete, must be expanded using a setting tool designated for the specific diameter of the drop-in anchor being installed.
- Sleeve Anchors – These are the most versatile of the masonry anchors because they can be used in most masonry base material, such as concrete, brick or block. The sleeve anchor is manufactured in 6 different diameters and different lengths to meet most application requirements. While different head styles are available, not all head styles are available in all diameters. The head styles are: acorn, hex nut, flat-head, and round head. Also, many of the sizes are available in both the zinc plated carbon steel and stainless steel. The diameter of hole required in the masonry material is equal to anchor diameter, and the anchor can be inserted through the hole in the fixture while the fixture is in place.
- Hammer Drive Anchor – This is a light duty expansion anchor available in 3/16 and 1/4” diameters. This anchor comes with a mushroom head and ,once set, cannot be removed without grinding off the head of the fastener. The hardened nail is struck by a hammer and, as it is driven into the anchor body, the anchor body expands against the inside walls of the hole in the base material.
- Machine Screw Anchor – Can be used in brick, block or concrete, with a threaded bolt required to be used to fasten the item to the anchor. This female anchor is set by using the correct designated setting tool and is made from a rust resistant material called Zamac. The internal threads of each anchor are national coarse threads, so any screw with national course threads will work. Eight different diameters are available from #8 to 3/4” with the designated diameter referring to the diameter of the screw that can be inserted into it.
- Single Expansion Anchor– This anchor works great in hard dense base material and requires a threaded machine bolt to expand the anchor. The expansion nut is pulled up into the anchor body as the bolt is turned clockwise. The designated diameter of the single expansion anchor is equal to the diameter of the bolt used with the anchor.
- Double Expansion Anchor – This anchor is designed for use in softer more suspect type base material where the holding values may be questionable. The double expansion anchor is designed so that the entire length of the anchor body expands and pushes against the side wall of the base material. This wide range of expansion gives the anchor a much better chance of obtaining holding values in most types of base materials.
- Lag Shield Anchor – It works well in most masonry base materials and requires the use of a lag screw for expansion. This anchor comes in six different diameters with each diameter coming in two different lengths: a short version and a long version. The short version is used in hard dense material such as red brick; the long version is used in softer base materials such as mortar joints or cinder block. The extra length provides deeper embedment, which, in most cases, will increase the holding values.
These anchors can be purchased from Concrete Fasteners, Inc., are in stock at our Cleveland, Ohio facility, and will ship the same day the order is received. Should you prefer to purchase through a phone call, dial 216-357-7433 and ask for Mike.
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.
Article Written By:
Mike Pistorino, Vice-President Operations
Concrete Fasteners, Inc. has over 40 years of experience selling concrete fasteners. 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 the order is received.