Concrete Anchors

The basic concept is simple. With a masonry bit, drill a hole into the concrete surface to the specifications necessary and then drop in a metal sleeve with a special design that will expand and grip the sides of the hole leaving either a tapped receptacle or post at the exposed end for attaching another object. The whole process is a wedge system that actually uses the resilience of the concrete to form a strong attachment anchor.

The product that you are typically looking for are drop-in or hammer drive anchors. Anchors are usually available in 304 or 316 stainless steel or carbon steel. The latter type is usually finished in zinc dichromate, trivalent blue chromate, or straight galvanized. They are all pretty much designed for permanent installation although some can be slightly counter sunk if they are only going to be used for a short amount of time.

A great example of this is when you decide to put a window in a concrete tilt-up. You will need to anchor a concrete saw to the surface you will be cutting. A drop-in wedge with a counter sink of a 1/16” is perfect for the job. Once the window is cut and the saw is removed you can patch over the anchor leaving it in place.

The Sanko CT-type drop-in anchors and GT-Type drop-in anchors are internally threaded controlled expansion anchors.  They are built to a .03mm tolerance in expansion differential.  These anchors have been designed to be used with a setting tool to ensure full anchor expansion.  This type of anchor is recessed in the concrete so if it is no longer needed simply plug or fill with cement to make the surface smooth again.  An example of this application would be the mounting of a heavy concrete saw used to cut windows and doors into cured concrete walls. This type of drop-in anchor is suitable for flush mounting applications.  The inside threads are machine rolled rather than cut which gives this product superior holding strength.  The GT type anchor is also a drop-in similar to the CT.  The main difference is the GT is designed with a lipped top for a semi-flush installation into concrete. 

The Sanko C-Type anchor is a hammer driven fastener.  This anchor features a hardened center pin that is driven through the center of the product to expand the anchor in cured concrete.  The C-Type is made of high strength steel with a greater leg expansion to ensure a firm gripping contact.  It includes a nut and washer that can be set to various depths.  It is very easy to install because the depth of the hole is not critical and no special tools are required for setting the product.  Just hammer the pin in and the anchor tensions itself automatically, holding the anchor in place.  Unlike other anchors, no torque wrench is required to set.  The C-Type anchor is set when the center pin is flush with the top of the bolt, making it very easy to inspect.  



How to choose the right anchor

Masonry anchors have come a long way over the years. It used to be, to attach anything to concrete walls was a major chore.  With new advancements most can be done "DIY" (do it yourself) with average tools. There are three different types of masonry anchors mechanical, powder-activated, chemical.

Masonry anchors work in two ways by expanding against the side of a hole and gripping the concrete or by friction against the sides of the hole. The holding sustainability of any anchor will depend on one the quality of concrete and the placement or position of anchor. Old and crumbly concrete will have weak holding power likewise if anchors are placed near edges or anchors are placed to close together the generated force can break the concrete. Generaly it is recommended that any anchor installation should be no closer than 5 inches from the edge. Two anchors shouldn't be placed closer than 10 inches from each other.

The most important factor in choosing proper anchors is the type of load it can carry. Anchors are rated for two types of loads, shear work loads (exerting force parallel to the surface of concrete). Tensile loads are caused when the fixture exerts force perpendicular to surface. Other load factors include static loads that are steady and constant for example circuit breaker boxes fastened to basement wall or sides of home. Dynamic or vibrating loads that are constantly changing. For example; when mounting a core drill to a wall the load on the anchors will be a dynamic load.  Standard recommendation is that any anchor chosen be rated for four times the weight it will carry. It's recommended that you watch anchor installation videos for any DIY (do it yourself) projects, and to follow the step by step instructions by the manufacturer. When choosing anchors the total load should be divided by the number of anchors that will carry weight.

When installing any type of anchor a hammer drill is recommended to drill the holes. Most anchors are made to go into concrete and not brick or block. The size of the hole must equal the size of the anchor that you are using. Drill the hole with the hammer drill, prior to drilling it is recommended that you determine the size needed by setting the hammer drill to that particular size or a piece of tape can be placed onto the drill bit to make sure you do not go deeper. Once done, drill the hole that is needed. It is recommended that proper eye equipment be used at all times when drilling. The hole once drilled must be cleaned of all concrete dust particles prior to installation of the anchor. This can be done by using a wire brush or compressed air vacuum to clean hole of debris. Once done then the anchor can be installed. A hammer drill is recommended to drill any and all holes. Masonry drill bits work by chipping the concrete away (as opposed to wood bits, which will cut wood away). If you use any standard electric drill you will find that the drill works slowly and can cause you to have a larger hole than needed or intended. For any concrete anchor to be effective the hole must be exact in diameter and in some case depth as well for the anchor to fit properly.
Masonry anchors come in four basic types; concrete screws, hammer anchors, one piece expansion , two step expansion that's used with standard screws. They are called two step screws because before installed inside the hole it must be spotted, due to the anchor being larger than fastener that will go into it. You'll have to position the material that's to be anchored and spot the location of the hole, then setting the material aside to drill and then insert the anchor. Finally you can place the material in position and fasten it down. An advantage to these anchors is the screws can be removed then reinserted and they're inexpensive.

There are no rules about which anchor to use in what situation but some helpful guidelines are available. To attach machinery to a concrete floor you want to use a heavy expansion anchor such as a drop-in or wedge anchor. Framing around a door or window opening it's recommended that hammer anchors be used. Shelf brackets on a foundation wall the use of concrete screws are generally the best choice because they can be removed if necessary. If installing a conduit to a foundation wall, it is recommended that you use hammer anchors or concrete screws. Applying mudsill to a foundation use a sleeve anchor for an occasional missing anchor bolt.  If starting from scratch and there are no bolts use either drop-in or wedge anchors.

The following tools and material checklist may be helpful for those who are new to concrete anchors. Have a steel measuring tape available. Secondly, a hammer drill as mentioned above. Lastly have other tools available like a hammer, screwdriver, and drill bits.

The Concrete Sawing and Drilling Association recently sponsored a research study at the University of Toledo on several different drop- in anchor manufacturers including Sanko, Hilti and Red Head. In this study the Sanko anchor was matched up against the other popular anchors in the market.

Sanko anchors were found to support approximately 15 % higher loads than the competition.