Anchoring to Concrete, Brick or Block

Choosing the concrete anchor best suited to your needs requires consideration of many project specifics, including the characteristics of the base material, such as quality, density and thickness; the type of fixture being fastened, the location of the project and the stresses that will be applied to the anchor.


Considerations:

What are the characteristics of the base material?

Every type of base material has its own limitations and advantages. Determining the properties of your base material will allow you to safely and successfully anchor your fixture.

  1. Hollow or Solid Core
  2. Density and Strength of the Base Material
  3. Thickness of Base Material

Is your base material solid or hollow core?

Hollow Core - drywall, plaster board. sheet rock, particle board, wafer board, plywood, plaster and lath, tile, glass, metal, fiber-glass, plastic and concrete block.

Drywall: A low density material formed between sheets of paper and used primarily for covering studded walls and ceilings. Exhibits relatively low pull-out resistance.

Drywall

Plaster and Lath: Thin wooden strips (lath) nailed to the studs or ceiling beams with low density plaster applied over them. Exhibits relatively good pull-out resistance.

Anchoring to Plaster and Lath

Hollow Core Concrete Block: Commonly used in basements and commercial properties. Exhibits relatively high pull-out depending on compressive strength of the block.

Anchoring to Hollow Core Concrete Block:
Solid Core - concrete, brick and mortar, stone, solid cinder block and wood.

Solid Concrete: Exhibits the highest pull-out resistance, but may have limitations due to steel bars, cable or wire mesh embedded in the concrete.

Solid Concrete:

Stone: Since there are a large variety and different types of stone that occur naturally, first identify the hardness and characteristics of the stone,  then match them up with the type of anchor needed. Although most anchors are not tested in stone, you may still be able to successfully anchor to it.

Stone

Brick or Mortar: Like stone, brick and mortar range from hard (brittle) to soft. In hard brick anchors with low-impact and/or low-torque are recommended. In soft brick,  a draw-up anchor, such as a sleeve anchor or machine screw anchor, is recommended.

Brick and Mortar

What is the density of the base material?

There are three degrees of density and strength of base materials:

  • Low Density - weak resistance to stress, i.e. drywall and cinder block.
  • Medium Density - moderate resistance to stress, i.e. plaster, tile fiber board and particle board.
  • High Density - significant resistance to stress, i.e. concrete, brick, concrete block and stone.

Resistance to stress will vary based on the density and thickness of the base material. Age and manufacturing standards for material will result in different failure points for each anchor.


What is the thickness of base material?
Measuring the thickness of the base material will help you to determine the length of the anchor needed for your project.

NOTE: For Hollow Core base material it is critical to have the right length anchor so as to be able to secure tightly. For Solid Core base material it is recommended that the thickness of the base material be at least 125% of the anchor embedment depth.


What type of fixture will you be fastening?
Once the characteristics of the base material have been determined, the next step is to address the properties of the fixture.

  1. Weight and Size of the Fixture
  2. Location of the Fixture
  3. Stresses Applied to the Fixture

What is the size and weight of the fixture to be fastened?

Size and weight of the fixture (or what is to be the load on the fixture, as in shelving) are critical in determining not only the type of anchor needed, but the number of anchors needed per application.

Example: If a fixture weighing 100 pounds needs to be anchored and the safe working load of the anchor selected is 50 pounds, then at least 2 anchors will be needed to safely secure the fixture. Additional anchors may be warranted, not because of weight, but because of the size of the fixture. When in doubt, it is best to use more anchors. Be careful, however, that the anchors are not placed to close together. It is typical within the industry to leave at least 10 anchor diameters between anchors.


What is the location of the fixture to be fastened?

Location plays a critical role in determining the type and material of the anchor used.

Considerations include:

  • Will the fixture be indoors, outdoors or subjected to chemical elements?
    • Zinc is acceptable for indoor use where there is no risk of chemicals.
    • Galvanized and Stainless Steel are acceptable for outdoor use.
    • Stainless Steel should be utilized for areas subject to possible contact with chemicals.
  • Will the fixture be fastened to a floor, wall or ceiling?
    • Different stresses are applied to a fixture in different applications. When fastening to a wall, shear strength must be considered in addition to tension strength. When fastening to a ceiling be sure to consider if there will be movement to consider.
  • Will the fixture be close to an unsupported edge?
    • The expansion anchor industry has established a minimum standard of ten (10) anchor diameters for spacing between anchors and five (5) anchor diameters from any unsupported edge. When vibration or sudden impact are part of the load conditions, spacing between anchors should be increased.

What types of stresses will be applied to the fixture?

Concrete fasteners are designed differently, accommodating different types of loads they are meant to secure. The following stresses are type of stresses that may be exerted on the fixture. These stresses are critical factors in selecting the right anchor.

Will your fixture be exposed to:

TENSION:

Tension stress is when the force acts in line with the fastener, tending to pull it out. Ceiling mounted fasteners are the most common applications that are subjected to tension stress.

Tension
SHEAR:

Shear stress is when a force acts at a right angle to the fastener, tending to break off the fastener. Wall mounted fasteners are the most common applications that are subjected to shear stress.

Shear
IMPACT:

Impact stress is when occasional or repetitive impacts subject fasteners to stress over and above those resulting from normal tension and shear forces. A railing would be a common application that is subjected to impact stress.

Impact
VIBRATION:

Vibration stress is when vibration in the base material or fixture cause movement, possibly loosening the fastener in the hole, thus reducing its holding power. Machinery, automobiles and wind would be common sources of vibration.

Vibration
COMBINATION:

Combination loads are when fasteners are subjected to two or more of these stresses. A common example of a combination load would be a drapery rod, where both tension and shear stresses are applied, as well as vibration and impact stresses.

Combination

Now that you have familiarized yourself with your project, you can select the appropriate anchor for your job. A complete list of links for available concrete anchors and fasteners can be found below.

Available Concrete Anchors
Wedge Anchor Leadwood Screw Anchor Nylon Nail-It Anchor
Sleeve Anchor Single Expansion Anchor Metal Hit Anchor
Drop-In Anchor Double Expansion Anchor Split Drive Anchor
Machine Screw Anchor Lag Shield Anchor Tapcon Screw

NOTE: The distance between anchors is critical. If installed to close to each other, the interaction of forces between fasteners will reduce the holding power of the anchor in the base material. As a general rule, the anchor & fastener industry has established the following minimum spacing standards: Ten (10) anchor diameters between anchors, five (5) anchor diameters from the edge.