The Purpose of Hold Down Straps in Concrete Foundations
The Purpose of Hold Down Straps in Concrete Foundations
The function and importance of hold down straps in concrete foundations is not something that home owners typically understand. As a result, many homeowners are shocked when they have to pay a contractor to replace or install new tie back anchors due to the failure of existing ones. Fortunately, this is not too expensive and there are many different options available to homeowners to make the repairs. This article explains what the straps are, what they do and why they are so important to your home’s stability.
A hold-down strap is a piece of high-strength material that bonds with both epoxy and concrete to form an unbreakable bond with the foundation. This prevents shear slides that occur when the bottom of a foundation wall moves inward. This is a common problem and it can cause serious damage to your foundation and basement. Using a hold-down strap prevents this movement and saves money and time over a costly structural repair.
This type of system is used to strengthen and stabilize walls of both block and poured concrete foundations. The straps are installed by demo’ing the concrete to expose the strap, cleaning or replacing the strap, and patching back the concrete. A foundation inspection will determine whether this type of repair is appropriate for your foundation and will help you choose the best option.
Why Do I Need Tie Back Anchors?
The primary purpose of a foundation is to resist forces that act on the walls. These forces can be from outside pressure, water or soil movement. If these forces exceed the walls’ capacity, they can move or even fail to hold the structure up. These forces are transmitted through a series of connections between the wood framing members and concrete foundation. The most common connection is through a sill plate (also known as the mudsill or sill plate) and the joists. These are not strong enough on their own and may need to be reinforced with tie back anchors.
There are a variety of options for tie backs and the most popular is a system that uses what is called a hold-down strap replacement. This is when a trench is excavated parallel to and below the foundation wall, demo’ing the concrete and a series of galvanized steel anchors are set in it. This helps anchor the framing to the foundation.
Another method is to use helical anchors that are driven into the ground and then attached to the joists with bolts. This is an effective method but if the soil is tough, it can be difficult to embed the anchors in a manner that will provide adequate resistance. In addition, helical anchors cannot be easily removed from the soil when they are no longer needed.