How to Anchor Sill Plates to Concrete Foundations

How to Attach Sill Plates to Concrete Foundations

Many homeowners have the skills and capabilities to complete their own home improvement projects and renovations. This can save immense amounts of money as well as help home owners develop new skill sets they can use in the future as new home improvements are needed. Large projects such as home additions, new garages or adding a patio can also be completed without hiring a professional. When building a new structure, it is critical to securely fasten it to the foundation or slab with the use of a sill plate.

A sill plate, also known as a sole plate, is the bottom horizontal member of a wall or building to which the vertical studs will be attached. Most sill plates are made from lumber- usually a 2x4, 2x6, 2x8 or 2x10. The sill plate is typically anchored to the foundation or slab of concrete, depending on the application. Before the next steps can take place, a sill plate must be anchored to the foundation to ensure proper construction and safety.

Before You Get Started
Before trying to anchor a sill plate to any type of foundation, it is important to determine which system is best for attaching the sill plates.

One method for fastening sill plates is the use of cast-in-place anchors, commonly referred to as “J” Bolts. “J” bolts are anchors in the shape of the letter J with threads on the end opposite of the bent end. These bolts are set in place before the concrete is poured. The use of “J” bolts provides the best holding values, but can be problematic for the do-it-yourselfer due to the expertise needed and complicated installation steps. The “J” bolts must be installed completely perpendicular and if not, numerous problems will occur when trying to attach the sill plate. Also, this method cannot be used when building a structure where there is an existing foundation, such as replacing a dilapidated garage. This could pose a serious problem for many home improvement projects.

There is a type of concrete anchor that can be used when working with sill plates in less complicated applications and those with existing foundations. One option for installing sill plates is the use of Wedge Anchors. This type of anchor is a post-installed anchor, meaning that it is placed in concrete after it is fully cured. These fasteners are designed for use in solid concrete only. Wedge anchors are available from 1/4" to 1 1/4" in diameter. The length of the wedge anchor is completely dependent upon the thickness of the material to be fastened. To determine the size of anchor needed, it is important to check your local building codes or with an engineer or architect. It is also critical to verify the holding values required for your particular application since the quality of concrete will vary in every single circumstance.

Choosing the Size Wedge Anchor to be used
Once the required holding values have been determined, use this wedge anchor sizing chart to determine the appropriate diameter and length. There are some other considerations when using wedge anchors. These include:

• Use a wedge anchor of suitable length for the specific application. This is determined by using the equation below:
Minimum embedment for the diameter being used +
Thickness of the material being fastened +
Thickness of the nut and washer =
Minimum length of the wedge anchor needed

• Ensure that the anchor will be further than the minimum distance from the concrete edge. The rule of thumb is a minimum of five anchor diameters from the unsupported edge of concrete. For example, if your wedge anchor is 1/2" in diameter, it must be installed a minimum of 2 1/2" from the unsupported edge.
• Determine the grade of steel and/or plating of the wedge anchor required for the specific application. Wedge anchors are available in three different finishes: Zinc plated, hot-dipped galvanized and stainless steel.

Step by Step Instructions
Concrete Wedge Anchors can be installed in a few steps. Basic instructions follow:
• On the concrete, mark where your holes will be drilled. Remember that anchors must be placed: a minimum of five anchor diameters from any unsupported edge and there should be a minimum of ten anchor diameters between any two anchors.
• Using a hammer drill, drill your holes using a carbide-tipped
masonry bit. The hole diameter should be the same diameter as
the wedge anchor.
• Clear the hole of all debris using compressed air, a shop-vac
or wire brush.
• Before inserting the wedge anchor into the hole, be sure to place
the washer on the head and thread the nut a couple of turns. By
not fully threading the nut, the threads of the
wedge anchor are protected.
• Carefully place the sill place in the correct position and insert the
wedge anchors into each hole through the sill plate.
• Hammer anchors into every hole ensuring that they are
installed to the desired depth and securely in place. This will
be the supporting plate to which studs will be placed later in the
renovation process so secure placement is important for the overall safety of the structure.
• Using a torque wrench, tighten every nut to guarantee they are tightened to the required torque value.

For more detailed information and further instruction, take a look at this Wedge Anchor Installation Video.

When using concrete wedge anchors, it is important to remember:
• Wedge anchors are very effective when the concrete is in good condition and minimum edge distances and spacing are maintained.
• Hole size is critical to the holding values of the wedge anchor. Hole diameter is equal to the anchor diameter when using ANSI standard carbide bits. The tolerances of ANSI standard bits are specifically matched to work well with wedge anchors.
• Wedge anchors have a required torque value. Take a look at this important anchor technical information page to determine the diameter of anchor to use for a range of required .

As with any home improvement or 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 as a basic overview of the steps for completing this project. Always refer to manufacturer’s instructions or consult a contracting expert. With a little research, planning and patience you are now ready to expand your home or create some new space!