Bottom Plate Screw Anchor: A Comprehensive Guide

Bottom plate screw anchors are used to fasten bottom plates to solid concrete applications. They are typically used by contractors in the precast, formwork, and steel construction industries. Bottom plate screw anchors are ideal for applications that require anchor removability. They are also used in medium-duty anchoring applications. The anchors are screwed into a hole, creating their own undercut by tapping the concrete hole. This cutting and locking mechanism, without expansion, enables the anchor to be used in close spacing and edge distance applications.

Bottom plate screw anchor installation

Planning:

Before starting the installation, it is crucial to determine the appropriate fastening system for attaching the bottom plate, also known as a sill plate, to the concrete foundation. The sill plate is the bottom horizontal member of a wall or building to which vertical studs will be attached. Common fastening methods include "J" bolts (cast-in-place anchors) and wedge anchors. "J" bolts provide superior holding values but require expertise and complicated installation steps. Wedge anchors, on the other hand, are suitable for less complicated applications or existing foundations.

Determining Wedge Anchor Size:

To determine the size of the wedge anchor required, consider the thickness of the material to be fastened and consult local building codes or an engineer/architect. Verify the holding values needed for your specific application, as concrete quality can vary. Use a wedge anchor sizing chart to select the appropriate diameter and length for your anchors.

Preparing the Concrete:

Mark the locations on the concrete where the holes will be drilled. Ensure that the anchors are placed a minimum of five anchor diameters from any unsupported edge, and maintain a minimum of ten anchor diameters between anchors.

Drilling and Cleaning the Holes:

Using a hammer drill, drill the holes using a carbide-tipped masonry bit. The hole diameter should match the diameter of the wedge anchor. Clear the holes of any debris using compressed air, a vacuum, or a wire brush.

Preparing the Wedge Anchors:

Place the washer on the head of each wedge anchor and thread the nut a couple of turns to protect the threads.

Installing the Sill Plate:

Position the sill plate correctly and insert the wedge anchors into the holes through the sill plate. Hammer the anchors into the holes to ensure they are securely in place and have reached the desired depth.

Tightening the Nuts:

Using a torque wrench, tighten the nuts on the wedge anchors to the required torque value.

Additional Considerations:

Remember that wedge anchors work best when the concrete is in good condition, and minimum edge distances and spacing are maintained. The hole size and diameter are critical factors in ensuring the optimal holding values of the wedge anchors.

Bottom plate screw anchor removal

Bottom plate screw anchors are used to secure the bottom plate of a wall to a concrete floor. There are several methods to attach a bottom plate to concrete, including cut nails (masonry nails), concrete nails, screws, wedge anchors, and construction adhesive.

To remove a bottom plate screw anchor, the specific method will depend on the type of fastener used. Here are some general steps and considerations for removing different types of anchors:

Cut Nails or Concrete Nails:

• Use a hammer and chisel to carefully pry and remove the nails from the concrete.
• If the nails are stubborn, you may need to use a nail punch or a screwdriver to drive them out.
• Be cautious not to damage the concrete surface surrounding the nails.

Screws:

• Use the appropriate screwdriver or power drill to unscrew and remove the screws.
• If the screws are stripped or damaged, you may need to use a screw extractor or a left-handed drill bit to remove them.

Wedge Anchors:

• Wedge anchors are typically very permanent and challenging to remove.
• You may need to use a hammer and chisel to break the anchor and remove it from the concrete.
• Be cautious to protect the surrounding concrete and wear appropriate safety gear.

Construction Adhesive:

• Removing construction adhesive can be challenging, as it is designed to create a strong bond.
• Try using a putty knife or a similar tool to carefully pry and scrape away the adhesive.
• You may need to use a solvent or adhesive remover to soften the adhesive and make it easier to remove.

It is important to wear the appropriate safety gear, including gloves, eye protection, and a respirator, when removing bottom plate screw anchors, especially when working with concrete or chemicals. Additionally, make sure to dispose of any debris or leftover materials properly.

Bottom plate screw anchor spacing

When constructing a new building, it is crucial to securely fasten the bottom plate, also known as the sill plate, to the foundation or slab of concrete. The bottom plate is the bottom horizontal part of a wall or building to which the vertical studs will be attached.

There are several methods for fastening bottom plates, including cast-in-place anchors ("J" bolts), wedge anchors, cut nails (masonry nails), concrete nails, screws, and construction adhesive.

When using cast-in-place anchors, it is important to ensure that the "J" bolts are installed completely perpendicular to the concrete. These bolts must be set in place before the concrete is poured. Wedge anchors, on the other hand, are placed in concrete after it is fully cured and are available in various diameters and lengths.

For bottom plates attached to concrete floors, special tools and fasteners are required. It is also important to take precautions against moisture damage, as concrete surfaces can accumulate excess moisture.

Regardless of the chosen fastening method, proper spacing of anchors is crucial. The California Wood Construction Wind and Seismic Code 2015 provides specific requirements for anchor spacing in Table 4.4.1.6. This table outlines the maximum anchor bolt spacing in inches for combined shear and wind uplift.

When using wedge anchors, it is recommended to maintain a minimum distance of five anchor diameters from any unsupported edge of the concrete. Additionally, there should be a minimum of ten anchor diameters between any two anchors. Proper spacing ensures the safety and structural integrity of the building.

Bottom plate screw anchor applications

Bottom plate screw anchors are used to install bottom plates to solid concrete applications. They are commonly used in the precast, formwork, and steel construction industries. Bottom plate screw anchors are ideal for applications that require anchor removability.

Bottom plate screw anchors are available in a variety of diameters and lengths to suit different applications. They are typically used in medium-duty anchoring applications. The anchors are case-hardened, which enables them to cut into concrete and lock themselves in place. This cutting and locking mechanism, without expansion, allows the anchors to be used in close spacing and edge distance applications.

To install a bottom plate screw anchor, a hole is drilled into the concrete using a hammer drill and a carbide-tipped masonry bit. The hole diameter should match the anchor diameter. After drilling, the hole is cleared of debris using compressed air, a vacuum, or a wire brush. The anchor is then screwed into the hole, creating its own undercut by tapping the concrete.

When choosing a bottom plate screw anchor, it is important to consider the holding values required for your application, as the quality of concrete can vary. Additionally, it is crucial to determine the appropriate length and diameter of the anchor based on the thickness of the material being fastened and the local building codes. Wedge anchors, for example, have specific minimum distance requirements from the concrete edge. Consulting with an engineer or architect can help ensure the correct size and type of anchor are selected for your specific application.

Bottom plate screw anchor testing

When testing bottom plate screw anchors, it is important to determine the best fastening system for the application. This will depend on various factors, such as the type of structure being built, the thickness of the material being fastened, and local building codes.

One common method for fastening bottom plates is to use cast-in-place anchors, known as "J" bolts. These are placed before the concrete is poured and provide excellent holding values. However, they require expertise to install correctly and are not suitable for structures with existing foundations. For structures with existing foundations, wedge anchors are a more suitable option as they are post-installed.

When testing bottom plate screw anchors, it is crucial to follow the appropriate procedure and criteria. The California Building Code specifies that when post-installed anchors are used, installation verification test loads, frequency, and acceptance criteria must be met. The test procedure should be permitted by an approved evaluation report, and all post-installed anchors must be tension tested.

The testing frequency will depend on the application of the anchors. For sill plate bolting applications, 10% of the anchors should be tested. For structural applications, all anchors must be tested, while for non-structural components, 50% or alternate bolts should be tested. The special inspector will select the anchors to be tested randomly.

The required test loads can be determined in several ways, including:

• Twice the maximum allowable tension load
• 1.25 times the maximum design strength of anchors
• The manufacturer's recommended installation torque

The acceptance criteria for post-installed anchors are based on approved evaluation reports. When testing with a hydraulic ram or spring-loaded apparatus, the anchors should maintain the test load for a minimum of 15 seconds without any discernible movement. When using a torque wrench, torque-controlled post-installed anchors should attain the specified torque within 1/2 turn of the nut. For screw-type anchors, the specified torque should be attained within 1/4 turn of the screw after initial seating of the screw head.

Frequently asked questions