How to Anchor Sills to a Concrete Block Foundation

A sill plate is the base for your home's framing.

When you secure anything, especially a sill plate, to a concrete block foundation, you must take extra steps to ensure it remains fastened to the concrete structure. Concrete is very hard and porous and requires special fasteners to hold objects securely. If you haphazardly attach the sill plate to the concrete block's foundation, the sill plate could work loose over time and cause structural damage to your home.

Things You'll Need

• Sill plate (2-inch-by 4-inch up to 2-inch-by-10-inch treated lumber board)
• Hand drill
• 1/4-inch carbide drill bit
• Nail
• Hammer
• Hammer drill
• 3/16-inch masonry bit
• 1/4-inch-diameter by 4-inch long concrete screws
• Screwdriver
• 1/2-inch carbide drill bit
• 1/2-inch masonry drill bit
• 1/2-inch diameter by 2 1/2-inch long wedge anchors
• Torque wrench

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Instructions

With Concrete Screws

1. Drill pilot holes through the widest face of your sill plate with a ¼-inch drill bit and hand drill. Space the pilot holes every 12 inches. Check your local building code requirements to determine the required size treated lumber board that you must use for your sill plate.

2. Place the sill plate onto the concrete foundation and mark the holes from the sill plate into the concrete. To mark the holes, place a ¼-inch nail into the hole and strike downward on it with a hammer. Place the sill plate off to the side.

3. Drill a 3/16-inch diameter hole at each marked location with a hammer drill and a 3/16-inch masonry drill bit. Drill the hole ½-inch deeper than the length of the concrete screws you plan to use.

4. Position the sill plate over the concrete foundation and line up the holes. Place the 4-inch long concrete screws into the holes on the sill plate and then drive them in with a screwdriver.

With Wedge Anchors

1. Drill holes through the widest face of your sill plate with a 1/2-inch carbide drill bit and hand drill. Space the holes every 12 inches. Check your local building code requirements to determine the required size treated lumber board that you must use for your sill plate.

2. Place the sill plate onto the concrete foundation and mark the holes from the sill plate into the concrete. To mark the holes, place a ¼-inch nail into the center of the hole and strike downward on it with a hammer. Place the sill plate off to the side.

3. Drill a hole at each marked location with a hammer drill and a ½-inch masonry drill bit. Drill the hole ½-inch deeper than the length of the concrete screws you plan to use.

4. Place the smooth ends of the wedge anchors into the ½-inch holes and then tap them in with the hammer until the threaded shafts are the only portion of the anchor that protrude from the concrete.

5. Position the sill plate over the threaded studs protruding from the concrete foundation.

6. Place the washer provided with the wedge anchor onto the threaded posts and then thread the nuts provided with the wedge anchors onto the threaded posts. Tighten the nuts with a wrench to 55 foot-pounds of torque with a torque wrench.

References

• Confast; How to Install a Concrete Screw; Michael Pistorino
• Concrete Fasteners; How to Attach Sill Plates to Concrete Foundations; Bob Carlisle