Plan the perfect garden with our interactive tool →

How to Repair Rotted Sill Plates on a Garage

Garage sill plates are located at the bottom of the garage wall where the wall meets the foundation or slab. These plates are subject to rot since they often come in contact with water or are attacked by termites. The competent do-it-yourselfer can replace these sills when they rot. You can expect to complete this type of job in one to two days, depending on the size and scope of the project.

Preparation and Removal

Step 1

Place a temporary support wall just beside the garage wall. Measure the height from the garage floor to the ceiling, and build the wall to the corresponding height. Tap the wall in place, and plumb the wall with a 4-foot level.

Step 2

Remove the garage siding so that the rotted sill is exposed. Gently pry the siding with a flat pry bar. Remove the siding six to 12 inches above the sill plates. Once the siding is loosened, pull the nails with the pry bar, and place the siding to the side for reattachment.

  • Place a temporary support wall just beside the garage wall.
  • Once the siding is loosened, pull the nails with the pry bar, and place the siding to the side for reattachment.

Step 3

Determine whether the sill is placed on a concrete slab or a concrete foundation. A concrete slab sill is always the same size as the wall framing and is attached directly to the wall. A concrete foundation sill sits beneath a framed floor and is not part of the wall framing. It is generally 8 inches wide or the width of the foundation.

Slab Concrete

Step 1

Detach the sill plate from the wall framing by cutting through the framing where it is connected to the plate. Cut through the nails where the sill attaches at the wall framing and below the sill plate where the plate attaches directly to the concrete slab.

Step 2

Cut the sill plate into 4-foot sections for easy removal. Pry the sill from the wall with a flat bar and remove all remaining debris from the concrete slab. Cut new treated sill plates and slide them beneath the wall framing.

  • Determine whether the sill is placed on a concrete slab or a concrete foundation.
  • A concrete slab sill is always the same size as the wall framing and is attached directly to the wall.

Step 3

Insert 3-inch wood screws through the wall framing at an angle and into the new sill plate. Drill holes through the sill plate and into the concrete with a hammer drill and insert concrete screws to hold the sill in place.

Concrete Foundation

Step 1

Remove the sill plate from beneath the floor framing. Drill a 1-inch hole beneath the floor framing where it meets the sill. Insert the reciprocating saw into the hole and cut through the rotted sill. Cut the sill into 4-foot sections.

Step 2

Do not cut through the anchor bolts that are anchored into the concrete foundation. The anchor bolts will be used to re-anchor the new sill plates. Pry the sill from the foundation with a flat bar.

  • Insert 3-inch wood screws through the wall framing at an angle and into the new sill plate.
  • Drill a 1-inch hole beneath the floor framing where it meets the sill.

Step 3

Place the new treated sill onto the concrete foundation and against the anchor bolts. Place pencil marks at the location of the anchor bolts. Cut 1-inch slots into the treated sill from the side of the pencil mark that extends to the center of the treated lumber.

Step 4

Slide the sill into place and tighten the anchor bolts down onto the new treated sill. Insert 3-inch wood screws through the floor framing and into the treated sill at an angle, spacing them four feet apart. Replace the siding on the garage.

Related Articles

Fixing a Rotted Sill Plate in a Garage
Fixing a Rotted Sill Plate in a Garage
How to Hang Curtain Rods in Cement or Metal
How to Hang Curtain Rods in Cement or Metal
How to Build Planters With Landscape Timbers
How to Build Planters With Landscape Timbers
How to Build a Breeze-Block Wall
How to Build a Breeze-Block Wall
How to Build a Bulkhead
How to Build a Bulkhead
How to Install USG Fiberock
How to Install USG Fiberock
How to Attach Paneling to Basement Walls
How to Attach Paneling to Basement Walls
How to Build a Pressure Treated Retaining Wall
How to Build a Pressure Treated Retaining Wall
How to Do Footings for Steel Posts
How to Do Footings for Steel Posts
How to Stabilize a Pergola
How to Stabilize a Pergola
How to Repair the Joints on Concrete Front Steps
How to Repair the Joints on Concrete Front Steps
How to Seal the Crotch of a Damaged Tree
How to Seal the Crotch of a Damaged Tree
Attaching a Hanging Planter to a Cinder Block Fence
Attaching a Hanging Planter to a Cinder Block Fence
How to Cut a Door in a Basement Foundation
How to Cut a Door in a Basement Foundation
How to Build a Garden Cart With Bicycle Wheels
How to Build a Garden Cart With Bicycle Wheels
How to Build a Rock Screen
How to Build a Rock Screen
How to Tie Wooden Posts to Cement Blocks
How to Tie Wooden Posts to Cement Blocks
Garden Guides
×