How to Seal Holes in the Garage Firewall


  • 1 Welder 
  • 1 8″ x 8″ steel plate
  • 1 Standard ” steel rod (with a ” diameter) 
  • 1 Threaded ” steel rod
  • Material to backfill with (could use soil from digging hole, sand, or clay)
  • ” x ” steel washer and bolt  
  • Wrench   


How to patch large holes

Clear away any debris and cut the hole into a rectangle for easier repair.
Benjamin Clapp/Getty Images

When it comes to large holes, calling in a professional can help you avoid errors that may require fixing the hole again in the future. “Particularly with large holes, because new drywall will likely need to be installed, you could end up with an uneven or patchy wall,” says Steckel. “Plastering is an art and doing it right is not easy. It can be incredibly frustrating and messy, and if there are any imperfections, once you paint, there is no other option than to do it again.”

However, if you decide to patch a large hole yourself, Steckel provides two options.

Option 1: Chicago patch

This is the more complicated method but will yield the most seamless-looking results. 

1. Square off the hole. If the hole is irregularly shaped, use a small saw blade or razor knife to transform it into a square. Remove any drywall debris or chipped paint and sand the area smooth.

2. Brace the hole. Place a piece of wood through the hole and attach it on both sides across the opening using drywall screws. It should be long enough to extend at least 1 inch past the edge of the hole on either side.

3. Prepare the drywall patch. Take a piece of drywall about twice the size of the hole. Line it up to the squared-off hole and use your sharp utility knife to trace the back of the drywall along the top and bottom edges of the hole. Carefully cut the lines deeper. Do not cut through the front paper. Snap off and peel away the excess drywall while leaving the front paper intact. Repeat, this time tracing the right and left sides of the hole. You should now have a piece of drywall that matches the hole completely with the front paper still attached.

4. Apply the patch. Put a generous coat of drywall compound on the wall surrounding the hole. Put a generous coat of compound on the inside paper portion of your custom piece. Press the patch into the hole, and use your biggest putty knife to flatten the paper to the wall. Allow the putty to dry (it will take about an hour).

5. Apply a second coat of compound. This time, add a thinner coat of drywall compound, taking care to spread it an inch or two past the original application. Then, smooth the edges until the compound is flush with the wall. Let this coat dry. If the patch still isn’t smooth, apply a third coat (skim coat) and feather the bumps out to make the edges as flush as possible. 

6. Lightly sand, prime, and paint. Sand the area, wipe with a damp cloth, let it dry, and then prime and paint. If your paint includes primer, you can skip the priming step.

Option 2: Regular patch

1. Square off the hole. If it is round or irregular in shape, use a razor knife or small saw blade to make the hole square. Clear any chipped paint or debris and sand smooth.

2. Brace the hole. Insert a piece of wood into the hole and screw it in on the left and the right. It should be long enough to extend at least 1 inch past the edge of the hole on either side.

3. Prepare the drywall patch. Cut a piece of drywall (all the way through the paper) so that it fills the hole, leaving less than a ½-inch gap all the way around.

4. Secure the patch. Using drywall screws, attach the patch to the wood brace behind it.

5. Apply mesh tape. Place the mesh tape over the gap (extend a inch or two past the hole) and use your knife to flatten it and make sure it is adhering. 

6. Apply the patch. Put a very generous first coat of mud along the gaps. Go a few inches further on either side of the tape, Flatten the drywall mud and allow it to dry (it will take about an hour).

7. Apply a second application. Add a thinner coat of drywall mud, extending it an inch or two past the previous application. Smooth the edges until the compound is flush with the wall. Let the coat dry. If the patch isn’t smooth, apply a third (skim) coat and feather the bumps out to make the edges as flush as possible.

8. Lightly sand, prime, and paint. Sand the area, wipe with a damp cloth, let dry, and then prime and paint. Skip the priming step if your paint includes primer.

How to patch a hole: Insert backer boards

Cut the backer boards about 4 in. longer than the

Cut the backer boards about 4 in. longer than the height of the hole. Pine or other soft wood works well. Hold them tight to the backside of the drywall when fastening them. Hold the boards carefully so the screw points won’t prick your fingers if they pop out the backside. The drywall screws will draw the boards in tight. Sink the screwheads slightly below the drywall surface. 

How to Fix a Medium-size Hole

Holes between 11/2 to 6 in. diameter

Holes ranging from 11/2 to 6 in. diameter must be bridged with an even stronger, more rigid material. We used a 4×4-inch galvanized-metal patch from Homax ($2.25) to repair a 2 1/2-in. diameter puncture caused by a doorknob. The company also makes 656- ($3) and 8×8-in. ($4.25) patches. The patch comes stuck to a 6-in.-sq. piece of adhesive-backed fiberglass mesh.

Install it in 3 steps:

  1. Peel off the paper backing and press it to the wall centered over the hole.
  2. Then spread on three coats of compound, letting each dry thoroughly before applying the next.
  3. The final coat should be at least 12 in. sq. so that the compound at the edges of the patch feathers out to the surrounding wall.

Note: For medium-size holes, peel off the backing sheet from the metal patch to expose the adhesive. Then press the patch to the wall.

Problem 3: Creeping Cracks

Step 1: Vertical drywall cracks will often appear above and below windows and doors. These hairline cracks are usually caused by lumber shrinkage and settling in the house frame. To repair the cracks, start by using a sanding sponge to sand the crack smooth. After sanding, vacuum the crack to remove all loose dust and debris.

Step 2: Next, use a narrow putty knife to apply a thin coat of joint compound to the crack. Wait for it to dry, then sand it smooth. Repeat, applying a second thin coat.

Step 3: To dissuade the crack from reappearing, spray the repair with a thin coating of elastic crack cover-up, such as Good-Bye Cracks.

Drive a popped nail below the surface

Drive a popped nail below the surface of the drywa

Drive a popped nail below the surface of the drywall with a hammer and a nail set. Cut away loose joint compound and paper shreds.

Preventative Measures General Maintenance      

Perform Your Own Inspection  

Perform your own mini inspection to ensure everything is: 

  • Tightened
  • Fastened
  • In the right place 

Check the roller brackets and bolts on the door that rolls down. 

Also, check the hardware itself as well as the structure of the garage. 

Check the support beams. Make sure nothing could be pushing the beams down or has the potential to put pressure on the roof, such as big trees.     

Replace the Weatherstrip 

The weatherstrip is the rubber seal on the bottom of your garage door. It may be old or cracked, and so every time it rains, water seeps into your garage. 

It also allows water on the inner walls and makes them weaker – especially if you live in an area prone to flooding. In fact, fixing the drainage before your next flood is probably your best bet.  

Weatherstripping is easy to find and even easier to install. 

You can get it at any local hardware store and replace it as soon as you get home. All you have to do is cut it and place it into the grooves inside the door. 

It already comes with the adhesive, so all you need is the weatherstripping and a pair of scissors.  

Take Care of Your Garage Door

The door itself does need to be examined to check for underlying issues. 

Check for water damage inside and out. Water damage could warp the door and weaken the structure of the garage wall.  

See if you need to make some changes to prevent this issue in the future. 

Problem 7: Patching Large Holes

Step 1: To repair a large hole in drywall, first draw a square outline around the hole using a 24-inch level. As you mark the four lines, be sure to center one vertical line on the center of a wall stud.

Step 2: Cut three sides of the square using a drywall saw, which is also called a jab saw because you start cutting by jabbing the saw’s pointed tip through the drywall. Lift away the debris as you cut to keep it from falling into the wall cavity.

Step 3: Remove the drywall on the remaining side of the outline by using a utility knife to cut down the center of the stud.

Step 4: Cut a one-by-four foot pine board six to eight inches longer than the square opening in the wall. Squeeze some construction adhesive onto the ends of the board.

Step 5: Slip the one-by-four into the hole with the glued surface facing the back of the drywall. Position the board so it extends into the opening by at least 1½ inches. Secure the board with two clamps.

Step 6: After the adhesive dries, cut a drywall patch to loosely fit into the hole. Apply some construction adhesive to the exposed surface of the one-by-four, then press the patch into place and secure it to the stud and to the one-by-four backing board with 1¼-inch drywall screws.

Step 7: Wipe down the wall and drywall patch with a slightly dampened sponge to remove any dust. Next, apply adhesive-backed fiberglass mesh drywall tape over the four seams of the patch. Overlap the tape at the corners for maximum strength, and center each piece directly over a seam. Firmly press down the tape for good adhesion.

Step 8: Use a four-inch drywall knife to apply the first layer of joint compound over the tape. Allow the compound to dry overnight.

Step 9: Smooth the dried compound with a hand-sanding pad fitted with a sanding screen.

Step 10: Use an eight-inch knife to apply several skim coats of joint compound over the repair, making each one slightly larger than the preceding one. Sand the final coat smooth with 220-grit sandpaper. Finish by rolling on a coat of primer, followed by two topcoats of paint. And note that, in some cases, it might be necessary to paint the entire wall to ensure the patch is undetectable.

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