Best Garage Door Charlotte
A threshold seal is a rubber or vinyl strip that mounts to the garage floor directly under the door. When the door closes, the bottom seal on the door presses down onto the threshold seal, creating a double barrier against water, pests, leaves, dust, and cold air. Most garages do not come with one -- the bottom seal alone is supposed to handle the gap between the door and the floor. But on many Charlotte garages, the bottom seal alone is not enough.
Why the Bottom Seal Is Not Always Enough
The bottom seal (also called an astragal) is the rubber strip attached to the bottom edge of the door. It presses against the garage floor when the door is closed. In a perfect world, it creates a tight seal all the way across. In reality, several things prevent that:
- Uneven floors. Many Charlotte garage floors are not perfectly flat. Concrete settles, cracks, and heaves over time, especially on Charlotte's clay soil. High and low spots in the floor mean the bottom seal makes contact in some places and has gaps in others.
- Worn bottom seal. The bottom seal compresses and hardens over time, especially in Charlotte's heat. An older seal may not be flexible enough to conform to the floor surface.
- Gap under the door. Some doors have a visible gap between the bottom of the door and the floor, even when closed. This can be caused by improper installation, settling, or a door that has been adjusted incorrectly.
- Sloped driveways. If the driveway slopes toward the garage (common in Charlotte neighborhoods with sloped lots), water runs straight to the garage floor. Even a good bottom seal can be overwhelmed by the volume of water during a heavy rain.
A threshold seal addresses all of these problems by raising the seal point above the floor surface and giving the bottom seal a raised, consistent surface to press against.
How Threshold Seals Work
A threshold seal is a long strip (usually sold in 8, 10, or 16-foot lengths) made of heavy-duty rubber or vinyl. It has a flat base that sits on the floor and a raised ridge or hump in the center. The base is glued to the concrete floor with adhesive. When the door closes, the bottom seal presses down onto the raised ridge, creating a compression seal.
Because the threshold seal sits on top of the concrete (raised about 1/2 to 1 inch), it fills in low spots and bridges small cracks in the floor. Water that would have seeped under the door now hits the raised rubber barrier and runs away from the garage.
What a Threshold Seal Blocks
- Rain and flooding. Charlotte gets 43 inches of rain per year, including intense summer thunderstorms that can dump 2 to 3 inches in an hour. A threshold seal keeps most of that water outside, even on a sloped driveway. It will not stop serious flooding, but it handles normal rain and driveway runoff.
- Pests. Mice, snakes, roaches, and ants enter garages through the gap under the door. Charlotte's warm climate means pest pressure year-round. A threshold seal eliminates the gap those pests use to get in.
- Leaves and debris. Wind blows leaves, pine needles, and dirt under the door. This is especially common in Charlotte's heavily wooded neighborhoods. A threshold seal keeps it out.
- Dust and pollen. Charlotte's pollen season (March through May) is legendary. A sealed garage stays much cleaner than one with gaps under the door.
- Cold air and drafts. In winter, cold air seeps under the door and makes the garage uncomfortably cold. Combined with good weather stripping on the sides and top, a threshold seal creates a fully sealed perimeter that keeps the garage warmer.
Types of Threshold Seals
Rubber Threshold Seals
The most common type. Made from extruded rubber (usually EPDM or neoprene) with a flat base and a raised center ridge. Comes in various heights -- 1/2 inch, 3/4 inch, and 1 inch are most common. Choose the height based on the size of your gap.
Cost: $30 to $70 for a two-car door (16 feet).
Aluminum-and-Rubber Threshold Seals
These have an aluminum base channel that screws into the concrete floor, with a replaceable rubber seal that snaps into the channel. The aluminum provides a more permanent mount than adhesive alone, and you can replace the rubber insert when it wears out without removing the base.
Cost: $60 to $120 for a two-car door.
Heavy-Duty Commercial Threshold Seals
Thicker, taller rubber seals designed for commercial loading docks and storage buildings. Overkill for most residential garages, but useful if you have a serious water problem or a large gap to fill.
Cost: $80 to $150 for a two-car door.
How to Install a Threshold Seal (DIY)
This is a straightforward DIY project that takes about an hour.
Materials Needed
- Threshold seal (measure your door width before buying)
- Concrete adhesive (many threshold seals come with adhesive; if not, use polyurethane construction adhesive)
- Tape measure
- Utility knife
- Wire brush or broom
- Caulk gun (if using tube adhesive)
- Heavy objects for weight (bricks, paint cans, etc.)
Step 1: Clean the Floor
The adhesive will not stick to a dirty surface. Sweep and scrub the concrete where the seal will go. Remove any oil stains, paint, loose concrete, or debris. A wire brush works well for stubborn spots. Let the concrete dry completely.
Step 2: Position the Seal
Close the garage door. Slide the threshold seal under the door from inside the garage, centered under the door's bottom seal. The raised ridge of the threshold should align with the center of the bottom seal so the bottom seal compresses onto the ridge when the door is closed.
Step 3: Mark the Position
With the seal in the right position, mark the front and back edges on the concrete floor with chalk or a marker. Then move the seal out of the way.
Step 4: Apply Adhesive
Apply a generous zigzag bead of adhesive between your marks on the concrete. Work in sections if the door is wide -- the adhesive starts to skin over in 10 to 15 minutes, so do not spread it all at once if you are working alone.
Step 5: Press the Seal in Place
Lay the threshold seal onto the adhesive, aligning it with your marks. Press it firmly into the adhesive across the full length. Place heavy objects (bricks, paint cans, a board with weights) along the length of the seal to hold it down while the adhesive cures.
Step 6: Let It Cure
Do not drive over or open the door for at least 12 to 24 hours, depending on the adhesive. Read the adhesive instructions for specific cure time.
Step 7: Test
After the adhesive has cured, open and close the door. The bottom seal should compress firmly onto the threshold seal with no gaps. If there are gaps at the ends or along the length, the bottom seal may need adjustment or replacement.
Threshold Seal + Bottom Seal: The Double Barrier
The best results come from having both a good bottom seal on the door and a threshold seal on the floor. The bottom seal provides the first line of defense, and the threshold seal provides the second. Where the bottom seal has gaps (from floor irregularities or wear), the threshold seal picks up the slack.
If your bottom seal is in bad shape, replace it at the same time you install the threshold seal. A worn bottom seal on top of a new threshold seal is only marginally better than a worn bottom seal alone. The two work together -- invest in both.
Will a Threshold Seal Interfere with Normal Use?
The raised ridge is only 1/2 to 1 inch tall. You drive over it every time you enter and exit the garage. It is a small bump, similar to a speed bump but much smaller. Most people do not even notice it after the first week. The rubber is flexible enough that it does not damage tires or scrape low vehicles.
One thing to be aware of: if you sweep or hose out the garage, the threshold seal will trap water inside. You need to open the door to let the water drain out, or use a squeegee to push it over the seal. This is a minor inconvenience for most people.
How Long Do They Last?
A quality rubber threshold seal lasts 5 to 10 years in Charlotte's climate. UV exposure from sunlight hitting the seal when the door is open degrades the rubber over time. The adhesive can also fail, especially on oily concrete or if the floor gets very hot in summer. Check the seal once a year and re-glue any sections that have come loose.
Aluminum-base models last longer because the mechanical fasteners (screws) do not fail like adhesive. The rubber insert wears out at the same rate, but replacing just the insert is cheap and quick.
Want help sealing your garage against water and pests? Call to connect with a Charlotte garage door service company.