Bottom Seal / Astragal Replacement
Replacing the bottom weather seal (astragal) on sectional overhead doors
Warnings
Identify the correct seal profile before purchasing. The three common types (T-end, bead-end, and flat) are NOT interchangeable. Check the retainer channel on the bottom of the door to determine the correct type.
Work with the door in the closed position to measure accurately and to prevent the door from moving during the procedure.
Required PPE
- Safety glasses
- Leather gloves
Tools Required
- Replacement bottom seal (match retainer channel type — T-end, bead, or flat)
- Tape measure
- Utility knife
- Pliers
- Flat-head screwdriver
- Lubricant (dish soap or silicone spray for seal insertion)
Procedure — 5 Steps
Identify the seal type and measure
With the door closed, examine the retainer channel on the bottom section. Determine whether it uses a T-end, bead-end, or flat-bottom seal. Measure the door width to cut the new seal to length — add 2–3 inches for trimming.
Remove the old seal
Open the retainer channel at one end by removing the end cap or crimp. Pull the old seal out of the channel by sliding it sideways. If the seal is stuck, use pliers to grip and pull. Clean any debris from the retainer channel.
Lubricate and insert the new seal
Apply a thin coat of dish soap or silicone spray to the edges of the new seal to help it slide through the retainer channel. Feed the seal into the channel from one end and push or pull it through to the other side. Work slowly to avoid kinking.
Trim and secure
Once the seal is fully seated, trim any excess with a utility knife. Replace end caps or re-crimp the channel ends to prevent the seal from sliding out. Verify the seal contacts the floor evenly across the full width of the door.
Test the seal
Close the door and check for light gaps under the bottom edge. The seal should compress slightly against the floor, creating a weather-tight barrier. Open and close the door a few times to verify the seal does not catch or bunch up.
Training Videos
Disclaimer: These videos are produced by third-party YouTube channels and are not affiliated with Doorbot. Video content may not align exactly with the procedures above, may depict techniques that differ from DASMA or manufacturer recommendations, and may show tasks that are dangerous if performed without proper training and equipment. Always follow the written procedure, your company's safety policies, and applicable industry standards. Use these videos as supplementary reference only.
References & Standards
- DASMA — Automatic Garage Door Opener Safety & Maintenance Guide
- Door manufacturer bottom seal specification chart