Notice daylight, a draft, or the odd bug and puddle sneaking in under the door? A gap at the bottom is common and usually a straightforward fix — but the right fix depends on why the gap is there. Here is how to sort it out.
1. A worn or flattened bottom seal (most common)
The rubber or vinyl strip along the bottom edge — the astragal — compresses to fill the gap between the door and the floor. Over the years it hardens, cracks, tears, or flattens out, and once it does, it stops sealing and daylight shows through. In our climate, UV and heat age it faster. Replacing the bottom seal is the usual answer and an affordable fix — see the weather seal page.
2. An uneven or sloped floor
Concrete is rarely perfectly level, and garage slabs are often poured to slope toward the door for drainage. If the floor dips in the middle or slopes unevenly, a standard bottom seal cannot bridge the low spots, so you get a gap even with a good seal. The fix here is a threshold seal — a rubber strip bonded to the floor that the door closes against — sometimes paired with a taller bottom seal. Great for keeping out driving rain and leaves.
3. A warped or bent bottom section
If the bottom panel itself is bowed, bent from a bump, or (on wood) warped, the door edge is no longer straight and a seal cannot fully close the gap. Depending on the damage, this may mean straightening or replacing the bottom panel. A quick look tells you whether the door edge is straight or not.
4. Worn or loose side and top seals
Gaps are not only at the bottom — the stop molding with weatherstripping along the sides and top seals those edges, and it dries and pulls away over time too. If you are chasing drafts, check all four edges while you are at it.
Why closing it matters here
A sealed door keeps out the Texas dust, summer heat, driving rain, and the mice, roaches, and wasps that love a warm garage — and it helps keep the space (and any adjoining rooms) more comfortable, part of the same payoff as an insulated door. Most gaps come down to a fresh seal, sometimes plus a threshold. Not sure which you need? We will take a look and match the right seal to your floor and door.
Key takeaways
- Most common cause: a worn or flattened bottom seal — an affordable fix.
- An uneven or sloped floor calls for a threshold seal bonded to the concrete.
- A bent or warped bottom panel may need straightening or replacement.
- Check the side and top seals too if you are chasing drafts.
- A sealed door keeps out heat, rain, dust, and pests.