**Safety verdict: DIY WITH CAUTION** # How to fix garage door gaps on sides? Last reviewed: 2026-08-20 Reviewed by [The GarageDude Editorial Desk](https://garagedude.shop/authors/editorial-team/) DIY with caution Safety verdict: DIY with caution Most garage draughts come from the bottom seal and the side stop moulding rather than through the door itself. Both are genuinely DIY parts. Replace the bottom seal to match the retainer profile on your door, and check that the floor itself is level enough for the seal to meet it. Common leak point Bottom seal Match Retainer profile Uneven gap means Balance or track Verdict Safe to DIY Always follow your specific model’s manual. Procedures vary by manufacturer and model year. ## The short version - The bottom seal slides into a retainer; match the profile (T-style, bead, U-shape) before buying. - Side and top stop moulding carries its own flexible flap and is usually nailed to the jamb. - A threshold seal bonded to the floor helps where the slab has settled or slopes inward. - Rodents and insects enter at the same gaps, so sealing is a pest fix as much as a draught fix. - A gap that is much larger on one side is usually a balance or track problem, not a seal problem. ## How does a garage door actually hold its own weight? A garage door is not lifted by the opener — it is lifted by the spring, and the opener only guides it. A residential door weighs 85 to 400 pounds, and the counterbalance holds that weight so the motor only has to overcome friction. That is why springs and cables are professional work while sensors and remotes are not: one group holds the stored energy and the other does not. [Garage door safety](https://garagedude.shop/safety/) covers the balance test and what an unbalanced door does to an opener. ## What does federal law actually require here? Every residential opener manufactured since January 1, 1993 for US sale must meet [16 CFR 1211](https://www.ecfr.gov/current/title-16/chapter-II/subchapter-B/part-1211): a closing door must begin reversing within 2 seconds of hitting an obstruction, a second independent protection system must exist, and the manual release must be red. §1211.16(b) also fixes the exact words your manual carries — among them “Have a qualified service person make repairs to cables, spring assemblies and other hardware.” — which is why this page's verdict is not our opinion. [What UL 325 and 16 CFR 1211 require](https://garagedude.shop/safety/ul-325/) covers the full standard. ## What is the one-minute test everyone should be doing? The reversal test, monthly, with a 2x4 laid flat in the door's path: it must reverse on contact. If it does not, stop using the opener until it is adjusted, repaired or replaced. It matters because this system fails silently — a door whose reversal has stopped working looks and sounds exactly like one that still does. CPSC recommends inspecting the door and opener every 30 days. [Children, pets and the garage door](https://garagedude.shop/safety/child-safety/) covers why the standard exists. ## At what point should I stop and call someone? - The door is very heavy by hand with the opener disconnected. The counterbalance has failed. - You can see a gap in the spring coil , or a cable that is frayed, slack, or off its drum. - The door sits crooked , higher on one side, or has come off its track. It is still under full tension. - The door does not reverse on the board test. The entrapment protection is not working. None of those is calling too early, and the rule worth teaching at home comes from that same federal text: “NEVER GO UNDER A STOPPED PARTIALLY OPEN DOOR.” ## Questions that come up next ### Does a door that reverses mean something is broken? No — the opposite. A door that stops and goes back up when it touches something is the entrapment protection doing exactly what 16 CFR 1211 requires. The fault worth investigating is a door that fails to reverse. ### Can I disable the photo eyes to get the door closed? No. That removes the external entrapment protection required since 1993, and it is the protection that exists because of the CPSC child fatality record. If a sensor is genuinely faulty, replace it — it is among the cheapest parts on the door. ### Is it safe to use the emergency release with the door open? The federally required manual text says to use it only when the door is closed wherever possible, because weak or broken springs may allow the door to fall rapidly. A great deal of DIY content advises the opposite. ### Should I replace one spring or both? If the door has two, quote both. The second is the same age and has taken the same number of cycles, so it is next. This is one of the few upsells in the trade that is genuinely honest. ## How to do it Before you start: Disconnect the opener and keep the door closed while you measure. A gap that is much larger on one side is a balance or track problem, not a seal problem. What you need: Replacement bottom seal matching your retainer profile, A tape measure, Soapy water as a lubricant for threading the seal - Identify the retainer profile on the bottom of your door before buying anything — T-style, bead, and U-shape retainers are not interchangeable. - Measure the door width and buy the seal slightly long; you trim it to fit at the end. - Close the door, pull the red release, and raise the door about waist height so you can reach the bottom edge comfortably. - Slide the old seal out of one end of the retainer. Years of grit make this harder than it sounds; soapy water helps. - Thread the new seal in from the same end, keeping it square so it does not twist inside the channel. - Lower the door and check the seal meets the floor along its whole length. An even gap means the seal; an uneven one means the door. - Trim the excess flush and re-engage the opener. ## Common mistakes - Buying a seal without checking the retainer profile. A T-style seal will not stay in a bead retainer, and it will fall out on the first cold morning. - Sealing a gap that is caused by a crooked door. You are treating the symptom. An uneven gap usually means the door is out of balance. - Nailing stop moulding tight against the door. It should just touch. Pressed hard, it drags the door and wears the seal in a season. ## Also asked as ### One or both? On a two-spring door the pair is wound to the same cycle life and has done the same work, so when one goes the other is at the end of its life whether or not it has broken yet. Replacing only the broken one buys a second call-out at full price, and leaves a door balanced by one new spring and one worn one. ## Related questions - [Garage door safety](https://garagedude.shop/safety/) - [Weather sealing & drafts](https://garagedude.shop/questions/weather-sealing-and-drafts/) - [How to close gap between garage door and floor?](https://garagedude.shop/questions/weather-sealing-and-drafts/how-to-close-gap-between-garage-door-and-floor/) - [How to install oversized rubber seal on amarr garage door?](https://garagedude.shop/questions/weather-sealing-and-drafts/how-to-install-oversized-rubber-seal-on-amarr-garage-door/) - [Are all garage door bottom seals the same?](https://garagedude.shop/questions/weather-sealing-and-drafts/are-all-garage-door-bottom-seals-the-same/) - [How much to repair garage door to keep out mice?](https://garagedude.shop/questions/weather-sealing-and-drafts/how-much-to-repair-garage-door-to-keep-out-mice/) - [Can a handyman replace the seal around the garage door?](https://garagedude.shop/questions/weather-sealing-and-drafts/can-a-handyman-replace-the-seal-around-the-garage-door/) - [Can snakes sneak under garage doors when closed?](https://garagedude.shop/questions/weather-sealing-and-drafts/can-snakes-sneak-under-garage-doors-when-closed/) ## Sources - [Door and Access Systems Manufacturers Association — technical data sheets](https://www.dasma.com/technical-data-sheets/) — DASMA Tier 2 - [Publication 523 — Non-Reversing Automatic Garage Door Openers Are a Hazard](https://www.cpsc.gov/s3fs-public/garage.pdf) — US Consumer Product Safety Commission Tier 1 accessed 2026-08-17 - [International Energy Conservation Code](https://codes.iccsafe.org/) — International Code Council Tier 1