Roof rat droppings on the garage floor, the seal still “looked fine.” Here is what we found.

The customer's call

“I found small dark droppings along the bottom of the garage door, inside the garage. About 30 of them. My wife is freaking out about the kids' bikes and the dog food. We just had the door installed seven years ago, the seal looks fine from outside, what is going on?”

This is the second-most-common call we get from Sandbridge oceanfront and Croatan: a perimeter that looks fine but is failing in three places at once. Salt air does not announce itself; it just eats your hardware while you are on the beach.

The pencil test from the driveway

Before dispatching, we asked the customer to do the pencil test on a video call: lay a pencil flat on the floor, close the door over it, look from outside. He saw daylight at both bottom corners and at about 4 feet in from the left jamb. That confirmed three things were happening at once:

• The bottom seal was no longer compressing against the floor at the corners.
• The retainer was probably bent or corroded on the left side (why a single-spot gap mid-door).
• The doorstop molding flap was likely failed on at least one jamb (rat had to climb in somewhere).

What we found on-site

Owner-tech David arrived at 11:40 AM. The first 10 minutes was the inspection.

1. Bottom seal: EPDM bulb, original 2018 install. Surface looked OK from outside. Pinch test showed it had lost roughly 60 percent of its compression set. UV and salt-air had baked the elasticity out. The corners had taken a permanent set, leaving roughly 5/16-inch gaps when the door closed. (House mouse: 1/4-inch. Norway rat: 1/2-inch. Young roof rat: in between.)
2. Aluminum retainer: the inside surface had white salt deposits and pitting. The left side was bent inward where a previous truck-loading incident had clipped it. Even a new seal would not have seated flat in that retainer.
3. Doorstop molding, left jamb: finger-jointed pine, painted twice over its life. Bottom 14 inches were spongy to thumb pressure. Paint blistered and peeling at the slab contact. Brown-rot fungi, classic in 70 percent humidity coastal climates.
4. Doorstop molding, right jamb: better but the vinyl flap had a 3-inch tear at about chest height. Roof rats climb, and we have found nests in Sandbridge garage rafters with entry traced to flap tears like this.
5. Header doorstop: intact, original PVC stop molding installed by the original builder. Surprisingly common; builders use PVC up top because that is what their lumber package called for, but pine on the jambs because the jambs use a different stock.
6. Rodent evidence on the inside panel: droppings along the bottom 6 inches, two small gnaw marks on the lower-corner door panel skin (not through), and a thin grease trail along the inside of the retainer track.

David's written quote on the tablet, line by line: full aluminum retainer replacement ($85), EPDM coastal-grade bulb seal ($249), stainless-mesh anti-rodent inner core ($60 for a 16-ft door), cellular PVC doorstop molding on both jambs ($289), fresh flexible vinyl flap caps included, and a 10-point post-install pencil test. $683 line total, billed at $549 after the bundle discount. Customer signed at 11:55 AM.

The install

Step 1, retainer (40 minutes)

We pulled the old retainer with a flat bar. Three of the original sheet-metal screws had corroded into the door panel and sheared off; we drilled them out with a left-hand bit so the new retainer would seat flat. The new aluminum retainer is the same Clopay profile but with a marine-grade anodize that resists the salt-pitting we just removed.

Step 2, EPDM seal + stainless mesh (15 minutes)

The seal is a P-bulb cross-section in coastal-grade EPDM. Inside the bulb cavity, before sliding, we threaded a stainless-steel mesh sleeve, what we call the “anti-rat core.” A rat that chews the EPDM hits stainless and gives up. We have not had a rodent break through one yet. Dish soap on the retainer slot, the seal slid through clean in one pull.

Step 3, doorstop molding (30 minutes)

We removed the pine doorstop on both jambs with a Bahco trim bar. The bottom 10 inches of the left jamb's pine had rotted into the joist behind it; we cleaned out the soft material, treated the wood substrate with a borate solution, and let it dry for 8 minutes while we measured the right jamb. New cellular PVC stop molding, pre-drilled at 6-inch intervals (PVC splits if you cold-nail it). Stainless trim screws, no galvanized in salt air. Fresh flexible vinyl flap, stapled with stainless 1/4-inch crowns.

Step 4, the post-install pencil test (5 minutes)

Pencil flat on the slab, door closed. From outside, we ran a flashlight along the bottom seal and both jamb seams. Zero daylight, zero gaps. Customer did the same test himself. We do not consider the job done until both of us see no light.

The numbers

• Aluminum retainer replacement, marine-grade anodize: $85
• Coastal-grade EPDM P-bulb seal, 16-ft: $249
• Stainless-mesh anti-rodent inner core, 16-ft: $60
• Cellular PVC doorstop molding, both jambs + header check: $289
• Bundle discount: −$134
• Total billed: $549
• Warranty: 5 years workmanship, parts as per manufacturer (Clopay retainer: 10-year limited).
• Time on site: 1 hour 30 minutes.

What we did differently than a big-box DIY approach

• We did not just slide a new seal into the old retainer. That is the most common DIY failure in coastal Hampton Roads. A pitted retainer will let a new seal walk back out within three months.
• We did not skip the doorstop molding. Replacing only the bottom seal would have left the left-jamb climb-path open. The rat would have been back within two weeks.
• We used stainless mesh, not just rubber. A standard EPDM bulb stops a mouse. It does not stop a hungry roof rat with time on its hands. Sandbridge has roof rats.
• We used cellular PVC, not pressure-treated pine. Pressure-treated pine still rots in 70 percent humidity, just slower than untreated. PVC does not rot. Period.
• We used stainless fasteners, not galvanized. Galvanized fasteners on the coast turn into a coffee filter in 4 years. The job we did today should last 15 years on the hardware.

Five months later

The customer texted David in November 2026: zero rat droppings since the install. He had also noticed the room over the garage felt warmer in October than it had the previous fall, and his September power bill was $23 lower than the same month last year. That is the energy math from the service page playing out in his real bill.

If your seal looks fine but you have evidence inside the garage

It is almost never just the seal. Run the pencil test, but also check the inside of the retainer for salt pitting, and squeeze the bottom 12 inches of your doorstop molding with your thumb. If anything feels spongy, it is rotted from the inside. We can usually quote the full perimeter rebuild over a phone photo before we dispatch.

Related

• Bottom Seal & Doorstop Molding Replacement service page
• Bottom seal replacement guide, 2026
• Salt-air corrosion guide
• Norfolk Ocean View salt-air cable failure case study