Home Sealing for Scorpions: The Entry Gaps Most Homeowners Miss

The entry gaps most Arizona homeowners miss when sealing for scorpions are the door between the garage and the house, the hole where the AC line set enters the wall, the weep holes at the base of the stucco, and the lifted corners of the garage door seal. Front door sweeps get installed and those four stay open, and a bark scorpion needs a gap only as thick as a credit card.

How Small a Gap a Scorpion Needs

The Arizona bark scorpion is a flat animal. An adult is 2 to 3 inches long but only a few millimeters thick, and it can pass through a gap of about 1/16 of an inch, roughly the thickness of a credit card. It also climbs any rough surface, so a gap at the roof line or at a second story window is as usable as one at the threshold. Sealing for scorpions is not about closing the obvious openings. It is about closing every opening that thin, which is a longer list than most people expect.

Sealing is also the part of a scorpion program that keeps working after the chemical is gone. A residual on the block wall breaks down in a summer. A weep hole screen lasts for years. The two are done together, treatment first and sealing after, so nothing is sealed inside.

The Gaps People Usually Get Right

The front door threshold and sweep. The patio slider, at least the part they can see. Window screens with visible holes. Those are worth doing and they are where most homeowners stop.

The Gaps They Miss

The garage to house door. This is the biggest one. It feels like an interior door, so it never gets a sweep, but the garage is outdoors as far as a scorpion is concerned. The garage door seal shrinks in the heat and lifts at the corners, scorpions walk in under it at night, and the garage to house door with a half inch gap under it is a straight path to the kitchen. A brush sweep on that door and a new bottom seal on the garage door close the most used scorpion entry in the Valley.

The AC line set entry. On nearly every Arizona home the refrigerant lines from the outdoor condenser go through the wall via a hole bigger than the lines, packed with expanding foam that crumbles within a few summers. Behind it is the wall cavity and, often, the attic. Copper mesh packed around the lines and a UV rated sealant over it closes it for good.

Weep holes. Stucco over foam has small openings every few feet along the base of the wall to let moisture out. They are the right size for a scorpion and they lead into the cavity behind the stucco. They must not be caulked, because that traps water in the wall. Stainless or aluminum weep hole screens keep them draining and keep scorpions out, and there are usually 30 to 60 of them on a single story home.

Plumbing penetrations. Under every sink and tub and behind the washer and the water heater, the drain and supply lines come up through the slab or the wall through an oversized hole. Scorpions come through the wall cavity and out of these into the cabinet, which is why they show up in bathrooms. Copper mesh and sealant at each one.

Dryer and bath vents, and attic vents. Flappers that do not close and screens that have rusted out. Hardware cloth over the attic and gable vents, and a working damper on the dryer vent.

The gap where tile roof meets fascia. An open channel along every eave on a tile roof unless it was bird stopped. Scorpions climb the stucco and walk in here, and so do roof rats.

Sliding door tracks and the corners of door frames. The slider seals in the middle and gaps at the ends of the track. The corners of an exterior door frame often have a gap where the weatherstrip does not reach.

Electrical and cable entries, hose bibs and the gas line. Each is another oversized hole through the wall.

Pool equipment conduit and the pipe penetrations at the pad, which lead into the wall or under the slab.

How to Survey Your Own House

Do it twice, once at ground level and once looking up. Go around the outside with a flashlight and a mirror on a stick and look at every place something passes through the wall. Then do it from inside: open every sink cabinet, pull the washer out, look behind the water heater, and check the garage to house door with the garage lights off and the house lights on, looking for light under and around it. A light test at night from outside works for every exterior door. Write down each gap and its size, because the material depends on it.

What to Seal It With

Copper mesh for penetrations, packed tight and covered with a sealant rated for sun. Weep hole screens, never caulk, for weep holes. Hardware cloth for vents and eave gaps. Brush or rubber sweeps for doors, and a new bottom seal for the garage door. Expanding foam only where it will be covered, because sun breaks it down and rats chew it. Sealing does not need a pesticide license, but on a scorpion program it is done by the technician who treated the house and knows where the activity was.

Bark scorpion stings are the point of all this. They peak in monsoon season when scorpions are displaced indoors, and the victims are barefoot people at night, children in beds and dogs. A sealed house is the difference between scorpions on the block wall and scorpions in the bathtub.

FAQ

If I seal the house do I still need treatment? Yes, for the yard and the wall. Sealing keeps them out of the living space; treatment brings the population down so they stop testing the seals. Treatment first, then sealing.

Can I caulk the weep holes? No. That traps moisture behind the stucco and damages the wall. Use screens.

How long does sealing last? Screens, copper mesh and hardware cloth last years in Arizona sun. Door sweeps and garage seals wear and get checked at service visits.

If scorpions are still showing up inside after a good yard treatment, a home sealing and pest exclusion survey from Green Ninja Pest Control finds the four gaps that are usually open and closes all of them in one visit.