Ortho Home Defense is designed to be sprayed in two main zones: along the exterior foundation of your house and in cracks and crevices indoors. Getting the placement right is what creates an effective barrier that stops insects before they settle in. Here’s exactly where to apply it, where to avoid it, and how often to reapply.
Outdoor Perimeter: The Most Important Zone
The exterior foundation is your primary target. Spray a continuous band along the base of your home where the foundation meets the ground, extending a few inches up the foundation wall and a few inches out onto the soil or concrete. This creates a chemical barrier that insects have to cross before reaching any entry point.
As you work your way around the house, pay extra attention to these spots:
- Door frames and thresholds, especially the garage door and any side or back entrances
- Window frames on the ground floor, including the sill and surrounding trim
- Where utility lines enter the house: pipes, cable lines, dryer vents, and outdoor faucet connections
- Expansion joints and weep holes in brick or siding
- Underneath decks and porches where they meet the foundation
The outdoor barrier breaks down faster than the indoor one due to rain, sun, and temperature swings. Ortho recommends reapplying outside every three months to keep the barrier effective.
Indoor Application: Cracks, Crevices, and Entry Points
Indoors, the product is meant for targeted application along cracks and crevices, not broad surface spraying. Focus on the places where insects enter and travel:
- Baseboards throughout ground-floor rooms, especially in kitchens and bathrooms
- Around interior door frames and window frames
- Under sinks where plumbing enters the wall
- Behind appliances like refrigerators, stoves, and washing machines
- Along the edges of closets and cabinets, particularly in the kitchen
- Where carpet meets the wall in basements or rooms with known pest activity
- Garage interiors along the floor-wall junction
On non-porous indoor surfaces like tile, sealed hardwood, and laminate, a single application provides up to 12 months of protection against ants, roaches, and spiders. Porous surfaces like unfinished concrete or bare wood absorb more product and may not last as long.
Where Not to Spray
Some areas are off-limits for safety and environmental reasons. Cover or remove all exposed food, including pet food and water bowls, before you spray. Don’t apply the product on kitchen countertops, cutting boards, or any surface where food is prepared. If any mist lands on food prep surfaces, wash them thoroughly with soap and water before using them again.
Outdoors, keep the spray away from storm drains, drainage ditches, gutters, and any area where runoff could reach bodies of water. The active ingredients are toxic to aquatic life. If you have an ornamental pond with fish, be careful to avoid overspray near it.
The product is also highly toxic to bees when they contact it directly or pick it up from treated surfaces. Avoid spraying on or near flowering plants, especially when pollinators are active.
How the Barrier Works
Ortho Home Defense contains two synthetic pyrethroids that work together. Both disrupt insect nervous systems on contact, causing paralysis and death. One provides fast knockdown while the other adds longer-lasting residual protection. Together they form an invisible residue on treated surfaces. Insects don’t need to eat the product. Simply walking across the treated band is enough to pick up a lethal dose.
This is why placement matters more than volume. A thin, even band in the right location outperforms heavy spraying in the wrong spots. You want insects to encounter the barrier before they reach living spaces, not after they’ve already settled in behind your walls.
Tips for a Better Application
Spray on a dry day when no rain is expected for at least 24 hours. Rain shortly after application washes the product away before it can bind to surfaces. If you’re using the Comfort Wand version, the built-in battery-powered sprayer delivers a consistent flow that makes it easier to lay down an even band without oversaturating any one spot.
Indoors, keep the area well ventilated while spraying and allow the product to dry completely before letting children or pets back into the room. Drying typically takes 30 minutes to a couple of hours depending on humidity and airflow. Once dry, the residue bonds to the surface and presents minimal exposure risk.
For the best year-round coverage, many people apply indoors once in early spring and maintain the outdoor perimeter on a quarterly schedule: spring, early summer, early fall, and optionally before winter if you’re in a mild climate where insects stay active. Mark your calendar so the outdoor barrier never fully lapses, since that three-month window is when gaps in protection start to appear.