How to Bolt a Catio to a House: The Structural Guide for Portland Homes
A catio is only as secure as its connection point. While the enclosure itself must be predator-proof, the attachment to the main house is where most failures occur. In the wet climate of the Pacific Northwest, simply nailing a frame to siding is not a viable long-term solution. It leads to two primary failures:
Structural Detachment: The weight of the structure pulls nails loose over time.
Water Intrusion: Improper sealing allows rainwater to seep behind the siding, causing dry rot in the home's sheathing.
This guide outlines the professional standard for securely bolting a catio to a residential structure.
Step 1: Locate the Structural Framing
Never anchor a catio solely to siding. Cedar siding, HardiePlank, and vinyl are "cladding," not structure. They cannot support the dynamic load of a catio (wind + weight). To ensure stability, the fasteners must penetrate the solid wood framing beneath the siding.
Vertical Attachment: Locate the wall studs, which are typically spaced 16 inches on center.
Horizontal Attachment: Locate the "rim joist" (the solid band of wood between floors) or the top/bottom plates of the wall.
Verification: Use a deep-scan stud finder to mark the center of the stud. If the fastener misses the stud, the connection has zero structural value.
Step 2: Select the Correct Hardware
Nails should never be used for structural attachment. They have low "pull-out" resistance and will loosen as wood expands and contracts with the seasons.
The Required Fastener: Use Structural Wood Screws (commonly known as Lag Screws or LedgerLOKs).
Specifications: A minimum of 3 inches in length is usually required to pass through the catio frame (1.5"), the siding (0.5"), and penetrate at least 1" into the house stud.
Coating: In Oregon, fasteners must be hot-dip galvanized or ceramic-coated to prevent rust when in contact with treated lumber or cedar.
Step 3: Creating the "Water Gap" (Stand-Offs)
One of the most critical errors in catio construction is bolting the wood frame directly flush against the house siding. This traps moisture between the two pieces of wood, creating a breeding ground for rot and moss.
The Solution: Install "Stand-Offs" or Spacers.
Place a thick washer (nylon or stainless steel) or a specific "deck spacer" between the catio frame and the house wall at every bolt point.
The Benefit: This creates a 1/4-inch air gap. Rainwater can flow down the siding behind the catio without getting trapped, allowing the siding to dry out naturally between storms.
Step 4: The Flashing & Caulk Protocol
Once the structure is bolted, the penetration points must be sealed to maintain the home's weather envelope.
Pre-Drill & Fill: Before driving the bolt, pre-drill the pilot hole and inject a small amount of silicone sealant into the hole. As the bolt drives in, it forces the sealant into the wood fibers.
Over-Flashing: For catios with a solid roof, install metal "Z-flashing" where the catio roof meets the house wall. This metal strip should tuck under the house siding and over the catio roof, ensuring water is diverted away from the connection.
Summary
A properly installed catio should feel like a permanent extension of the home. If the structure wobbles when shaken, or if water pools against the house siding, the installation is defective.
