Grade 2 minimum. Often the actual break-in entry point.
Garage-to-house
Grade 2. Treat as exterior — the garage is rarely secure.
Interior doors
Grade 3 fine. Office, gun-safe room, kids' rooms.
Quick Rule
Grade 1 front · Grade 2 secondary exterior · Grade 3 interior. "Smart" features don't change the mechanical strength — a Grade 3 smart lock is still a Grade 3 lock.
Door Frame Matters More Than the Lock
Reinforced strike plate with 3-inch screws into framing stud. Most forced entries split the frame, not the cylinder.
Connectivity tiers (2026)
Failure modes to plan for
Bluetooth only Best battery (1-2 yr). No remote unless bridge.
Wi-Fi direct Remote. Worst battery. Worst attack surface.
Z-Wave (S2) Security ecosystem. Needs hub.
Matter over Thread ★ Future-proof. Every platform.