Smart locks for an HDB gate and main door: how to pick a pair that work together

Most smart-lock articles are written for houses with one front door. In Singapore, HDB flats and many condos have a metal gate and a main door, and the gate is the one you unlock while holding groceries. If only the door is smart, you still fish for keys every day.

Gate lock and door lock are different products

A gate is a metal frame with a thin profile and no door leaf to bore into. It needs a rim lock that mounts on the surface, with a latch that catches the gate frame, and it must open from both inside and outside because you lock it from the corridor when you leave and from the hallway at night. The Aqara Smart Gate Lock U500 is built for exactly this, with fingerprint and key on both sides and a doorbell button on the outside.

A main door has a thick timber leaf and usually an existing mortise cutout. Here you choose between a mortise lock, which replaces the whole body and gives you a handle plus deadbolt, and a deadbolt-only lock that keeps your existing handle. Face-recognition locks and camera-peephole locks are mortise designs.

The methods, ranked by daily usefulness

1. Fingerprint. Under a second, works with wet hands on good sensors, and the one everyone in the family uses. Enrol two fingers per person.
2. Phone or watch tap. With Apple Home Key or an NFC card, you tap the lock. Useful when hands are full of a child.
3. Face recognition. Hands-free. Best on the main door, which faces you squarely; less reliable on a gate at an angle.
4. PIN. For helpers, visitors and the day your finger is cut. Set time-limited codes and delete them from your phone.
5. App unlock from anywhere. For the delivery that arrives while you are at work. Requires the hub to be online.
6. Mechanical key. Never remove it. It is the fallback when everything else fails.

Making one touch open both

This is the part that needs both locks in the same system. When both locks are Matter devices, or bridged through the same Aqara hub, an automation can say: when the gate unlocks with a registered fingerprint, unlock the door and turn on the hallway light. On the way out, locking the door from outside can turn off every light and the air-con and set the home to away.

In practice we run this logic in Home Assistant, with the locks also visible in Apple Home or Google Home so the family has a simple app. Some clients prefer the door to stay locked until they reach it; that is a one-line change.

What to check before you order

• Gate profile. Send the installer a photo of the gate latch area with a ruler. Some decorative gates need a spacer plate.
• Door thickness and cutout. Measure the leaf (most are 40 to 50 mm) and photograph the edge of the door with the existing lock removed if possible.
• Opening direction. Left or right hand, inward or outward.
• Fire rating. Some condo main doors are fire-rated; the lock must not compromise it.
• Region. Buy the international or Singapore version. Locks are the worst place to save money on a China set: voice prompts, app enrolment, firmware and warranty all differ.
• Power. Rechargeable lithium packs last longer; AA batteries are easier to swap. Both are fine. Check there is an emergency power port on the outside.

The pair we install most

Aqara Smart Gate Lock U500 on the gate, and one of our own Matter-over-Thread door locks on the main door: Guard Face for fingerprint, PIN, NFC and face on a 6068 mortise body, or Guard Pro when the client wants a camera peephole and video intercom in the door itself. Both join the same Matter home, so the scenes above work on day one. We fit the locks during the carpentry-and-doors stage of the renovation, when the new main door is hung, so the cutout is exact rather than adapted.

Questions people ask

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