Mortise Locks UK: Sizes, Measuring and Smart Lock Compatibility
Mortise locks are common across UK timber doors, commercial doors, hotel rooms and some higher-security residential setups. If you are upgrading to a smart lock, understanding your mortise size, backset, centres and door preparation is one of the most important steps before ordering.
Quick Answer
A mortise lock sits inside a pocket cut into the edge of the door. To check smart lock compatibility, you need to measure the backset, centres, case size, forend plate and door thickness. Some doors suit a mortise-compatible smart lock, while others may be better suited to a single-latch, tubular or surface-mounted retrofit smart lock. If you are unsure, send ArdanShield clear photos of your door edge, handle area and current lock plate before ordering.
What is a Mortise Lock?
A mortise lock is fitted inside a cut-out pocket in the edge of the door. This pocket is known as the mortise. Unlike a simple tubular latch, a mortise lock case can combine several functions in one unit, such as a latch, deadbolt, spindle, cylinder and handle operation depending on the design.
Mortise locks are commonly found on UK timber doors, some external residential doors, internal doors, commercial doors and hotel room doors. They are often chosen because they provide a more substantial lock body and a cleaner, integrated finish.
Why this matters for smart locks
Smart locks are not universal. A smart lock designed for a single-latch tubular door may not fit a mortise door without major changes, and a mortise-style smart lock must match the door preparation closely. Measuring first prevents ordering the wrong type of lock.
Mortise vs Tubular and Surface Locks
Before choosing a smart lock, it helps to know which lock style is already fitted to your door. The terms can sound similar, but the fitting requirements are very different.
Mortise lock
A larger lock case sits inside the edge of the door. It may combine latch and deadbolt functions and usually needs accurate measuring before replacement.
Tubular or single latch
A simpler latch mechanism fitted through a bore hole. Many retrofit smart locks are designed around this style of door preparation.
Surface or nightlatch
A rim-mounted lock body sits on the inside face of the door, often with an external cylinder. This is sometimes called a Yale-style setup.
Common UK Mortise Sizes and Codes
Mortise lock codes are often used to describe key dimensions, but exact specifications can vary by manufacturer. Always measure the existing lock rather than relying on the stamped code alone.
| Code or family | Typical use | What to check |
|---|---|---|
| 2885 | Compact internal or external timber door setups. | Check backset, centres, case depth and available door thickness carefully. |
| 3085 / 3585 / 4085 / 4585 / 5085 / 6085 / 7085 | Residential and property doors with different backset requirements. | The first numbers often relate to backset family, while 85 commonly indicates the centres family. Confirm actual dimensions before ordering. |
| 3092 / 3592 / 4092 / 4592 | Doors using a 92 mm centres family or deeper handle/cylinder layout. | Often relevant where handle-to-cylinder spacing differs from 85 mm families. |
| 5050 / 6068 | Popular mortise families often seen with selected smart lock integrations. | Check case depth, forend size, spindle position, cylinder position and door thickness. |
| Sliding mortise options | Sliding patio, balcony or specialist sliding doors. | Use a sliding-specific mortise with the correct hook or bolt profile. Standard swing-door locks are not usually suitable. |
Important note on lock codes
A code is useful, but it is not enough on its own. Two locks can look similar but differ in case depth, forend plate, spindle position, handedness, cylinder type or latch direction. Photos and measurements are always the safest route.
How to Measure Your Mortise Lock
You do not need to be a locksmith to gather the basic measurements, but accuracy matters. Use a tape measure and take clear photos before removing anything from the door.
- Backset: Measure from the edge of the door to the centre of the spindle or key/cylinder. This determines where the handle or cylinder sits on the door face.
- Centres or PZ: Measure from the centre of the handle spindle to the centre of the cylinder or keyhole. Common families include 85 mm and 92 mm, but always confirm your own door.
- Case depth: Measure the full depth of the lock case inside the door pocket.
- Case height: Measure the height of the lock body, not just the visible plate.
- Forend or faceplate: Measure the visible plate on the door edge, including length and width.
- Door thickness: Measure the thickness of the door itself, as smart locks often have minimum and maximum thickness ranges.
- Handing and latch direction: Check whether the door is left-handed or right-handed and whether the latch needs to be reversible.
Best photos to send
For a quick compatibility check, send a photo of the door edge showing the full lock plate, a photo of the handle area from inside and outside, and a photo showing the door open so the latch, bolt and frame keep can be seen clearly.
Not Sure What Size Your Door Needs?
Send ArdanShield clear photos of your door edge, handle area and current lock body. We can help you work out whether you need a mortise-compatible smart lock, a tubular retrofit lock, a surface-style option or a different approach.
Ask for Compatibility AdviceSmart Lock Compatibility: What to Check Before Ordering
Mortise doors can be excellent candidates for smart lock upgrades, but only when the smart lock and door preparation match. The wrong lock can lead to poor alignment, installation difficulty or a lock that simply does not fit.
Door preparation
Check whether the door is already prepared for a mortise case, tubular latch, multipoint lock or surface-mounted nightlatch.
Lock body dimensions
Backset, centres, case depth, case height and forend size must be suitable for the chosen smart lock.
Door thickness
Smart lock front and rear panels need to clamp through the door correctly, so thickness range matters.
Power and batteries
Check where the batteries sit and whether there is enough space around the handle, spindle and cylinder area.
App ecosystem
Choose TTLock for focused smart lock management or Tuya/Smart Life where broader smart home device compatibility is more important.
Gateway and signal
For remote features, confirm whether the lock has built-in WiFi or needs a compatible gateway. Good 2.4 GHz WiFi coverage near the door is important.
TTLock or Tuya?
TTLock is often chosen for focused smart lock control, access codes, app management and gateway-supported remote features where compatible. Tuya or Smart Life may suit users who want their lock to sit within a wider smart home ecosystem alongside other compatible devices such as lights, sensors or cameras.
Which ArdanShield Smart Lock Fits This?
The best ArdanShield lock depends on your door type. A single-latch timber door, a mortise-style door, a uPVC door and a hotel room door may all need different hardware.
Popular Single-Latch and Retrofit Smart Locks
If your door uses a standard single-latch or tubular preparation, these options may be suitable depending on measurements and door setup.
FusionGuard™Fingerprint, PIN and app control for compatible single-latch door setups.
FortiLock™Biometric, RFID and app-based access for compatible smart lock installations.
SecureWave™A retrofit-style option for suitable Yale-style or surface-lock door setups.
Mortise, Multipoint and Biometric Options
If your door uses a mortise, multipoint or more substantial handle set, these options may be more relevant where compatible.
ApexLock™ WiFi Smart LockTTLock system with an elegant handle design for compatible door setups.
SwiftLock™ WiFi Smart LockTuya-based option for compatible uPVC and composite-style doors.
VisionLock™ Facial Recognition Smart LockPremium facial recognition option for compatible mortise-style installations.
Browse by collection
Explore all smart locks, compare WiFi smart locks, view facial recognition smart locks, or choose compatible smart lock accessories.
Fitting Out Hotels or Multi-Property Doors?
Mortise locks are especially important in hotels, serviced accommodation, HMOs and multi-room properties because door consistency matters. A small difference in case size, cylinder position or handle centres can affect the whole project.
For hotel and multi-room projects
If you are fitting multiple doors, confirm the existing lock case, cylinder type, door thickness, handle centres and required guest access workflow before buying. For reception-managed or multi-room setups, view the ArdanShield Hotel Series or contact ArdanShield for a project specification check.
Explore Hotel SeriesContact ArdanShieldCare and Maintenance
Once fitted, a mortise smart lock should be treated as both a mechanical lock and an electronic device. Good maintenance helps keep the mechanism smooth and the smart features reliable.
- Keep the latch and bolt aligned: If the door drops or rubs, the lock may struggle to engage properly.
- Use suitable lock lubricant: Use an appropriate lock lubricant on moving parts. Avoid heavy oils that can attract dust and debris.
- Check batteries regularly: Replace batteries together and follow the product guidance. In colder areas, suitable battery choice can help reliability.
- Keep apps and firmware updated: Where supported, updates can improve reliability, security and device performance.
- Protect from unnecessary exposure: Check weather suitability before using any smart lock on highly exposed external doors.
Common Mistakes to Avoid
Measuring only the faceplate
The visible plate is not enough. You also need the case depth, backset, centres and door thickness.
Assuming all 85 mm locks match
Centres are only one measurement. Case size, forend plate, spindle position and latch direction can still differ.
Ignoring multipoint mechanisms
uPVC and composite doors often use multipoint systems, which need careful compatibility checks.
Forgetting WiFi coverage
Remote features depend on the lock, gateway and signal quality. A weak signal near the door can cause problems.
Choosing the wrong ecosystem
TTLock and Tuya can suit different use cases. Check the product platform before buying gateways or accessories.
Buying before asking
If you are unsure, photos and measurements can save time, money and installation frustration.
Related Reading
TTLock Troubleshooting Guide
A practical guide for common TTLock setup and troubleshooting questions.
Read the guideTTLock and Tuya Gateways
Understand how gateways support compatible remote access and smart lock integration.
Read the guideFusionGuard™ Product Guide
Learn more about FusionGuard™ and suitable single-latch smart lock setups.
Read the guideFortiLock™ Product Guide
A useful guide for homeowners and property managers considering FortiLock™.
Read the guideSmart Lock Accessories
Browse compatible gateways and accessories for supported smart lock setups.
View accessoriesMortise Lock and Smart Lock Compatibility FAQs
Can I add a smart lock to any mortise door?
Not always. It depends on the mortise case, backset, centres, handle layout, cylinder position, door thickness and available space. Some doors may suit a mortise-compatible smart lock, while others may suit a tubular or surface-style retrofit lock better.
What are backset and centres?
Backset is the distance from the edge of the door to the centre of the spindle or cylinder. Centres, sometimes called PZ, is the distance from the centre of the handle spindle to the centre of the cylinder or keyhole.
What does 85 mm or 92 mm mean on a mortise lock?
These usually refer to the centres family, meaning the distance between the handle spindle and cylinder or keyhole. You still need to check the full lock case dimensions before ordering.
Should I choose TTLock or Tuya?
TTLock is usually best suited to focused smart lock management, while Tuya or Smart Life may be better if you want wider smart home automation with compatible devices. The right choice depends on the lock model and the system you want to build.
Do I need a gateway for a smart mortise lock?
It depends on the lock. Some features may work locally, while remote unlocking, live updates or wider access management may need built-in WiFi or a compatible gateway such as a TTLock Smart Gateway or Tuya Smart Gateway.
How do I know which smart lock fits my door?
Measure the backset, centres, case size, forend plate and door thickness. If you are unsure, send ArdanShield clear photos of the door edge, lock plate, handle area and frame keep before ordering.
Need Help Checking Your Mortise Lock Size?
Send ArdanShield your door photos, measurements and any codes stamped on the lock plate. We’ll help you understand whether your door needs a mortise-compatible smart lock, single-latch smart lock, retrofit option or hotel-style access solution.
Get Compatibility HelpBrowse Smart Locks