IN-FOCUS: DIN Locks

If you’ve worked with commercial doors or specified hardware for large building projects, chances are you’ve come across DIN mortice locks. But what exactly makes a lock “DIN-compliant”? And why are they the go-to choice for so many contractors, locksmiths, and building managers?

In this post, we’ll break down what DIN mortice locks are, how they differ from traditional UK lock cases, and why they’ve become a standard in commercial and modular construction.

A DIN mortice lock is a type of lock that conforms to DIN standards - a set of German engineering specifications established by the Deutsches Institut für Normung (DIN). These standards ensure uniformity in size and fitting, making DIN mortice locks compatible across a wide range of doors and hardware.

Here’s a breakdown of what makes a DIN mortice lock distinctive:

Key Features:

• Standardised dimensions: The most common is DIN 18251, which specifies:
            o   Backset (distance from the edge of the door to the keyhole): 55mm or 60mm
            o   Case Height: 165mm
            o   Case Depth: 85mm or 90mm
            o   Centres (Distance from spindle to centre of keyhole): 72mm
            o   Fixing Centres: 38mm
            o   Faceplate height: 235mm
            o   Faceplate width: 20mm
• Case height/width, spindle position, and bolt placement are all consistent.
• Reversible latch: Many DIN locks are handed, but can be easily reversed for left or right-hand doors
• Through-fixing holes: Aligned to DIN handle sets and escutcheons
• Euro profile cylinder compatibility: Most are made to accept a standard Euro cylinder
• Common in commercial & public buildings: Especially across Europe

These locks are commonly found in:

• Office buildings and corporate fit-outs
• Hotels and hospitality venues
• Apartment blocks and housing associations
• Public buildings like schools and hospitals
• Modular and prefabricated construction
• Anywhere modularity, fire safety, or large-scale repeat installations are required.

Ease of replacement: If you’re replacing an old DIN lock, you can swap in a new one with minimal fuss

Consistent fitting: Ideal for modular or large-scale builds (like hotels, offices, apartments)

Quality & compliance: DIN-certified locks are typically built to high safety and durability standards.

DIN stands for Deutsches Institut für Normung, or the German Institute for Standardization. It's Germany’s official standards body and part of the ISO (International Organization for Standardization).

DIN standards cover everything from screws to software, but in the context of locks and door hardware, they ensure interchangeability, quality, safety, and compatibility.

DIN standards are especially influential in commercial and residential building hardware. Here are the most relevant ones:

• Defines dimensions for lock cases, follower positions, fixing holes, latch and bolt placement.
• Ensures all DIN mortice locks (regardless of brand) will fit DIN-standard door prep.
• Comes in different classes (1–4), based on durability and application (e.g., internal vs. external doors).

• Sets basic requirements for the design and function of lock cases, including material quality and fire safety.

• Specifies measurements and fixing methods for lever handles, roses, escutcheons to match DIN locks.

• Focuses on locks for fire and smoke-resistant doors, including stress tolerances and heat resistance.

• Sets security grades (ES0 to ES3) for protective fittings, such as anti-drill and anti-pull features on escutcheons.

• Standard door prep: Builders can rout a DIN-standard cutout, and installers can fit any compliant lock - saves time and money.
• Cross-brand compatibility: You can mix a lock from one manufacturer with handles or cylinders from another.
• Global exports: DIN-compliant products are easier to sell across the EU and internationally.