Understanding latches
An essential part in making sure a door shuts properly, door latches need to be robust and long-lasting, due to the nature of their usage and the frequent everyday usage they require. We will cover some essential knowledge on latches, which is fundamental to understanding their functionality in a lock.
What are the different types of latches?
There are 2 types of latches – latch and bolt. A latch automatically springs into the strike plate to hold the door into the closed position until the handle is operated. Contrastingly, a bolt can be withdrawn to allow the door to swing free, then manually thrown to secure the door.
How to select the right latch?
Selecting a latch that is suitable for your application may be challenging, therefore it is necessary to ask the right questions:
- What function do you require – latch or bolt?
- What security level is required?
- How far back from the door edge will the door handles be positioned? (This will determine the required backset)
- What handles are best suited?
- Is it a fire door?
Depending on the furniture you are fitting the latch on (i.e.door handles, knobs, locks) you must consider the length of the casing, common for that purpose.
Terminology
When searching for the correct latch, it is natural to familiarise yourself with the terminology used in order to differentiate between the separate elements of the latch.
Dimensions
You will find a tubular mortice latch on most door handles. While they come in a few different sizes, the most popular sizes in the UK are 76mm and 63mm. Here is a simple diagram of latch dimensions, to help you avoid confusion and identify the product you need quicker.
- Bolt projection/ throw
- Backset
- Case size
- Height
- Width
Is it for a fire door?
When choosing a latch for any door, you want to be sure you get the best-suited one, however, that is essentially important when you are making a decision on a fire door. Fire resistance within door assemblies serves 3 main purposes: to restrict the initial development of the fire, to restrict the spread of the fire and to protect designated escape routes. Whenever fitting a latch to a fire door, it must be fire door tested and fitted with an intumescent kit to avoid any possible legal liabilities.
When selecting a latch for a fire door, keep a look out for certification FD30 (provides 30 minutes of fire door resistance) and FD60 (provides 60 minutes of fire door resistance).
What standards are latches graded against?
There are several standards latches and locking systems can be graded against. As mentioned above, if you are looking at installing a latch on a fire door the most important thing to look out for is fire tested latches. EN 12209 classifies mechanically operated locks, latches and locking plates using an 11-digit coding system. Each digit refers to a particular feature of the product measured against the standard’s performance requirements.
Additionally, due to Brexit, after 1st January 2023, all products require a UKCA grading as well, for all goods that are imported, manufactured and intended for the UK market.
