Accurately measuring your door for a lock depends completely on what kind of lock you'll be using. The
two most prominent types of lock are deadlocks and sashlocks, so we'll concentrate on these two for now.
The process for measuring a door for any other type of lock will probably be a variation on the process used
for these main two.
A simple deadlock (deadbolt) is an effective and easy way to boost the security of your house. Most
burglars make entry through door and windows, and the visible presence of a deadbolt can often be enough to
make an opportunistic thief reconsider targeting you. Installing deadlocks can also save you cash on your
home insurance; get in touch with your insurer to see if you can benefit.
If you've already purchased your deadlock and you're measuring your door to fit it, then the process is a
little easier, and we'll discuss this first. If you haven't yet bought your deadlock and you're measuring
your door to find which size is best for you, it's a bit more complicated, and we'll come back to it in a
moment.
First, if you've already bought your deadlock, then open the packaging in which it came. You'll find a
template - it's usually made of paper or card - which you can use to mark out where you want your bolt to go,
and make the correct measurements accordingly. With the template close by, and a tape measure and pencil in
hand, first judge whether you want your deadbolt above or below your current door hardware. It's most common
to position the deadlock lower on the door, but there's no real reason for this and the bolt can safely be
positioned anywhere you want.
There is one convention worth bearing in mind though, and it's this: place your deadlock at least twelve
inches away from the existing door hardware, whether you choose to install the bolt above or below it. This
is because it's best to spread the strength provided by locking mechanisms down the length of the door,
rather than concentrating it neatly in one area.
Once you've settled on a position for the deadbolt, tape the template in place, ensuring that it's square
and level with the door, and use your pencil to mark where the drill holes will go. Then repeat the process
on the other side of the door. Simple. Your door is now measured and ready to fit the deadbolt.
However, if you haven't yet bought your deadbolt, you probably won't have a template to use. Therefore,
to measure your door you need to improvise the measurements. First, measure the backset of your current door
hardware. The backset is the horizontal distance from the edge of a door to the centre of a lockset; thus,
the distance a lockset is 'set back' from the edge of a door is called its backset. It's usually 1 ¾ inches
or 2 ¼ inches (or 44mm and 57mm). Then, after settling on the location you'd like for your deadlock, measure
the backset from the edge of the door in that location and mark it with your pencil. Repeat the process on
the other side of the door. Now check whether your door will accept either the smaller or larger case lock,
67mm or 80mm, without interfering with any recessed panels, glass or embedded decoration.
Since a mortice sashlock is a little more complicated - but very similar to a deadlock - the measurements
you need are not so different. The first measurement is the 'stile' of the door. The stile is the
horizontal distance from the edge of the door to the edge of any paneling or glass your door might have. If
your door's surface is completely flat, without any panels, glass or embedded decoration, then you don't need
to measure this. If your door does have panels, glass or embedded decoration, then you need to measure the
distance between the edge of the door and the beginning of them. Obviously the stile measurement varies
between door designs, but it's usually around 90mm to 125mm.
You don't need to worry whether your door is left- or right-handed. The majority of locks are
reversible.
The stile will decide which size of lock you can use. Determine whether you can fit a 67mm deep or an 80mm
deep lock without interfering with any of the door features. Once you have determined this, look at which
backset will best suit your door, either the smaller 44/45mm or larger 57/60mm backset. Now consider how
wide the backplate of your lever handle set is or the diameter of the rose your lever is on and make sure
the position of the handle set on the door is acceptable. Check particularly that the backplate or rose will
not interfere with any panelling, door frames or, if the doors are double and rebated, that the handle plates
don't cover any of the rebate.
If your door has been pre-drilled for a mortice lock, then you will need to measure the backset, which in
this case would be the distance from the edge of the door to the centre of the pre-drilled hole. If there
are two holes drilled, one above the other, you'll need to know their distance from one another.
Most other types of locks will require similar - if not identical - measurements. If the lock you need to
measure your door for is mounted to the surface, then follow the procedure outlined above. We hope this
information helps you choose the right lock for you; if you have any further questions please contact us via
the details on our Contact Us page or
browse our resources for the information you need.