It's the first question almost everyone asks, and it's the right one. A smart lock is only as good as its fit — so before you fall for the fingerprint reader, it's worth a minute to check the thing that actually matters: your door. The good news is that for most UK homes, the answer is a simple yes.
A retrofit smart lock like a Simpled doesn't replace your door or your existing mechanism. It works with the lock you already have. That's why fitting takes about twenty minutes with a screwdriver rather than a locksmith and a lost weekend. But "most doors" isn't "every door", so here's exactly what to look at.
The three things that decide it
1. Door thickness
This is the big one. A Simpled fits doors between 40mm and 80mm thick. That range covers the vast majority of UK front doors, but it's worth measuring rather than guessing. Open your door and measure the edge — the flat face where the door meets the frame — with a tape measure. If you land anywhere from 40 to 80mm, you're in.
2. Door type
Simpled is designed for uPVC and composite doors — the two most common front-door types in Britain. uPVC doors are the plastic-framed ones, often white or grey. Composite doors are the solid, heavier ones made from layered materials, usually with a wood-effect or coloured finish. Both are ideal for a retrofit lock because they typically use a standard multipoint mechanism.
3. Your existing lock mechanism
Most uPVC and composite doors use a multipoint lock — the kind where lifting the handle throws several bolts up and down the door at once, and a key in the cylinder locks it in place. That cylinder is almost always a euro-cylinder, the standard hourglass-shaped barrel used across the UK and Europe. A Simpled works with this arrangement: it drives the same mechanism you already lift and turn by hand.
If your front door is uPVC or composite, between 40 and 80mm thick, with a multipoint lock and a euro-cylinder, a Simpled will almost certainly fit. Those three boxes are what a smart lock cares about.
A couple of words worth knowing
You may run into two bits of locksmith vocabulary. Neither should worry you, but it helps to recognise them.
Euro-cylinder is just the name for that standard barrel your key goes into. It's measured in two halves from the central screw — the internal side and the external side — and those two measurements are how a cylinder is sized to your door. Backset is the distance from the edge of the door to the centre of the keyhole. Fitters mention it because it affects how hardware lines up, but for a retrofit lock you generally don't need to work it out yourself.
If any of that starts to feel like homework, that's rather the point of the next bit.
Why the free checker exists
We built the compatibility checker precisely so you don't have to become an amateur locksmith to buy a lock. Rather than asking you to measure cylinders and decode backsets, it walks you through a few plain questions about your door and tells you honestly whether a Simpled fits. If it won't, it says so — no surprises, no returns dance.
It takes about a minute, and it's the single most useful thing you can do before ordering. Measure your door thickness, know whether it's uPVC or composite, and let the checker handle the rest.
Your 60-second checklist
- Measure the door edge — is it between 40 and 80mm?
- Is it a uPVC or composite door?
- Does lifting the handle throw the bolts (a multipoint lock)?
- Is there a standard euro-cylinder your key turns?
- Not sure on any of these? Run the free checker.
Let's settle it in a minute.
Answer a few questions about your door and we'll tell you honestly whether a Simpled fits — before you spend a penny.
