By this stage, the door should already be hung and aligned properly in the frame.
This isn’t the point where I expect to find a door that is miles out and start setting it up from scratch.
The frame has been installed.
The door has been hung.
The hinges have been dealt with.
The door has been aligned.
The closer and other hardware have been fitted.
Now I want to check that everything is still where it should be.
This is really the final gap check and any small adjustment before I move on to the next stages of the installation.
The Door Should Already Be Aligned
I think it’s important to separate aligning the door from checking the finished gaps.
The main work should already have been done when the door was hung and aligned.
If I get to this stage and the door is substantially out, I don’t just start moving things around until the measurements look right.
I’ll go back and find out why.
It could be:
- The frame
- The hinges
- The door
- The fixing
- The alignment
- Something putting pressure on the door
- Or a combination of things
As I covered earlier in the series, the door should be moving properly in the frame before you start trying to compensate for problems with other components.
Part 12 is really about checking and fine-tuning, not rescuing a badly installed door.
Check the Gaps Again
I’ll check the gap around the whole door rather than just looking at one point.
I’ll look at:
- The head
- The hinge side
- The lock side
- The bottom of the door
- The meeting stile on pairs, where applicable
- Any changes in the gap as I move around the door
The actual permitted gap needs to come from the door manufacturer’s installation instructions and the relevant fire-door evidence.
BWF guidance generally gives 2–4 mm at the top and sides, but the manufacturer’s requirements for the particular door take priority.
So I don’t believe in blindly applying one number to every fire door.
Look at the Whole Gap
Don’t just put a gap gauge in one place and say:
“That’s 3 mm. Done.”
Look at what is happening all the way around the door.
You want the gaps to be consistent and within the permitted requirements.
If the gap is changing significantly as you move along the door, I want to know why.
The pattern of the gap can tell you something about what’s happening with the doorset.
It could point towards:
- Hinge alignment
- Frame alignment
- Door position
- Frame movement
- Installation problems
- Or something else affecting the way the door is sitting
This is why I don’t see measuring gaps as simply taking a measurement for a record.
The gap can tell you what’s happening to the door.
Sometimes It Only Needs a Small Tweak
This is where I might use a wedge.
If everything is basically right but the door or frame just needs a small tweak to get the gaps sitting properly, I’ll sometimes use a wedge to help move it into the position I want.
I’m not talking about using wedges to compensate for a badly installed frame.
This is a small adjustment when you’re already close.
Once I’m happy with the position, I make sure the adjustment is properly dealt with rather than leaving something sticking out where it shouldn’t.
And if a wedge or packer is protruding beyond the frame line, I’ll cut it back below the frame line.
You don’t want bits of timber or packing sticking past the frame where they can interfere with the next stages of the installation or simply look untidy once the job is finished.
The same applies to packers that are sticking out.
If I’ve finished the adjustment, I want the frame to look finished as well.
Where packers form part of the frame fixing arrangement, they should of course be retained and used in accordance with the particular doorset’s installation requirements. BWF guidance specifically says packers behind fixings should be of suitable specification and have proven performance for the fire-door application.
Frames Can Settle
Another reason I like checking the gaps again at this stage is that the installation isn’t necessarily completely static the moment you’ve finished hanging the door.
A frame can settle slightly.
The door can settle slightly.
You’ve also added the rest of the hardware and seals and operated the door repeatedly.
Sometimes I’ll get a door looking right when I first hang it and then, after I’ve carried on with the rest of the installation, I’ll find that something has moved slightly.
It might only need a small tweak.
Sometimes you can come back a few hours later or the following day and notice a slight change.
I’m not saying every frame will move, or that you should deliberately leave every door waiting overnight.
It’s simply something I’ve learned to allow for.
That’s why I like checking the gaps again rather than assuming that because they were right earlier, they’re automatically still right now.
Consistent Gaps Look Better
There is also a simple practical reason for getting the gaps right.
It looks better.
You can have a door that technically opens and closes but the gaps look all over the place.
Stand back and look at it and you can see it immediately.
A consistent gap gives the whole doorset a much more professional appearance.
When you’re fitting doors, you’re not just trying to make something that works.
You want it to look like it has been fitted properly as well.
That’s particularly noticeable on a run of doors.
When all the doors have clean, consistent gaps, the whole installation looks better.
Operate the Door Again
Once I’m happy with the gaps, I’ll operate the door again.
I’m checking:
- It opens freely
- Nothing is rubbing or binding
- The gaps remain consistent
- The door sits correctly against the stop
- The latch engages properly
- The closer operates correctly
- The seals aren’t causing an unexpected problem
- Nothing I’ve fitted has altered the position of the door
This is important because you’re not checking the door as a static object.
You’re checking the doorset working as a doorset.
Don’t Chase Every Fraction of a Millimetre
Once the door is properly installed, I don’t want to spend all day chasing tiny variations that don’t actually require correcting.
I’m looking for the door to be within the requirements for that particular doorset and to operate correctly.
If it needs a small adjustment, I’ll make it.
If it needs a major adjustment, I’ll stop and find out why.
A major adjustment at this stage is usually telling you that something earlier in the installation needs looking at.
The aim isn’t to make every measurement identical to the last fraction of a millimetre.
The aim is to have a properly installed, correctly operating doorset with gaps that comply with the requirements for that particular door.
This Is My Final Gap Check
Once I’m happy with the position of the door and the gaps, I consider this stage done.
I’ve already done the substantial alignment work earlier in the installation.
This is the final check to make sure everything is still where I want it after the rest of the installation has taken place.
Then I can move on.
The next stage is fitting the intumescent and smoke seals, followed by the later finishing and final checks.
🟧 Professional Installer’s Tip
Get the big things right early, then check the small things at the end.
I don’t want to be trying to rescue a badly aligned door at this stage.
I want to be making the small tweaks that sometimes become necessary as the installation settles.
And when I’m finished, I want the door to work properly and look properly fitted.
Continue the Fire Door Installation Series
← Previous: Part 11 – Installing a Fire Door Closer
Part 12 – Measuring & Setting Fire Door Gaps — You are here
