You’ve checked the opening.

You’ve measured it at multiple points.

You’ve checked the wall depth, the floor, the structure and the fixing positions.

Now it’s time to put the new frame into the opening.

This is where all that preparation starts to pay off.

A manufactured doorset should already have been produced to the required dimensions and margins, but don’t assume that means it will simply drop into every opening perfectly.

The building is still the building.

The frame is the accurate part.

---

Offer the Frame Into the Opening

Most made-up doorsets arrive with the doors already installed in the frame.

They will usually have some form of travel brace fitted across the bottom to help keep the frame at its manufactured width during transportation.

That brace is normally cut to the width of the doorset and can be useful when you’re getting the frame into position.

Personally, I prefer to remove the door from the frame and install the frame separately.

It’s much easier to work accurately with the frame without the weight and movement of the door getting in the way.

The door can then be hung once the frame has been installed.

There are different methods of doing this and other installers will have their own techniques.

The important thing is that the frame gets installed without being distorted.

---

The Inside Head Is Your Main Datum

When I install a frame, the inside head of the frame is my main datum.

This is what I’m working to.

Most doorsets are manufactured with the required clearances already built into them. As a typical example, you might have approximately:

• 3 mm at the sides
• 3 mm at the top
• 10 mm underneath

But these aren’t universal fire-door dimensions.

Always check the actual manufacturer’s specification for the doorset you’re installing.

The important thing at this stage is to make sure you get the required clearance underneath the frame.

If you don’t have enough clearance because of the floor, you may have to make an appropriate adjustment, which can sometimes mean trimming the bottom of the frame leg.

Don’t simply assume the 10 mm figure applies to every doorset.

---

Check the Head First

I personally start with the hinge side of the frame.

I put the frame into the opening and check the head first.

Is it level?

If it isn’t, I want to understand why.

Is the floor uneven?

Is the opening itself out?

Does one leg need raising?

Does the other need trimming?

Does the head need more room?

This is why I like to physically offer the frame into the opening early.

You’ve measured everything, but now you’re looking at the actual frame in the actual opening.

Sometimes that’s when the building tells you something your tape measure didn’t.

---

Centralise the Frame

Where possible, I like to centralise the frame in the opening.

If I’ve removed an existing doorset, I also look at where the old frame was positioned.

This can be important for the finished appearance.

For example, the existing skirting board can give you a useful reference for where the architrave needs to finish.

I’ve seen people install a replacement frame without considering this, only to find afterwards that the skirting has to be cut back on one side and there is a gap on the other.

Or they end up leaning the architrave across to try to make it work, leaving an unusually large quirk.

A few minutes thinking about the finished position before fixing the frame can save a lot of unnecessary finishing work.

---

Equalise the Frame Within the Wall Depth

Once I’ve got the head where I want it, I look at the frame’s position within the wall depth.

If the available gap allows it, I push the frame to one side, measure the remaining gap and divide that measurement by two.

That gives me a starting point for the packing on the opposite side.

The idea is to get the frame properly positioned within the wall, rather than simply fixing it wherever it happens to sit.

---

Don’t Let the First Fix Pull the Frame Out of Alignment

Before putting in the first screw, I want the frame aligned with the wall.

This is important.

If you get the top of the frame lined up correctly and then put a fixing in while it’s sitting out of line, the fixing can pull the frame away from the position you’ve just established.

So get the frame where you want it before committing to the first fixing.

---

Packers

Once the position is established, the frame needs to be properly packed at the fixing point.

I normally put the first fixing at the top and use the appropriate packer behind the frame.

The packer needs to support the fixing correctly.

I find it useful to push the packer in approximately 10 mm where the frame construction allows it.

That means I only have to trim it back on one side rather than having to cut both sides.

The exact packer arrangement needs to follow the doorset manufacturer’s installation requirements.

---

Laser Alignment

Always Work From the Same Side of the Laser Line

One small thing that makes a big difference to accuracy is to always work to one side of the laser line.

Don’t keep switching from one side of the line to the other when you’re making your adjustments. Pick your reference side and consistently work from it.

When you’re working to very small tolerances, even the thickness of the laser line itself can introduce uncertainty if you’re not consistent.

Choose your reference edge and always work to that same side of the laser line.

It sounds like a small thing, but when you’re working to 1 mm or even 0.5 mm, these little details matter.

When I’m using a laser, I use it as a reference line for the frame.

I can hold the laser against the wall in line with the head, or use the external edge of the wall where the plasterers have used a metal trim.

That can be particularly useful because the metal trim allows the laser to be held in position magnetically without me having to physically hold it.

I first use the laser to get the frame in line with the wall across its width.

I then move the laser around to the door-hanging side and use it to establish the jamb plumb.

Once I have the position, I can make the first fixing at the bottom.

This gives me a fixed point at the top and bottom.

I then keep the laser in position and work progressively up the jamb, bringing the frame into line as I go and fixing it.

---

You Don’t Have to Use a Laser

A laser is one method, but it isn’t the only method.

If you’re using a long level, you can use the level itself as a straight edge to help line the frame up.

On the hinge side, the long level can be used as a reference against the frame rather than simply relying on the bubble.

Another useful method is to use the door leaf itself.

If the hinge-side door is hanging in the frame, you can close the door and use the door as your alignment reference.

Pack across it until the relationship is correct, checking both directions.

You’re effectively checking the frame against the component that actually has to operate in it.

---

Double Doors

The same principle can be used with double doors.

You can hang both leaves and bring them together, or work with one side, to establish how the doors meet when closed.

The important thing is to get the leaves properly aligned rather than simply making the frame look straight.

The door itself can tell you a lot about what the frame is actually doing.

---

The Old-School String Method

There are also traditional ways of checking a frame.

One old method is to put temporary fixing points at the four corners and run string diagonally across the frame, creating an X.

When the frame is correctly aligned, the strings should meet at the centre.

It’s a simple way of checking the geometry of the frame without modern laser equipment.

There are plenty of different methods that work.

The important thing is understanding what you’re trying to establish.

---

Fix the Hinge Side First

I always prefer to work from the hinge side.

The head is my fixed datum, so I establish that first and work from it.

Once the head and hinge side are positioned, I work progressively down and back up the frame, keeping everything aligned as I go.

After getting the first fixing at the bottom, I may need to make a small adjustment to the head.

This is particularly relevant when the wall itself isn’t perfectly true.

Once I’ve completed one side, I recheck the head and then move across to the other jamb.

I keep the frame correctly positioned within the wall depth and repeat the process.

---

Watch for the Frame Moving as You Fix

This is one of the things you learn with experience.

You can get the frame exactly where you want it, put in a fixing, and then discover that something has moved somewhere else.

Sometimes the frame naturally wants to bow.

The bottom of a jamb can also flare out.

That’s where your packing and alignment method becomes important.

Don’t just keep tightening fixings and hope the frame sorts itself out.

If the frame has moved, use the appropriate method to bring it back into position.

Sometimes that means carefully using a lever and adding or removing packing until the frame is straight again.

---

The Screw Can Help You Make Small Adjustments

There is another useful detail that can help when making small adjustments.

Many wood screws have an unthreaded section near the head.

If you slightly loosen the fixing, the frame can sometimes move in and out a few millimetres because the unthreaded section allows some movement without the thread gripping the frame in the same way.

This can be useful when making small positional adjustments.

A lever can also be used carefully to move the frame while you add or remove packing.

The important thing is not to damage the frame or the surrounding construction while doing it.

---

Don’t Leave Your Packers Loose

Once you’ve established the correct position, the fixing needs to secure the frame with the appropriate packing in place.

I don’t leave packers loose because they can move or fall out.

The fixing and packer need to work together to support the frame at that point.

Again, the exact fixing and packing arrangement should always follow the manufacturer’s tested installation method for the doorset you’re fitting.

---

Fixing Positions

The manufacturer’s fixing positions always take priority.

They vary between doorsets, but you will commonly encounter arrangements where fixings are positioned up to around 200 mm from either end and no more than 600 mm apart.

Those figures are not a universal fire-door rule.

Check the manufacturer’s installation instructions for the actual frame you’re installing.

If the fixing positions don’t work with the structural opening, don’t simply move them wherever you like.

This is where the preparation you did in Part 4 becomes important.

---

Predrill Hardwood Frames

Hardwood frames should be predrilled appropriately before installing the fixing.

I normally use around a 4 or 5 mm drill bit, depending on the fixing and the particular frame.

You don’t want to force a fixing into hardwood simply because you’ve got the screw in your hand.

If the fixing is too tight, you can damage the frame or the screw.

And rounding out the screw head is one of the worst things you can do.

Remember that these doorsets need ongoing maintenance.

Somebody may need to remove or adjust that fixing in the future.

Make life easier for them.

---

Lightly Countersink the Fixing

I also like to lightly countersink the screw head into the surface of the frame.

Only countersink the surface.

Don’t go unnecessarily deep.

You’re simply giving the fixing head somewhere to sit neatly.

Taking a large amount of material out of the frame just to bury the screw isn’t good practice.

---

Be Careful When Removing or Loosening Fixings

If you need to back a screw out to make an adjustment, be careful.

Don’t simply wind it out aggressively and tear the timber around the fixing.

You can spelch the timber as the screw comes out, particularly if the frame has been tightly fixed.

Make the adjustment carefully and maintain the support of the frame while you’re doing it.

---

Hide the Fixings Where Appropriate

Where the frame construction allows it, I prefer to hide the fixings.

Depending on the particular frame, this can sometimes mean positioning them within the rebated intumescent seal groove, or behind the stop lath on a door lining.

But there is an important rule here:

Never move a fixing simply because you want to hide it.

The manufacturer’s specified fixing positions and tested installation method come first.

A neat-looking fixing in the wrong position isn’t a good installation.

---

Think About Maintenance

A doorset isn’t finished when you’ve got the last screw in.

It has to be inspected and maintained throughout its life.

That’s why I think about things like screw access, screw heads and damage to the frame while I’m installing it.

If you’ve rounded off the screw head or damaged the timber around it today, you’ve potentially created a problem for whoever has to maintain the doorset later.

Install it properly, but think about the next person who has to work on it.

---

The Frame Isn’t Finished Yet

One thing I don’t do is pretend that the frame is completely finalised before the door is fitted.

You can get the frame accurately positioned and fixed, but you don’t completely know how everything is going to behave until the door is actually hanging in it.

There are often small adjustments to make once the door is fitted.

That’s why the frame installation is a process of continually checking and correcting rather than fixing everything and walking away.

---

The Door Becomes the Final Check

Once the frame is installed, the door can be hung.

Now you can see how the actual doorset behaves.

The door gives you another opportunity to check:

• the frame geometry
• alignment
• hinge side
• latch side
• closing relationship
• floor clearance
• whether the frame has moved during fixing.

If there are small adjustments to make, this is where they become apparent.

The frame may look perfect on its own, but the door is the component that ultimately proves whether the geometry works.

---

---

Part 5 — Key Points

• Offer the frame into the opening before committing to installation.
• Most made-up doorsets arrive assembled and may have a travel brace to maintain their manufactured width.
• Removing the door and installing the frame separately can make accurate installation easier.
• Use the inside head of the frame as your main datum.
• Check the head first.
• Start from the hinge side.
• Check the required clearance underneath the frame.
• Don’t assume a particular undercut applies to every doorset.
• Consider the relationship between the frame, wall depth, architrave and existing skirting.
• Centralise the frame where appropriate.
• Use the manufacturer’s fixing positions.
• Pack correctly at fixing points.
• Keep checking the frame as you progressively fix it.
• Use a laser, long level, door leaf or other suitable method to establish alignment.
• Watch for the frame bowing or flaring.
• Understand how fixings and packers can create fulcrum points and alter the frame elsewhere.
• Use careful adjustment rather than simply tightening fixings harder.
• Predrill hardwood frames appropriately.
• Lightly countersink fixing heads where appropriate.
• Don’t round out or damage fixing heads.
• Don’t damage the frame when removing or adjusting fixings.
• Hide fixings where the tested frame construction permits it.
• Think about future maintenance.
• Remember that the door itself becomes an important final check of the frame.

---

← Previous: Part 4 – Checking the Opening

Part 5 – Installing a Fire Door Frame — You are here

Next: Part 6 – Preparing the Fire Door Leaf →

The frame is now installed.

But this is where you find out whether all that careful work has actually paid off.

In the next part we’ll look at hanging the door, using the door itself to check the frame, getting the leaf correctly aligned, dealing with small adjustments and making sure the door operates correctly within the frame.