How to fit a door frame

Video by Skill Builder. This walk-through is based on the video “Want PERFECT Door Frames? Watch This Now” from Skill Builder, where carpenter Robin Clevett walks through the door lining fitting process in detail. The section on using a spreader bar to set the head width consistently is particularly handy — it’s the kind of trick that takes minutes to set up and saves a lot of fiddling later.

1. Measure the opening and check it for square

Before you unwrap a new door lining, measure the rough opening in three places — top, middle, and bottom. Openings in older East Kent properties are rarely truly square, and if the head of the lining is going in at an angle you need to know about it now rather than after you’ve fixed it. The width of the lining needs to be at least 6 mm narrower than the opening on each side to give you packing room.

Check the opening for plumb on both sides too. A masonry opening that leans significantly will need wedges to bring the lining plumb, and that takes longer to do neatly if the lean is more than about 10 mm over the height of the frame. It depends on the age of the house — in properties from the 1930s to the 1970s, which make up a lot of the housing stock in and around Sandwich, this is fairly common.

2. Assemble the lining frame on the floor

Most door lining sets come as two side legs and a head piece. Assemble them on the floor first, checking the internal width against the door leaf you plan to hang. You need roughly 2 mm clearance on each side of the door — so if the door is 762 mm wide, the inside of the lining should be about 766 mm. Too tight and the door will bind; too loose and you will see daylight around the edges.

Use a spreader bar — a scrap of timber cut to the exact internal width — temporarily wedged between the two legs near the bottom. This stops the legs bowing in or out while you carry the assembled frame to the opening. It sounds like an extra step, but it saves a lot of re-measuring once the frame is upright.

3. Offer the frame into the opening and pack the legs plumb

Lift the assembled frame into the opening. The legs should sit on the floor or on a small packing piece if the finished floor has not yet been laid — allow for the floor finish thickness so the door clears it when open. Check one leg for plumb with a long spirit level, then wedge it into position with folded timber packers. Do the same on the other side.

This is where many DIYers rush. Check plumb in two directions — face plumb (is the lining leaning into or out of the room?) and edge plumb (is it leaning sideways?). Both need to be right. That said, face plumb is the one that catches people out most often, especially when the wall surface is not flat.

4. Fix through the packers into the masonry or stud

Once the frame is plumb and the packers are tight, drill and fix through the lining legs into the wall behind. In a masonry opening, use 100 mm frame fixings or plugs and screws. In a stud partition, 65 mm screws into the king studs will do the job. Fix at the top, bottom, and at least one point mid-height on each leg.

Do not over-tighten the fixings. Pull them snug until the lining is held firmly, then check with the spirit level again. It is very easy to pull a leg slightly out of plumb by over-driving a screw into a compressible packing piece. If that happens, back the screw off half a turn and recheck.

5. Fix the head piece and check the frame for square

Once both legs are plumb and fixed, fit the head piece. In most lining sets the legs are rebated or housed to accept the head, so it should drop into position. Check that the head is level — not just sitting on top of two plumb legs, because if the opening itself is slightly racked, the legs may be plumb but the head still out of level. Adjust the packing under one leg if needed.

Now check the frame for square by measuring the two diagonals. They should be within about 2 mm of each other. If they are not, the door will not sit square in the frame when closed, and no amount of hinge adjustment will fully fix it later. Take the time to get this right now — it takes five minutes and saves considerably more.

6. Remove the spreader bar, trim packers, and prepare for the door

Once all fixings are in and you are happy the frame is plumb, level, and square, remove the spreader bar from the bottom. Trim any protruding packers flush with a hand saw so they do not foul the architrave later. Check the inside face of the lining is flush with the plasterboard or plaster face — if it sits proud, the architrave will not sit flat.

The frame is now ready for the door to be hung. Mark the hinge positions on the lining at this stage, before the architrave goes on, as it is much easier to work with a clear face. If you are plastering around the frame, mask the lining face first to keep it clean — dried plaster splashes take longer to remove than they take to prevent.

When to call a handyman

Call Richard if the rough opening needs widening or the lintel above it is causing movement, if a rotted or damaged existing frame needs cutting out cleanly before the new one goes in, or if you are fitting several frames in one go and want the job done quickly and consistently. Hanging the door onto a newly fitted frame — mortising hinges and fitting a latch — is a natural next step that is much easier to do while everything is still accessible.