Fitting a front door takes a competent DIY-er most of a day and a joiner around half of one. The work splits into four parts: taking the old one out, getting the new frame plumb and square, fixing it, and sealing around it. The frame decides whether the job goes well. The door is the easy part.
A joiner replacing a doorset in an existing opening will be done in three to five hours. Doing it yourself for the first time, allow a full day and treat anything faster as a bonus.
Two things stretch it. An opening that has to be made good, because the old frame has taken plaster or brick with it. And a threshold that needs building up or cutting down to meet the new frame.
The part you cannot rush is the frame. Fixing a frame that is 3 mm out of plumb takes ten minutes to correct at the time and cannot be corrected afterwards without taking it out again.
Sometimes, and it depends on what you are starting with rather than on what you want.
A timber frame in sound condition, square, with no rot at the bottom of the jambs, can take a new door leaf. You are then matching a new door to an old frame, which means the hinge positions, the lock case, the leaf thickness and the rebate depth all have to line up. It is fiddly rather than difficult.
A uPVC or aluminium frame is a different matter. The leaf and the frame are made as a system, so replacing one without the other is rarely practical.
Check the bottom 150 mm of both jambs and the threshold before you decide. That is where a timber frame rots first, it is where the damp comes from, and a new door hung in a soft frame will drop within a year.
Tools. A spirit level long enough to span the frame, a drill with masonry bits, a hammer, chisels, a handsaw, a mallet, packers or shims, a caulking gun, a utility knife and a tape. A multi-tool earns its place when you get to the old frame
Materials. Frame fixings sized for your wall, expanding foam or insulation for the perimeter, exterior-grade sealant, and a damp-proof course strip if the threshold needs one.
A second person. Not optional on a glazed doorset. One person holds and one person levels, and the lift into the opening needs two sets of hands whatever the weight.
A way to close the hole. A sheet of ply cut to the opening, or a tarpaulin and battens. If the job runs late, this is what stands between you and an open house overnight.
Take the door leaf off its hinges first and put it somewhere out of the way. The frame comes out far more easily once the weight has gone, and you can see what you are cutting.
Cut through the sealant and the architrave, then look for the fixings. Older timber frames are usually screwed or nailed through the jambs into the brickwork behind, and the heads are often filled over.
Cut the jambs through the middle rather than trying to lever the whole frame out in one piece. Two shorter halves come away from the brick without taking plaster and render with them.
Clear the opening back to a sound surface, and check what the threshold is sitting on before you build anything back up.
This is the part that decides the outcome, and the sequence matters more than the speed.
Dry fit first. Offer the frame into the opening with no fixings and no foam. Check it goes in, check the gaps are even, and check the threshold sits flat. Correcting the opening is easier now than in twenty minutes.
Level the threshold before anything else. Everything above it takes its reference from the threshold, so a threshold out of level puts the whole frame out.
Plumb the hinge jamb, then fix it. Pack behind it at the hinge positions, check the level again after each fixing, and do not tighten everything before you have checked all of it.
A frame pulled tight against a hollow behind it will bow.
Fix the lock jamb to the door, not to the tape measure. Hang or close the leaf and set the lock jamb so the gap is even the whole way down. That gap is what the seal compresses into.
Check the diagonals. Measure corner to corner both ways. Equal diagonals mean a square frame, and a square frame means a door that closes with one finger in ten years.
Insulate the perimeter gap, then seal it. Foam or mineral wool fills the void so the gap is not a cold bridge, and the sealant on the outside face keeps water out of it.
Seal the outside before you finish the inside. Weather comes from one direction, and the outside bead is the one doing the work.
Leave a drainage path at the threshold rather than sealing it solid across the bottom. Water that gets in has to get out, and a fully sealed threshold traps it against the frame.
Then hang the door, fit the furniture, and check the lock throws cleanly before you put the tools away. Adjusting a hinge now takes two minutes.
Four situations where the money is well spent.
The opening needs structural work, because there is no lintel or the lintel has failed. The wall is stone, cob or anything that will not take a standard frame fixing. The door is wider than a single leaf and heavy with it. Or the house is listed, where the work has to satisfy a conservation officer as well as you.
A joiner fitting a doorset you supplied is also a common arrangement, and it is often the best of both: factory pricing on the door, professional hands on the frame.
Replacing an external door is notifiable work. Where a FENSA or Certass registered installer would self-certify, a door you fit yourself has to be notified to your local authority Building Control instead. Contact them before the door arrives rather than after it is in.
