Find the draught before you buy anything to fix it. Most people start with a brush strip at the bottom of the door, and most front door draughts come from the hinge-side corner, the letterplate, or the joint between frame and brickwork. Ten minutes with a lit incense stick tells you where the air is actually moving.
Three different complaints get described as a draughty door, and they need three different responses. Work out which one you have before you spend anything.
Air leakage is the fixable one, and it is the one this article is mostly about. Sealing gaps is cheap, quick and effective.
A cold door with no air movement is a different problem. Old single-glazed panels, thin timber leaves and uninsulated cores conduct heat outwards, and no amount of draught-proofing changes that. A heavy curtain helps. Replacement helps. A brush strip does nothing.
Cold air pooling at the bottom often has nothing to do with the door leaf. Water and air both find their way under a failing cill, and the sensation at ankle height is identical whichever it is. Check outside as well as inside.
Do this before buying anything. It takes ten minutes and it decides everything that follows.
Smoke pulled sideways or blown back shows you air movement your hand cannot feel. Do the letterplate and the keyhole as separate checks, because they leak independently of the door's fit.
One more test worth doing. Close the door on a sheet of paper and pull it out. Firm resistance at the top, middle and bottom means the door is sealing evenly. Slack in one place tells you the leaf is not meeting the gasket there, which is an adjustment problem rather than a sealing problem.
The order matters, because the free fixes address the causes and the paid fixes address the symptoms. Working backwards is why people buy draught excluders that do not help.
First: adjust the door. A leaf that is not pulled evenly into its gasket leaks along one edge, and the fix is a compression screw rather than a product. This is the single most common cause of a draughty uPVC or composite door, and our adjustment guide walks through it. Cost: nothing.
Second: check the gaskets. Run a finger along the rubber seal in the frame. Soft and flexible is healthy. Hard, shiny, flattened or cracked means the gasket has perished, and no adjustment recovers a dead gasket. Replacement gasket is sold by the metre and pushes into the same channel.
Third: deal with the letterplate and the keyhole. An unbrushed letterplate is a permanent hole in your front door, and it leaks more than most gaps around the edge. A letterplate brush or draught excluder plate costs very little. An escutcheon with a cover does the same for the keyhole.
Fourth: the threshold. Threshold seals, brush strips and weather bars address the gap under the door. This is where most people start and where the leak usually is not, though on older doors it can be genuine.
Fifth: the frame-to-wall joint. See below. This one is not a DIY seal.
Last: consider the door itself. If the leaf has bowed, the frame has moved, or the hardware is worn, the door has reached the end of what maintenance can do.
The gap between the door frame and the brickwork should be filled with insulating material during installation, precisely to stop air moving through it. Our own fitting instructions specify this, and it is one of the steps most likely to be rushed or skipped.
When it is skipped, air travels behind the frame, through the wall cavity, and into the room around the reveal rather than around the door. The symptoms mislead: you feel cold air near the door, so you seal the door, and nothing improves.
How to tell. Run the back of your hand along the junction between the frame and the plaster, all the way round, on a windy day. Air movement there rather than at the door edge points behind the frame. Look also for cracked or missing sealant on the outside face of the same joint.
The fix depends on access. Externally, raking out and replacing failed sealant is straightforward. Internally, removing the architrave to expose and fill the void is a job worth giving to a fitter. Filling it with expanding foam through a small hole is a common shortcut and a poor one, because uncontrolled foam can bow the frame and create a worse problem than the draught.
Here is the part that gets left out of every draught-proofing guide, and it catches people every winter.
Moisture in your home has to go somewhere. In a leaky house it leaves through the gaps.
Seal the gaps and the moisture stays, and it condenses on the coldest surface it can find, which is often the inside of the front door or the glass beside it.
So a run of successful draught-proofing can be followed within weeks by water running down the inside of the door. The draught-proofing did not cause a damp problem. It revealed a ventilation problem that the draughts were masking.
Three things keep that in check. Use extract ventilation when cooking and showering, and let it run on after you finish.
Keep trickle ventilators open, including in winter, because they are there to provide the background airflow the gaps used to.
And if condensation appears on the door rather than the glass, check whether the door is cold because it conducts heat rather than because it leaks, since those need opposite treatments.
Usually not, and we manufacture doors, so take that as it is intended.
Draught-proofing an existing door that is otherwise sound is cheap, fast, and does most of what a new door would do for comfort. If the door adjusts properly, the gaskets are healthy and the frame is sound, sealing it is the right answer and a new door is an expensive way to reach the same place.
Replacement earns its place when the door has a fault sealing cannot reach. A bowed leaf. A frame that has moved out of square. Worn hardware that no longer pulls the door in. Rot at the bottom of a timber door. Single glazing you want to change. Security you are not happy with.
And there is an honest caveat about energy savings. A draughty door wastes heat and fixing it improves comfort noticeably. Justifying a new doorset on the heating bill alone is a harder case, and comfort, condition, security and appearance are usually the real reasons people replace. Better to say that than to promise a payback we cannot stand behind.
