A cold draught around a front door does not automatically mean the whole door needs replacing. Air commonly enters through the letterbox, keyhole, bottom edge or compressed weather seals around the frame. The correct fix depends on whether the problem is a missing seal, poor adjustment, worn hardware or a door that no longer sits squarely in the frame.
Early October is a good time to check these small gaps before regular heating begins. UK energy-efficiency guidance distinguishes unwanted draughts from intentional ventilation: seal accidental gaps, but do not block trickle vents, ventilation grilles or airflow required for combustion and indoor air quality.
Find the actual air path before buying anything
On a breezy day, feel around the closed door with the back of your hand. Check the letterbox, keyhole, corners, threshold and entire perimeter. Visible daylight is an obvious clue, but a whistling noise or moving curtain can reveal smaller gaps.
Do not judge the door only at one height. A door can seal tightly near the lock and leak at the top hinge corner if it has dropped slightly.
If the door also sticks or scrapes, read how to distinguish hinge adjustment, planing and damp-related movement before adding thicker seals.
Letterbox draughts: brush, flap or worn cassette?
The letterbox is a direct opening through the door, so even a small failure in its flap or brushes can create a noticeable cold stream. Energy Saving Trust guidance recommends a purpose-made letterbox flap or brush and stresses measuring the opening before buying.
Check whether the outer flap closes fully after post passes through. A warped flap, tired spring or badly fitted internal brush can leave a permanent gap. A replacement internal draught excluder is often a straightforward job if the existing letterbox is sound.
If the entire letterplate is loose, water-stained or pulling away from the door, simply adding a brush may hide a larger fixing problem. The plate needs to sit firmly against the door without creating a route for rainwater.
Gaps around the sides and top of the door
Doors normally use compressible seals around the frame. Over time these can flatten, tear, shrink or pull out of their channel. On older timber frames there may be no modern seal at all.
Self-adhesive foam is cheap and useful for some simple gaps, but it must be the right thickness. A strip that is too thin does nothing; a strip that is too thick can stop the latch engaging or place unnecessary pressure on hinges.
Brush or wiper-type seals can be better where there is movement. For uPVC and composite doors, the correct gasket profile is important. Randomly adding foam on top of a failed factory gasket may make the door harder to close without restoring an even seal.
What about a draught under the front door?
A gap at the threshold can be treated with a brush, hinged flap or an adjustment to the door/threshold system, depending on the construction. First check whether the gap is even across the width.
- Even gap: a suitable bottom seal may be enough.
- Large gap on one corner: alignment may be wrong.
- Door rubs at the opposite corner: the leaf may have dropped.
- Threshold is loose or damaged: repair the threshold rather than covering the symptom.
Do not fit a seal that drags heavily across the floor every time the door opens. It will wear quickly and may make the door unpleasant to use.
When the draught is really an alignment problem
Weather strips only work if the door presses against them evenly. Warning signs of misalignment include a latch that needs force, a handle that must be lifted excessively, unequal gaps, rubbing and a seal that is compressed on one side but untouched on the other.
On some uPVC and composite doors, hinge or keeps may be adjustable. On timber doors, movement can come from loose hinges, seasonal swelling, worn screw holes or frame movement. The repair should address the cause rather than simply fitting an increasingly thick strip.
If the handle or latch is also behaving badly, see the guide to a loose door handle or latch that will not spring back.
Do not block designed ventilation
Draught proofing means stopping uncontrolled gaps. It does not mean sealing every route by which air can move through a home. Energy Saving Trust advises against blocking vents and other airflow needed for safety and air quality.
This matters particularly in homes with combustion appliances, high moisture levels or existing condensation. If you are unsure whether an opening is accidental or intentional, identify it before sealing.
When a handyperson can help
A handyperson can often replace simple seals, fit a letterbox brush, tighten hinges, renew fixings, adjust straightforward door hardware and improve minor gaps. More complex work may need a specialist if the problem involves a multipoint lock, badly distorted frame, failed sealed door unit, structural movement or a fire door with specific performance requirements.
For a broader seasonal check, the UK autumn home maintenance checklist covers gutters, fences, paths, lighting and other small jobs worth handling before winter.
You can also compare local professionals through the FindHandyman.uk directory.
FAQ
What is the quickest way to stop a letterbox draught?
A correctly sized internal brush or flap is often the simplest improvement if the letterplate itself is secure and closes properly.
Should I add foam weather strip around a uPVC door?
Not automatically. First inspect the existing gasket and alignment. Extra foam can make the door difficult to latch if the original seal or hinge adjustment is the real issue.
Can I seal a gap under an internal door?
Be cautious. Internal door gaps often help planned air movement through the home. Do not block ventilation without understanding how the building is ventilated.
Does a draught mean I need a new door?
No. Many draughts come from replaceable seals or minor alignment problems. Replacement is more likely when the door or frame is significantly damaged, distorted or unable to seal despite proper adjustment.
Key point: find the air path first. A five-pound brush can fix a genuine letterbox draught; it cannot fix a door that has dropped in its frame.
For current UK guidance, see the Energy Saving Trust page on draught proofing.