Patio Door Draughts: Causes, Fixes and When to Call a Glazier

Patio door draughts usually come from one of four places: worn seals, a door that has dropped out of alignment, a failed sealed glass unit, or gaps around the frame. Most can be found with a simple walk-round and a few minutes of checking. This guide shows you how to find the source, what you can safely fix yourself, and when a professional repair will do more good than another roll of adhesive strip.

Why patio doors let the cold in

A patio door has a long perimeter, a lot of glass and a locking mechanism that must pull the door tight against its seals every time you close it. If any one of those wears, you feel it.

The Energy Saving Trust explains that draught proofing stops unwanted cold air entering your home by sealing gaps around doors, windows and floors, which reduces heat loss and makes rooms more comfortable. Patio doors are often the biggest single opening on the back of a house, so they are a sensible place to start.

The usual culprits are:

Compressed or perished seals. Rubber gaskets flatten and crack with age and sun exposure.
Misalignment. Hinges or rollers wear and the door leaf drops or twists.
Worn locking points. The keeps no longer pull the door tight.
Gaps at the threshold. Debris, damaged tracks or a missing bottom seal let air under the door.
Failed glass units. Misting between the panes suggests the seal has gone, and the glass loses insulating performance.

Find the draught before you fix it

Guessing wastes money and can leave a door that no longer closes. Spend ten minutes on diagnosis first.

Pick a cold, breezy day. The difference between inside and outside temperature makes leaks easier to feel.
Use the back of your hand. Move slowly around the edges, the lock side and the bottom.
Do the paper test. Close a strip of paper in the door at several points. If it slides out without resistance, the seal is not making contact there.
Look at the wear marks. Check whether the seals are flattened, split or missing in places, and whether the keeps on the frame show uneven scuffing.
Check the glass. Condensation or a cloudy film trapped between the panes points to a failed unit rather than a seal problem.

Check alignment first

Many homeowners reach for new weather strip when the real problem is mechanical. Frames can settle over time, especially in older properties, and the door leaf shifts so that locks and seals no longer make full contact. Checking alignment before assuming a seal needs replacing is often more effective, since extra stripping can interfere with smooth operation.

Signs that your door has dropped or shifted:

The door rubs on the frame or the threshold.
The handle is stiff to lift or the lock is hard to turn.
You can see an uneven gap around the door.
The door only feels secure if you lean on it while locking.

On hinged uPVC patio and French doors, hinge adjustment is often possible with an Allen key, and our guide to stopping uPVC door draughts covers seals and trickle vents in more detail. Sliding doors usually have adjustable rollers at the bottom of the leaf. If adjustment does not cure the problem, worn hinges, rollers or locking mechanisms are the likely reason, and these can be replaced without replacing the door. Our locks, handles and hinges repairs cover exactly this kind of wear.

Seals: what to look for and what to replace

If alignment is sound, the seals are next. Seals fall into a few broad types, and the right one depends on your door.

Type of seal	Where it sits	Best suited to
Rubber or EPDM gasket	In a groove around the frame or sash	Modern uPVC and aluminium doors
Brush strip	Along the base or sliding edge	Sliding doors and gaps that move
Compression strip	Self-adhesive, on the frame rebate	Hinged timber and older doors
Threshold or bottom seal	Across the door base	Gaps under the door

The Energy Saving Trust notes that if you have modern windows and doors with seals on the openings, they may already be draught proofed enough. So check whether your seals have simply worn out before adding anything on top.

Replacing a gasket in a modern door

Many uPVC and aluminium doors use a push-in gasket that can be pulled out and replaced. Profiles vary, so take a short length of the old seal with you when buying a replacement. Do not stretch the gasket as you fit it, because it will shrink back and open a gap at the corners.

Adding adhesive strip to older doors

On older timber doors, self-adhesive compression strip is a common fix. The Energy Saving Trust says the job needs careful measurement so the door can still close properly. If you have to force the handle up, the strip is too thick.

A note on period homes

If your property is listed or in a conservation area, think carefully before changing the doors. Local authority guidance, such as Bath and North East Somerset Council’s retrofit guidance, favours repairing original features and using discreet brush or compression seals. St Albans council guidance likewise says careful repair should be considered before replacement, especially where historic detail is involved.

Sliding patio doors: tracks, brushes and rollers

The leaf sits in a track, and draughts often come through the meeting stile, where the two leaves overlap, or along the track itself.

Clean the track. Grit and dust stop the door seating properly and wear the rollers. A vacuum and a small brush do the job.
Inspect the pile brushes. These small brush strips seal the sliding gap. When they flatten or fall out, the door loses its seal.
Check the rollers. Worn rollers let the leaf sag, which opens a gap at the top corner of the meeting stile.

If you have had building or decorating work done recently, dust and plaster can clog tracks and brushes. Proper window cleaning after construction lets you see the real condition of the glass and frame before you decide what needs repair.

When the glass is the problem

Sometimes the cold you feel is not an air leak at all. A glass unit whose seal has failed no longer insulates properly. You will usually see misting or condensation between the panes that cannot be wiped away. The door may feel cold to the touch near the glass and radiate chill into the room even when no air is moving.

In these cases, adding strips to the frame will not help. The fix is to replace the glass unit, not the whole door. Where the frame is sound, a glass-only replacement keeps the door you have, fits new sealed units to the existing frame, and avoids the disruption of removing the whole door set.

This also has a regulatory advantage. Building Control guidance from Hampshire says that replacing only the glass unit of a patio door does not require Building Regulations approval, whereas replacing the whole door or frame must comply with Part L. That means using an installer registered with a competent person scheme such as FENSA or CERTASS, or applying to Building Control. Always check the rules for your own property with your local authority, as requirements can differ.

We offer double glazed door repairs that include glass replacement for patio and French doors, and our guide to French door glass replacement explains why keeping the frame can make sense.

Keep your trickle vents open

Stopping draughts is not the same as sealing a home airtight. The Energy Saving Trust is clear that draught proofing is aimed at uncontrolled air leaks, and that homes need background ventilation, such as trickle vents and wall vents, to keep air quality healthy and prevent damp.

Never block or seal trickle vents on the door or frame, even if you feel a slight breeze through them.
If your home is already fairly well sealed, speak to a professional before adding more draught proofing.
If you see heavy condensation on the inside of the glass or walls, it may be an indoor moisture problem and not a failed door seal.

Our view: repair the part that has failed

Our view at Cloudy2Clear Windows.

Since 2005 we have been installing, replacing and repairing double glazed windows and doors for homes and businesses. In that time, the pattern we see most often is a door that is perfectly serviceable but has one failed part: a tired seal, a worn hinge, a sagging roller, or a misted glass unit. We think replacing the whole door is usually the wrong first step.

If the frame is sound, replacing just the glass or the failed component restores comfort with less disruption, less waste and a shorter wait. It is also in line with council guidance that repair is often the more sustainable option where an existing door is structurally sound. We offer a 25-year guarantee.

Not every draught needs us. A worn compression strip or a dirty track is something a careful homeowner can sort out in an afternoon. We can help where the draught has more than one cause, or where the glass, hinges and locking points all show wear together.

Upgrading the glass while you are at it

Once your door is sealed and aligned, upgrading the glass can improve comfort further. We can fit soundproofing glass units and insulated glass in your existing frames. The Energy Saving Trust’s page on energy efficient windows and doors gives a range of options from simple upgrades to full replacement, so you can see where glass upgrades fit.

Need a hand with your patio door?

If you have run through the checks and the draught remains, or you can see misting in the glass, we can help. Cloudy2Clear Windows repairs and replaces the glass in patio doors across the UK, keeping your existing frame wherever it is sound. See our double glazed door repairs page or visit our home page to get in touch. Our phone lines are open Monday to Friday, 8:30am to 6:30pm.

Our guide on what causes a window draught has more detail.

Frequently asked questions

How do I draught proof a uPVC patio door?

Start by checking the rubber gaskets for splits or flattening, and replace any that have worn. Then check the hinge or roller alignment. Keep trickle vents open.

What can I put on my patio doors to stop draughts?

Brush strips suit sliding doors and bottom gaps, while compression strips suit hinged doors with consistent gaps. Gaskets are best for modern uPVC and aluminium frames.

My patio door is misaligned. How can I fix it?

Hinged doors can often be adjusted at the hinges with an Allen key, and sliding doors usually have adjustment screws on the rollers. If the door still drops, rubs or will not lock firmly, worn hinges, rollers or locking points probably need replacing.

Do I need Building Regulations approval to replace the glass in a patio door?

According to Hampshire’s Building Control Partnership, replacing only the glass unit does not need approval, but replacing the whole door or frame does. Check with your local authority for your own property.