How do i weatherproof and draught proof my doors and windows? (2026)

Overview

Weatherproofing and draught proofing work best when you treat them as a diagnosis-and-repair job, not just a quick strip-and-stick fix. Doors and windows usually leak in three places: the opening sashes or door leaf, the frame-to-wall joint, and worn or damaged thresholds, hinges or hardware that stop the unit closing tightly. Start by checking whether the problem is draughts, rain penetration, condensation, or a combination, because the remedy is different for each. Draught proofing normally means adding or replacing gaskets, brush strips or thresholds so the moving parts seal when closed. Weatherproofing often means renewing cracked external sealant, repairing damaged putty or glazing seals, and making sure drainage holes in modern frames stay clear so any water that gets in can drain back out. Choose products that match the material and movement of the gap, and follow the manufacturer’s instructions for preparation and application. Clean, dry surfaces matter, especially for adhesive-backed strips and sealants. Avoid over-sealing: windows and doors still need to open, lock, ventilate where designed, and drain properly. If you have decayed timber, failed double glazing, loose frames, significant water staining, or suspected structural movement, a simple DIY seal is unlikely to last and may trap moisture, so it is better to get the underlying defect repaired first.

Who this is for

Homeowners and tenants with permission who want to reduce draughts and minor rain ingress around doors and windows, where the units are basically sound and operating normally.

What you’ll need

• Torch or bright lamp
• Thin tissue or light paper to help detect draughts
• Mild cleaner and clean cloths
• Suitable replacement weatherstripping or draught excluder for the door or window type
• Exterior-grade sealant suitable for the frame material and location
• Sealant gun if using cartridge sealant
• Scraper or remover for old sealant where appropriate
• Scissors or a sharp utility knife
• Tape measure
• Step stool or suitable ladder if safely needed for access
• Manufacturer instructions for the specific door, window or sealing product

Before you start

Check whether the issue is air leakage, rain leakage, condensation, or poor operation. Inspect the frame, sash or door leaf, hinges, locks, threshold and surrounding wall for rot, cracking, distortion or movement. Confirm any replacement seals are compatible with the frame material and opening style. For modern windows and doors, identify drainage or weep holes and trickle vents so you do not block them. If you are renting or the product is still under warranty, check your agreement and warranty conditions before making changes.

Step-by-step

1. 1

   Find the exact leak or draught path

   On a windy day, or by moving a tissue slowly around the edges, identify where air is entering: around the sash or door leaf, at the meeting rails, under the door, or at the frame-to-wall junction. For rain problems, look for staining, damp patches, failed external sealant, damaged cills, open joints, or blocked drainage holes.

   Why: Different leak paths need different fixes. Sealing the wrong place can waste time or trap water.

2. 2

   Check operation, alignment and condition first

   Open and close the door or window fully. Make sure it latches properly and compresses the existing seals when shut. Tighten any obviously loose fixings you can safely access if the manufacturer allows it, and inspect for worn hinges, dropped doors, distorted frames, rotten timber, cracked glass seals or damaged thresholds.

   Why: If the unit is out of alignment or deteriorated, new seals alone often will not make proper contact or last.

3. 3

   Clean and prepare the surfaces

   Remove dirt, dust, grease and any loose or failed old sealing material from the areas you will treat. Let the surface dry fully. If replacing old sealant, cut it out carefully without damaging the frame finish, then clean the joint as recommended by the sealant manufacturer.

   Why: Seals and adhesive strips fail early on dirty, damp or unstable surfaces.

4. 4

   Replace or add draught seals to opening parts

   Fit the correct type of weatherstripping for the window or door style and the size of the gap, following the product and frame manufacturer guidance. Compression seals suit many hinged openings; brush or wiper seals are often used for sliding components and thresholds. Place the seal so it contacts evenly when closed but does not stop smooth operation or locking.

   Why: The right seal reduces uncontrolled air leakage while still allowing the unit to work as designed.

5. 5

   Renew external sealant at fixed joints if needed

   Where the frame meets the wall or trim, apply an exterior-rated sealant only to sound, appropriate joints that are meant to be sealed. Tool it neatly so it bonds well and sheds water. Do not seal over drainage routes, movement joints not intended for that product, or concealed defects you have not diagnosed.

   Why: Good perimeter sealing helps stop wind-driven rain and outside air entering around the frame.

6. 6

   Address the threshold and bottom edge

   If draughts are coming under a door, inspect the threshold, sill and any bottom seal. Replace a worn sweep or threshold seal with a compatible product, and make sure the door still clears flooring and closes fully. For external doors, also check that water will shed away from the threshold rather than pond against it.

   Why: The bottom edge is a common draught path and often needs a different seal from the sides and top.

7. 7

   Keep drainage and ventilation working

   Clear any visible drainage or weep holes in window and door frames using a gentle method that will not damage the frame. Make sure trickle vents, where fitted, remain operable and are not sealed shut.

   Why: Many modern frames are designed to manage small amounts of water internally and drain it safely outside. Blocking drainage can make leaks worse.

8. 8

   Test after fitting and monitor in bad weather

   Close and lock the window or door, check for smooth operation, then retest for draughts. After the next spell of wind or rain, inspect again for leaks, sticking, or sections where the seal is not contacting evenly.

   Why: A successful repair should improve comfort without causing binding, poor locking or trapped water.

Why this works

Draught proofing works by reducing uncontrolled air movement through gaps, which improves comfort and can reduce heat loss. Weatherproofing works by restoring the outer line of defence against wind-driven rain while allowing any incidental water that enters designed drainage channels to escape safely.

Common mistakes to avoid

• Using the wrong type or thickness of seal so the door or window will not close properly
• Applying new adhesive seals onto dusty, greasy or damp surfaces
• Sealing over frame drainage holes or weep slots
• Confusing condensation with rain penetration and treating the wrong problem
• Trying to seal around rotten timber, loose frames or failed hardware instead of repairing the underlying defect
• Blocking or disabling trickle vents that are intended to provide background ventilation

Troubleshooting

Compare your options

Alternatives

• Have worn hinges, locks, handles or keeps adjusted or replaced so the existing seals compress properly
• For badly deteriorated or obsolete units, consider professional refurbishment or replacement rather than repeated patch repairs
• Use secondary glazing or heavy lined curtains for comfort improvement where replacement is not practical, while still maintaining safe ventilation

Pro tips

• Take a photo of existing seals before removing them so you can match the profile more accurately.
• Replace one section at a time if you are unsure how the original was fitted.
• Test fit seals loosely before cutting all pieces to final length.
• For recurring leaks, inspect in daylight from both inside and outside rather than relying on a quick indoor check.
• Keep a note of the product used in case you need matching replacements later.

Legal & regulatory notes

Requirements for ventilation, means of escape, and replacement windows or external doors vary by country and local building rules. Do not block designed ventilation openings, and be cautious about alterations to escape windows or fire doors. If you are in a listed, heritage or strata-managed property, additional permissions or material requirements may apply.

Cost considerations

Simple draught sealing is usually a low-cost maintenance task compared with replacing a whole window or door, but repeated patching can be poor value if the frame is warped, rotten or poorly installed. The bigger cost driver is often hidden defects such as failed joinery, water damage or the need for hardware adjustment or replacement.

Frequently asked questions

Sources & references

Guidance on this page is traced to documented sources. Last checked 25 September 2026.

• Energy Saving Trust · industry

  Supports the general principle that draught proofing doors and windows reduces unwanted air leakage and can improve comfort and energy efficiency.

• NHBC - Condensation and ventilation guidance · industry

  Supports distinguishing condensation from rain penetration and the importance of maintaining appropriate ventilation rather than simply sealing everything.

• uPVC Windows and Doors Group - Maintenance advice · industry

  Supports the need to keep drainage channels and weep holes clear and to maintain seals, hinges and hardware on glazed doors and windows.

• Citizens Advice - Renting and home repairs · secondary

  Supports checking responsibility and permission before making repairs if you are a tenant.

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