Draught-proofing doors and windows without a full refit is often the sensible route in London homes, especially where the frames are basically sound but cold air is getting through gaps, worn seals or loose ironmongery. A full replacement is not always needed, and in period flats or conservation areas it can be expensive, slow and sometimes restricted by lease or planning conditions.
The mistake we see is people buying rolls of foam strip, sticking it everywhere, then wondering why the window will not shut or why condensation appears on the glass a week later. Done badly, draught-proofing can trap moisture, damage paintwork, foul locks and hinges, or block ventilation that should be left alone.
A careful job is about finding the actual air path, choosing the right seal, and leaving the property able to breathe. In a Victorian terrace, a mansion block flat or a shopfront office, the details matter more than the product on the packet.
Understand Why the Draught Is Getting In
Most draughts come from movement and shrinkage rather than one dramatic fault. Timber expands and contracts, sash cords stretch, old putty cracks, hinges wear, and doors drop slightly on their hinges after years of use. In London housing stock, we often find front doors that have been painted ten times, sash windows with uneven meeting rails, and poorly fitted secondary glazing that leaves a gap along one side.
It matters because a draught is not just a comfort issue. Cold air across a room can make the heating run longer, and warm moist air hitting cold surfaces can lead to mould around reveals and window boards. The aim is to reduce uncontrolled air leakage while keeping proper ventilation in place, especially where gas appliances, extractor fans or trickle vents are involved.
Building Regulations Part F deals with ventilation, and it is there for good reason. Do not seal fixed vents, air bricks or purpose-made ventilation grilles just because they feel cold. If there is any doubt around a gas appliance, open flue or combustion air supply, get it checked by a Gas Safe registered engineer before blocking anything.
Find the Air Path Before Buying Seals
Start with a slow inspection on a windy day if you can. Run the back of your hand around the window frame, meeting rail, letterbox, keyhole, floor threshold and door stops. A smoke pencil or a thin strip of tissue will show movement, but keep candles away from curtains, paint flakes and old draught excluders.
Look for daylight around the door edge, rattling sash windows, cracked sealant between frame and wall, and gaps beneath skirting near bay windows. In basement flats and raised ground floor conversions, draughts can also travel through floor voids and appear around the bottom of the architrave, so sealing the window alone will not always solve it.
Make a note of each gap before you buy anything. A 2 mm gap around a casement window needs a different seal from an 8 mm gap under a front door, and using the wrong size often creates more trouble than it fixes.
Tighten and Adjust the Moving Parts
Before fitting new draught strips, check that the door or window closes properly. Loose hinges, worn keeps, misaligned sash catches and dropped uPVC doors all create gaps that no foam strip will cure for long. Sometimes the best draught-proofing is a 20-minute adjustment rather than another layer of seal.
On timber doors, we check hinge screws, the latch keep, the door stop and the threshold. If screws no longer bite into old timber, the fix may involve plugging the screw holes and refitting the hinge square. For uPVC or composite doors, adjustment usually means setting the hinges and locking points correctly, which should be done carefully to avoid stressing the multipoint lock.
A typical small adjustment visit in London may sit around £80-£180 plus materials, depending on access, condition and how many openings need attention. If a door needs planing, rehanging or a new threshold, it can move closer to £180-£350 for a more involved carpentry job.
Fit the Right Seal for Each Gap
Self-adhesive foam is cheap, usually £5-£15 a roll, but it is not the right answer for every opening. It compresses quickly on busy doors and can stop a window from latching if the gap is small. We use it only where the surface is clean, dry, even and not under heavy wear.
For timber windows and doors, brush seals, rubber compression seals or carrier-mounted draught strips are usually more reliable. On sash windows, a proper brush pile system can reduce rattling as well as draughts, but the meeting rails and parting beads need careful work. A basic draught-proofing treatment for one sash window often falls around £120-£280, while a more detailed sash overhaul with new cords, beads and locks can be £350-£700 per window depending on size and condition.
For external doors, look at the full set rather than one edge. That can include a compression seal around the frame, a drop-down seal or brush strip at the bottom, an escutcheon over the keyhole, a letterbox with internal brushes, and a threshold bar. Materials might be £25-£90 for a simple door set, but the fit is what makes it work.
Seal the Frame-to-Wall Joint Properly
A common draught path is not the opening part of the window at all, but the joint between the frame and the wall. You may see cracked decorator’s caulk, loose plaster, gaps behind old architrave or dried-out mastic outside. In older Kensington and Chelsea properties, bay windows are especially prone to this because the structure moves slightly and the external joints take weather from several angles.
Internally, loose material should be cut out before any new caulk is applied. Flexible decorator’s caulk can work for small internal gaps, but larger voids may need backing rod first so the sealant has something to work against. Externally, use a suitable exterior-grade frame sealant, not interior caulk, and avoid bridging weep holes on uPVC frames.
Small internal sealing work might cost £90-£200 as part of a handyman visit. If the external sealant has failed on upper-floor windows, safe access changes the price, and a professional should inspect it rather than leaning out of the window with a tube of silicone.
Repair Rotten or Damaged Timber Before Sealing
Draught-proofing over soft timber is a false economy. If a sill, lower sash rail or door bottom is rotten, a new seal will not hold properly and moisture will keep getting in. Press the timber gently with a screwdriver handle, not the sharp end, and look for spongy areas, flaking paint, dark staining or open joints.
Minor local repairs can often be handled with resin repair systems or new timber spliced into the damaged section. Larger decay, especially where the frame is structural or the sash is badly distorted, needs a joiner or carpenter to assess it. Our carpentry services team often deals with these repairs before any draught-proofing is fitted, because the seal is only as good as the surface beneath it.
As a rough London guide, small resin timber repairs may be £120-£300, while more involved splicing to a sash or door section can be £300-£750 plus decorating. Listed buildings and some conservation area properties may also restrict replacement styles, glazing changes and external appearance, so do not assume a modern replacement is the easiest option.
Leave Ventilation Where It Is Needed
A warmer room can still become a damp room if every bit of airflow is blocked. Trickle vents, extractor fans, air bricks and under-door gaps to rooms with mechanical extraction may be doing a job. Kitchens, bathrooms and rooms used for drying clothes are the first places where over-sealing shows up as condensation.
If you have a gas fire, open-flued boiler, solid fuel appliance or any appliance that relies on room air, do not alter nearby ventilation without advice. Gas work must be carried out by a Gas Safe registered engineer, and ventilation for combustion is a safety matter, not a comfort choice. Carbon monoxide alarms should be fitted where required, but they are not a substitute for correct air supply and professional inspection.
For flats in blocks, also remember fire doors. Flat entrance doors often need to meet fire safety requirements, including appropriate closers, strips and seals. Do not plane, drill or alter a fire door casually, and check leasehold rules or managing agent requirements before changing hardware.
Finish the Surfaces So the Work Lasts
Once draught strips, sealant or timber repairs are in place, the surrounding decoration protects the work. Bare timber edges take in moisture quickly, and cracked paint around sills is often where the next failure begins. We normally prime bare timber, fill fine defects, sand cleanly and repaint with suitable interior or exterior coatings.
On outside joinery, timing matters. Paint and sealant should not be applied to wet timber, and winter mornings in London can leave surfaces damp long after the rain stops. For external repairs, spring to early autumn usually gives the best working conditions, although small internal draught-proofing can be done at any time of year.
If decoration is part of the repair, our decorating services team can finish the repaired areas neatly rather than leaving visible patchwork around the frame. That is particularly useful in rental properties where a quick fix still needs to look presentable.
Plan the Timing, Budget and Access
Autumn is when most people notice draughts, but it is also when trades get busy with heating, roofing and weatherproofing calls. If you know a front door whistles every winter or a sash window rattles in high winds, book the inspection before the first cold snap. It is easier to test, adjust and paint when the weather is still workable.
For budgeting, these are realistic ballpark figures we see across London properties:
- DIY foam, brush strips and simple sealant: roughly £10-£60 in materials for one or two openings.
- Professional adjustment and basic draught-proofing to a door or small window: often £100-£250.
- Detailed sash window draught-proofing: commonly £120-£280 per window, more if cords, beads or locks need replacing.
- Timber repair plus draught-proofing and local decoration: typically £250-£900 depending on decay and finish.
- Secondary glazing panels for difficult windows: often £300-£900 per window, depending on size and specification.
Call a professional rather than attempting DIY if the window is high level, the glass is cracked, the timber is rotten, the door is a fire door, the lock or multipoint mechanism is binding, or there is any gas appliance ventilation nearby. For landlords, it is also worth keeping records of repairs, especially where damp complaints, fire doors or tenant comfort are involved.
If the work involves several trades, one visit can save time. A draught may need a carpenter for the frame, a decorator for the finish and a handyman for smaller seals and fittings. Kensington Maintenance Services Ltd handles this type of joined-up property maintenance across local homes, rented flats and business premises, so the job is not left half-done between trades.
Frequently Asked Questions
Q1: Can I draught-proof sash windows without replacing them?
Yes, if the sash boxes and timber are sound. Brush seals, new parting beads, adjusted catches and sometimes new cords can make a big difference without a full replacement.
Q2: Will draught-proofing stop condensation?
Not always. It can reduce cold air movement, but condensation is also linked to ventilation, heating patterns and moisture from cooking, washing and drying clothes.
Q3: Is self-adhesive foam good enough for doors?
It can work as a short-term fix on an even, low-use door. For a busy front door, a properly fitted compression seal, threshold seal and letterbox brush usually lasts longer.
Q4: Do I need permission to draught-proof windows in a conservation area?
Basic internal draught-proofing usually does not need permission, but visible external changes, replacement windows or listed building work may need approval. Check before altering original joinery.
Q5: When should a professional inspect the problem?
Get a professional inspection if there is rot, cracked glass, sticking locks, high-level access, a fire door, or any concern about ventilation for gas appliances.
The main lesson is simple: draught-proofing works best when the gap, the frame and the ventilation are all dealt with properly, not when strips are stuck on at random. If you want draught-proofing doors and windows without a full refit and would rather have the cause checked before spending money on the wrong fix, our Kensington Maintenance Services Ltd team can inspect, adjust, repair and seal the openings properly. You can get a quote or contact us through the site and we will advise on the most sensible repair for your property.