Greater London · England
South Hampstead Window Mastic
Mastic around window and door frames, sills and patio doors in South Hampstead, with a 12-month guarantee on every job. Ask us for a quote.
- Gaps between the frame and the inside reveal
- Draughts coming in around windows and doors
- Black, perished sealant on frames
Window mastic in South Hampstead, done properly
The mastic around a window or door seals the gap between the frame and the wall. Once that seal fails, wind and rain find the gap. The old mastic is removed and the joint resealed with a flexible exterior sealant. Typical jobs include hard, cracked sealant around windows and untidy mastic left by window fitters, across timber windows & doors, composite doors and uPVC windows.
London has a lot of flats and conversions, where windows are often on upper floors. Who looks after the outside of the frames can depend on the lease, so check that first, and access in South Hampstead is something to talk through when you book.
Our work is backed for twelve months, in South Hampstead and everywhere else we cover.
- Where
- South Hampstead (NW3, NW8, NW6)
- Region
- Greater London
- Guarantee
- 12 months on all our work
- Quotes
- A clear price before work begins
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
Surface by surface
Patio & French doors
Patio and French doors have the longest joints on most houses. The threshold and the bottom corners take the most water, so they get particular care.
Composite doors
A composite door generally sits in a plastic outer frame, and the joint around it is sealed like a window. We match the colour to the frame.
DIY versus a professional finish
If you do try it yourself, take your time over the preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it fails, we can still redo it.
Some sealant jobs are within reach of a careful DIYer, like a short, easy-to-reach joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
What affects the cost of window mastic
You’ll get a clear quote before we start. It takes into account:
- Whether old sealant or filler has to be cut out
- How easy the joints are to reach
- How many areas need sealing
- The size of the job
What it costs depends on the amount of work, how hard the old material is to remove and access to the work. You’ll have a clear quote before any work starts.
What to tell us for a quote
The more you tell us, the more accurate the quote. When you ask for a quote, tell us:
- Where the job is, and your postcode
- How we’d reach the joints
- If it’s domestic, commercial or a hotel
- The rough size of the job
The more we know about the job, the more useful the quote. Let us know the location, the problem and roughly how many joints, and add photos by email if you can.
Landlords, agents and businesses in South Hampstead
We also work for property managers and facilities teams in South Hampstead and across Greater London. Several sites can be quoted together, and we are fully insured for the work.
For anyone letting property in or around South Hampstead, jobs at different addresses can go on one quote. Just tell us the addresses and what each one needs, and pictures by email help.
Your questions about window mastic in South Hampstead
Can you do window mastic in South Hampstead?
Yes, South Hampstead is within the area we cover. Our work covers London and the South East. You can ring 0345 464 0079 or send us an email and tell us what needs doing, and we’ll give you a clear price.
Is parking a problem for a job in South Hampstead?
London parking needs a little planning, so let us know about permits, bays or a driveway when you book. That way the visit can be planned around it.
What information do you need?
Let us know what needs doing and where, plus pictures if you have them. We’ll ask anything else we need to know.
How long does it take to reseal the windows on a house?
A handful of frames is a short visit. We confirm the timing with your quote.
Do you seal inside as well as outside?
Yes. Draughts often come through the inside gap too, so sealing both is often worthwhile.
Are you insured?
Yes. We’re fully insured for domestic and commercial work.
What does window mastic cost?
It depends on the job, so we quote each one individually. To get one, ring 0345 464 0079 or send us an email and let us know what needs doing and where.
Do you remove the old sealant?
Yes. Sealing over the old bead is the commonest cause of early failure, and it’s something we never do.
Towns and villages near South Hampstead
What else we do in South Hampstead
Keeping the joints in good condition
Once the sealant has cured, a few habits help it last:
- Avoid blasting the frames with a pressure washer
- Air rooms to keep condensation down around windows
- Keep solvents and bleach off the sealant
- Keep paint off silicone joints
Have a look at the joints once a year, ideally after winter. Small splits are simple to catch before they leak, and if anything looks wrong, just ring 0345 464 0079 or drop us an email.
Water trapped behind a failed joint can start rot in timber frames and sills. Rotten timber needs a joiner, not a sealant, so early resealing is worth it.
What happens on the day
At the end, we look at the finished work together. The visit itself usually takes a few hours for a few frames, or a day or more for a whole house, depending on how much there is to do. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in South Hampstead. A visitor permit or a nearby bay makes the visit run more smoothly.
- We start by checking each window and door with you.
- Next the failed sealant is cut away and the joint cleaned.
- Where gaps are deep, backing rod goes in first.
- New exterior sealant goes on in a matching colour and is tooled smooth.
- Finally we tidy up and check each joint.
Before we arrive
- Tell us about access, such as stairs, a lift or high-level joints
- Let us know if you’ve seen damp or leaks
- Let us know about earlier repairs to the joints
Getting a quote
To get a quote, ring 0345 464 0079 or drop us an email and tell us where the job is and what the problem looks like. We’ll give you a clear quote before any work starts.
Read more
What sealant work cannot fix
Some problems need a builder, plumber or other trade rather than us:
- Rotten timber, which needs a joiner first
- Worn gaskets, brush seals or a door that has dropped
- Penetrating damp from a failed cavity tray or render
If in doubt, call 0345 464 0079 or drop us an email and we will say what we think.
What we seal
- uPVC windows
- Timber windows & doors
- Aluminium frames
- Window sills
- Patio & French doors
- Composite doors
South Hampstead homes and the weather
In London conversions and blocks, the lease decides who is responsible for the frames, so check that before you book. With historic houses such as Winfield House (about 0.9 miles south-east) nearby, there’s older building stock in the area around South Hampstead as well as newer homes. In older buildings, older timber frames in brick or stone need a different approach from a modern uPVC window.
In the older streets around Church of All Souls, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. For landlords with property near South Hampstead station, cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets. Managing a site like The UCL Academy? Then the mastic around its windows and doors needs looking after like any other building’s.
South Hampstead is about 1 mile south of Hampstead, in Greater London. Wherever you are in the NW3 postcode area, our applicators can take on window mastic. We cover 764 towns and villages across Greater London, large and small.
We work across the NW3, NW8 and NW6 postcode area for window mastic and the streets around it. You will find streets such as Avenue Road, Acacia Road and Harben Road, and we cover them all. We also cover Swiss Cottage (1 mile north), St John's Wood (1 mile south), Haverstock (1 mile east), Belsize Park (1 mile east) and Primrose Hill (1 mile east). We also work in nearby towns such as London (4 miles south-east), Kensington (3 miles south-west), St Pancras (3 miles south-east), Shoreditch (4 miles east), Walthamstow (7 miles north-east) and Hoxton (4 miles east).
Near you in South Hampstead
Typical jobs here are in homes near Cafe Med pub, St. Mary's Town and Country School and Holy Trinity CofE Primary School. Nearby too are Cecil Sharp House (1.1 miles east) and Primrose Hill (0.6 miles east). There’s a railway station in South Hampstead itself: South Hampstead station. Well-known places in the area include Isokon Gallery (0.8 miles north-east) and O2 Centre (0.5 miles north-west). Open spaces near South Hampstead include Adelaide Nature Reserve and The Long Water.