Greater London · England
Window Mastic in Belsize Park
Mastic around window and door frames, sills and patio doors in Belsize Park, with a 12-month guarantee on every job. Ask us for a quote.
- Gaps left after new windows were fitted
- Hard, cracked sealant around windows
- White mastic on grey or black frames
Aftercare tips
Simple care keeps the joints in good condition. Our advice:
- Walk round the house once a year and look at the joints
- Keep jet washers away from the mastic
- Repaint timber before it’s bare
- Keep paint off silicone joints
Silicone cannot normally be painted, so if you are planning to paint the frames or walls, tell us beforehand. We can use a paintable sealant where that matters.
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.
Window mastic for homes and businesses in Belsize Park
If you can feel air around a shut window, the gap is often at the frame. Resealing that joint can make a room feel noticeably less draughty. If the draught is through the window seals instead, we’ll tell you. We work on composite doors, aluminium frames and window sills, and common reasons people get in touch are untidy mastic left by window fitters and sealant in the wrong colour for the frame.
From mansion-block windows to modern glazing in new flats, London has every kind of frame. The mastic around them dries out and cracks with age, letting in draughts and water.
We guarantee the work for a year. If there’s a problem with our work within the year, let us know and we will sort it.
- Where
- Belsize Park (NW3, NW5, NW1)
- Region
- Greater London
- Cover
- One year on every job
- Price
- A clear price before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
Nearby places to Belsize Park
More services for Belsize Park
Windows and doors in Belsize Park
Compared with the north and west, the South East gets less rain, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind. In London conversions and blocks, the lease decides who is responsible for the frames, so it’s worth checking before booking.
As a London address, Belsize Park can be tricky for parking: let us know about parking bays, permits or a driveway. For an older house near a landmark such as Church of St Mary the Virgin, frames set in older brick or stone need a sealant that suits the wall as well as the frame.
Belsize Park is about 1 mile south-east of Hampstead, in Greater London. For window mastic in and around Belsize Park, please phone 0345 464 0079 or drop us an email for a quick quote. We cover Greater London from our Crawley base. Belsize Park is one of 764 places in Greater London where we work for window mastic.
We cover every part of NW3, NW5 and NW1 for window mastic and the streets around it. Window mastic is available to properties on Eton Road, Lawn Road and Ornan Road and the roads around them. We also cover Haverstock (1 mile north), Primrose Hill (1 mile south), South Hampstead (1 mile west), Swiss Cottage (1 mile west) and Chalk Farm (1 mile east). Further out, we also cover London (4 miles south-east), Kensington (4 miles south-west), Shoreditch (4 miles east), Walthamstow (7 miles north-east), Hoxton (3 miles east) and Whitechapel (4 miles south-east).
What’s near Belsize Park
We work in homes and buildings around The Washington pub, Primrose Hill and St. Mary's Town and Country School. Also close by are Cecil Sharp House (0.8 miles south-east) and St Paul's Church of England Primary School (within half a mile south). The closest station to Belsize Park is South Hampstead station, about 0.7 miles west. Well-known places in the area include Wellington Hospital (0.9 miles south-west) and O2 Centre (0.8 miles west). Not far away are Adelaide Nature Reserve and The Long Water.
How the visit works
Our applicators work methodically: protection first, then preparation, sealing and a tidy-up. For most jobs that takes a few hours for a handful of frames, longer for a whole house and we leave things clean and tidy. In Belsize Park, flats, stairs and shared entrances are part of the routine. Mention any building rules, key holders or managing agents when you book.
- We check how each frame can be reached safely.
- Old, cracked mastic is removed completely, along with any loose debris.
- Frame and wall are cleaned and must be dry before sealing.
- Backing rod fills deep voids and the sealant goes in on top.
- The joint is shaped to shed water and the area tidied.
Getting ready for the visit
- Tell us about any water getting in
- Mention if the joints have been sealed before
- Tell us if parking is tricky
Ask for a quote
We quote each job on its own. Simply call 0345 464 0079 or send us an email and describe the job.
Read more
Landlord and commercial work in Belsize Park
If you manage several properties in or around Belsize Park, jobs at different addresses can be quoted together. Send us the addresses and the work at each, and photos by email help.
Whether it’s one flat or a portfolio, the work is the same standard: the old material taken out, careful preparation and a 12-month guarantee.
Common questions in Belsize Park
I let a flat near South Hampstead station. Can you help?
Yes, rental work is part of what we do. You can phone 0345 464 0079 or drop us an email with the address and a few details, and we will give you a fixed price before any work starts.
Is parking a problem for a job in Belsize Park?
Parking in Belsize Park, as in most of London, takes a little planning: a visitor permit or a nearby bay makes the day run more smoothly, so mention what’s available when you book.
Can you match the sealant to my frames?
Yes. Grey and black frames get grey or black sealant, and wood-effect frames usually suit brown.
Are you ARBOMaster approved?
Yes. We are an ARBOMaster approved applicator, the approved applicator scheme for Arbo sealants.
Where are you based?
Mr Mastic is based in Crawley. Our applicators cover Belsize Park, along with the rest of our area.
Are you insured?
Yes. Mr Mastic is fully insured, and we have been doing sealant work for more than 20 years.
What do you need from me for a quote?
Only a few details: where it is, what you’ve noticed and how we reach it. Then phone 0345 464 0079 or drop us an email.
What do you put in the joint?
Quality sealants from brands including Arbo and Everbuild, picked for each joint. We explain the product when we quote.
What we’re called out for in Belsize Park
Plenty of failed mastic was poorly applied in the first place. Sealant run over dust, wet brick or loose mortar didn’t grip properly, and it lets go sooner than it should.
Any of these means the joints need attention:
- Draughty joints inside around the window
- Sealant in the wrong colour for the frame
- Cracked or shrunken mastic around the frame
- Old mastic that has gone black or come away
Schools such as Fine Arts College are buildings too, and larger buildings have plenty of frames, and the mastic around each one ages.
What your quote should include
- Whether the sealant suits the joint
- The length of the guarantee
- Who turns up on the day
- Whether all the old sealant comes out first
What affects the quote in Belsize Park
The quote reflects the job in front of us. We look at:
- The old material and how stubborn it is
- The product the joint needs
- The size of the job
- Whether the work is at height
Homes and businesses are quoted the same way: the amount of work, how we reach it and what it needs, plus any working-time requirements on site. Call for a quick quote and we will explain what it covers.
Helping us quote
When you contact us, it’s useful to know:
- Where the job is, and your postcode
- How we’d reach the joints
- If someone has resealed it before
- Pictures of the joints, sent by email
To get a quote, phone 0345 464 0079 or drop us an email and tell us where the job is and what the problem looks like. You’ll have a clear quote before work begins.
Leave it or put it right?
A cracked joint around a frame lets rain into the wall. Left long enough, it can stain inside walls, spoil plaster and rot wooden frames. Resealing now is a small job by comparison. In London conversions, one flat’s bathroom is often above another flat’s ceiling, so a small leak from tired sealant can mean a neighbour’s ceiling and a lot of disruption. Dealing with it early is far simpler.
What you pay reflects the work, not a rough estimate. That is why we ask about the job first.
Why Belsize Park customers choose us
- A sealant colour to suit the surroundings
- We never seal over old sealant
- Every job guaranteed for a year
- Trusted Arbo and Everbuild sealants
Read what affects the cost or customer reviews.
Should I try it myself first?
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 does not work out, we can still put it right.
Too much sealant is as bad as too little. A thick, smeared bead looks untidy and doesn’t move well, and getting the depth right matters as much as the look.