Greater London · England
New Barnet Window Mastic
We cover New Barnet for mastic around window and door frames, sills and patio doors. Old material cut out, joints cleaned and sealed neatly and every job guaranteed for a year.
- Black, perished sealant on frames
- Sealant in the wrong colour for the frame
- Gaps left after new windows were fitted
Honest limits
A few problems are outside what sealant work can do:
- A sash or casement that will not close properly
- Misting between the panes of a double-glazed unit (that needs a new unit)
- Worn gaskets, brush seals or a door that has dropped
Not sure which it is? You can phone 0345 464 0079 or send us an email and we will tell you honestly before you book.
Joints and surfaces we work on
- Timber windows & doors
- Composite doors
- Patio & French doors
- uPVC windows
- Window sills
- Aluminium frames
Window mastic in New Barnet
Homes in New Barnet have every kind of window: uPVC, aluminium, timber and composite, plus patio doors, French doors and sills. Each gets a sealant chosen for the frame and the wall it meets. We work on uPVC windows, composite doors and timber windows & doors, and common reasons people get in touch are hard, cracked sealant around windows and black, perished sealant on frames.
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, which is when draughts and damp patches appear in homes in New Barnet.
All of our work is guaranteed for twelve months, and the guarantee is the same wherever you are.
- Location
- New Barnet (EN5, EN4, N20)
- Region
- Greater London
- Cover
- One year on every job
- Quotes
- A clear quote up front
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Leave it or put it right?
Failed mastic isn’t a reason to replace sound windows. If the frames and glass are in good order, resealing the joints is often all that is needed. Problems with the glass or gaskets are for a window company, and we’ll say so. Converted houses in London often have a bathroom above someone else’s living room, so a small leak from tired sealant can mean a neighbour’s ceiling and a lot of disruption. Putting it right early is much less trouble.
No two jobs are quite the same, so each one gets its own quote. The number of joints, how easy they are to reach and the sealant needed all make a difference.
What you get with us
- A 12-month guarantee on all work
- Neat joints and a tidy finish
- An ARBOMaster approved applicator
- Over 20 years’ experience
Read our cost guide or customer reviews.
Aftercare tips
Aftercare is simple:
- Repaint timber before it’s bare
- Make sure the drainage slots are not blocked
- Look round the frames every year or so
- Clean frames with a soft cloth and soapy water
Timber frames need their paint kept up, because bare, wet timber moves more and pulls at the joint. Paint up to the joint, not over the silicone.
Water gets in quietly when mastic fails. You might not see it until plaster blows or a damp patch appears inside. Early resealing stops it reaching that point.
Window mastic in New Barnet: local notes
With historic houses such as Wyllyotts Manor (about 3.8 miles north) nearby, there’s older building stock in the area around New Barnet as well as newer homes. Where a home is older, older frames set in brick or stone need a sealant that suits them, and sometimes that is traditional sand mastic. 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.
Letting a property close to New Barnet station? Then cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets. For an older house near a landmark such as Holy Trinity Lyonsdown, the windows may be timber, sash or later replacements, and each needs the right sealant against the wall.
New Barnet is about 1 mile east of Barnet, in Greater London. We carry out window mastic for homeowners, landlords and businesses in New Barnet and the surrounding area. New Barnet is one of 764 places in Greater London we cover for window mastic. There’s also a page for London, roughly 11 miles from New Barnet.
Jobs for window mastic in EN5, EN4 and N20 works the same way as everywhere else we cover. Local streets include York Road, Park Road and Henry Road, and we cover them all. Other places close to New Barnet include Barnet (1 mile west), Cockfosters (1 mile north-east), East Barnet (1 mile south-east), Underhill (1 mile west) and Whetstone (1 mile south). Within a short drive, we also cover London (11 miles south), City of Westminster (9 miles south), Marylebone (9 miles south), Kensington (10 miles south), St Pancras (8 miles south) and Shoreditch (9 miles south-east).
Local landmarks in New Barnet
Around New Barnet, our work takes us to homes and buildings near Trent School Cockfosters, East Barnet School and The Alexandra pub and the streets around them. There’s a railway station in New Barnet itself: New Barnet station. Nearby you’ll also find Spires Shopping Centre (1.6 miles north-west) and Francis Skaryna Belarusian Library and Museum (2 miles south). Not far away are Greenhill Gardens and Darland's Lake.
Questions from New Barnet
Is parking a problem for a job in New Barnet?
In much of London, parking needs planning: a visitor permit or a nearby bay makes the day run more smoothly.
Do you work for landlords with property near New Barnet station?
Yes, we work for landlords and agents. You can call 0345 464 0079 or send us an email with the address and a few details, and we’ll give you a fixed price before any work starts.
Can new sealant go over the old?
No. Fresh sealant doesn’t stick to old sealant, and anything trapped underneath, including mould and water, stays there. We remove it all first.
Can you do upstairs windows?
Yes, where it’s safe. For high or awkward windows, we’ll tell you what access is needed.
Can you match the sealant to my frames?
Yes. We can use white, brown, anthracite grey, black or clear, so the joint suits the frame.
Which products do you use?
The product depends on the job: anti-fungal sanitary silicone in wet areas, and other sealants where joints move or face the weather. Brands we use include Arbo and Everbuild.
Can you quote for more than one area?
Yes. Tell us about everything you’d like done and you’ll get one quote.
Is the work guaranteed?
Yes, for 12 months. A yearly look at the joints helps them last.
Also near New Barnet
What else we do in New Barnet
Work for landlords, hotels and businesses
We regularly work with letting and managing agents. Tell us the address, the job and how access works and we will give you a quote.
From a single let to a portfolio, the work is the same standard: the old material taken out, careful preparation and a 12-month guarantee.
Common problems we fix in New Barnet
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.
People normally contact us when they notice something like this:
- Leaking joints at the ends of sills
- Cracked internal joints between frame and plaster
- Cracked or shrunken mastic around the frame
- Mastic that is falling out in pieces
For site and facilities teams at buildings such as St Mary's CofE Primary School, the mastic around its windows and doors needs looking after like any other building’s.
Questions to ask before booking
- Who turns up on the day
- Are they insured?
- How the colour is chosen
- How long the guarantee is
The process
When we get to you, we compare the joints with what we discussed. If anything is different, we explain it before carrying on. Most jobs then take a few hours for a handful of frames, longer for a whole house. In a London area like New Barnet, the main things to plan are parking and access: tell us about permits, visitor bays or off-street space, which floor we are working on and whether there’s a lift.
- First we look at every frame and agree the list.
- The old mastic is cut out and the surfaces cleaned back.
- Deep gaps are filled with backing rod to set the depth.
- A flexible, weatherproof sealant is applied in a colour to suit the frame.
- Finally we tidy up and check each joint.
Preparing for the visit
- Mention if the joints have been sealed before
- For indoor joints, keep the area dry beforehand if you can
- Let us know if you’ve seen damp or leaks
Ask for a quote
Every job is quoted individually. Simply ring 0345 464 0079 or send us an email and describe the job.
Related advice
What affects the cost of window mastic
Some jobs are bigger than they look, and some smaller. The main factors:
- Any working-time requirements on site
- Whether the work is at height
- Any mould that needs treating
- The type of sealant required
We do not show prices on the website, because each job is priced on what it involves. For a quick quote, please ring 0345 464 0079 or drop us an email and we will talk you through it.
What to tell us for a quote
Photos help, but a description is a good start. Please mention:
- What’s wrong with the joints now
- Whether it has been sealed before
- The rough size of the job
- Any access issues, like height or stairs
The more we know about the job, the more useful the quote. Let us know the location, the problem and roughly how many joints.