Greater London · England
Window Mastic in High Barnet
Mastic around window and door frames, sills and patio doors for High Barnet, backed by a one-year guarantee. Call for a quick quote.
- Draughty joints inside around the window
- Rain getting in at the frame or under the sill
- Gaps where the sill meets the wall
What sealant work can’t fix
Honest advice matters more to us than a booking, so here’s what new sealant won’t do:
- Misting between the panes of a double-glazed unit (that needs a new unit)
- Worn gaskets, brush seals or a door that has dropped
- Soft or decayed wood in the frame
Not sure which it is? You can phone 0345 464 0079 or drop us an email and we will tell you honestly.
Surfaces we seal
- Composite doors
- Window sills
- Timber windows & doors
- Aluminium frames
- Patio & French doors
- uPVC windows
How we handle window mastic in High Barnet
Mr Mastic’s applicators have more than 20 years’ experience with window and door sealants. We’re fully insured ARBOMaster approved applicators, and we give a 12-month guarantee on the work. We work on aluminium frames, composite doors and timber windows & doors, and people most often call us about cracked sealant at the sill ends and a bead that doesn’t match the frame.
Many London homes are flats, with windows high above the street. In a converted house or block, the lease generally says who is responsible for the windows, so it’s worth checking before booking.
Whatever the size of the job, you get the same one-year guarantee.
- Where
- High Barnet (EN5)
- Region
- Greater London
- Guarantee
- One year on every job
- Quote
- A clear price before work begins
- Call
- 0345 464 0079
- Updated
- 26 October 2026
How to look after the new joints
Once the sealant has cured, a few habits help it last:
- Air rooms to keep condensation down around windows
- Clear any debris from frame drain holes
- Do not aim a pressure washer at the joints
- Clean frames with a soft cloth and soapy water
Check the drainage slots in the frames are not blocked, so water can run away instead of sitting against the joint.
A failed joint lets water into the wall a little at a time. You might not see it until plaster blows or a damp patch appears inside. Catching it early keeps the fix to a reseal.
Your questions about window mastic in High Barnet
Is parking a problem for a job in High Barnet?
Parking in High Barnet, 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 do window mastic in High Barnet?
Yes. Our work covers London and the South East, and High Barnet is part of that. You can call 0345 464 0079 or send us an email and let us know what needs doing, and we’ll give you a clear quote.
Do you work for letting agents?
Yes, regularly. We can quote for several properties at once, and between tenancies is a good time for the work.
Do I have to be there?
For indoor joints, yes, someone needs to let us in. Once we’ve agreed the job, you do not need to watch us work.
Do you work for hotels and businesses?
Yes. Hotels, offices and other businesses use us.
Are you an approved applicator?
Yes. Mr Mastic is an ARBOMaster approved applicator, and we’re fully insured.
Do the sealants smell?
Sometimes, a little. Any smell clears as the sealant cures, and ventilation helps.
Are you insured?
Yes. We are fully insured, and we can confirm the details when we quote.
What we’re called out for in High Barnet
On timber frames, paint and putty build up around the joint. Mastic painted over many times cracks with the paint, and timber moves with moisture as well as temperature.
Any of these means the joints need attention:
- Black, perished sealant on frames
- Draughts coming in around windows and doors
- Untidy mastic left by window fitters
- Gaps where the sill meets the wall
Rented homes near Hadley Wood station change hands often, and sound mastic around windows and doors keeps out the draughts and damp that tenants notice first.
What your quote should include
- What the quote includes, VAT included or not
- Who does the work, and how experienced they are
- What happens if the job turns out different
- What product goes in the joint
Also near High Barnet
Also in High Barnet
How it works
There isn’t much for you to do on the day. Point us to the joints and we will get on with it. The work itself takes most of a day for a typical house, less for a few frames. For a job in High Barnet, parking and access are the things to plan: tell us about permits, visitor bays or off-street space, which floor we are working on and whether there’s a lift.
- We check how each frame can be reached safely.
- Old, cracked mastic is removed completely.
- Frame and wall are cleaned and must be dry before sealing.
- Backing rod fills deep voids and the sealant goes in on top.
- We tool the joint so water runs off, then clear up.
Before we arrive
- Move anything stored near the joints
- Keep children and pets away from the work area
- For business premises, tell us about site rules or sign-in
Ask for a quote
To get a quote, call 0345 464 0079 or email us with the location and a short description of the problem. You will have a clear quote before work begins.
Related advice
What window mastic looks like in High Barnet
The South East is one of the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. With historic houses such as Wyllyotts Manor (about 2.9 miles north) nearby, there’s older building stock in the area around High Barnet as well as newer homes. In older buildings, older timber frames in brick or stone need a different approach from a modern uPVC window.
High Barnet is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book. For an older house near a landmark such as Christ Church, frames set in older brick or stone need a sealant that suits the wall as well as the frame.
High Barnet is about 1 mile north-west of Barnet, in Greater London. From the centre of High Barnet to the outskirts, window mastic is available for homes and businesses alike. Our Greater London coverage runs to 764 places, High Barnet among them. Our London page covers work nearby (12 miles or so).
Every address in EN5 is within our area for window mastic, from the main roads to the quietest streets. Streets in the area include Byng Road, Park Road and Kings Road, and we cover them all. High Barnet sits on or near the A1081. If you’re just outside High Barnet, we cover Hadley (1 mile east), Arkley (1 mile south-west), Kitts End (1 mile north), Totteridge (1 mile south) and Rowley Green (2 miles west). Further out, we also cover London (12 miles south-east), City of Westminster (10 miles south), Marylebone (10 miles south), Kensington (11 miles south), St Pancras (10 miles south-east) and Shoreditch (11 miles south-east).
Around High Barnet
We work in homes and buildings around Susi Earnshaw Theatre School, The White Lion pub and Queen Elizabeth's School. The nearest railway station is Hadley Wood station, roughly 1.6 miles north-east of the centre. Well-known places in the area include Spires Shopping Centre (less than half a mile east) and Barnet General Hospital (0.5 miles south-west). Not far away are Barnet Countryside Centre and Darland's Lake.
Different surfaces, different methods
Aluminium frames
Bi-fold and sliding aluminium doors have long frame joints, and the threshold joint takes a lot of water. We prepare and reseal every joint, backing the deep ones.
Composite doors
An exposed front door gets wind-driven rain. Those corners get the most care.
DIY versus a professional finish
Sealing over old silicone is the commonest DIY error. New silicone won’t bond to old, so it peels away and traps moisture behind it. All the old material has to come out first.
The difference is mostly in the preparation and the product. Joints are cleaned back to sound surfaces and dried, and the sealant is chosen for how the joint moves and where it is, then guaranteed for a year.
Landlords, agents and businesses in High Barnet
A neglected joint can let water reach the structure, which is a bigger problem in a rented property. Resealing at the right time is simple maintenance.
We also work for businesses, from offices to washrooms and kitchens. On commercial sites, working times can be discussed when we quote.