Greater London · England
North Finchley Window Mastic
Mastic around window and door frames, sills and patio doors for North Finchley, backed by a 12-month guarantee. Ask us for a quote.
- Gaps where the sill meets the wall
- Untidy mastic left by window fitters
- Damp patches on the reveal after heavy rain
Window mastic in North Finchley
Most frames have an outside joint and an inside one. The external joint is the weather seal; inside, the joint between frame and plaster stops draughts and tidies the reveal. We seal one or both, depending on what’s needed. We are often asked to deal with leaking joints at the ends of sills and black, perished sealant on frames, on composite doors, uPVC windows and window sills.
London homes have every kind of window, from timber sashes in period terraces to aluminium and uPVC in newer blocks. The mastic around them dries out and cracks with age, which is when draughts and damp patches appear in homes in North Finchley.
We stand behind the work with a 12-month guarantee, so you’re covered after we’ve gone.
- Place
- North Finchley (N12, N20, N11)
- Region
- Greater London
- Guarantee
- A year, on every job
- Quote
- A clear price before any work starts
- Phone
- 0345 464 0079
- Last updated
- 26 October 2026
What we are called out for in North Finchley
Every frame moves through the day. Sun on a frame makes it expand, and it contracts again overnight, while the brick or render around it hardly moves. If the sealant can’t stretch, it splits.
Signs it’s time to call us include:
- Cracked sealant at the sill ends
- Draughty joints inside around the window
- Mastic that has split away from the wall
- Damp patches on the reveal after heavy rain
If you let a flat or house near New Southgate station, cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets.
Before you book anyone
- Are they insured?
- What happens if the job turns out different
- Whether the sealant suits the joint
- What guarantee comes with the work
Towns and villages near North Finchley
Also in North Finchley
How the visit works
On the day, we start by going over the job with you, so there are no surprises. Surfaces next to the work are protected before any work begins. The work generally takes most of a day for a typical house, less for a few frames. For a job in North Finchley, parking and access are the things to plan: let us know about parking, the floor we’ll be working on and any lift or shared entrance.
- We check how each frame can be reached safely.
- All the failed sealant is cut away, along with any loose debris.
- Frame and wall are cleaned and must be dry before sealing.
- Deep voids are backed, then the sealant is gunned in.
- We tool the joint so water runs off, then clear up.
Preparing for the visit
- Tell us about any water getting in
- Move anything stored near the joints
- Try not to wet indoor joints just before the visit
How to get a quote
Want a quote for window mastic? Please ring 0345 464 0079 or email us and tell us about the job. We’ll explain what we’d do and send you a clear quote before work begins.
Related advice
Should I try it myself first?
Sealing over old silicone is the commonest DIY error. Silicone doesn’t stick to old silicone, so it lifts and traps water and mould underneath. Everything old must be removed first.
If you’ve already had a go yourself, that is fine. We remove it and do the joint properly.
For landlords and businesses
Letting agents often deal with us directly. Send the address, what’s needed and the access arrangements.
We also work for property managers and facilities teams. Several sites can go on one quote, and we are fully insured.
North Finchley homes and the weather
Rainfall in the South East is lower than in much of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. In London conversions and blocks, the lease decides who is responsible for the frames, so it’s worth checking before booking.
Schools such as Sacks Morasha Jewish Primary School are buildings too, and the mastic around its windows and doors needs looking after like any other building’s. North Finchley is in London, so parking needs planning: let us know about parking bays, permits or a driveway.
North Finchley is about 1 mile north of Finchley, in Greater London. We carry out window mastic for householders, landlords and businesses in North Finchley and nearby. Across Greater London, we cover 764 places, and North Finchley is one of them. For nearby work, see our London page, about 9 miles away.
Here we cover the N12, N20 and N11 postcode area for window mastic. Local streets include High Road, Lodge Lane and Percy Road. You will find North Finchley on the A1000, which makes it straightforward to reach. Close by, we work in Woodside Park (1 mile west), Oakleigh Park (1 mile north), Whetstone (1 mile north), Friern Barnet (1 mile east) and Finchley (1 mile south). We also work in nearby towns such as London (9 miles south-east), City of Westminster (7 miles south), Marylebone (7 miles south), Kensington (8 miles south), St Pancras (7 miles south) and Shoreditch (8 miles south-east).
Landmarks near North Finchley
In North Finchley, that means homes and buildings near Friary Park, Woodhouse College and The Bohemia pub. Nearby too are Francis Skaryna Belarusian Library and Museum (0.5 miles west) and St Michael's Catholic Grammar School (under half a mile south-west). The closest station to North Finchley is New Southgate station, roughly 1.4 miles east of the centre. A little further out are Finchley Memorial Hospital (0.8 miles south) and Francis Skaryna Belarusian Library and Museum (0.5 miles west). Open spaces near North Finchley include Darland's Lake and Glebelands Local Nature Reserve.
Looking after it afterwards
Once the sealant has cured, a few habits help it last:
- Clean frames with a soft cloth and soapy water
- Air rooms to keep condensation down around windows
- Do not aim a pressure washer at the joints
- Keep drainage slots and sill grooves clear
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.
On timber windows, water behind the joint can lead to rot. Once wood has rotted, it needs repair before it can be sealed, so it pays to reseal before that happens.
Common questions in North Finchley
I let a flat near New Southgate station. Can you help?
Yes, rental work is part of what we do. You can call 0345 464 0079 or send us an email with the address and a few details, and we will give you a fixed price before we start.
Is parking an issue for window mastic in North Finchley?
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.
Do you remove the old sealant?
Always. Sealing over old sealant is the main reason resealing fails early, and it’s something we never do.
Can you get sealant to suit coloured frames?
Yes. White, brown, anthracite grey, black and clear sealants are all available, so the joint suits the frame.
Are you insured?
Yes, we’re fully insured for domestic and commercial work.
Can resealing stop a draught around my window?
Often, yes. The gap between frame and wall is a common source of draughts, and sealing the inside and outside joints closes that path.
Can I do it myself?
It depends on the job. High-level, external movement and fire-rated joints are professional jobs, while a short indoor joint may be within reach.
Are you ARBOMaster approved?
Yes. Mr Mastic is an ARBOMaster approved applicator and we are fully insured too.
Why deal with it now?
The work is quick compared with the damage it prevents: the visit takes a morning for a couple of windows and a door. Wait for damp to appear and there may be plaster and decorating to sort out too. In London conversions, one flat’s bathroom is often above another flat’s ceiling, and a slow leak from a failed seal can end up in the flat below. Putting it right early is much less trouble.
Combining jobs into one visit usually makes better use of the time than several visits, so tell us about everything that needs sealing. You will get one clear quote for the whole job.
Why North Finchley clients choose us
- Colour picked to suit the job
- Domestic, commercial and hotel work
- We never seal over old sealant
- Quality sealants from Arbo and Everbuild
Read what affects the cost and customer reviews.
What we can’t put right
Before booking, it’s worth knowing the limits:
- Rotten timber, which needs a joiner first
- Worn gaskets, brush seals or a door that has dropped
- A sash or casement that won’t close properly
If in doubt, call 0345 464 0079 or email us and we will say what we think before booking.
Surfaces we seal
- uPVC windows
- Patio & French doors
- Composite doors
- Aluminium frames
- Timber windows & doors
- Window sills