Greater London · England
Sand mastic for sash & case windows in Finchley, Greater London
Sand mastic across Finchley and nearby, with old sealant always removed completely and a 12-month guarantee.
- Cracked mastic round a front door frame
- Weathered mastic on the most exposed windows
- Patchy fillers round a sash window
The process
There isn’t much for you to do on the day. Point us to the joints and we’ll get on with it. The job generally takes a few hours for a single window, longer for several, including the tidy-up. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. If the building has a concierge, managing agent or access rules, tell us when you book.
- We start by checking each surround and agreeing the joints to renew.
- Old, loose mastic is raked out and the joint cleaned.
- Large voids are packed out first, so the mastic isn’t too thick.
- Sand mastic is mixed and applied by hand, then shaped to the joint.
- The mastic is finished to sit tidily against the stone or brick.
Getting ready for the visit
- Keep pets and children clear of the area while we work
- Mention if the joints have been sealed before
- Tell us about access, such as stairs, a lift or high-level joints
Ask for a quote
Every job is quoted individually. Just call 0345 464 0079 or email us with the details and send pictures if you have them.
Read more
About our sand mastic in Finchley
For a listed home or one in a conservation area, ask your local planning authority if consent is needed before window work. Sand mastic is often favoured as a like-for-like material. We work on period & listed homes, stone surrounds and tenement windows, and people most often call us about draughts and rain around sash boxes and old cement repairs round a window that have failed.
Much of London’s older housing was built with timber sash windows, some still in place and some long since replaced. Either way, the mastic between frame and brickwork is what stops draughts and rain getting in, in Finchley as anywhere.
There’s a 12-month guarantee on every job.
- Location
- Finchley (N3, N2, N12, NW11)
- Region
- Greater London
- Guarantee
- One year on every job
- Price
- A clear price before any work starts
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
Work for landlords, hotels and businesses
Hotels need rooms back in use, so the work can be planned room by room. We’ve worked in hotels as well as homes and businesses.
Housing providers, facilities teams and property managers book us too in Finchley and across Greater London. We can quote a run of properties together, and we are fully insured for the work.
Leave it or put it right?
Cement-based fillers and modern sealants don’t always suit a period surround. Sand mastic is the like-for-like choice, which can matter on listed and conservation-area homes. 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 for homes in Finchley.
What you pay reflects the work, not guesswork. That’s why we ask a few questions first and agree the price before starting.
Why choose Mr Mastic in Finchley
- Sanitary silicone with an anti-fungal additive in wet areas
- We leave the area clean and tidy
- We’re fully insured
- 4.9 on Google from 180+ five-star reviews
Read our cost guide and customer reviews.
Surface by surface
Brick reveals
Brick reveals round timber windows are often pointed with sand mastic. It suits older brickwork.
Stone surrounds
Old stone surrounds are often uneven, so the gap isn’t the same all the way round. Sand mastic is shaped by hand to suit.
Windows and doors in Finchley
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. In London conversions and blocks, the lease decides who is responsible for the frames, so it’s worth checking before booking.
For site and facilities teams at buildings such as Manorside Primary School, the mastic around its windows and doors needs looking after like any other building’s. Finchley is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book. Homes close to St Paul's Finchley include some older properties, and frames set in older brick or stone need a sealant that suits the wall as well as the frame.
Finchley is about 6 miles north of City of Westminster, in Greater London. We provide sand mastic to homeowners, landlords and businesses in Finchley and the surrounding area. Finchley is one of 764 towns and villages in Greater London we cover. There’s also a page for London, roughly 8 miles from Finchley.
We work across N3, N2, N12 and NW11 for sand mastic and the streets around it. Whether your property is on Station Road, Chaplin Square and Market Place or anywhere close by, our applicators can take on the job. With the B1462 close by, Finchley is simple for us to get to. We also cover the places around Finchley: Church End (1 mile west), Woodside Park (1 mile north), North Finchley (1 mile north), Friern Barnet (2 miles north-east) and Oakleigh Park (2 miles north). Within a short drive, we also cover London (8 miles south-east), City of Westminster (6 miles south), Marylebone (6 miles south), Kensington (7 miles south), St Pancras (6 miles south-east) and Shoreditch (7 miles south-east).
Around Finchley
Locally, jobs take us to homes and businesses close to The Elephant Inn, Bishop Douglass School and Francis Skaryna Belarusian Library and Museum and the streets around them. Other local landmarks include Victoria Park (under half a mile north) and Woodhouse College (1 mile north-east). Finchley’s nearest station is New Southgate station, about 1.9 miles north-east of the centre. Well-known places in the area include Finchley Memorial Hospital (within half a mile north-east) and Grand Arcade (1 mile north). Open spaces near Finchley include Highgate Hill and Lakeside Nature Reserve.
Can I do it myself?
Too much sealant is as bad as too little. A thick, smeared bead looks untidy and doesn’t move well, and the joint depth matters as much as the finish.
If you’ve already had a go yourself, that is fine. We cut it out and start again, so tell us about it when you ask for a quote.
Towns and villages near Finchley
What else we do in Finchley
Aftercare tips
Aftercare is simple, and it makes a real difference:
- Have rotten timber repaired before new mastic goes in
- Keep modern sealant off the mastic
- Inspect the joints round the windows every year or so
- Check with your local planning authority if your home is listed
Avoid painting over the new mastic, as traditional guidance advises. Ask us before any decorating around it.
Renewing mastic before redecorating saves doing it twice. Painting over failed mastic hides the problem for a while.
When something else is needed
We’d rather tell you now than do work that will not last, so here’s what sealant can’t put right:
- Timber that has rotted
- Sash cords, weights and draught-proofing of the sashes
- Damaged stone surrounds
If in doubt, ring 0345 464 0079 or email us and we will say what we think.
Surfaces we seal
- Brick reveals
- Tenement windows
- Stone surrounds
- Timber door frames
- Sash and case windows
- Period & listed homes
Finchley questions
I let a flat near New Southgate station. Can you help?
Yes, rental work is part of what we do. Just phone 0345 464 0079 or send us an email and tell us about the property, and we’ll give you a clear quote.
Is parking a problem for a job in Finchley?
Parking in Finchley, 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.
Are you an approved applicator?
Yes. Mr Mastic is an ARBOMaster approved applicator, and we are fully insured.
Does someone need to be in?
We need access to the joints, so we’ll agree that with you when we book. Indoors, that normally means someone at home.
Do you come to Finchley?
Yes. We work in Finchley, as part of our work across South East England, London and Scotland. For a quote, ring 0345 464 0079 or drop us an email.
What does sand mastic cost?
The cost depends on the size of the job, access and how much old sealant has to come out. Call for a quick quote and we’ll talk you through it.
What do you need from me for a quote?
The location, the problem and the rough size of the job. Photos by email help too.
How long does sand mastic take to go off?
Not right away. The skin forms first, and the full set comes later, and we’ll tell you what to expect.