Greater London · England
Sand Mastic in Barnet
Our applicators work in Barnet on traditional burnt sand mastic around sash and case windows and doors in stone and brick. Old material cut out, joints cleaned and sealed neatly and a one-year guarantee.
- Cracked mastic round a front door frame
- Cement or filler used on old window joints that has cracked
- Gaps where the frame meets the masonry
Sand mastic in Barnet, done properly
We renew sand mastic around sash windows and doors in stone and brick. Out comes the old, loose mastic, and new mastic is applied and shaped by hand. We work on sash and case windows, timber door frames and stone surrounds, and the jobs we see most are old cement repairs round a window that have failed and a silicone bead on a sash window that spoils the look.
London has a lot of flats and conversions, where windows are often on upper floors. In a converted house or block, the lease normally says who is responsible for the windows, so it’s worth checking before booking, and access in Barnet is something to talk through when you book.
All our work comes with our one-year guarantee.
- Place
- Barnet (EN5, EN4, N20, N11)
- Region
- Greater London
- Cover
- 12 months on all our work
- Quote
- A clear quote up front
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
How we quote for sand mastic
There’s no set price list, because no two jobs are the same. The quote depends on:
- How much there is to do
- Any mould that needs treating
- The product the joint needs
- When we can work, for business premises
What it costs depends on the size of the job, how much old material has to come out and access to the work. We give a clear quote before work begins, so you know where you stand.
Helping us quote
A few details help us give you an accurate quote. When you ask for a quote, tell us:
- The address or postcode of the job
- How we’d reach the joints
- A few pictures by email, if you can
- Roughly how big the job is
Every job is quoted individually, so the first step is telling us about yours. Simply call 0345 464 0079 or send us an email and describe the job, and photos are welcome.
Common questions in Barnet
Can parking be tricky for a visit in Barnet?
In much of London, parking needs planning: a visitor permit or a bay close to the door helps a lot, so mention what’s available when you book.
Do you work for landlords with property near New Barnet station?
Yes, landlords and agents are among the people we work for. Just ring 0345 464 0079 or send us an email with the address and what needs doing, and we’ll give you a clear price.
Do I have to be there?
That depends on where the joints are. For work indoors, someone needs to let us in.
Do you have insurance?
Yes. We are fully insured.
Which products do you use?
It depends on the joint: anti-fungal sanitary silicone in wet areas, and other sealants where joints move or face the weather. We use products from Arbo and Everbuild.
How long will you be here?
It depends on the size of the job, but most jobs take a few hours per window, depending on the condition of the joints. We will give you a better idea when we quote.
Can I add another job to the visit?
Yes. Just list everything you need and you’ll get one quote.
What is sand mastic?
Sand plus a binder based on linseed oil. It’s applied by hand and shaped to suit the surround.
When it isn’t the sealant
New sealant cannot fix everything, and we’ll tell you before any work starts. It won’t solve:
- Crumbling stone or brickwork round the window
- Planning or listed building consent (your local planning authority decides)
- Broken panes
Not sure which it is? You can ring 0345 464 0079 or drop us an email and we will tell you honestly before you book.
Joints and surfaces we work on
- Period & listed homes
- Stone surrounds
- Timber door frames
- Tenement windows
- Brick reveals
- Sash and case windows
For landlords and businesses
Landlords and letting agents in Barnet can book us as well as householders. Resealing between tenancies is a simple way to keep a property in good order.
We regularly work with letting and managing agents. Tell us the address, the job and how access works and we’ll give you a quote.
Different surfaces, different methods
Sash and case windows
The box of a sash and case window sits in the stone or brick opening. The gap round it is pointed with sand mastic.
Brick reveals
Loose mastic comes out and deep gaps are packed before the new mastic goes in.
What we do, step by step
Before we leave, we go over the finished joints with you and tell you how long to leave it. The visit itself usually takes a few hours for a single window, longer for several, depending on the size of the job. 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.
- First, we look at the surrounds with you and agree what needs doing.
- The loose and crumbling mastic is raked out and the joint cleaned.
- We pack any deep gaps so the mastic sits at the right depth.
- We mix the sand mastic and apply it by hand, shaping it to the joint.
- The finish is dressed so it sits neatly against the stone or brick.
Getting ready for the visit
- Try not to wet indoor joints just before the visit
- Mention any parking rules near the property
- Tell us about access, such as stairs, a lift or high-level joints
Ask for a quote
Want a quote for sand mastic? Please ring 0345 464 0079 or email us with a few details. We’ll explain what we’d do and give you a clear price before any work starts.
Read more
Keeping the joints in good condition
To keep the joints looking good and working properly:
- Clear gutters so water doesn’t pour onto the windows
- Ask us before painting near the mastic
- Take care around the mastic when scraping paint
- Do not run silicone over sand mastic
When preparing windows for paint, take care around the mastic. It can be damaged by heavy scraping.
Good mastic helps keep the frame dry. Failed mastic lets water reach the timber, which can lead to rot.
Towns and villages near Barnet
Other services in Barnet
Why deal with it now?
A silicone bead can be quicker, but on period stone or brick it often looks out of place. Sand mastic suits the building and blends with the stone or brick. Damp from a failed joint spreads quietly in older London brickwork and timber, and by the time it shows on a wall or ceiling in Barnet, the repair is bigger than the sealant job would have been.
A failed joint rarely gets cheaper to fix by waiting. If you’re unsure, call 0345 464 0079 or email us and we’ll give you an honest view and a quote.
Why choose Mr Mastic in Barnet
- ARBOMaster approved applicator
- Every job guaranteed for a year
- 180+ five-star Google reviews
- Full insurance on every job
Read our cost guide or our reviews.
What sand mastic looks like in Barnet
London and the South East are among the drier parts of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. In a converted house or block, who looks after the windows depends on the lease, so it’s worth checking before booking.
As a London address, Barnet can be tricky for parking: tell us about permits, visitor bays or off-street space when you book. Homes close to St John's United Reformed Church include some older properties, and the joint between an old wall and a newer frame is generally the first place rain gets in. If you let a flat or house near New Barnet station, any sash windows need sound mastic to keep draughts and rain out.
Barnet is about 9 miles east of Watford, in Greater London. Wherever you are in the EN5 postcode area, we cover sand mastic for homes and businesses. Across Greater London, we cover 764 places, and Barnet is one of them. Our London page covers work nearby, about 11 miles away.
Here we cover the EN5, EN4, N20 and N11 postcode area for sand mastic. Whether your property is on Station Road, High Street and Sambroke Square or anywhere close by, we can help. Barnet is on the B193 and A1081, which makes it straightforward to reach. We also cover Underhill (1 mile west), New Barnet (1 mile east), Monken Hadley (1 mile north-west), Hadley Wood (1 mile north-east) and Cockfosters (1 mile east). Larger places within reach include London (11 miles south), City of Westminster (9 miles south), Marylebone (9 miles south), Kensington (10 miles south), St Pancras (9 miles south) and Shoreditch (10 miles south-east).
Local landmarks in Barnet
We work in homes and buildings around Queen Elizabeth's Girls' School, The Railway Tavern and Highlands Gardens, among other places. For rail, the closest station is New Barnet station, roughly 0.6 miles east. Well-known places in the area include Barnet General Hospital (1.2 miles west) and Francis Skaryna Belarusian Library and Museum (2.1 miles south). Open spaces near Barnet include Darland's Lake and Greenhill Gardens.