Greater London · England
Sand Mastic in Clerkenwell
We cover Clerkenwell for 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 12-month guarantee.
- Wind and rain getting in round a sash window
- Tired mastic found when preparing windows for paint
- Cracked mastic round a front door frame
Sand mastic for homes and businesses in Clerkenwell
Sand mastic has long been used to fill the joint between timber frames and masonry. It’s a mix of sand and a linseed-oil-based binder and built up by hand. On older homes, it suits the building far better than silicone. Typical jobs include gaps where the frame meets the masonry and old sand mastic that has cracked, crumbled or fallen out, across tenement windows, period & listed homes and sash and case windows.
London has a lot of flats and conversions, where windows are often on upper floors. In a converted house or block, the lease usually says who is responsible for the windows, so it’s worth checking before booking.
There’s a 12-month guarantee on every job, large or small.
- Where
- Clerkenwell (N1, EC1V, WC1X)
- Region
- Greater London
- Guarantee
- 12 months on all our work
- Quotes
- Quoted before any work starts
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Clerkenwell homes and the weather
With historic houses such as Dr Johnson's House (about 0.8 miles south) nearby, there’s older building stock in the area around Clerkenwell as well as newer homes. In older buildings, older timber frames in brick or stone need a different approach from a modern uPVC window. Rainfall in the South East is lower than in much of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
For an older house near a landmark such as St James's Church, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. If you look after a building such as St Peter and St Paul RC Primary School, the mastic around its windows and doors needs looking after like any other building’s.
Clerkenwell is about 2 miles north of London, in Greater London. If you need sand mastic in Clerkenwell, it’s easy to get a quote: please phone 0345 464 0079 or email us. We cover Greater London from our Crawley base. Clerkenwell is one of 764 places in Greater London where we work.
Work in N1, EC1V and WC1X is quoted and booked the same way as anywhere else. Sand mastic is available to properties on Long Lane, City Road and Noel Road and the roads around them. With the A1 and A5201 close by, Clerkenwell is simple for us to get to for sand mastic. Other places close to Clerkenwell include Farringdon (1 mile south), Angel (1 mile north), Smithfield (1 mile south), Holborn (1 mile south-west) and St Pancras (1 mile west). Further out, we also cover Kensington (5 miles south-west), Walthamstow (5 miles north-east), Hampstead (4 miles north-west), Ruislip (14 miles west), Brompton (3 miles south-west) and Stockwell (4 miles south).
Near you in Clerkenwell
We work in homes and buildings around Barts Health Archives, The Sekforde pub and Elizabeth Garrett Anderson School. You will also find Tech City College (less than half a mile north-east) and King Square Gardens (under half a mile north-east). There’s a railway station in Clerkenwell itself: Farringdon station. Nearby you will also find Brunswick Centre (0.9 miles west) and Montfichet's Tower (0.9 miles south). Green spaces nearby include St. James's Park Lake and Ludgate Hill.
What happens on the day
On the day, there’s very little for you to do. Point us to the joints and we’ll get on with it. The work itself takes a few hours for a single window, longer for several from start to finish. In Clerkenwell, flats, stairs and shared entrances are part of the routine. Mention any building rules, key holders or managing agents when you book.
- We check each window surround and the condition of the joint.
- We rake out the old mastic and clean the joint.
- Large voids are packed out.
- New sand mastic is applied and shaped by hand.
- We finish the mastic to a tidy line.
Preparing for the visit
- Tell us about any water getting in
- Clear items away from the joints we’re working on
- Mention any tricky access
Get a quote
Asking for a quote is easy: tell us what needs doing and where, and roughly how big it is. Photos by email help us understand the job.
Advice
Honest limits
We will always be straight with you, so here’s what new sealant will not do:
- Sashes that need overhauling
- Decisions on consent for listed homes
- Putty and glazing repairs
Not sure which it is? You can ring 0345 464 0079 or drop us an email and we’ll tell you honestly before you book.
Joints and surfaces we work on
- Tenement windows
- Stone surrounds
- Timber door frames
- Brick reveals
- Sash and case windows
- Period & listed homes
Also near Clerkenwell
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What affects the quote in Clerkenwell
Jobs vary more than people expect. The main factors:
- The number and length of the joints
- Working hours on commercial sites
- How easy the joints are to reach
- The number of rooms or windows
A few things move the cost up or down: the old material and how easily it comes out, any mould to treat, and whether the work is at height. Your quote takes all of that into account.
What to tell us for a quote
When you call or email, these details help:
- The type of property
- Access, such as stairs, a lift or height
- Whether it has been sealed before
- The rough size of the job
We do not publish a price list. Instead, your job gets its own clear quote. To arrange one, phone 0345 464 0079 or drop us an email.
Can I do it myself?
If you’ve already had a go yourself, that’s fine. We remove it and do the joint properly.
If you are set on DIY, put the effort into preparation: take out all the old sealant, make sure the joint is clean and dry, and give it the full cure time. If it fails, we can still redo it.
How the job changes by surface
Sash and case windows
Most of our sand mastic work is on sash windows. Each joint round the box is raked out and renewed.
Period and listed homes
On a listed home or in a conservation area, the right material matters. Sand mastic is often the preferred finish.
Clerkenwell questions
Can you do sand mastic in Clerkenwell?
Yes. We work across London and the South East, and Clerkenwell is part of that. You can ring 0345 464 0079 or email us and tell us what needs doing.
Is parking a problem for a job in Clerkenwell?
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.
Is it worth trying it myself?
That depends on the joint. Work at height, movement joints, fire-rated gaps and large areas are best left to a professional, while a short indoor joint may be within reach.
Is it OK to seal over old sealant?
No, and we never do. It may look fine at first, but the new layer lifts away from the old one. Removing the old sealant completely is the only lasting way.
I rent my home. Can I book you?
Yes. Ask your landlord first, and we can send them the quote if that helps.
Do you have insurance?
Yes. Mr Mastic is fully insured, and we’ve been doing sealant work for more than 20 years.
Do you guarantee sand mastic work?
You get our 12-month guarantee on every job.
Should I check with the council before work on a listed or conservation-area home?
Checking first is sensible. Your local planning authority can say if consent is needed for listed or conservation-area properties.
Landlord and commercial work in Clerkenwell
In hotels, rooms out of use cost money, so the work can be planned room by room around your bookings where we can. We have worked in hotels as well as homes and businesses.
Mouldy or split sealant often shows up at the end of a tenancy, and it’s quick to put right between tenancies. Several properties can be quoted together.
Do you need sand mastic in Clerkenwell?
Sand mastic slowly weathers. It dries out, cracks and loses its grip on the stone or timber.
It’s worth asking for a quote if you see:
- A silicone bead on a sash window that spoils the look
- Old cement repairs round a window that have failed
- Tired mastic found when preparing windows for paint
- Gaps where the frame meets the masonry
If you let a flat or house near Farringdon station, cracked sand mastic around sash windows lets in the draughts tenants complain about.
What your quote should include
- What happens if they find a problem under the old sealant
- Is the old sealant removed completely?
- What the quote includes, VAT included or not
- Are they insured?