Greater London · England
External & façade joints in Clerkenwell, Greater London
Sealing brickwork movement joints, render, cladding and façade joints for Clerkenwell, backed by a 12-month guarantee. Ask us for a quote.
- Joints where the bead has come unstuck
- Plants rooting in failed movement joints
- Movement joints with cracked, split or missing sealant
Surface by surface
Cladding and façade panels
Where a cladding system has its own specified sealant, we follow it or an approved alternative. Tell us what the building has when you get in touch.
Concrete and blockwork
Blockwork and concrete shrink over time and move with the seasons. Their movement joints are sealed over backing rod with a flexible sealant.
About our external mastic in Clerkenwell
A movement joint is a deliberate break that lets a wall expand and contract. The sealant in it has to stretch and squeeze for years, so once it splits or hardens, the joint stops working and water gets in. We work on joints between brick and frames, copings & trims and brickwork movement joints, and common reasons people get in touch are brick movement joints where the sealant has split and failed seals between different materials.
Modern London flats rely on sealed movement joints and cladding joints. Older terraces have their own weak points: gutter joints, roofline trims and the joint where an extension meets the original wall, and both kinds of building are found across London.
All our work is covered by our 12-month guarantee.
- Place
- Clerkenwell (N1, EC1V, WC1X)
- Region
- Greater London
- Guarantee
- One year on every job
- Quote
- A clear price before work begins
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
For landlords and businesses
A neglected joint can let water reach the structure, which matters even more when someone else lives there. Keeping joints in good order is simple maintenance.
Mouldy or split sealant often shows up at the end of a tenancy, and it’s easy to sort out between tenants. Several properties can be quoted together.
What we’re called out for in Clerkenwell
Poor preparation causes many early failures: joint faces that were dusty or damp, unprimed where they needed it, or still carrying old sealant. The new sealant then lets go long before it should.
People usually contact us after spotting something like this:
- Movement joints with cracked, split or missing sealant
- Old sealant gone brittle and cracked
- Plants rooting in failed movement joints
- Rain getting behind render or cladding at a joint
Clerkenwell is in London, so parking needs planning: let us know about parking bays, permits or a driveway.
Before you book anyone
- What insurance they hold
- How the colour is chosen
- Which sealant they’ll use, and why
- What the quote includes, VAT included or not
How to look after the new joints
A little care helps the new joints last. We recommend:
- Avoid pressure-washing directly into sealant joints
- Leave the joints unpainted unless we’ve said otherwise
- Act on the first splits you see
- Make sure movement joints are not pointed over
Only paint over the joint if we have confirmed the sealant can take paint. Many exterior sealants are not designed to be painted, and paint can crack as the joint moves.
Leave a failed movement joint and water keeps getting into the wall. That can lead to damp patches, staining and frost damage which cost more to put right than the joint.
Towns and villages near Clerkenwell
More services for Clerkenwell
Your questions about external mastic in Clerkenwell
Can you help a landlord with a rental near Farringdon station?
Yes, we work for landlords and agents. Just call 0345 464 0079 or drop us an email and tell us about the property, and we’ll send you a clear quote.
Is Clerkenwell in your area for external mastic?
Yes, Clerkenwell is within the area we cover. We work across London and the South East. You can ring 0345 464 0079 or drop us an email and let us know what needs doing.
Do you seal joints where cladding meets other materials?
Yes. Joints between dissimilar materials are a big part of external work. We use a flexible sealant suited to both surfaces with primer where required.
How long does the job take?
Most jobs take a few hours for a handful of joints, longer for a whole elevation, including preparation and clearing up. Your quote will say how long we expect yours to take.
Is there any odour?
There can be a smell while the sealant cures, which fades as it sets. Ventilation helps.
Where is Mr Mastic based?
Our base is in Crawley, West Sussex, and we work across South East England, London and Scotland.
Can you match the colour of my brickwork?
The sealant colour is picked to suit the wall so the joint blends in. There’s a wide choice of exterior colours.
Do you take out the old sealant first?
Yes, always, and completely. New sealant won’t bond properly to old, so the joint is cleaned back first.
How the visit works
At the end, we look at the finished work together. The work normally takes anything from a few hours to several days, depending on the building, depending on the size of the job. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in Clerkenwell. It helps if you can point us to a visitor permit or a bay close to the door.
- Each joint is checked and the colour of the new sealant agreed.
- Failed sealant is removed back to clean, sound faces.
- Backing rod goes in so the sealant can stretch between the two faces.
- Primer is applied wherever the sealant needs it.
- We gun in low-modulus sealant and tool it neatly.
Getting ready for the visit
- Mention if the joints have been sealed before
- Move anything stored near the joints
- Try not to wet indoor joints just before the visit
Getting a quote
If you are in Clerkenwell and need external mastic, ring 0345 464 0079 or send us an email. Tell us what the problem is and where, and we’ll agree the price before any work begins.
Advice
Should I try it myself first?
What a professional job adds is preparation and the right product. We take joints back to clean, dry surfaces, and the sealant is matched to the joint and its conditions.
Sealing over old silicone is the commonest DIY error. Silicone doesn’t stick to old silicone, so it peels away and traps moisture behind it. All the old material has to come out first.
Outside joints around Clerkenwell
Historic houses like Dr Johnson's House (about 0.8 miles south) are a reminder that the area around Clerkenwell has older buildings as well as new. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material. Compared with the north and west, the South East gets less rain, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day.
Homes close to St James's Church include some older properties, and old and new materials meet at the roofline and walls, which is where sealant earns its keep. If you look after a building such as St Peter and St Paul RC Primary School, movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
Clerkenwell is about 2 miles north of London, in Greater London. If you need external mastic in Clerkenwell, it’s easy to get a quote: please call 0345 464 0079 or send us an email. We’re based in Crawley and cover Greater London, Clerkenwell included. Our Greater London coverage runs to 764 places, and Clerkenwell is one of them.
Postcode districts we cover here for external mastic: N1, EC1V and WC1X. You’ll find streets such as Long Lane, City Road and Noel Road. You’ll find Clerkenwell on the A1 and A5201, which makes it straightforward to reach with everything needed for external mastic. Nearby, we also carry out external mastic in 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).
What’s near Clerkenwell
Locally, jobs take us to homes and businesses close to Barts Health Archives, The Sekforde pub and Elizabeth Garrett Anderson School, among other places. You’ll also find Tech City College (under half a mile north-east) and King Square Gardens (less than half a mile north-east). There’s a railway station in Clerkenwell itself: Farringdon station. A little further out are Brunswick Centre (0.9 miles west) and Montfichet's Tower (0.9 miles south). For a walk, there’s St. James's Park Lake and Ludgate Hill.
How we quote for external mastic
We quote each job individually. These are the things that affect it:
- Working hours on commercial sites
- The amount of work
- The product the joint needs
- How many areas need sealing
Combining jobs into one visit usually makes better use of the time than several visits, so it’s worth mentioning everything you’d like done. You will get one clear quote for the whole job.
Asking for a quote
To help us quote quickly, please include:
- Photos by email, if that is easy
- Whether it’s a home or a business
- How many joints, rooms or windows are involved
- The address or postcode of the job
Getting a quote is simple: tell us what needs doing and where. A few pictures by email make the job easier to understand, and we will take it from there.