Greater London · England
Cockfosters External Mastic
Sealing brickwork movement joints, render, cladding and façade joints for Cockfosters, backed by a 12-month guarantee. Ask us for a quote.
- Water getting into walls through failed joints
- Plants rooting in failed movement joints
- Movement joints filled with mortar instead of sealant
How to look after the new joints
Joint life depends on how it’s used and looked after. We suggest:
- Deal with leaking gutters that soak the joints below
- Do not let climbing plants root in the sealant
- Get split or bare joints resealed while the damage is small
- Tell anyone working on the walls about the movement joints
Look over the joints once a year, ideally after winter. Splits, gaps at the edges or plants in the joint are early warning signs.
Water getting behind cladding or render can go unnoticed for a long time. When it finally shows inside, the joint may have been open for years so early resealing is worth it.
How we handle external mastic in Cockfosters
As ARBOMaster approved applicators, we choose exterior sealants to suit the joint and the surfaces. Porous or awkward surfaces are primed where the sealant needs it and we use one wherever it does. If you have sealant that has lost its bond to the brick or render and plants rooting in failed movement joints, we can help, on joints between brick and frames, render & cladding joints and brickwork movement joints alike.
London’s terraces and conversions often share walls, gutters and downpipes with their neighbours, so one failed joint can cause damp for more than one household. For a flat in Cockfosters, check the lease for who looks after the outside.
You get a one-year guarantee, the same in Cockfosters as everywhere else we work.
- Place
- Cockfosters (EN4, N14)
- Region
- Greater London
- Cover
- One year on every job
- Quote
- Quoted before any work starts
- Phone
- 0345 464 0079
- Updated
- 26 October 2026
What we do, step by step
There’s no need to move everything out, only the area right around the joints. We protect the rest, and the work takes a few hours for a handful of joints, longer for a whole elevation for a typical job. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in Cockfosters. It helps if you can point us to a visitor permit or a bay close to the door.
- We start by walking round the building and agreeing the joints and the access.
- Every bit of old sealant and any mortar or debris is cut out.
- Joint faces are cleaned back and primed if the sealant needs it.
- Backing rod sized to the joint goes in to set the depth.
- We apply the sealant, tool it and check the whole run.
Preparing for the visit
- Mention if the joints have been sealed before
- Clear the area around the work
- Mention any parking rules near the property
Ask for a quote
A good description makes for an accurate quote. Let us know the location, the problem and roughly how many joints.
Related advice
Questions from Cockfosters
Can you do external mastic in Cockfosters?
Yes. Our work covers London and the South East, and Cockfosters is part of that. Just phone 0345 464 0079 or email us with a few details of the job, and we will give you a clear quote.
Can parking be tricky for a visit in Cockfosters?
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 use backing rod?
We fit closed-cell backing rod wherever the joint depth needs controlling. It controls the depth and stops the sealant bonding to the back.
Where do you work from?
Mr Mastic is based in Crawley. Our applicators cover Cockfosters.
Can you reach joints on upper floors?
Each building is different. Send us pictures and a rough idea of the height.
What sealant do you use?
Products from Arbo and Everbuild, among others, chosen to suit the joint. We explain the product when we quote.
Do you work for hotels and businesses?
Yes. We can plan bigger jobs in stages.
When will the joints need doing again?
That depends on the wall, the weather and the movement. Look for splits, hardening or edges coming away.
What we are called out for in Cockfosters
Sunlight, wet weather and frost wear exterior sealant down. In time it goes hard, crazes on the surface and stops stretching, so the next time the wall moves, it splits or pulls away.
These are the problems we are asked about most:
- Joints with sealant missing in places
- Leaking joints around cladding and façade panels
- Weeds or debris growing in open joints
- Sealant pulling away from one side of the joint
Homes close to Christ Church include some older properties, and the joints between older walls, newer extensions and the roofline need a sealant that can move.
Before you book anyone
- Whether you can choose the colour
- What product goes in the joint
- How much experience the applicator has
- How the surfaces are prepared before sealing
What external mastic looks like in Cockfosters
Historic houses like Wyllyotts Manor (about 3.4 miles north-west) are a reminder that the area around Cockfosters has older buildings as well as new. In older buildings, older walls and rooflines need a sealant that moves with them and suits the material. London and the South East are among the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
Managing a site like Trent CofE Primary School? Then larger buildings have long runs of movement joint that eventually need resealing. As a London address, Cockfosters can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
Cockfosters is about 1 mile east of Barnet, in Greater London. For external mastic in and around Cockfosters, it’s easy to get a quote: please phone 0345 464 0079 or send us an email. We cover Greater London from our Crawley base. We cover 764 towns and villages across Greater London, large and small. For nearby work, see our London page.
We cover every part of the EN4 and N14 postcode area for external mastic. You’ll find streets such as Park Road, Grove Road and Bevan Road, all of which we cover. Cockfosters sits on or near the A111. Other places close to Cockfosters include New Barnet (1 mile south-west), Hadley Wood (1 mile north-west), East Barnet (1 mile south), Oakwood (1 mile south-east) and Osidge (1 mile south-east). Within a short drive, we also cover London (11 miles south), City of Westminster (10 miles south), Marylebone (9 miles south), Kensington (11 miles south), St Pancras (9 miles south) and Shoreditch (9 miles south).
Near you in Cockfosters
Locally, jobs take us to homes and businesses close to The Cock Inn, Trent School Cockfosters and Belmont Open Space. Cockfosters’s nearest station is New Barnet station, roughly 0.8 miles west. Well-known places in the area include Francis Skaryna Belarusian Library and Museum (2.8 miles south-west) and Chase Farm Hospital (2.5 miles north-east). Not far away are Covert Way and Darland's Lake.
Why deal with it now?
Done well, a resealed joint is a neat, straight line that suits the wall. A rushed bead with no backing looks untidy and does not last so it’s worth doing right. In a flat in Cockfosters, failed sealant seldom stays inside your own four walls: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
Rather than a set price list, we price the job in front of us: the amount of work, the old material and the access. You’ll know the price before we begin.
Why choose Mr Mastic in Cockfosters
- Neat joints and a tidy finish
- Anti-fungal silicone where joints get wet
- Colour picked to suit the job
- 12-month guarantee on every job
Read what affects the cost or what customers say.
What affects the cost of external mastic
Every job gets its own quote. These are the things that affect it:
- The number of rooms or windows
- The size of the job
- Mould in or behind the old joints
- Any working-time requirements on site
Some things make a job bigger or smaller: how much old sealant there is and how stubborn it is, any mould to treat, and whether the work is at height. Your quote takes all of that into account.
Asking for a quote
There’s no need for technical detail. Just tell us:
- Any previous sealing or DIY work
- How we’d reach the joints
- How many joints, rooms or windows are involved
- Pictures of the joints, sent by email
Call for a quick quote, or send an email if you’d rather. Tell us about the joints that need doing and we’ll explain what’s involved and give you a clear price.
Places near Cockfosters
More services for Cockfosters
Work for landlords, hotels and businesses
We also work for businesses, from offices to washrooms and kitchens. On commercial sites, working times can be discussed when we quote.
Hotels need rooms back in use, so we plan the work room by room. Hotel work is part of what we do, alongside homes and businesses.
What we cannot put right
Sealant isn’t the answer to every problem, and we’d rather say so up front. It won’t solve:
- Cutting new joints into brickwork, which is building work rather than sealant work
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
- Loose or hollow render, which needs re-rendering
If you are not sure, just ring 0345 464 0079 or drop us an email and we will give you a straight answer before you book.
What we seal
- Façade panels
- Render & cladding joints
- Copings & trims
- Brickwork movement joints
- Joints between brick and frames
- Concrete & block