Greater London · England
Cannon Hill External Mastic
Movement joints in Cannon Hill need attention? We remove the old material, prepare the joints and seal them properly, with a 12-month guarantee.
- Old sealant gone brittle and cracked
- Cracked joints where brick meets render or frames
- Panel joints letting water in
About our external mastic in Cannon Hill
External mastic is a job where short cuts show quickly. Overfilled joints, missing backing rod and sealant laid over old sealant rarely last long. We take the old material out and do it properly. If you’re dealing with failed sealant between panels on a façade and movement joints filled with mortar instead of sealant, we can put it right, whatever the surface.
In London terraces and converted houses, gutters and walls are often shared with the house next door, so a leaking gutter joint or failed wall joint can affect more than one home. For a flat in Cannon Hill, check the lease for who looks after the outside.
The work is guaranteed for twelve months. If something is not right with it in that time, tell us and we will put it right.
- Place
- Cannon Hill (SW20, SM4, KT3)
- Region
- Greater London
- Cover
- 12 months on all our work
- Quote
- Quoted before any work starts
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
Aftercare tips
So the new joints stay in good condition:
- Act on the first splits you see
- Avoid pressure-washing directly into sealant joints
- Look over the joints every year, ideally after winter
- Keep water from gutters off the wall
Keep the joints clear of soil, plants and climbing growth. Damp material against the sealant shortens its life.
Small splits are the time to act. At that stage it’s a simple cut out and reseal.
For landlords and businesses
We work for letting agents and landlords as well as householders. Sealant work between tenants keeps a property looking cared for before the next move-in.
In hotels, rooms out of use cost money, so we plan the work room by room. Hotel work is part of what we do, alongside homes and businesses.
How it works
Every visit runs the same way: we look at the joints together, protect the area around them, carry out the job and tidy away. It normally takes a few hours to a few days, depending on the length of joint and the access. In Cannon Hill, as in most of London, parking needs a little planning. A visitor permit or a nearby bay makes the visit run more smoothly.
- Each joint is checked and the colour of the new sealant agreed.
- We take out the old sealant until the faces are sound.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- We prime the faces where required.
- A low-modulus exterior sealant is gunned in and tooled to a neat finish.
Before we arrive
- Clear items away from the joints we are working on
- Mention any leaks or damp you’ve noticed
- Where the joints are inside, avoid wetting them before we arrive
How to get a quote
If you are in Cannon Hill and need external mastic, phone 0345 464 0079 or drop us an email. A short description of the job and where it is helps us quote, and you’ll get a clear quote before work begins.
Read more
DIY versus a professional finish
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 does not work out, we can still put it right.
If you’ve already had a go yourself, that’s fine. We cut it out and start again, so tell us about it when you ask for a quote.
What happens if it’s left?
Mortar or ordinary filler might look like a quick way to close an open joint, but it locks the joint solid. The movement then cracks the brickwork or render nearby. A flexible sealant over backing rod is what the joint needs. In a flat in Cannon Hill, failed sealant seldom stays inside your own four walls: water can reach the neighbours below, and gaps in fire-rated joints affect the whole building.
A few things move the cost up or down: how much old sealant there is and how stubborn it is, whether mould needs treating, and whether the work is at height. Your quote takes all of that into account.
Why choose Mr Mastic in Cannon Hill
- Quality sealants from Arbo and Everbuild
- Anti-fungal sanitary silicone in wet areas
- Homes, businesses and hotels
- Any old sealant cut out fully, not covered over
Read our cost guide and what customers say.
Cannon Hill buildings and the weather
The South East is one of the drier parts of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. In terraces and conversions, gutters and walls are often shared with the neighbours, so check who is responsible for the outside before booking.
As a London address, Cannon Hill can be tricky for parking: tell us about permits, visitor bays or off-street space when you book. Managing a site like Hillcross Primary School? Then larger buildings have long runs of movement joint that eventually need resealing. If you let a flat or house near South Merton station, failed wall and movement joints let damp in, so they’re worth checking between tenancies.
Cannon Hill is about 1 mile north-west of Morden, in Greater London. Anywhere in SW20, we cover external mastic for homes and businesses. Cannon Hill is one of 764 towns and villages in Greater London where we work. There’s also a page for London, about 9 miles away.
Jobs for external mastic in SW20, SM4 and KT3 is quoted and booked the same way as anywhere else. Whether your property is on Aylward Road, Camborne Road and Botsford Road or anywhere close by, our applicators can take on the job. We also cover the places around Cannon Hill: Bushey Mead (1 mile north-west), Raynes Park (1 mile west), Wimbledon Chase (1 mile north), West Barnes (1 mile west) and Merton Park (1 mile north-east). Further out, we also cover London (9 miles north-east), City of Westminster (8 miles north), Marylebone (9 miles north), Kensington (7 miles north), St Pancras (10 miles north-east) and Shoreditch (11 miles north-east).
Around Cannon Hill
Around Cannon Hill, our work takes us to homes and buildings near The Edward Rayne pub, Cannon Hill Common and Harris Academy Wimbledon. The nearest railway station is South Merton station, roughly 0.5 miles north-east. A little further out are St. Anthony's Hospital (1.5 miles south) and Wimbledon Museum (1.6 miles north). Not far away are Cherry Wood and Henman Hill.
When something else is needed
We’d rather tell you now than do work that won’t last, so here’s what sealant can’t put right:
- Rising or penetrating damp from elsewhere in the wall
- Loose or hollow render, which needs re-rendering
- Cracking across the wall rather than at a joint
If you are not sure, just phone 0345 464 0079 or email us and we will give you a straight answer before you book.
What we seal
- Brickwork movement joints
- Joints between brick and frames
- Render & cladding joints
- Façade panels
- Concrete & block
- Copings & trims
Cannon Hill questions
Can parking be tricky for a visit in Cannon Hill?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. That way the visit can be planned around it.
Can you help a landlord with a rental near South Merton station?
Yes, we work for landlords and agents. Just ring 0345 464 0079 or send us an email and tell us about the property, and we’ll give you a clear price.
Are you an approved applicator?
Yes. We’re approved under the ARBOMaster scheme.
Will there be a smell?
There can be a smell while the sealant cures. Ventilation helps.
Do you guarantee your work?
Yes, for a year. If there’s a problem with our work in that time, tell us and we will put it right.
Do you work in Cannon Hill?
We do. Cannon Hill is part of the area we cover.
How often do external joints need resealing?
It varies from wall to wall: joints on exposed walls or with a lot of movement age sooner. A yearly look will tell you when they need doing. Every job carries our one-year guarantee.
Do you work for hotels and businesses?
Yes. Hotels, offices and other businesses use us, and we’re fully insured.
Towns and villages near Cannon Hill
Also in Cannon Hill
How the job changes by surface
Joints between dissimilar materials
Brick against render, concrete against metal, stone against timber: every change of material is a joint. We seal the joint with a flexible exterior sealant so neither cracks the other.
Copings and trims
Copings expand and contract through the day, so the joints need a sealant that stays flexible year round.