Greater London · England
External Mastic in London
External mastic for London, by sealant specialists with 20+ years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Weeds or debris growing in open joints
- Movement joints with cracked, split or missing sealant
- Water getting into walls through failed joints
External mastic in London
Failed sealant is cut out, the depth set with closed-cell backing rod, and the joint resealed with a low-modulus sealant made for outside. We pick a colour that sits well with the wall so the line blends in. Typical jobs include cracked joints where brick meets render or frames and joints pointed up with cement by mistake, on render & cladding joints, concrete & block and brickwork movement joints.
Landlords and managing agents in London have plenty of walls and rooflines to keep an eye on. A failed joint above a door or a dripping gutter end is usually the first sign.
Every job comes with a one-year guarantee.
- Location
- London (CR0, E14, CR4, SW11)
- Wider area
- Greater London
- Guarantee
- A year, on every job
- Price
- Quoted before any work starts
- Phone
- 0345 464 0079
- Last updated
- 26 October 2026
External mastic in London: local notes
Rainfall in the South East is lower than in much of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. With historic houses such as Mansion House (about 1 mile north) nearby, there’s older building stock in the area around London as well as newer homes. In older buildings, older walls and rooflines need a sealant that moves with them and suits the material.
In the older streets around St George the Martyr, an extension built onto an older house moves differently, and the joint between them takes the strain. Rented homes near Elephant & Castle station change hands often, and split movement joints are easy to miss on a rental until damp shows inside. Schools such as Charles Dickens Primary School are buildings too, and larger buildings have long runs of movement joint that eventually need resealing.
London is in Greater London. If you need external mastic in London, please ring 0345 464 0079 or email us for a quick quote. We are based in Crawley and cover Greater London, London included. Our Greater London coverage runs to 764 places, and London is one of them.
Here we cover the CR0, E14, CR4 and SW11 postcode area for external mastic. Local streets include Walcot Square, Surrey Square and Sutherland Square. With the A2 and A10 close by, London is easy for our applicators to reach. Other places close to London include Walworth (1 mile south), Bermondsey (1 mile east), Camberwell (2 miles south), South Bermondsey (2 miles south-east) and Surrey Canal (2 miles south-east). We also work in nearby towns such as City of Westminster (3 miles west), Marylebone (3 miles north-west), Kensington (5 miles west), Walthamstow (7 miles north-east), Hampstead (5 miles north-west) and Ruislip (14 miles west). As one of the bigger places in Greater London, London has every kind of property, from flats to offices.
What’s near London
Locally, jobs take us to homes and businesses close to Newington Gardens, Trinity Arms Public House and London School of Musical Theatre, among other places. Nearby too are St Mary-at-Hill (0.9 miles north-east), Ark Globe Academy (under half a mile south) and The BFI Reuben Library (1 mile north-west). London has its own railway station: Elephant & Castle station. Other landmarks nearby include Surrey Dispensary (less than half a mile south-east) and Baynard's Castle (0.9 miles north). The countryside around London includes Bellenden Road Nature Garden and St. James's Park Lake.
Nearby places to London
Other services in London
What affects the quote in London
The quote reflects the job in front of us. We take into account:
- Whether there’s mould to deal with
- The product the joint needs
- How much old sealant there is and how hard it is to remove
- Access and height
Homes and businesses are quoted the same way: the amount of work, the access and the products needed, plus any working-time requirements on site. Call for a quick quote and we’ll go through it with you.
What to tell us for a quote
A few details help us give you an accurate quote. When you get in contact, it helps to mention:
- The problem you’ve noticed
- The address or postcode of the job
- Any previous sealing or DIY work
- Whether it’s a home or a business
Asking for a quote is easy: let us know what needs doing and where, and roughly how big it is. A few photos by email make the job easier to understand, and we will come back to you with a quote.
How it works
All our tools and materials come with us in the van, so there’s nothing for you to buy. After a quick look at the joints together, we protect the area and start. It normally takes a few hours to a few days, depending on the length of joint and the access. In London, we work in everything from flats and family homes to offices and hotels. Whichever it is, tell us how to get in, where to park and where the work is.
- First, the joints are inspected and the access agreed.
- 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.
- We fit closed-cell backing rod to control the depth.
- We apply the sealant, tool it and check the whole run.
Before we arrive
- Tell us if parking is tricky
- Tell us about access, such as stairs, a lift or high-level joints
- Mention if the joints have been sealed before
How to get a quote
For external mastic in London, call 0345 464 0079 or email us. Tell us what the problem is and where, and you’ll get a clear quote before work begins.
Advice
Keeping the joints in good condition
How long the joints last depends on use and care. We suggest:
- Keep water from gutters off the wall
- Check the sealant is paintable before painting near it
- Keep movement joints as flexible joints, not mortar
- Act on the first splits you see
Don’t paint over the new sealant unless we’ve said the product is paintable. Paint can crack on a flexible joint, and paint can crack as the joint moves.
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.
When it isn’t the sealant
We will not take on work that will not last, so here’s what sealant cannot put right:
- Cracked brickwork or render that needs a builder or plasterer
- Render that is blown, hollow or coming away
- Adding movement joints to masonry that has none
If you are not sure, just ring 0345 464 0079 or email us and we’ll give you a straight answer.
Where we work in London
- Façade panels
- Brickwork movement joints
- Copings & trims
- Render & cladding joints
- Concrete & block
- Joints between brick and frames
London: your questions answered
Is external mastic in London guaranteed?
Every job comes with our 12-month guarantee, wherever it is. We are also fully insured and ARBOMaster approved.
I let a flat near Elephant & Castle station. Can you help?
Yes. We work for landlords and letting agents as well as homeowners, and several properties can be quoted together. Just phone 0345 464 0079 or send us an email with the address and what needs doing, and we will give you a clear quote.
Do I have to be there?
For indoor joints, yes, someone needs to let us in. After that, you can carry on with your day.
Can you match the colour of my brickwork?
There’s a good range of exterior colours, including greys, browns, whites and stone tones. We choose the closest to your brick or render so the joint doesn’t draw the eye.
How do you reach high-level joints?
That depends on how high the joints are and the ground below. Ground-floor joints are simple; for higher ones, send details and we will confirm the access.
Are you insured?
Yes. Mr Mastic is fully insured, with over 20 years’ experience in sealant work.
Do you seal joints where cladding meets other materials?
Yes. Different materials move at different rates, so a flexible sealant is needed where they meet. We choose one that suits both surfaces.
Are you an approved applicator?
Yes. We hold ARBOMaster approved applicator status and we are fully insured too.
What the job involves on each surface
Brickwork movement joints
Clay brickwork grows slightly over its life and moves with the weather. The movement joint takes that up, so its sealant has to stay flexible.
Joints between dissimilar materials
Each side of the joint may need its own preparation. Both surfaces are cleaned and primed as the product requires.
Landlord and commercial work in London
Failed sealant is one of the commonest items on a check-out report, and it’s easy to sort out between tenants. Several properties can go on one quote.
We also work for businesses, from offices to washrooms and kitchens. On commercial sites, working times can be discussed when we quote.
Why deal with it now?
A properly done movement joint is an even line in a colour that suits the wall. A rushed bead with no backing looks untidy and does not last so it’s worth doing right. In flats, shops and offices in London, a failed joint can let water into the unit below or behind a wall, where it’s often found late and is bigger to put right.
What it costs depends on how much there is to do, how hard the old material is to remove and access to the work. We give a clear quote before we start.
Why us?
- One-year guarantee on every job
- Sealant colour chosen to suit
- Approved under the ARBOMaster scheme
- Tidy, careful work
Take a look at our cost guide or our reviews.