Greater London · England
External & façade joints in Blackheath, Greater London
Specialist external mastic for Blackheath: the right sealant, proper preparation and a neat finish. Ask us for a quick quote.
- Brick movement joints where the sealant has split
- Old sealant gone brittle and cracked
- Panel joints letting water in
Can I do it myself?
Some sealant jobs are within reach of a careful DIYer, such as a straightforward joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
Not every job suits DIY: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.
External mastic in Blackheath, done properly
A movement joint is a deliberate break that lets a wall expand and contract. Its sealant has to flex with the building, season after season, so once it splits or hardens, the joint stops working and water gets in. If you have hard, crazed mastic that has stopped moving and rain getting behind render or cladding at a joint, we can put it right, on façade panels, joints between brick and frames and concrete & block alike.
Outside work in London starts with access: side passages, upper floors and where to park. For a home in Blackheath, tell us how high the joints are and how to reach the back of the building.
Big or small, it’s backed by our 12-month guarantee.
- Where
- Blackheath (SE3, SE13, SE10)
- Wider area
- Greater London
- Cover
- One year on every job
- Price
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
Different surfaces, different methods
Cladding and façade panels
Cladding and façade panels are normally separated by sealed joints. We reseal them with a sealant suited to the panel material.
Brickwork movement joints
People sometimes point up a brick movement joint by mistake. If that’s happened, we rake it out and reseal it properly where it can be done safely.
Places near Blackheath
Other services in Blackheath
What we’re called out for in Blackheath
If plants are growing out of a joint, the sealant has generally failed or was never there. Roots and dirt hold water against the wall.
People normally contact us when they notice one of these:
- Joints with sealant missing in places
- Failed seals between different materials
- Weeds or debris growing in open joints
- Damp patches traced to an open external joint
For landlords with property near Blackheath station, outside joints that have cracked can let damp into a rental, so check them between lets.
Questions to ask before booking
- Which sealant they’ll use, and why
- Whether all the old sealant comes out first
- What the cure time is
- How the surfaces are prepared before sealing
What happens on the day
The work is kept neat and contained to the area we are working on, so you can get on with your day. Expect the work to take a few hours for a handful of joints, longer for a whole elevation. In Blackheath, flats, stairs and shared entrances are part of the routine. Mention any building rules, key holders or managing agents when you book.
- We inspect the joints and agree which need resealing and how they’ll be reached.
- We cut out the failed sealant and rake out any dirt or growth.
- We clean both faces of the joint and prime them where the product calls for it.
- We push in closed-cell backing rod so the sealant is the right depth and bonds to the sides only.
- A flexible exterior sealant is applied and tooled in a colour to suit the wall.
How to prepare
- Mention any leaks or damp you’ve noticed
- Mention any sign-in or site rules at work premises
- Keep children and pets away from the work area
Ask for a quote
We do not publish a price list, as no two jobs are quite the same. Instead, we give you a clear quote for your job. To arrange one, call 0345 464 0079 or send us an email.
Advice
Honest limits
It helps to know what we cannot do too:
- Damp that is not coming from the joint
- Failed render or damaged cladding panels
- Cutting new joints into brickwork, which is building work rather than sealant work
Not sure which it is? You can call 0345 464 0079 or drop us an email and we will tell you honestly before booking.
Surfaces we seal
- Façade panels
- Copings & trims
- Brickwork movement joints
- Joints between brick and frames
- Render & cladding joints
- Concrete & block
What external mastic looks like in Blackheath
In terraces and conversions, gutters and walls are often shared with the neighbours, so it’s worth agreeing who is responsible before work starts. With historic houses such as Queen's House (about 0.9 miles north-west) nearby, there’s older building stock in the area around Blackheath as well as newer homes. In older buildings, older walls and rooflines need a sealant that moves with them and suits the material.
Homes close to Church of All Saints include some older properties, and the joints between older walls, newer extensions and the roofline need a sealant that can move. As a London address, Blackheath can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
Blackheath is about 1 mile south-east of Greenwich, in Greater London. If you need external mastic in Blackheath, please call 0345 464 0079 or email us for a quick quote. We’re based in Crawley and cover Greater London, Blackheath included. Blackheath is one of 764 towns and villages in Greater London where we work for external mastic.
Work in SE3, SE13 and SE10 is quoted and booked the same way as anywhere else. Local streets include Pond Road, Heath Lane and Wemyss Road, and we cover them all. If you are just outside Blackheath, we cover Vanbrugh Park Estate (1 mile north), Greenwich (1 mile north-west), Maze Hill (1 mile north), Lewisham (1 mile south-west) and Westcombe Park (1 mile north-east). Larger places within reach include London (5 miles north-west), City of Westminster (8 miles north-west), Marylebone (7 miles north-west), Kensington (9 miles west), St Pancras (7 miles north-west) and Shoreditch (5 miles north-west).
Near you in Blackheath
Typical jobs here are in homes near The Princess Of Wales Pub, Blackheath Proprietary School and Manor House Gardens and the streets around them. There’s a railway station in Blackheath itself: Blackheath station. Other landmarks nearby include Lewisham Shopping Centre (1.1 miles south-west) and Royal Observatory (0.7 miles north-west). Open spaces near Blackheath include Tower Hill and Birdbrook Road Nature Reserve.
FAQs for Blackheath
Can you do external mastic in Blackheath?
Yes, Blackheath is within the area we cover. We work across London and the South East. Just call 0345 464 0079 or drop us an email with a few details of the job.
Is parking an issue for external mastic in Blackheath?
In much of London, parking needs planning: a visitor permit or a nearby bay makes the day run more smoothly.
Can you seal over the old sealant?
No, because it fails. The old sealant always comes out first, so the new joint bonds to clean surfaces.
Do you work for letting agents?
Yes, often. We can quote for several properties at once, and between tenancies is a good time for the work.
Do you do commercial work?
Yes. We’ve worked for hotels, offices and other businesses, and we’re fully insured.
When will the joints need doing again?
It depends on the exposure, the movement and the product. Sealant is a maintenance item, so check the joints once a year and reseal when it splits.
Can you reach joints on upper floors?
It depends on the building. Where joints can be reached safely, we’ll do them. Give us some details and we will confirm the access.
Do the sealants smell?
It depends on the product. Some smell for a while, some hardly at all.
What affects the cost of external mastic
We quote each job individually. These are the things that affect it:
- How easy the joints are to reach
- Whether there’s mould to deal with
- How much old sealant there is and how hard it is to remove
- Any working-time requirements on site
What it costs depends on the size of the job, how much old material has to come out and access to the work. We give a clear quote before any work starts.
Asking for a quote
Before you ask for a quote, have a think about:
- Whether it’s a home or a business
- Roughly how big the job is
- Photos by email, if that’s easy
- Where the property is
Quotes start with a quick conversation. Describe the problem, the location and the size of the job. When it suits you, call 0345 464 0079 or send us an email.
Keeping the joints in good condition
Joint life depends on how it’s used and looked after. We suggest:
- Wash walls gently around the sealant
- Look over the joints every year, ideally after winter
- Tell anyone working on the walls about the movement joints
- Keep soil, plants and ivy away from the joints
Avoid pressure-washing straight into the joints. A strong jet can damage the edges of the bead.
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.