Greater London · England
External & façade joints in Coldharbour, Greater London
Sealing brickwork movement joints, render, cladding and façade joints for Coldharbour, backed by a 12-month guarantee. Ask us for a quote.
- Gaps where render, brick and frames meet
- Water getting into walls through failed joints
- Panel joints letting water in
DIY sealant or a professional job?
Sealing over old silicone is the commonest DIY error. Silicone does not stick to old silicone, so it lifts and traps water and mould underneath. All the old material has to come out first.
If you do try it yourself, take your time over the preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it doesn’t work out, we can still put it right.
How we handle external mastic in Coldharbour
Movement joints let brickwork, render and cladding expand and shrink without cracking. Its sealant has to flex with the building, season after season, and when it fails, the wall takes the strain and water finds a way in. We work on copings & trims, façade panels and joints between brick and frames, and common reasons people get in touch are moss and dirt in joints with no sealant left and rigid filler in a joint that should flex.
Modern London flats rely on sealed movement joints and cladding joints. Period houses have different weak points, such as gutter joints, trims and the line where an extension meets the old wall.
Big or small, you get the same one-year guarantee in Coldharbour and across Greater London.
- Where
- Coldharbour (E14, SE10, E22)
- Region
- Greater London
- Guarantee
- 12 months on all our work
- Price
- A clear quote up front
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
Signs you need external mastic in Coldharbour
Sometimes a movement joint was filled with mortar or a rigid filler. The joint can’t move, so the wall cracks somewhere else instead.
The most common problems we see are:
- Rain getting behind render or cladding at a joint
- Hard, crazed mastic that has stopped moving
- Leaking joints around cladding and façade panels
- Sealant pulling away from one side of the joint
Managing a site like Woolmore Primary School? Then movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
What your quote should include
- Which sealant they’ll use, and why
- How the surfaces are prepared before sealing
- When the joint can take water or movement
- How much experience the applicator has
What affects the cost of external mastic
We do not publish a price list, because no two jobs are the same. The quote depends on:
- Any working-time requirements on site
- The number and length of the joints
- The type of sealant required
- Mould in or behind the old joints
What you pay reflects the work, not a rough estimate. That’s why we ask about the job first.
Helping us quote
When you contact us, these details help:
- If it’s domestic, commercial or a hotel
- Any access issues, like height or stairs
- Pictures of the joints, sent by email
- The address or postcode of the job
Getting a quote is simple: let us know the job and the location, and roughly how big it is. A few pictures by email make the job easier to understand.
For landlords and businesses
Hotels need rooms back in use, so the work can be planned room by room. We have worked in hotels as well as homes and businesses.
Failed sealant is one of the commonest items on a check-out report, and it’s easy to sort out between tenants. We can quote for more than one property at once.
Towns and villages near Coldharbour
Other services in Coldharbour
How the visit works
Good joint work is mostly preparation, and we do not rush it. Every joint is cleaned and dried before new material goes in. In total, it normally takes anything from a few hours to several days, depending on the building. In Coldharbour, flats, stairs and shared entrances are part of the routine. Mention any building rules, key holders or managing agents when you book.
- 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.
- Backing rod sized to the joint goes in to set the depth.
- The exterior sealant is applied, tooled and checked along its length.
Getting ready for the visit
- Tell us about any previous sealing or DIY attempts
- Tell us about access, such as stairs, a lift or high-level joints
- Mention any sign-in or site rules at work premises
Get a quote
We do not publish a price list. Instead, we send you a clear quote for your job. To arrange one, ring 0345 464 0079 or send us an email.
Related advice
What the job involves on each surface
Concrete and blockwork
Big joints in concrete need careful depth control. We size the backing rod to the gap.
Brickwork movement joints
Brick movement joints are often mistaken for a missing mortar line. Where one has been mortared, we cut it out and reseal it with sealant if the joint can be cleared.
What external mastic looks like in Coldharbour
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. Historic houses like Queen's House (about 1.5 miles south) are a reminder that the area around Coldharbour has older buildings as well as new. Where a home is older, older brick and stone need a sealant that suits them, at the right joint depth.
As a London address, Coldharbour can be tricky for parking: tell us about permits, visitor bays or off-street space when you book. In the older streets around All Saints Church, old and new materials meet at the roofline and walls, which is where sealant earns its keep.
Coldharbour is about 2 miles north of Greenwich, in Greater London. Every kind of property in Coldharbour can book us for external mastic. Every job comes with our 12-month guarantee. Our Greater London coverage runs to 764 places, Coldharbour among them.
Postcode districts we cover here for external mastic: E14, SE10 and E22. That includes homes and businesses on Canada Square, Simpson's Road and Amsterdam Road. Being close to the A1206 and A1261, Coldharbour is easy for our applicators to reach. Neighbouring places we cover for external mastic include Blackwall (1 mile north-east), London Docklands (1 mile west), Poplar (1 mile north-west), Canary Wharf (1 mile west) and Heron Quays (1 mile west). Further out, we also cover London (4 miles west), City of Westminster (6 miles west), Marylebone (6 miles west), Kensington (8 miles west), St Pancras (5 miles west) and Shoreditch (3 miles north-west).
Around Coldharbour
We work in homes and buildings around Canary Wharf College 3, Mudchute Park and Farm and Tower Hamlets College. Coldharbour’s nearest station is Canary Wharf station, about 0.5 miles north-west. Other landmarks nearby include Old Royal Naval College (1.3 miles south) and Poplar Hospital (0.6 miles north). The countryside around Coldharbour includes Tower Hill and Lavender Pond.
Looking after it afterwards
No joint lasts for ever, but care makes a real difference. Our tips:
- Walk round the building once a year and look at the joints
- Keep movement joints as flexible joints, not mortar
- Check the sealant is paintable before painting near it
- Act on the first splits you see
Do not let soil, plants or ivy build up against the new joints. Damp material against the sealant shortens its life.
Water getting behind cladding or render can go unnoticed for a long time. By the time there’s a damp patch, the damage can be well established, so it’s worth resealing at the first signs.
Common questions in Coldharbour
I let a flat near Canary Wharf station. Can you help?
Yes, landlords and agents are among the people we work for, and several properties can be quoted together. You can ring 0345 464 0079 or drop us an email with the details for a clear quote.
Is parking an issue for external mastic in Coldharbour?
Parking in Coldharbour, as in most of London, takes a little planning: a visitor permit or a nearby bay makes the day run more smoothly.
Do you use backing rod?
Closed-cell backing rod sets the depth of the sealant and stops it sticking to the back of the joint. Then the sealant bonds to two faces and can move.
Are you an approved applicator?
Yes. Mr Mastic is an ARBOMaster approved applicator and we’re fully insured too.
Where is Mr Mastic based?
We’re based in Crawley, West Sussex, and we cover South East England, London and all of Scotland.
How long does external mastic take?
A typical job takes a few hours for a handful of joints, longer for a whole elevation, including the preparation. We’ll confirm how long when we quote.
What does external mastic cost?
The cost depends on the size of the job, access and how much old sealant has to come out. Ask us for a quote and we’ll talk you through it.
Do you have insurance?
Yes. We’re fully insured, and we can confirm the details when we quote.