Greater London · England
External Mastic in Northumberland Heath
External mastic in Northumberland Heath from a team with over 20 years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Weathered mastic that no longer stretches
- Joints with sealant missing in places
- Moss and dirt in joints with no sealant left
When to call us in Northumberland Heath
Buildings move more than people expect. Brickwork grows a little over the years, blockwork and concrete shrink, and all of it moves with heat and moisture. The sealant in the movement joints takes that strain.
Signs it’s time to call us include:
- Gaps where render, brick and frames meet
- Leaking joints around cladding and façade panels
- Joints where the bead has come unstuck
- Weathered mastic that no longer stretches
For an older house near a landmark such as St Paul's, old and new materials meet at the roofline and walls, which is where sealant earns its keep.
Questions to ask before you book
- What the cure time is
- Whether all the old sealant comes out first
- Are they insured?
- How hidden problems are handled
About our external mastic in Northumberland Heath
Movement joints let brickwork, render and cladding expand and shrink without cracking. The sealant in it has to stretch and squeeze for years, so once it splits or hardens, the joint stops working and water gets in. We are often asked to deal with rigid filler in a joint that should flex and joints where the bead has come unstuck, across brickwork movement joints, render & cladding joints and concrete & block.
Newer London blocks are built with movement joints in brick and render, and with cladding joints sealed with mastic. Older terraces have their own weak points: gutter joints, roofline trims and the joint where an extension meets the original wall, and both kinds of building are found across London.
Each job carries a 12-month guarantee, whatever its size.
- Where
- Northumberland Heath (DA8, DA7)
- Wider area
- Greater London
- Guarantee
- 12 months on all our work
- Quotes
- A clear price before we start
- Phone
- 0345 464 0079
- Last updated
- 26 October 2026
Nearby places to Northumberland Heath
Also in Northumberland Heath
Walls and rooflines in Northumberland Heath
London terraces and converted houses often share gutters, downpipes and walls, so it’s worth agreeing who is responsible before work starts. Historic houses like Hall Place and Gardens (about 1.8 miles south) are a reminder that the area around Northumberland Heath has older buildings as well as new. In older buildings, older brick and stone need a sealant that suits them, at the right joint depth.
Northumberland Heath is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book. Letting a property close to Barnehurst station? Then failed wall and movement joints let damp in, so they’re worth checking between tenancies.
Northumberland Heath is about 3 miles north-west of Dartford, in Greater London. Jobs in Northumberland Heath get the same care as everywhere else we work: the old material taken out, joints prepared properly and a 12-month guarantee. Northumberland Heath is one of 764 towns and villages in Greater London where we work. For nearby work, see our London page.
Our applicators cover all of DA8 and DA7 for external mastic. Whether your property is on Mill Road, Penda Road and Chalk Road or anywhere close by, our applicators can take on the job. If you are just outside Northumberland Heath, we cover Bexley Riverside (1 mile south-east), Erith (1 mile north), Barnehurst (1 mile south), Belvedere (1 mile north-west) and Lessness Heath (1 mile north-west). Larger places within reach include London (11 miles west), City of Westminster (14 miles west), Marylebone (14 miles west), St Pancras (13 miles west), Shoreditch (11 miles west) and Walthamstow (11 miles north-west).
Landmarks near Northumberland Heath
Typical jobs here are in homes near Trinity School, The Royal Oak pub and Braeburn Park, among other places. Northumberland Heath’s nearest station is Barnehurst station, roughly 0.6 miles south-west. Well-known places in the area include Erith Museum (0.7 miles north-east) and Erith and District Hospital (less than half a mile north). Not far away are Crossness Nature Reserve.
Your questions about external mastic in Northumberland Heath
Is parking a problem for a job in Northumberland Heath?
Parking in Northumberland Heath, as in most of London, takes a little planning: a visitor permit or a bay close to the door helps a lot, so mention what’s available when you book.
Is Northumberland Heath in your area for external mastic?
Yes, Northumberland Heath is within the area we cover. Our work covers London and the South East. You can ring 0345 464 0079 or drop us an email and tell us what needs doing, and we will give you a clear price.
How long before the joint can be used?
Most sealants are touch-dry well before they’re fully cured. We’ll tell you how long to leave the joint before we leave.
Do I need to be at home?
If the work is inside, we need someone to let us in. After that, you can carry on with your day.
What’s an expansion joint in brickwork?
A movement joint is a planned break in the wall that absorbs expansion and shrinkage. It’s sealed with a flexible sealant, not mortar.
Where are you based?
We work from Crawley. We cover Northumberland Heath and the rest of Greater London.
Do you seal joints where cladding meets other materials?
Yes. Materials like render, brick, metal and uPVC all move differently, so the joint between them must be flexible. We choose one that suits both surfaces.
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 12-month guarantee.
What happens on the day
On the day, we start by going over the job with you. Surfaces next to the work are protected before work begins. The work generally takes anything from a few hours to several days, depending on the building. In Northumberland Heath, flats, stairs and shared entrances are part of the routine. If the building has a concierge, managing agent or access rules, tell us when you book.
- We inspect the joints and agree which need resealing and how they’ll be reached.
- The old mastic and anything lodged in the joint is removed.
- Both sides are cleaned back to sound material and primed if needed.
- Closed-cell backing rod is fitted to set the depth and stop three-sided bonding.
- A flexible exterior sealant is applied and tooled in a colour to suit the wall.
How to prepare
- Mention any sign-in or site rules at work premises
- Let us know about earlier repairs to the joints
- Keep pets and children clear of the area while we work
Getting a quote
Getting a quote is simple: let us know the job and the location. A few pictures by email make the job easier to understand, and we will take it from there.
Related advice
DIY versus a professional finish
Some sealant jobs are within reach of a careful DIYer, like a short, easy-to-reach joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
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 doesn’t work out, we can still put it right.
Aftercare tips
Looking after new joints is easy:
- Make sure movement joints aren’t pointed over
- Point out the joints to other trades
- Keep water from gutters off the wall
- Clear growth from the base of walls and joints
Avoid pressure-washing straight into the joints. High-pressure water can lift the edges and let water in behind.
Small splits are the time to act. Then it’s a straightforward cut-out and reseal with no damage behind it to deal with.
How the job changes by surface
Copings and trims
Joints in copings, parapets and trims are exposed to the worst of the weather. Each is resealed with a weatherproof, flexible sealant.
Concrete and blockwork
Blockwork and concrete shrink over time and move with the seasons. Their movement joints are sealed over backing rod with a flexible sealant.
What happens if it’s left?
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. Damp from a failed joint spreads quietly in older London brickwork and timber, and by the time it shows on a wall or ceiling in Northumberland Heath, the repair is bigger than the sealant job would have been.
We don’t show prices on the website, because each job is priced on what it involves. For a quick quote, please phone 0345 464 0079 or drop us an email.
Why Northumberland Heath clients choose us
- 4.9 on Google from 180+ five-star reviews
- Sanitary silicone with an anti-fungal additive in wet areas
- We leave the area clean and tidy
- Trusted Arbo and Everbuild sealants
When it is not the sealant
We will not take on work that will not last, so these are the limits:
- Structural movement, which needs a surveyor or engineer
- Rising or penetrating damp from elsewhere in the wall
- 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’ll give you a straight answer.
Surfaces we seal
- Façade panels
- Joints between brick and frames
- Concrete & block
- Copings & trims
- Brickwork movement joints
- Render & cladding joints