Greater London · England
Eltham External Mastic
Our applicators work in Eltham on sealing brickwork movement joints, render, cladding and façade joints. Old material cut out, joints cleaned and sealed neatly.
- Joints pointed up with cement by mistake
- Moss and dirt in joints with no sealant left
- Movement joints with cracked, split or missing sealant
When something else is needed
In fairness, there are a few things sealant won’t fix:
- Rising or penetrating damp from elsewhere in the wall
- Failed render or damaged cladding panels
- Walls that need new movement joints cut into them
If you are not sure, just ring 0345 464 0079 or email us and we’ll give you a straight answer before booking.
Surfaces we seal
- Joints between brick and frames
- Façade panels
- Brickwork movement joints
- Copings & trims
- Render & cladding joints
- Concrete & block
External mastic in Eltham
As ARBOMaster approved applicators, we choose exterior sealants to suit the joint and the surfaces. Porous or awkward surfaces are primed where the sealant needs it and we use one wherever it does. If you’re dealing with damp patches traced to an open external joint and joints where the bead has come unstuck, we can put it right, whatever the surface.
London’s terraces and conversions often share walls, gutters and downpipes with their neighbours, so a leaking gutter joint or failed wall joint can affect more than one home. For a flat in Eltham, check the lease for who looks after the outside.
We guarantee the work for a year. If something isn’t right with it in that time, tell us and we’ll put it right.
- Place
- Eltham (SE9, SE12, DA15, BR7)
- Region
- Greater London
- Cover
- A year, on every job
- Quote
- A clear price before any work starts
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Towns and villages near Eltham
More services for Eltham
The process
When we get to you, we check the joints match what you told us. If anything is different, we explain it before carrying on. Most jobs then take a few hours for a handful of joints, longer for a whole elevation. In a London area like Eltham, the main things to plan are parking and access: let us know about parking, the floor we’ll be working on and any lift or shared entrance.
- Each joint is checked and the colour of the new sealant agreed.
- We take out the old sealant until the faces are sound.
- Backing rod goes in so the sealant can stretch between the two faces.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
Before we arrive
- Mention any leaks or damp you’ve noticed
- Move anything stored near the joints
- Try not to wet indoor joints just before the visit
Ask for a quote
We quote each job on its own, so the first step is telling us about yours. Just phone 0345 464 0079 or drop us an email with the details.
Related advice
External mastic in Eltham: local notes
Historic houses like Eltham Palace (about 0.4 miles north-west) are a reminder that the area around Eltham has older buildings as well as new. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material. 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.
As a London address, Eltham can be tricky for parking: tell us about permits, visitor bays or off-street space when you book. If you live in an older home near Church of Holy Trinity, the joints between older walls, newer extensions and the roofline need a sealant that can move.
Eltham is about 7 miles west of Dartford, in Greater London. We carry out external mastic for homes and businesses in Eltham and nearby. We cover 764 towns and villages across Greater London, from the larger towns to small villages. You can also see our page for London, roughly 8 miles from Eltham.
Every address in SE9, SE12, DA15 and BR7 is within our area for external mastic, from the main roads to the quietest streets. Local streets include Eltham High Street, Tarnwood Park and Elmslie Court. Eltham sits on or near the A20 and B263. If you’re just outside Eltham, we cover Middle Park (1 mile west), New Eltham (1 mile south-east), Well Hall (1 mile north), Coldharbour (1 mile south) and Avery Hill (1 mile north-east). Larger places within reach include London (8 miles north-west), City of Westminster (10 miles north-west), Marylebone (10 miles north-west), Kensington (12 miles west), St Pancras (9 miles north-west) and Shoreditch (8 miles north-west).
Local landmarks in Eltham
In Eltham, that means homes and buildings near Horn Park, Eltham Church of England Primary School and The Greyhound Public House, among other places. Eltham has its own railway station: Mottingham station. A little further out are Eltham Community Hospital (less than half a mile north) and Metropolitan Police Museum (2.1 miles east). Green spaces nearby include The Tarn and Summer Hill.
How to look after the new joints
No joint lasts for ever, but care makes a real difference. A few tips:
- Clear growth from the base of walls and joints
- Tell anyone working on the walls about the movement joints
- Look over the joints every year, ideally after winter
- Avoid pressure-washing directly into sealant joints
Give the sealant the cure time we tell you before anything rubs against it. Most exterior sealants skin fast but take longer to cure right through.
Gaps, plants or missing sealant in a joint are worth getting looked at. Early work is quicker and leaves a better finish.
Your questions about external mastic in Eltham
I let a flat near Mottingham station. Can you help?
Yes. We work for landlords and agents as well as homeowners, and several properties can go on one quote. You can phone 0345 464 0079 or send us an email with the details for a clear quote.
Can you do external mastic in Eltham?
Yes, Eltham is within the area we cover. We work across London and the South East. Just call 0345 464 0079 or email us with a few details of the job.
What does external mastic cost?
The cost depends on the size of the job, access and how much old sealant has to come out. Call for a quick quote and we’ll talk you through it.
Is it messy?
No. The area is protected while we work and cleaned up afterwards.
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. That way it bonds to the two sides only and can stretch.
Do I have to be there?
Access is agreed with you when the job is booked. Indoors, that normally means someone at home.
Where do you work from?
We work from Crawley. We cover Eltham and the rest of Greater London.
Are you insured?
Yes. We’re fully insured for every job we do.
Leave it or put it right?
Sealing over the top of old mastic does not hold for long. New sealant doesn’t bond well to old, weathered sealant, so the old joint is cut out fully first. In London conversions, one flat’s bathroom is often above another flat’s ceiling, and a slow leak from a failed seal can end up in the flat below. Putting it right early is much less trouble for homes in Eltham.
There are no prices on our website, because the cost depends so much on the job itself. For a quick quote, please call 0345 464 0079 or send us an email and we’ll talk you through it.
What you get with us
- 4.9 on Google from 180+ five-star reviews
- Quality sealants from Arbo and Everbuild
- White, clear, grey or coloured to suit, where the product allows
- Fully insured
Take a look at what affects the cost or what customers say.
Landlords, agents and businesses in Eltham
Letting agents often deal with us directly. Tell us the address, the job and how access works.
For anyone letting property in or around Eltham, jobs at different addresses can be quoted together. Send us the addresses and the work at each.
When to call us in Eltham
Joints sealed without backing rod, or far too deep, rarely last. If the sealant sticks to the back as well as the sides, it cannot stretch and rips as the joint opens.
Signs it’s time to call us include:
- Hard, crazed mastic that has stopped moving
- Weeds or debris growing in open joints
- Panel joints letting water in
- Joints where the bead has come unstuck
Letting a property close to Mottingham station? Then split movement joints are easy to miss on a rental until damp shows inside.
What your quote should include
- Is VAT in the price?
- How hidden problems are handled
- Whether they’re fully insured
- What preparation is included
Should I try it myself first?
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.
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and getting the depth right matters as much as the look.