Greater London · England
External & façade joints in Sydenham, Greater London
Movement joints in Sydenham need attention? We cut out the old, prepare the joints and apply the right sealant, with a one-year guarantee.
- Weeds or debris growing in open joints
- Rain getting behind render or cladding at a joint
- Gaps where render, brick and frames meet
When something else is needed
We will not take on work that will not last, so here’s what sealant can’t put right:
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
- Render that’s blown, hollow or coming away
- Walls that need new movement joints cut into them
If you’re not sure, just ring 0345 464 0079 or send us an email and we’ll give you a straight answer before booking.
Surfaces we seal
- Copings & trims
- Brickwork movement joints
- Façade panels
- Render & cladding joints
- Concrete & block
- Joints between brick and frames
External mastic in Sydenham, done properly
Ground-floor and low-level joints are straightforward to reach. For joints higher up, give us some details of the building and we will confirm what’s needed to reach them safely. If you have hard, crazed mastic that has stopped moving and rain getting behind render or cladding at a joint, we can help.
London’s terraces and conversions often share walls, gutters and downpipes with their neighbours, so one failed joint can cause damp for more than one household. In a converted house in Sydenham, it’s worth checking who is responsible for the outside before booking.
All our work comes with a one-year guarantee.
- Where
- Sydenham (SE26, SE20, SE23)
- Wider area
- Greater London
- Guarantee
- 12 months on all our work
- Quotes
- A clear quote up front
- Phone
- 0345 464 0079
- Updated
- 26 October 2026
Places near Sydenham
More services for Sydenham
Aftercare tips
So the new joints stay in good condition:
- Never let anyone fill a movement joint with mortar
- Check the sealant is paintable before painting near it
- Show decorators and builders where the movement joints are
- Don’t let climbing plants root in the sealant
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.
External mastic in Sydenham: local notes
Compared with the north and west, the South East gets less rain, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. In terraces and conversions, gutters and walls are often shared with the neighbours, so check who is responsible for the outside before booking.
Managing a site like Kirkdale School? Then movement joints, cladding joints and gutters on larger buildings need the same care as a house’s. In the older streets around Church of St Bartholomew, the joints between older walls, newer extensions and the roofline need a sealant that can move.
Sydenham is about 3 miles south-east of East Dulwich, in Greater London. For external mastic in and around Sydenham, please ring 0345 464 0079 or email us for a quick quote. We are based in Crawley and cover Greater London, Sydenham included. Our Greater London coverage runs to 764 places, and Sydenham is one of them.
Here we cover the SE26, SE20 and SE23 postcode area for external mastic. Streets in the area include Byne Road, Lucas Road and Cator Road. Other places close to Sydenham include Penge (1 mile south), Crystal Palace (1 mile south-west), Sydenham Hill (1 mile north-west), Perry Vale (1 mile north-east) and Anerley (1 mile south-west). Further out, we also cover London (5 miles north), City of Westminster (7 miles north-west), Marylebone (8 miles north-west), Kensington (8 miles north-west), St Pancras (7 miles north) and Shoreditch (7 miles north).
Local landmarks in Sydenham
Typical jobs here are in homes near St Bartholomews's Church of England Primary School, Sydenham High School and Mayow Park and the streets around them. Sydenham has its own railway station: Sydenham station. Nearby you will also find Greenwich Castle (4.3 miles north-east) and Crystal Palace Museum (1 mile west). For a walk, there’s Dacres Wood and Knight's Hill.
For landlords and businesses
Water getting past a failed joint can damage the building, which is a bigger problem in a rented property. Keeping joints in good order is simple maintenance.
We work for letting agents and landlords as well as householders. Sealant work between tenants keeps a property looking cared for before the next move-in.
How it works
Good joint work is mostly preparation, and we don’t rush it. Joints are cleaned back and dried before anything new goes in. In total, it normally takes a few hours to a few days, depending on the length of joint and the access. In a London area like Sydenham, the main things to plan are parking and access: let us know about parking, the floor we will 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
- Where the joints are inside, avoid wetting them before we arrive
- For business premises, tell us about site rules or sign-in
- Keep children and pets away from the work area
How to get a quote
To get a quote, phone 0345 464 0079 or send us an email with the location and a short description of the problem. We’ll send you a clear quote before any work starts.
Advice
Common problems we fix in Sydenham
Sunlight, wet weather and frost wear exterior sealant down. Over the years it hardens, cracks on the surface and loses its give, so the next time the wall moves, it splits or pulls away.
The problems people usually mention when they call are:
- Plants rooting in failed movement joints
- Failed sealant between panels on a façade
- Joints with sealant missing in places
- Movement joints filled with mortar instead of sealant
As a London address, Sydenham can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
What to look for in a quote
- Whether the sealant suits the joint
- How the joint is cleaned and prepared
- Whether you can choose the colour
- When the joint can take water or movement
Common questions in Sydenham
Can parking be tricky for a visit in Sydenham?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. That way the visit can be planned around it.
Do you cover Sydenham for external mastic?
Yes, Sydenham is within the area we cover. Our work covers London and the South East. You can phone 0345 464 0079 or email us and let us know what needs doing.
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.
What information do you need?
The location, the problem and the rough size of the job. Photos by email help too.
What colours does the sealant come in?
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 does not draw the eye.
How long will you be here?
That depends on how much there is to do, but as a guide it takes a few hours to a few days, depending on the length of joint and the access. We will give you a better idea when we quote.
Do you have insurance?
Yes. Full insurance covers our work, and we can confirm the details when we quote.
Can I do it myself?
Some simple jobs can be done by a careful DIYer. The usual mistakes are sealing over old sealant, sealing a damp joint and using too much.
Quotes for external mastic in Sydenham
Jobs vary more than people expect. The main factors:
- The type of sealant required
- How many areas need sealing
- Working hours on commercial sites
- Whether there’s mould to deal with
The cost reflects the work involved, not guesswork. That is why we ask about the job first and give you a clear price before work begins.
Asking for a quote
Before you ask for a quote, have a think about:
- Where the job is, and your postcode
- How we’d reach the joints
- The problem you’ve noticed
- If it’s domestic, commercial or a hotel
Need a quote? Please call 0345 464 0079 or email us and tell us about the job. You’ll know what we plan to do, and what it will cost, before any work begins.
Why act early in Sydenham
Pointing a movement joint with mortar might seem a neat fix, but it locks the joint solid. The movement then cracks the brickwork or render nearby. The correct repair is a flexible sealant with the right backing. 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 Sydenham, the repair is bigger than the sealant job would have been.
There are no prices on our website, because each job is priced on what it involves. Call for a quick quote.
Why us?
- 4.9 on Google from 180+ five-star reviews
- More than 20 years in sealant work
- Approved under the ARBOMaster scheme
- A 12-month guarantee on all work
See what affects the cost and what customers say.