Greater London · England
Penge External Mastic
Specialist external mastic for Penge: careful preparation, the right product and tidy work. Ask us for a quick quote.
- Brick movement joints where the sealant has split
- Old sealant gone brittle and cracked
- Rigid filler in a joint that should flex
External mastic for homes and businesses in Penge
External mastic is a job where short cuts show quickly. Overfilled joints, missing backing rod and sealant laid over old sealant all tend to fail early. We strip the joint back and start again. If you are dealing with joints pointed up with cement by mistake and damp patches traced to an open external joint, we can put it right.
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. In a converted house in Penge, it’s worth checking who is responsible for the outside before booking.
All of our work is guaranteed for twelve months.
- Location
- Penge (SE20, SE19, SE26)
- Wider area
- Greater London
- Guarantee
- A year, on every job
- Quotes
- A clear quote up front
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
What sealant work cannot fix
Sealant is not the answer to every problem, and we’ll tell you before work begins. It will not solve:
- Adding movement joints to masonry that has none
- Movement that’s more than a sealant joint can take
- Damp that is not coming from the joint
If you’re not sure, just phone 0345 464 0079 or drop us an email and we’ll give you a straight answer before you book.
Where we work in Penge
- Concrete & block
- Joints between brick and frames
- Copings & trims
- Render & cladding joints
- Façade panels
- Brickwork movement joints
Surface by surface
Cladding and façade panels
Panels heat up and cool down quickly, so the joints work hard every day. We choose the product to suit.
Render joints
Render is weaker at the surface than brick, so a low-modulus sealant is kinder to the joint edges. We prime where the product needs it.
Aftercare tips
Aftercare is simple:
- Keep movement joints as flexible joints, not mortar
- Tell anyone working on the walls about the movement joints
- Look over the joints every year, ideally after winter
- Get split or bare joints resealed while the damage is small
Only paint over the joint if we’ve confirmed the sealant can take paint. Paint can crack on a flexible joint and spoil the finish.
Act while the splits are small. At that stage it’s a simple cut out and reseal.
When to call us in Penge
UV, rain and frost all age exterior sealant. 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.
These are the problems we are asked about most:
- Panel joints letting water in
- Rigid filler in a joint that should flex
- Plants rooting in failed movement joints
- Failed seals between different materials
Rented homes near Penge West station change hands often, and outside joints that have cracked can let damp into a rental, so check them between lets.
Questions to ask before booking
- Whether the sealant suits the joint
- Are they insured?
- Whether all the old sealant comes out first
- Which colour the sealant will be
Questions from Penge
Do you work for landlords with property near Penge West station?
Yes. We work for landlords and agents as well as householders. You can ring 0345 464 0079 or drop us an email with the details for a clear quote.
Can you do external mastic in Penge?
Yes, Penge is within the area we cover. We work across London and the South East. You can ring 0345 464 0079 or send us an email and tell us what needs doing, and we’ll give you a clear quote.
Do you hold any approvals?
Yes. We’re an ARBOMaster approved applicator, the approved applicator scheme for Arbo sealants.
What information do you need?
A short description and the location. We’ll ask anything else we need to know.
Should I try DIY first?
You can, for simple jobs. Preparation is everything: all the old sealant out, and a clean, dry joint. We can always put it right if it fails.
Will you leave a mess?
Very little: the area around the joints is protected first, and we clear up the old sealant and our materials before we leave.
Is there a guarantee?
Yes, always. There’s a 12-month guarantee on every job.
Which products do you use?
It depends on the joint: anti-fungal sanitary silicone in wet areas, and other sealants where joints move or face the weather. We use products from Arbo and Everbuild.
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:
- The size of the job
- How easy the joints are to reach
- Any mould that needs treating
- How much old sealant there is and how hard it is to remove
Leaving a failed joint normally makes the job bigger, not smaller. If you’re not sure whether it needs doing, phone 0345 464 0079 or email us and we’ll give you an honest view and a quote.
What to tell us for a quote
When you call or email, these details help:
- Photos by email, if that is easy
- Whether it’s a home or a business
- If someone has resealed it before
- Roughly how big the job is
For a quick quote, get us on the phone, or email us if that’s easier. Tell us about the joints that need doing and we’ll talk you through the work and give you a clear quote.
Nearby places to Penge
Other services in Penge
What happens on the day
A visit follows a simple pattern: we check the joints, protect the area around them, carry out the job and clear up. It generally takes a few hours to a few days, depending on the length of joint and the access. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. If the building has a concierge, managing agent or access rules, tell us when you book.
- We look at every joint and agree a colour to suit the wall.
- Failed sealant is removed back to clean, sound faces.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
Preparing for the visit
- Let us know about parking restrictions
- Where the joints are inside, avoid wetting them before we arrive
- Let us know about stairs, lifts or work at height
Get a quote
A good description makes for an accurate quote. Tell us where the job is, what’s wrong and how much there is.
Read more
External mastic in Penge: local notes
The South East is one of the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. In terraces and conversions, gutters and walls are often shared with the neighbours, so check who is responsible for the outside before booking.
Penge is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book. Schools such as Harris Primary Academy Crystal Palace are buildings too, and movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
Penge is about 1 mile west of Beckenham, in Greater London. Our applicators cover external mastic for homeowners, landlords and businesses in Penge and the surrounding area, as part of our work across Greater London. We cover 764 towns and villages across Greater London, from the larger towns to small villages. We also work in London, about 6 miles from Penge.
Our applicators cover all of SE20, SE19 and SE26 for external mastic and the streets around it. Local streets include High Street, Anerley Station Road and Station Road. Main roads around Penge include the A234, which makes travel easy. We also cover the places around Penge: Anerley (1 mile west), Crystal Palace (1 mile north-west), Sydenham (1 mile north), Gipsy Hill (1 mile north-west) and Upper Norwood (1 mile west). Within a short drive, we also cover London (6 miles north), City of Westminster (8 miles north-west), Marylebone (8 miles north-west), Kensington (8 miles north-west), St Pancras (8 miles north) and Shoreditch (8 miles north).
Around Penge
Typical jobs here are in homes near Crystal Palace School, Crooked Billet pub and Crystal Palace Dinosaurs and the streets around them. Penge has its own railway station: Penge West station. A little further out are St Christopher's Hospice (0.5 miles north) and Crystal Palace Museum (0.8 miles north-west). The countryside around Penge includes Dulwich Upper Wood and Knight's Hill.
DIY sealant or a professional job?
What a professional job adds is preparation and the right product. We take joints back to clean, dry surfaces, and the sealant is chosen for how the joint moves and where it is, then guaranteed for a year.
Sealing over old silicone is the commonest DIY error. Silicone doesn’t stick to old silicone, so it peels away and traps moisture behind it. Everything old must be removed first.