Greater London · England
Beckenham External Mastic
Sealing brickwork movement joints, render, cladding and façade joints in Beckenham, with a one-year guarantee on every job. Call for a quick quote.
- Old sealant gone brittle and cracked
- Sealant that has lost its bond to the brick or render
- Gaps where render, brick and frames meet
Looking after it afterwards
So the new joints stay in good condition:
- Keep movement joints as flexible joints, not mortar
- Avoid pressure-washing directly into sealant joints
- Fix overflowing gutters above sealed joints
- Get split or bare joints resealed while the damage is small
If you have more work done on the wall, such as new render, cladding or an opening, show the contractor the movement joints. They must stay as flexible joints, never rendered or pointed over.
A joint that has stopped moving pushes the movement elsewhere, often as cracks near the joint. Resealing it early helps prevent that.
External mastic in Beckenham, 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 access is needed. If you are dealing with weathered mastic that no longer stretches and moss and dirt in joints with no sealant left, we can help.
Working on the outside of a London home means planning access: shared paths, upper floors and parking. In Beckenham, joints up high may need ladders or other access, which is worth talking through when you book.
The work is covered for a year after we finish. If anything isn’t right with it, ring 0345 464 0079 or email us.
- Place
- Beckenham (BR3, SE26, BR4, SE20)
- Region
- Greater London
- Cover
- One year on every job
- Quotes
- A clear quote up front
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
How it works
We bring everything the job needs with us, so you don’t need to buy or prepare anything. Once we have agreed what’s being done, the area is protected and the work begins. Most jobs take a few hours to a few days, depending on the length of joint and the access. In Beckenham, as in most of London, parking needs a little planning. A visitor permit or a nearby bay makes the visit run more smoothly.
- 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.
- Primer is applied wherever the sealant needs it.
- We gun in low-modulus sealant and tool it neatly.
How to prepare
- Move anything stored near the joints
- Where the joints are inside, avoid wetting them before we arrive
- On commercial sites, let us know about site rules
Ask for a quote
Quotes start with a quick conversation. Describe the problem, the location and the size of the job, and we’ll explain how we’d tackle it. Whenever you are ready, phone 0345 464 0079 or email us.
Related advice
Surface by surface
Render joints
Render has movement joints and stop beads that need sealing. We reseal them with a flexible exterior sealant that suits the render colour.
Copings and trims
Joints in copings, parapets and trims are exposed to the worst of the weather. We reseal them with an exterior sealant suited to the material.
DIY versus a professional finish
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and the joint depth matters as much as the finish.
If you’re 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 does not work out, we can still put it right.
Also near Beckenham
What else we do in Beckenham
Work for landlords, hotels and businesses
Landlords and letting agents in Beckenham can book us as well as homeowners. Resealing between tenancies keeps a property looking cared for.
Housing providers, facilities teams and property managers book us too. Several sites can go on one quote.
Beckenham: your questions answered
Can parking be tricky for a visit in Beckenham?
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.
Can you help a landlord with a rental near Beckenham Junction station?
Yes. We work for landlords and agents as well as householders, and several properties can go on one quote. Just call 0345 464 0079 or email us with the address and what needs doing, and we will give you a clear price.
Where do you work from?
Mr Mastic is based in Crawley. Our applicators cover Beckenham.
What should I tell you?
Where the job is, what the problem is and roughly how big it is. If you can, email a few pictures.
Do I need to be at home?
It depends on the job. For work indoors, someone needs to let us in, and for outside work we’ll agree access with you when we book.
What is backing rod for?
That’s backing rod, a closed-cell foam. It stops the sealant going in too deep and bonding to three sides so it can flex with the joint.
What sealant do you use?
The product depends on the job: sanitary silicone where it gets wet, and sealants suited to movement or weather elsewhere. We use products from Arbo and Everbuild.
How long does external mastic last?
That varies with the weather the wall faces, how much it moves and the sealant used. Treat it as a maintenance item and look at it yearly and renew it when it starts to fail.
When it is not the sealant
Sealant is not the answer to every problem, and we’d rather say so up front. It won’t solve:
- Damp that is not coming from the joint
- Subsidence or other structural problems
- Cutting new joints into brickwork, which is building work rather than sealant work
If you’re not sure, just ring 0345 464 0079 or send us an email and we will give you a straight answer.
Where we work in Beckenham
- Render & cladding joints
- Concrete & block
- Copings & trims
- Joints between brick and frames
- Brickwork movement joints
- Façade panels
What happens if it’s left?
An open joint keeps letting water into the wall with every downpour. In cold weather, frost can damage wet brick and render, so the damage spreads beyond the joint. In a flat in Beckenham, failed sealant seldom stays inside your own four walls: water can reach the neighbours below, and gaps in fire-rated joints affect the whole building.
Commercial jobs are quoted on the same basis as homes: the amount of work, the access and the products needed. Ask us for a quote and we will explain what it covers.
What you get with us
- Sealant colour chosen to suit
- Full insurance on every job
- Arbo and Everbuild products
- Anti-fungal sanitary silicone in wet areas
Take a look at our cost guide or customer reviews.
What external mastic looks like in Beckenham
Historic houses like Bromley Palace (about 2.1 miles east) are a reminder that the area around Beckenham has older buildings as well as new. In older buildings, older walls and rooflines need a sealant that moves with them and suits the material. In terraces and conversions, gutters and walls are often shared with the neighbours, so it’s worth agreeing who is responsible before work starts.
Schools such as Harris Primary Academy Beckenham Green are buildings too, and larger buildings have long runs of movement joint that eventually need resealing. Homes close to Christ Church include some older properties, and older walls, gutters and the joints where extensions meet them need a flexible sealant. As a London address, Beckenham can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
Beckenham is about 7 miles south-east of London, in Greater London. Homes, rented property, offices and hotels in Beckenham is covered for external mastic. Every job comes with our 12-month guarantee. Our Greater London coverage runs to 764 places, and Beckenham is one of them. Our London page covers work nearby (7 miles or so).
All of BR3, SE26, BR4 and SE20 is within our area for external mastic. You will find streets such as High Street, The Drive and Stanmore Terrace, all of which we cover. Beckenham sits on or near the B230 and B251. If you are just outside Beckenham, we cover Penge (1 mile west), Bell Green (2 miles north), Bellingham (2 miles north), Southend (2 miles north) and Sydenham (2 miles north-west). Further out, we also cover London (7 miles north-west), City of Westminster (9 miles north-west), Marylebone (9 miles north-west), Kensington (10 miles north-west), St Pancras (9 miles north-west) and Shoreditch (8 miles north).
What’s near Beckenham
We work in homes and buildings around Harris Academy Beckenham, Beckenham Place Park and The George Inn and the streets around them. There’s a railway station in Beckenham itself: Beckenham Junction station. Well-known places in the area include Greenwich Castle (5 miles north) and The Glades (1.9 miles east). For a walk, there’s Summer Hill and Dacres Wood.