Greater London · England
External Mastic in New Malden
External mastic for New Malden and the surrounding area: careful preparation, the right product and tidy work. Ask us for a quick quote.
- Joints with sealant missing in places
- Movement joints filled with mortar instead of sealant
- Sealant pulling away from one side of the joint
External mastic in New Malden
Failed sealant is cut out, the depth set with closed-cell backing rod, and the joint resealed with a low-modulus sealant made for outside. The colour is chosen to suit the brick or render. Typical jobs include rigid filler in a joint that should flex and panel joints letting water in, on concrete & block, brickwork movement joints and joints between brick and frames.
Outside work in London starts with access: side passages, upper floors and where to park. For a home in New Malden, tell us how high the joints are and how to reach the back of the building.
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.
- Location
- New Malden (KT3, KT1, SW20)
- Region
- Greater London
- Cover
- One year on every job
- Quote
- A clear quote up front
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
What we do, step by step
Our applicators work methodically: protect, prepare, seal, tidy. Typically it takes a few hours for a handful of joints, longer for a whole elevation and we leave things clean and tidy. In New Malden, 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.
- Failed sealant is removed back to clean, sound faces.
- Backing rod goes in so the sealant can stretch between the two faces.
- We prime the faces where required.
- A low-modulus exterior sealant is gunned in and tooled to a neat finish.
How to prepare
- Tell us about access, such as stairs, a lift or high-level joints
- Tell us about any previous sealing or DIY attempts
- Keep pets and children clear of the area while we work
Ask for a quote
Getting a quote is simple: let us know what needs doing and where. Photos by email help us understand the job.
Related advice
Surface by surface
Concrete and blockwork
Blockwork and concrete shrink over time and move with the seasons. We reseal their joints with backing rod and a flexible product.
Cladding and façade panels
If the façade has a specified sealant, that’s what we use or an approved alternative. Tell us what the building has when you get in touch.
What happens if it’s left?
The longer a joint stays open, the more water the wall takes in. Wet masonry is more easily damaged by frost near the open joint, so the problem grows beyond the joint itself. In a flat in New Malden, failed sealant seldom stays inside your own four walls: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
The cost reflects the work involved, not guesswork. That is why we ask about the job first and give you a clear quote before we start.
Why book with us
- ARBOMaster approved applicator
- Neat joints and a tidy finish
- Any old sealant cut out fully, not covered over
- White, clear, grey or coloured to suit, where the product allows
See what affects the cost and our reviews.
Towns and villages near New Malden
Other services in New Malden
Outside joints around New Malden
With historic houses such as Southside House (about 1.6 miles north-east) nearby, there’s older building stock in the area around New Malden as well as newer homes. In older buildings, older brick and stone need a sealant that suits them, at the right joint depth. Rainfall in the South East is lower than in much of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
As a London address, New Malden can be tricky for parking: let us know about parking bays, permits or a driveway. If you let a flat or house near New Malden station, split movement joints are easy to miss on a rental until damp shows inside.
New Malden is about 3 miles south-west of Wimbledon, in Greater London. Homes, rented property, offices and hotels in New Malden can book us for external mastic, old or new, large or small. The work is guaranteed for a year. Across Greater London, we cover 764 places, and New Malden is one of them. You can also see our page for London, about 10 miles away.
Postcode districts we cover here for external mastic: KT3, KT1 and SW20. You’ll find streets such as High Street, Ashcombe Square and Melrose Gardens, all of which we cover. Main roads around New Malden include the B283, which makes travel easy. If you’re just outside New Malden, we cover Motspur Park (1 mile north-east), West Barnes (1 mile east), Norbiton (1 mile north-west), Coombe (1 mile north) and Raynes Park (1 mile east). We also work in nearby towns such as London (10 miles north-east), City of Westminster (9 miles north-east), Marylebone (9 miles north-east), Kensington (7 miles north), St Pancras (11 miles north-east) and Shoreditch (12 miles north-east).
Landmarks near New Malden
Locally, jobs take us to homes and businesses close to Beverley Park, The Glasshouse pub and Holy Cross School and the streets around them. New Malden has its own railway station: New Malden station. Nearby you’ll also find Chessington Castle Hill (3.3 miles south) and Bentall Centre (1.9 miles west). For a walk, there’s Rose Walk and Kingston Hill Road area.
What we cannot put right
New sealant cannot fix everything, and we’ll tell you before any work starts. It will not solve:
- Cracks in the bricks or render themselves, away from the joints
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
- Walls that need new movement joints cut into them
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
- Render & cladding joints
- Façade panels
- Concrete & block
- Copings & trims
- Brickwork movement joints
- Joints between brick and frames
New Malden: your questions answered
Do you work for landlords with property near New Malden station?
Yes. We work for landlords and letting agents as well as homeowners. You can phone 0345 464 0079 or send us an email with the details for a clear quote.
Can parking be tricky for a visit in New Malden?
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 match the colour of my brickwork?
The sealant colour is picked to suit the wall so the joint blends in. There’s a wide choice of exterior colours.
Can you reach joints on upper floors?
That depends on the building and the joints. Where joints can be reached safely, we’ll do them. Give us some details and we’ll confirm the access.
Will you leave a mess?
Very little: the area around the joints is protected first, and we tidy up before we go.
Can you seal joints between two different materials?
Yes. We cut out the old sealant, prepare both faces and reseal with a flexible exterior product. We pick a colour that works with both materials.
Can I do it myself?
For a simple, easy-to-reach joint, a careful DIYer can do a reasonable job. The usual mistakes are sealing over old sealant, sealing a damp joint and using too much.
What’s an expansion joint in brickwork?
Brickwork, render and cladding all move a little, so long walls have planned gaps to take that movement. It’s closed with backing rod and a flexible sealant.
Landlord and commercial work in New Malden
From a single let to a portfolio, the work is the same standard: old sealant fully removed, joints prepared properly and a one-year guarantee.
We also work for property managers and facilities teams. We can quote a run of properties together, and we are fully insured.
Signs you need external mastic in New Malden
Sometimes a movement joint was filled with mortar or a rigid filler, often by someone who didn’t know what it was for. With the joint locked solid, the movement turns into cracks elsewhere in the wall.
The problems people usually mention when they call include:
- Hard, crazed mastic that has stopped moving
- Weeds or debris growing in open joints
- Leaking joints around cladding and façade panels
- Sealant that has lost its bond to the brick or render
For site and facilities teams at buildings such as Christ Church New Malden CofE Primary School, larger buildings have long runs of movement joint that eventually need resealing.
What your quote should include
- The length of the guarantee
- Whether VAT is included
- When the joint can take water or movement
- How hidden problems are handled
Should I try it myself first?
A careful DIYer can reseal a simple joint, 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.
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is chosen for how the joint moves and where it is.