Greater London · England
External Mastic in Keston
External mastic in Keston from a team with over 20 years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Sealant that has lost its bond to the brick or render
- Joints pointed up with cement by mistake
- Rain getting behind render or cladding at a joint
Keeping the joints in good condition
How long the joints last depends on use and care. Here’s what we suggest:
- Keep high-pressure jets off the joints
- Deal with leaking gutters that soak the joints below
- Act on the first splits you see
- Keep movement joints as flexible joints, not mortar
If you have more work done on the wall, such as new render, cladding or an opening, show the contractor the movement joints. They should be kept open and resealed, not filled.
Water getting behind cladding or render can go unnoticed for a long time. When it finally shows inside, the joint may have been open for years so early resealing is worth it.
External mastic in Keston, done properly
A movement joint is only as good as its depth. Closed-cell backing rod sets the depth and stops the sealant sticking to the back, leaving it bonded to two faces so it can move with the wall. If you’re dealing with panel joints letting water in and gaps where render, brick and frames meet, we can help, on joints between brick and frames, render & cladding joints and façade panels alike.
Outside work in London starts with access: side passages, upper floors and where to park. For a home in Keston, tell us how high the joints are and how to reach the back of the building.
Our work is backed for twelve months, in Keston and everywhere else we cover.
- Location
- Keston (BR2)
- Region
- Greater London
- Cover
- A year, on every job
- Quote
- Quoted before any work starts
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
How the visit works
At the end, we look at the finished work together and tell you how long to leave it. The work normally takes anything from a few hours to several days, depending on the building, depending on the amount of work. In a London area like Keston, the main things to plan are parking and access: tell us about permits, visitor bays or off-street space, which floor we’re working on and whether there’s a lift.
- First we look over the joints with you, agree which to renew and talk through access.
- The old mastic and anything lodged in the joint is removed.
- We clean both faces of the joint and prime them where the product calls for it.
- Backing rod goes in next, setting the depth and keeping the sealant off the back of the joint.
- We gun in a flexible exterior sealant in a colour that suits the wall and tool it neatly.
Before we arrive
- Keep children and pets away from the work area
- Move anything stored near the joints
- Mention if the joints have been sealed before
Ask for a quote
Quotes start with a quick conversation. Describe the problem, the location and the size of the job, and we’ll talk you through what we’d do. When it suits you, phone 0345 464 0079 or drop us an email.
Related advice
Landlord and commercial work in Keston
Businesses can book us for washrooms, kitchens, offices and more. For commercial premises, we can talk through working times when we quote.
From a single let to a portfolio, the work is the same standard: the old material taken out, careful preparation and a 12-month guarantee.
Towns and villages near Keston
Also in Keston
Why it’s worth doing now in Keston
Mortar or ordinary filler might look like a quick way to close an open joint, but it locks the joint solid. The wall then cracks somewhere else. A flexible sealant over backing rod is what the joint needs. Converted houses in London often have a bathroom above someone else’s living room, and a slow leak from a failed seal can end up in the flat below. Dealing with it early is far simpler.
Doing several joints on one visit usually makes better use of the time than several visits, so tell us about everything that needs sealing. We’ll send you a clear quote for the lot.
Why Keston clients choose us
- 20+ years of sealant experience
- Experience in homes, commercial sites and hotels
- A 12-month guarantee on all work
- We leave the area clean and tidy
Read how sealant jobs are priced and our reviews.
Questions from Keston
Is parking an issue for external mastic in Keston?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. The visit is then planned around what’s available.
Can you do external mastic in Keston?
Yes. Our work covers London and the South East, and Keston is part of that. Just ring 0345 464 0079 or drop us an email with a few details of the job, and we will send you a clear quote.
Do you remove the old sealant?
Always. Sealing over old sealant is the main reason resealing fails early, so we never do it.
What’s an expansion joint in brickwork?
A vertical gap in a long brick wall is normally a movement joint. It gives the wall room to move, and it should be sealed with a flexible sealant.
Will you leave a mess?
No. The area is protected while we work and cleaned up afterwards.
What sealant do you use?
Products from Arbo and Everbuild, among others, chosen to suit the joint. We will tell you what we are using and why.
Will the new joint stand out?
We choose a sealant colour to suit the brick, stone or render, so the joint sits quietly in the wall. Exterior sealants come in a good range of colours.
Is the work guaranteed?
Yes, for a year. If anything is not right with the work within the year, let us know and we’ll sort it.
Outside joints around Keston
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. With historic houses such as Down House (about 2.2 miles south-east) nearby, there’s older building stock in the area around Keston as well as newer homes. In older buildings, older brick and stone need a sealant that suits them, at the right joint depth.
If you let a flat or house near Hayes (Kent) station, outside joints that have cracked can let damp into a rental, so check them between lets. If you look after a building such as Keston Church of England Primary School, larger buildings have long runs of movement joint that eventually need resealing.
Keston is about 3 miles south of Bromley, in Greater London. If you need external mastic in Keston, please phone 0345 464 0079 or drop us an email for a quick quote. We’re based in Crawley and cover Greater London, Keston included. Our Greater London coverage runs to 764 places, Keston among them. You can also see our page for London, about 11 miles away.
Postcode districts we cover here for external mastic: BR2. External mastic is available to properties on Church Road, Greys Park Close and Heathfield Road. Other places close to Keston include Nash (1 mile west), Farthing Street (1 mile south-east), Locksbottom (1 mile north-east), Leaves Green (2 miles south) and Hayes (2 miles north-west). We also work in nearby towns such as London (11 miles north-west), City of Westminster (13 miles north-west), Marylebone (13 miles north-west), Kensington (14 miles north-west), St Pancras (13 miles north-west) and Shoreditch (12 miles north).
Local landmarks in Keston
We work in homes and buildings around South Park, Ravens Wood School and The Greyhound pub, among other places. The nearest railway station is Hayes (Kent) station, about 1.5 miles north-west of the centre. Other landmarks nearby include Princess Royal University Hospital (1.1 miles east) and Bethlem Museum of the Mind (1.5 miles north). For a walk, there’s West Kent Golf Course nature reserve and Summer Hill.
What we are called out for in Keston
Using the wrong sealant is another common reason. A high-modulus or general-purpose sealant can be too rigid for a busy joint, so it pulls away from the edges.
If you can see any of these, it’s time to have the joints looked at:
- Brick movement joints where the sealant has split
- Failed sealant between panels on a façade
- Gaps where render, brick and frames meet
- Weeds or debris growing in open joints
As a London address, Keston can be tricky for parking: let us know about parking bays, permits or a driveway.
What to look for in a quote
- Whether they’re fully insured
- What the cure time is
- What happens if they find a problem under the old sealant
- Whether the sealant suits the joint
How the job changes by surface
Joints between dissimilar materials
Each side of the joint may need its own preparation. Both surfaces are cleaned and primed as the product requires.
Render joints
Render is weaker at the surface than brick, so a sealant that stretches easily protects the edges. We prime where the product needs it.
DIY sealant or a professional job?
Overfilling a joint is a classic DIY mistake. A thick, smeared bead looks untidy and does not move well, and the joint depth matters as much as the finish.
The difference is mostly in the preparation and the product. Joints are cleaned back to sound surfaces and dried, and the sealant is matched to the joint and its conditions, then guaranteed for a year.