Greater London · England
External Mastic in Netherne on-the-Hill
External mastic across Netherne on-the-Hill and nearby, with every bit of old sealant taken out first.
- Failed sealant between panels on a façade
- Moss and dirt in joints with no sealant left
- Brick movement joints where the sealant has split
About our external mastic in Netherne on-the-Hill
External mastic is a job where short cuts show quickly. New sealant over old, joints packed with mortar and beads with no backing all tend to fail early. We take the old material out and do it properly. Typical jobs include joints pointed up with cement by mistake and sealant pulling away from one side of the joint, across concrete & block, copings & trims and façade panels.
Newer London blocks are built with movement joints in brick and render, and with cladding joints sealed with mastic. Older terraces have their own weak points: gutter joints, roofline trims and the joint where an extension meets the original wall.
There’s a 12-month guarantee on every job, whatever its size.
- Location
- Netherne on-the-Hill (CR5)
- Wider area
- Greater London
- Guarantee
- 12 months on all our work
- Quotes
- A clear price before we start
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
Work for landlords, hotels and businesses
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.
How it works
All our tools and materials come with us in the van. After a quick look at the joints together, we protect the area and start. Most jobs take a few hours to a few days, depending on the length of joint and the access. In a London area like Netherne on-the-Hill, the main things to plan are parking and access: tell us about permits, visitor bays or off-street space, which floor we are working on and whether there’s a lift.
- We start by walking round the building and agreeing the joints and the access.
- Every bit of old sealant and any mortar or debris is cut out.
- Joint faces are cleaned back and primed if the sealant needs it.
- We fit closed-cell backing rod to control the depth.
- We apply the sealant, tool it and check the whole run.
Preparing for the visit
- Let us know about parking restrictions
- For business premises, tell us about site rules or sign-in
- Try not to wet indoor joints just before the visit
How to get a quote
For external mastic in Netherne on-the-Hill, ring 0345 464 0079 or send us an email. A short description of the job and where it is helps us quote, and you will get a clear quote before any work starts.
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What happens if it’s left?
A failed movement joint lets water into the wall, behind render and cladding. Dealing with it early keeps the repair to the joint, instead of the wall and finishes around it. In older London homes, water behind a failed joint soaks into brick and timber without much sign, and once it shows in Netherne on-the-Hill, the repair is bigger than a sealant job.
A failed joint rarely gets cheaper to fix by waiting. If you’re unsure, phone 0345 464 0079 or drop us an email for an honest opinion and a quote.
Why choose Mr Mastic in Netherne on-the-Hill
- Full insurance on every job
- Quality sealants from Arbo and Everbuild
- White, clear, grey or coloured to suit, where the product allows
- Colour picked to suit the job
Can I do it myself?
Overfilling a joint is a classic DIY mistake. A thick, smeared bead looks untidy and doesn’t move well, and getting the depth right matters as much as the look.
The biggest DIY mistake is sealing over old sealant. New silicone won’t bond to old, so it lifts and traps water and mould underneath. All the old material has to come out first.
Walls and rooflines in Netherne on-the-Hill
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 it’s worth agreeing who is responsible before work starts.
If you look after a building such as Coulsdon Sixth Form College, larger buildings have long runs of movement joint that eventually need resealing. Rented homes near Coulsdon South station change hands often, and failed wall and movement joints let damp in, so they’re worth checking between tenancies. Homes close to Church of St Margaret include some older properties, and old and new materials meet at the roofline and walls, which is where sealant earns its keep.
Netherne on-the-Hill is about 2 miles south of Coulsdon, in Greater London. For external mastic in and around Netherne on-the-Hill, it’s easy to get a quote: please phone 0345 464 0079 or drop us an email. We cover Greater London from our Crawley base, Netherne on-the-Hill included. We cover 764 towns and villages across Greater London, from the larger towns to small villages. We also work in Crawley, around 13 miles away.
We cover every part of CR5 for external mastic and the streets around it. You’ll find streets such as The Village Square, Rookery Mead and Netherne Lane, and we cover them all. Other places close to Netherne on-the-Hill include Hooley (1 mile west), Merstham (2 miles south), Chaldon (2 miles south-east), South Merstham (2 miles south) and Gatton (2 miles south-west). Larger places within reach include London (14 miles north), City of Westminster (15 miles north), Kensington (15 miles north), Brompton (14 miles north), Stockwell (12 miles north) and Orpington (12 miles north-east).
Around Netherne on-the-Hill
We work in homes and buildings around Shabden Park. The nearest railway station is Coulsdon South station, roughly 1.6 miles north. Nearby you will also find The Belfry (3.8 miles south) and East Surrey Museum (2.9 miles east). For a walk, there’s South London Downs National Nature Reserve and Colley Hill.
Common questions in Netherne on-the-Hill
Do you cover Netherne on-the-Hill for external mastic?
Yes. Our work covers London and the South East, and Netherne on-the-Hill is part of that. Just ring 0345 464 0079 or drop us an email with a few details of the job, and we’ll give you a clear price.
Is parking an issue for external mastic in Netherne on-the-Hill?
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.
Is it OK to seal over old sealant?
No, and we never do. It can look neat for a few weeks, but the new layer lifts away from the old one. Removing the old sealant completely is the only lasting way.
I’m a tenant. Can you help?
Yes, though it’s best to check with your landlord first. Landlords are often happy for the work to be arranged.
Do you work for hotels and businesses?
Yes. We work in offices, washrooms, hotels and other commercial premises. We can talk about working times when we quote.
Do you work for letting agents?
Yes. As well as homeowners, we work for landlords, agents, businesses and hotels across Greater London.
How long does external mastic take?
It depends on the size of the job, but most jobs take a few hours for a handful of joints, longer for a whole elevation. We will give you a better idea when we quote.
Do you seal joints where cladding meets other materials?
Yes. Materials like render, brick, metal and uPVC all move differently, so the joint between them must be flexible. We choose one that suits both surfaces.
Surface by surface
Concrete and blockwork
Big joints in concrete need careful depth control. Backing rod sized to the joint sets it so the sealant is not too deep.
Brickwork movement joints
Brick movement joints are often mistaken for a missing mortar line. If that is happened, we rake it out and reseal it properly if the joint can be cleared.
Other services in Netherne on-the-Hill
When it is not the sealant
We won’t take on work that won’t last, so here’s what sealant cannot put right:
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
- Adding movement joints to masonry that has none
- Cracked brickwork or render that needs a builder or plasterer
If in doubt, call 0345 464 0079 or send us an email and we will say what we think.
Surfaces we seal
- Joints between brick and frames
- Copings & trims
- Brickwork movement joints
- Render & cladding joints
- Façade panels
- Concrete & block
What affects the quote in Netherne on-the-Hill
Some jobs are bigger than they look, and some smaller. The main factors:
- Working hours on commercial sites
- How many rooms, windows or areas are involved
- How easy the joints are to reach
- The number and length of the joints
Combining jobs into one visit is normally more efficient than separate visits. We’ll give you a clear quote for the lot.
Asking for a quote
Photos help, but a description is a good start. Try to tell us:
- Where the job is, and your postcode
- Any access issues, like height or stairs
- Photos by email, if that’s easy
- Whether it’s a home or a business
We quote each job on its own, so the first step is telling us about yours. Simply ring 0345 464 0079 or email us and describe the job and send pictures if you have them.