Greater London · England
Coulsdon External Mastic
We cover Coulsdon for sealing brickwork movement joints, render, cladding and façade joints. Old material cut out, joints cleaned and sealed neatly.
- Plants rooting in failed movement joints
- Panel joints letting water in
- Sealant pulling away from one side of the joint
How we handle external mastic in Coulsdon
We cut out failed sealant, set the joint depth with closed-cell backing rod and reseal with a low-modulus exterior sealant. The colour is chosen to suit the brick or render so the line blends in. If you have damp patches traced to an open external joint and joints pointed up with cement by mistake, we can put it right.
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.
Every job is covered by our one-year guarantee.
- Place
- Coulsdon (CR5, CR8, CR3)
- Region
- Greater London
- Cover
- 12 months on all our work
- Quote
- Quoted before any work starts
- Phone
- 0345 464 0079
- Updated
- 26 October 2026
External mastic in Coulsdon: local notes
London and the South East are among the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. Historic houses like Nonsuch Mansion (about 4.9 miles north-west) are a reminder that the area around Coulsdon 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.
Schools such as Smitham Primary School are buildings too, and larger buildings have long runs of movement joint that eventually need resealing. Homes close to St Andrew's Church include some older properties, and the joints between older walls, newer extensions and the roofline need a sealant that can move.
Coulsdon is about 13 miles south of London, in Greater London. Anywhere in CR5, our applicators can take on external mastic. 764 places in Greater London are on our list, from the larger towns to small villages. Our London page covers work nearby.
Every address in CR5, CR8 and CR3 is within our area for external mastic. That includes homes and businesses on Hadleigh Grove, Farthing Way and Dobson Close and the roads around them. With the B276 and B2030 close by, Coulsdon is easy for our applicators to reach. We also cover Woodcote (1 mile north), Old Coulsdon (1 mile south-east), Woodmansterne (1 mile west), Chipstead (1 mile south-west) and Purley (2 miles north-east). Larger places within reach include London (13 miles north), City of Westminster (14 miles north), Marylebone (14 miles north), Kensington (13 miles north), St Pancras (15 miles north) and Shoreditch (15 miles north).
Near you in Coulsdon
Locally, jobs take us to homes and businesses close to Dollypers Hill, Coulsdon Sixth Form College and The Pembroke pub. There’s a railway station in Coulsdon itself: Coulsdon South station. Well-known places in the area include Croydon Airport Visitor Centre (3 miles north) and Purley War Memorial Hospital (2 miles north-east). Green spaces nearby include Duppas Hill and Mercers Lake.
Nearby places to Coulsdon
Other services in Coulsdon
Signs you need external mastic in Coulsdon
Many joints fail because they were sealed too deep or with nothing behind them. Sealant bonded to three sides has nowhere to go and tears as soon as the joint widens.
The problems people generally mention when they call include:
- Joints where the bead has come unstuck
- Moss and dirt in joints with no sealant left
- Failed sealant between panels on a façade
- Damp patches traced to an open external joint
For landlords with property near Coulsdon South station, failed wall and movement joints let damp in, so they’re worth checking between tenancies.
What to look for in a quote
- How the joint is cleaned and prepared
- How long the guarantee is
- Is the old sealant removed completely?
- Who does the work, and how experienced they are
What affects the quote in Coulsdon
For a quick quote, just ask. What matters most is:
- Any mould that needs treating
- The size of the job
- When we can work, for business premises
- How easy the joints are to reach
No two jobs are quite the same, so each one gets its own quote. Size, access and the product the joint needs all make a difference, and we will explain the quote if you ask.
What we need to know
There’s no need for technical detail. It helps if you can tell us:
- Access, such as stairs, a lift or height
- Where the property is
- What’s wrong with the joints now
- Whether it has been sealed before
A good description makes for an accurate quote. Tell us where the job is, what’s wrong and how much there is, and email pictures if that’s easy.
What happens on the day
When we get to you, we compare the joints with what we discussed. If anything is different, we explain it before carrying on. Most jobs then take a few hours to a few days, depending on the length of joint and the access. In a London area like Coulsdon, 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 look at every joint and agree a colour to suit the wall.
- We take out the old sealant until the faces are sound.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- Primer is applied wherever the sealant needs it.
- We gun in low-modulus sealant and tool it neatly.
Before we arrive
- Keep children and pets away from the work area
- Let us know if you’ve seen damp or leaks
- Clear items away from the joints we are working on
How to get a quote
Call for a quick quote, or send an email if you’d rather. Tell us about the joints that need doing and we’ll explain what’s involved and send you a clear quote.
Read more
How to look after the new joints
No joint lasts for ever, but care makes a real difference. Our tips:
- Keep movement joints as flexible joints, not mortar
- Get split or bare joints resealed while the damage is small
- Keep water from gutters off the wall
- Avoid pressure-washing directly into sealant joints
Do not let soil, plants or ivy build up against the new joints. Anything that holds water against the joint wears it out sooner.
An open movement joint lets rain into the wall every time it pours. That can lead to damp patches, staining and frost damage which cost more to put right than the joint.
DIY versus a professional finish
If you’ve already had a go yourself, that is fine. We cut it out and start again, so just mention it when you contact us.
Some jobs are best left to a professional: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.
When something else is needed
A few problems are outside what sealant work can do:
- Structural movement, which needs a surveyor or engineer
- Adding movement joints to masonry that has none
- Cracks in the bricks or render themselves, away from the joints
If in doubt, phone 0345 464 0079 or drop us an email and we will say what we think.
Surfaces we seal
- Copings & trims
- Brickwork movement joints
- Render & cladding joints
- Concrete & block
- Joints between brick and frames
- Façade panels
Work for landlords, hotels and businesses
Letting agents and landlords in Coulsdon can book us as well as homeowners. Sealant work between tenants is a simple way to keep a property in good order.
In hotels, rooms out of use cost money, so we plan the work room by room around your bookings where we can. We’ve worked in hotels as well as homes and businesses.
Common questions in Coulsdon
Can you do external mastic in Coulsdon?
Yes, Coulsdon is within the area we cover. Our work covers London and the South East. Just phone 0345 464 0079 or email us with a few details of the job, and we will give you a clear price.
Is parking an issue for external mastic in Coulsdon?
In much of London, parking needs planning: a visitor permit or a bay close to the door helps a lot.
Are you an approved applicator?
Yes. Mr Mastic is an ARBOMaster approved applicator and we are fully insured too.
Is the work guaranteed?
Yes, always. Each job is guaranteed for twelve months, wherever you are.
When will the joints need doing again?
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.
Can new sealant go over the old?
No, it will not last. It may look fine at first, but the new layer lifts away from the old one. The old sealant has to come out completely.
How long does external mastic take?
That depends on the amount of work, but as a guide it takes a few hours to a few days, depending on the length of joint and the access. We will tell you when we quote.
Will it make a mess?
Very little: the area around the joints is protected first, and we tidy up before we go.