West Sussex · England
External Mastic in Keymer
Professional external mastic in and around Keymer, with old sealant always removed completely.
- Failed seals between different materials
- Weathered mastic that no longer stretches
- Joints pointed up with cement by mistake
What we do, step by step
Good joint work is mostly preparation, and we don’t rush it. Joints are cleaned back and dried before anything new goes in. All told, the work takes anything from a few hours to several days, depending on the building. In a smaller place like Keymer, parking is seldom the issue; lanes, gates and long drives are worth mentioning. For outside work, side access and the height of the joints help us plan.
- Each joint is checked and the colour of the new sealant agreed.
- 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.
- A low-modulus exterior sealant is gunned in and tooled to a neat finish.
How to prepare
- Where the joints are inside, avoid wetting them before we arrive
- Clear the area around the work
- Let us know about parking restrictions
Getting a quote
Need a quote? Please call 0345 464 0079 or drop us an email and tell us about the job. We’ll explain what we’d do and send you a clear quote before work begins.
Advice
About our external mastic in Keymer
External mastic is a job where short cuts show quickly. New sealant over old, joints packed with mortar and beads with no backing rarely last long. We strip the joint back and start again. We are often asked to deal with joints pointed up with cement by mistake and hard, crazed mastic that has stopped moving, across render & cladding joints, façade panels and brickwork movement joints.
Houses in smaller places like Keymer can stand more in the open than those in a built-up town, so exposed walls and rooflines take more wind-driven rain. That is where gutter joints and wall joints tend to fail first.
Our work is backed for twelve months.
- Place
- Keymer (BN6)
- Wider area
- West Sussex
- Guarantee
- 12 months on all our work
- Quote
- A clear price before any work starts
- Call
- 0345 464 0079
- Updated
- 26 October 2026
For landlords and businesses
From a single let to a portfolio, you get the same standard of work: the old material taken out, careful preparation and a 12-month guarantee.
Failed sealant is one of the commonest items on a check-out report, and it’s easy to sort out between tenants. Several properties can be quoted together.
Keymer: your questions answered
Do you work for landlords with property near Hassocks station?
Yes, we work for landlords and agents. You can call 0345 464 0079 or email us with the address and a few details, and we will give you a fixed price before we start.
Do you cover smaller places like Keymer?
Yes, we do. Our work covers London and the South East, from towns to the smallest places. The journey is planned ahead, so it helps to know about access.
Should I try DIY first?
Sometimes. The key is preparation: remove all the old material and work on a clean, dry joint. We can always put it right if it fails.
Do I have to be there?
That depends on where the joints are. Inside work needs someone to give us access, and for outside work we will agree access with you when we book.
When is the sealant fully cured?
Cure times vary by product and the conditions. We tell you how long to leave it before we go.
What is a movement joint?
A movement joint is a planned break in the wall that absorbs expansion and shrinkage. It should be filled with flexible sealant, never mortar.
What should I tell you?
Where the job is, what the problem is and roughly how big it is. Photos by email help too.
Do you work for hotels and businesses?
Yes. We can plan bigger jobs in stages to suit the site.
What sealant work can’t fix
It helps to know what we can’t do too:
- Failed render or damaged cladding panels
- Cracks in the bricks or render themselves, away from the joints
- Subsidence or other structural problems
If you’re not sure, just ring 0345 464 0079 or drop us an email and we’ll give you a straight answer.
Where we work in Keymer
- Concrete & block
- Render & cladding joints
- Façade panels
- Copings & trims
- Joints between brick and frames
- Brickwork movement joints
Why act early in Keymer
Resealing a run of joints in one go is normally better than patching one at a time. Joints of the same age tend to fail together and it means sorting access once. Homes in smaller places like Keymer can face more weather, and failed outside joints let damp into walls. Indoors, a failed seal lets water into floors and panels as it would anywhere.
Instead of a standard rate, we look at what your job involves: how many joints, what’s in them now and how we reach them. You will know the price before we begin.
Why us?
- We leave the area clean and tidy
- Fully insured
- Quality sealants from Arbo and Everbuild
- ARBOMaster approved applicator
Read our cost guide or our reviews.
How the job changes by surface
Render joints
Rendered walls have joints at beads, openings and changes of material. They’re resealed in a sealant that suits the render.
Joints between dissimilar materials
Brick against render, concrete against metal, stone against timber: every change of material is a joint. We seal the joint with a flexible exterior sealant so neither cracks the other.
External mastic in Keymer: local notes
The South East is one of the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
If you let a flat or house near Hassocks station, split movement joints are easy to miss on a rental until damp shows inside. In the older streets around St Cosmas and St Damian Church, old and new materials meet at the roofline and walls, which is where sealant earns its keep. For site and facilities teams at buildings such as The Windmills Junior School, larger buildings have long runs of movement joint that eventually need resealing.
Keymer is about 2 miles south of Burgess Hill, in West Sussex. Whether you’re in the middle of Keymer or further out, we cover external mastic for every kind of property, from flats and houses to offices and hotels. Across West Sussex, we cover 371 places, and Keymer is one of them. Our Brighton page covers work nearby.
We cover every part of BN6 for external mastic. If you need external mastic at a property on Flowers Close, The Quadrant and Kymer Gardens or anywhere close by, we can help. Nearby, we also carry out external mastic in Hassocks (1 mile west), Ditchling (1 mile east), Clayton (1 mile south-west), Hurst Wickham (1 mile north-west) and Westmeston (2 miles south-east). We also work in nearby towns such as Crawley (13 miles north), Horsham (13 miles north-west), Worthing (14 miles south-west), Haywards Heath (5 miles north), East Grinstead (15 miles north) and Shoreham-by-Sea (8 miles south-west).
Near you in Keymer
Around Keymer, our work takes us to homes and buildings near The Greyhound Public House and Downlands Community School and the streets around them. The nearest railway station is Hassocks station, roughly 0.5 miles west of the centre. Well-known places in the area include The Dene Hospital (3.2 miles north-west) and Clayton Castle (1.2 miles south-west). Not far away are Ditchling Beacon and Bedelands Farm Nature Reserve.
Nearby places to Keymer
More services for Keymer
Should I try it myself first?
The difference is mostly in the preparation and the product. Joints are cleaned back to sound surfaces and dried, and the sealant is chosen for how the joint moves and where it is, then guaranteed for a year.
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.
How to look after the new joints
How long the joints last depends on use and care. Here’s what we suggest:
- Walk round the building once a year and look at the joints
- Tell anyone working on the walls about the movement joints
- Leave the joints unpainted unless we’ve said otherwise
- Don’t let climbing plants root in the sealant
Don’t paint over the new sealant unless we’ve said the product is paintable. Many exterior sealants are not designed to be painted.
If you can see gaps, plants or bare sections in a joint, have it checked. Early work is quicker and leaves a better finish.