West Sussex · England
Coolham External Mastic
Sealing brickwork movement joints, render, cladding and façade joints for homes and businesses in Coolham and across West Sussex. Fully insured, ARBOMaster approved and guaranteed for a year.
- Hard, crazed mastic that has stopped moving
- Movement joints filled with mortar instead of sealant
- Weeds or debris growing in open joints
External mastic in Coolham, done properly
Movement joints let brickwork, render and cladding expand and shrink without cracking. Its sealant has to flex with the building, season after season, and when it fails, the wall takes the strain and water finds a way in. If you have hard, crazed mastic that has stopped moving and water getting into walls through failed joints, we can put it right, on brickwork movement joints, copings & trims and joints between brick and frames alike.
Somewhere as small as Coolham, homes and farm buildings often face open ground, where walls and rooflines take the weather head on. Joints on those walls need a sealant that moves with the building and stays in place.
A one-year guarantee comes as standard.
- Where
- Coolham (RH13)
- Wider area
- West Sussex
- Guarantee
- One year on every job
- Quotes
- Quoted before any work starts
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
Why deal with it now?
Resealing a run of joints in one go is usually better than patching one at a time. Joints of the same age tend to fail together and it means sorting access once. Around Coolham, older homes often have timber in their floors and frames, where water from a failed joint can cause rot if it’s left.
What you pay reflects the work, not a rough estimate. That is why we ask about the job first and send you a clear quote before work begins.
Why book with us
- Domestic, commercial and hotel work
- Quality sealants from Arbo and Everbuild
- Every job guaranteed for a year
- We’re fully insured
Take a look at what affects the cost and our reviews.
Common problems we fix in Coolham
UV, rain and frost all age exterior sealant. In time it goes hard, crazes on the surface and stops stretching, so the next time the wall moves, it splits or pulls away.
It’s worth asking for a quote if you see:
- Failed seals between different materials
- Sealant pulling away from one side of the joint
- Water getting into walls through failed joints
- Panel joints letting water in
Letting a property close to Billingshurst station? Then outside joints that have cracked can let damp into a rental, so check them between lets.
Questions to ask before you book
- Whether all the old sealant comes out first
- What happens if the job turns out different
- What the quote includes, VAT included or not
- Whether they’re fully insured
Surface by surface
Brickwork movement joints
Brick movement joints are often mistaken for a missing mortar line. Where one has been mortared, we cut it out and reseal it with sealant.
Copings and trims
Coping joints that leak let water straight down into the wall. Resealing them is a small job that protects a lot.
How we quote for external mastic
Your quote is based on your job. We look at:
- How many areas need sealing
- Mould in or behind the old joints
- The product the joint needs
- Whether old sealant or filler has to be cut out
Commercial jobs are quoted on the same basis as homes: how much there is to do, how we reach it and what it needs, along with when we can work on site. Ask us for a quote and we will go through it with you.
What to tell us for a quote
Photos by email are helpful but not essential. Please mention:
- Photos by email, if that’s easy
- If it’s domestic, commercial or a hotel
- Where the job is, and your postcode
- What’s wrong with the joints now
If you are in Coolham and need external mastic, phone 0345 464 0079 or send us an email. Tell us what the problem is and where, and we will agree the price before any work begins.
Places near Coolham
Also in Coolham
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. After that, the work takes a few hours to a few days, depending on the length of joint and the access. Somewhere like Coolham needs a little journey planning: let us know about lanes, gates and parking. Everything for the job comes with us, so a second trip is avoided where possible.
- First, the joints are inspected and the access agreed.
- We cut out the old mastic and rake out anything in the joint.
- The faces are brushed clean and primed where the product requires it.
- We fit closed-cell backing rod to control the depth.
- The exterior sealant is applied, tooled and checked along its length.
Before we arrive
- Keep children and pets away from the work area
- Let us know about earlier repairs to the joints
- Mention any leaks or damp you’ve noticed
Ask for a quote
Quotes start with a quick conversation. Describe the problem, the location and the size of the job. When it suits you, phone 0345 464 0079 or send us an email.
Read more
For landlords and businesses
Failed sealant is one of the commonest items on a check-out report, and it’s easy to sort out between tenants. We can quote for more than one property at once.
We also work for property managers and facilities teams in Coolham and across West Sussex. Several sites can be quoted together.
Common questions in Coolham
Can you help a landlord with a rental near Billingshurst station?
Yes. We work for landlords and letting agents as well as homeowners. Just phone 0345 464 0079 or send us an email with the address and what needs doing, and we’ll give you a clear quote.
Will you come out to Coolham?
Yes, Coolham is covered. Our work covers London and the South East, and smaller places are part of that. The journey is planned ahead, so it helps to know about access.
How much does external mastic cost in Coolham?
We do not publish prices, because the cost depends on the job: its size, the old material, access and the product needed. You will get a clear quote before we start.
What do you put in the joint?
Each joint gets the product that suits it. Movement, water and weather all affect the choice, and we will explain our choice.
What’s an expansion joint in brickwork?
Most straight vertical gaps in brickwork are movement joints. It gives the wall room to move and needs a flexible seal, not mortar.
How long before the joint can be used?
Many sealants skin over quickly but take longer to cure fully. We will give you the cure time for the product we used.
Does someone need to be in?
If the work is inside, we need someone to let us in. Once we’ve agreed the job, you don’t need to watch us work.
Where is Mr Mastic based?
Mr Mastic is based in Crawley. We cover Coolham and the rest of West Sussex, along with the rest of our area.
Walls and rooflines in Coolham
London and the South East are among the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
For an older house near a landmark such as St Mary's Mission Church, the joints between older walls, newer extensions and the roofline need a sealant that can move. Managing a site like William Penn School? Then larger buildings have long runs of movement joint that eventually need resealing.
Coolham is about 6 miles south-west of Horsham, in West Sussex. Across the RH13 area, we cover external mastic for homes and businesses. Our West Sussex coverage runs to 371 places, Coolham among them. For nearby work, see our Crawley page, about 12 miles away.
Postcode districts we cover here for external mastic: RH13. Whether your property is on Coolham Road and West Chiltington Lane or anywhere close by, our applicators can take on the job. If you’re just outside Coolham, we cover Goose Green (3 miles south), Gay Street (3 miles south-west), Adversane (3 miles west), North Heath (3 miles west) and West Chiltington (3 miles south-west). Further out, we also cover Crawley (12 miles north-east), Horsham (6 miles north-east), Worthing (12 miles south), Haywards Heath (13 miles east), Burgess Hill (12 miles east) and Littlehampton (14 miles south-west).
Local landmarks in Coolham
Typical jobs here are in homes near The Selsey Arms Public House. The closest station to Coolham is Billingshurst station, about 2.4 miles north-west of the centre. A little further out are Christs Hospital School Museum (3.9 miles north-east). For a walk, there’s Knepp Wildland.
Can I do it myself?
Some jobs are best left to a professional: high-level joints, fire-rated gaps, external movement joints and big jobs call for the right materials, safe access and experience.
If you’re set on DIY, put the effort into preparation: take out all the old sealant, make sure the joint is clean and dry, and give it the full cure time. If it fails, we can still redo it.