Kent · England
Comp External Mastic
Professional external mastic in and around Comp, with every bit of old sealant taken out first and a 12-month guarantee.
- Moss and dirt in joints with no sealant left
- Old sealant gone brittle and cracked
- Gaps where render, brick and frames meet
About our external mastic in Comp
Movement joints let brickwork, render and cladding expand and shrink without cracking. Its sealant has to flex with the building, season after season, so once it splits or hardens, the joint stops working and water gets in. We work on copings & trims, render & cladding joints and joints between brick and frames, and common reasons people get in touch are moss and dirt in joints with no sealant left and water getting into walls through failed joints.
External sealant needs dry, clean surfaces, so work around Comp is planned for dry weather. Let us know about access to every wall, plus any garages or outbuildings.
The work is guaranteed for twelve months. If there’s a problem with our work within the year, let us know and we’ll sort it.
- Place
- Comp (TN15)
- Region
- Kent
- Cover
- One year on every job
- Quotes
- A clear price before work begins
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
What the job involves on each surface
Concrete and blockwork
Concrete faces can be dusty and porous, so preparation is key. A primer goes on where the product requires one before sealing.
Cladding and façade panels
Panels heat up and cool down quickly, so the joint sealant has to cope with frequent movement. We choose the product to suit.
FAQs for Comp
Is Comp within the area you cover?
Yes, Comp is covered. 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.
Can you help a landlord with a rental near Borough Green & Wrotham station?
Yes, we work for landlords and agents. You can phone 0345 464 0079 or email us with the address and a few details, and we’ll give you a fixed price before work begins.
Is there any odour?
That depends on the sealant. Some smell for a while, some hardly at all, and any smell fades as they cure.
Should I try DIY first?
For a simple, easy-to-reach joint, a careful DIYer can do a reasonable job. Most DIY failures come from sealing over old material, wet joints or too much sealant.
When is the sealant fully cured?
That depends on the sealant used, so follow the cure time we give you.
Will the old sealant be removed?
Yes, always, and completely. New sealant will not bond properly to old, so any old material comes out before anything new goes in.
Where are you based?
Mr Mastic is based in Crawley. We cover Comp and the rest of Kent, along with the rest of our area.
Can new sealant go over the old?
No. The old sealant always comes out first.
How we quote for external mastic
The price is agreed before any work begins. It takes into account:
- How much old sealant there is and how hard it is to remove
- How many rooms, windows or areas are involved
- Access and height
- Which sealant suits the joint
What you pay reflects the work, not guesswork. That is why we ask a few questions first.
Asking for a quote
When you call or email, it’s useful to know:
- If someone has resealed it before
- Whether it’s a home or a business
- Pictures of the joints, sent by email
- What’s wrong with the joints now
Asking for a quote is easy: let us know what needs doing and where. A few photos by email make the job easier to understand, and we will take it from there.
Nearby places to Comp
Other services in Comp
Should I try it myself first?
Too much sealant is as bad as too little. A thick, smeared bead looks untidy and doesn’t move well, and the joint depth matters as much as the finish.
What a professional job adds is preparation and the right product. Joints are cleaned back to sound surfaces and dried, and the sealant is chosen for how the joint moves and where it is.
Walls and rooflines in Comp
The South East is one of the drier parts of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. Historic houses like Old Soar Manor (about 1.7 miles south-west) are a reminder that the area around Comp 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.
If you look after a building such as Platt Church of England Voluntary Aided Primary School, its movement joints, gutters and trims need looking after like any other building’s. If you let a flat or house near Borough Green & Wrotham station, outside joints that have cracked can let damp into a rental, so check them between lets.
Comp is about 3 miles west of Kings Hill, in Kent. We carry out external mastic for homes and businesses in Comp and the surrounding area, as part of our work across Kent. We cover 922 towns and villages across Kent. We also work in London, around 24 miles away.
All of TN15 is within our area for external mastic. We also cover the places around Comp: Platt (1 mile north-west), Wrotham Heath (1 mile north-east), Crouch (1 mile south-west), Claygate Cross (1 mile south-west) and Borough Green (1 mile west). Further out, we also cover Maidstone (8 miles east), Dartford (12 miles north-west), Sevenoaks (7 miles west), Royal Tunbridge Wells (11 miles south), Gravesend (10 miles north) and Tonbridge (7 miles south-west).
Local landmarks in Comp
Around Comp, our work takes us to homes and buildings near The Blue Anchor pub and Wrotham School, among other places. The nearest railway station is Borough Green & Wrotham station, roughly 1.5 miles west. Well-known places in the area include Ightham Court (2.3 miles west) and Beechin Wood Archery Museum (less than half a mile west).
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.
A neglected joint can let water reach the structure, which matters even more when someone else lives there. Resealing at the right time is simple maintenance.
How the visit works
On the day, there’s very little for you to do. Show us the job and we will take it from there. The job generally takes anything from a few hours to several days, depending on the building, including the tidy-up. Somewhere like Comp needs a little journey planning: let us know about lanes, gates and parking. We bring what the job needs, so it can be finished in one trip where possible.
- Each joint is checked and the colour of the new sealant agreed.
- Failed sealant is removed back to clean, sound faces.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
Before we arrive
- Mention any leaks or damp you’ve noticed
- Mention any sign-in or site rules at work premises
- Where the joints are inside, avoid wetting them before we arrive
Getting a quote
For a quick quote, get us on the phone, or send an email if you’d rather. Describe what needs sealing and we will explain what’s involved and give you a clear quote.
Read more
Looking after it afterwards
No joint lasts for ever, but care makes a real difference. A few tips:
- Point out the joints to other trades
- Look over the joints every year, ideally after winter
- Make sure movement joints are not pointed over
- Clear growth from the base of walls and joints
Do not paint over the new sealant unless we have said the product is paintable. Many exterior sealants are not designed to be painted, and paint can crack as the joint moves.
Water getting behind cladding or render can go unnoticed for a long time. By the time there’s a damp patch, the damage can be well established, so it’s worth resealing at the first signs.
Signs you need external mastic in Comp
Poor preparation causes many early failures: joint faces that were dusty or damp, unprimed where they needed it, or still carrying old sealant. The new sealant then lets go long before it should.
If you can see any of these, it’s time to have the joints looked at:
- Joints with sealant missing in places
- Sealant that has lost its bond to the brick or render
- Leaking joints around cladding and façade panels
- Moss and dirt in joints with no sealant left
For an older house near a landmark such as Church of St Mary, an extension built onto an older house moves differently, and the joint between them takes the strain.
What your quote should include
- Whether the sealant suits the joint
- How hidden problems are handled
- Whether all the old sealant comes out first
- When the joint can take water or movement