Kent · England
Sand mastic for sash & case windows in Coldharbour, Kent
Sand mastic for Coldharbour, by sealant specialists with 20+ years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Mastic round period door frames that has failed
- Silicone on a period window that looks wrong
- Open joints round the window box
For landlords and businesses
We also work for property managers and facilities teams. Several sites can go on one quote.
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.
Sand mastic in Coldharbour, done properly
On many period windows, sand mastic looks right and suits the building. On modern frames we’d normally use a flexible sealant and we’ll explain which is best for yours. We work on stone surrounds, brick reveals and timber door frames, and common reasons people get in touch are weathered mastic on the most exposed windows and old sand mastic that has cracked, crumbled or fallen out.
Homes in small places like Coldharbour often stand in the open, with little to shelter their windows from wind and rain. Exposed frames and sills lose their mastic sooner than sheltered ones.
We guarantee the work for a year. If something isn’t right with it in that time, tell us and we’ll put it right.
- Where
- Coldharbour (TN11)
- Region
- Kent
- Cover
- One year on every job
- Quote
- A clear quote up front
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
Surface by surface
Period and listed homes
Period homes look their best with traditional materials.
Stone surrounds
The stone is treated with care while raking out the old mastic.
How we quote for sand mastic
We quote each job individually. These are the things that affect it:
- Whether old sealant or filler has to be cut out
- The type of sealant required
- The size of the job
- When we can work, for business premises
Homes and businesses are quoted the same way: the amount of work, the access and the products needed, plus any working-time requirements on site. Call for a quick quote and we will explain what it covers.
Asking for a quote
To help us quote quickly, let us know:
- Whether it’s a home or a business
- What’s wrong with the joints now
- Where the property is
- If someone has resealed it before
It all starts with a short chat. Describe the problem, the location and the size of the job. When it suits you, ring 0345 464 0079 or drop us an email.
Looking after it afterwards
How long the joints last depends on use and care. We suggest:
- Don’t paint over the new mastic
- Have rotten timber repaired before new mastic goes in
- Don’t run silicone over sand mastic
- Inspect the joints round the windows every year or so
Do not run silicone over the new mastic. If anything cracks, get it looked at before trying a quick fix.
Once mastic starts to crumble, rain gets in. It can soak into the frame and the surrounding masonry, so renewing it early is worth it.
Signs you need sand mastic in Coldharbour
Timber frames move with the seasons. The movement cracks the mastic over time.
Look out for any of the following:
- Draughty sash windows at the surround
- Old sand mastic that has cracked, crumbled or fallen out
- Old cement repairs round a window that have failed
- Window mastic to renew ahead of painting
For an older house near a landmark such as Parish Church of St John, the joint between an old wall and a newer frame is generally the first place rain gets in.
Before you book anyone
- How long to leave it before use
- How the colour is chosen
- What insurance they hold
- What product goes in the joint
Nearby places to Coldharbour
Also in Coldharbour
Coldharbour homes and the weather
Historic houses like Ightham Mote (about 2.2 miles north) are a reminder that the area around Coldharbour has older buildings as well as new. Where a home is older, older timber frames in brick or stone need a different approach from a modern uPVC window. 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.
Rented homes near Hildenborough station change hands often, and cracked sand mastic around sash windows lets in the draughts tenants complain about. Managing a site like St Margaret Clitherow Catholic Primary School? Then larger buildings have plenty of frames, and the mastic around each one ages.
Coldharbour is about 2 miles north of Tonbridge, in Kent. We carry out sand mastic for homes and businesses in Coldharbour, as part of our work across Kent. Our area takes in 922 places across Kent, from the larger towns to small villages. Crawley is on our list too, about 21 miles from Coldharbour.
We work across TN11 for sand mastic and the streets around it. We also cover Hildenborough (1 mile south-west), Hilden Park (1 mile south), Watt's Cross (1 mile west), Budds (1 mile north) and Stocks Green (2 miles south-west). Larger places within reach include Maidstone (12 miles east), Dartford (15 miles north), Sevenoaks (5 miles north-west), Royal Tunbridge Wells (6 miles south), Gravesend (15 miles north) and Northfleet (15 miles north).
Around Coldharbour
Around Coldharbour, our work takes us to homes and buildings near Hugh Christie Technology College and The Flying Dutchman Public House and the streets around them. The closest station to Coldharbour is Hildenborough station, about 1.6 miles south-west of the centre. A little further out are Tonbridge Castle (2.2 miles south) and The Milne Museum (2 miles south). For a walk, there’s Tudeley Woods RSPB reserve and Barden Lake.
DIY sealant or a professional job?
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is chosen for how the joint moves and where it is, and the work is guaranteed for a year.
Sealing over old silicone is the commonest DIY error. New silicone won’t bond to old, so it peels away and traps moisture behind it. Everything old must be removed first.
What we do, step by step
The work is kept neat and contained to the area we’re working on, so you can carry on as normal. Expect the work to take anything from a few hours to a full day, depending on how many windows. Somewhere as small as Coldharbour, access is often the only tricky part. For outside work, also let us know about exposed walls and any outbuildings involved.
- We check the window surrounds and agree which joints need renewing.
- The loose and crumbling mastic is raked out and the joint cleaned.
- Deep voids are packed so the mastic is the right thickness.
- Sand mastic is mixed and applied by hand, then shaped to the joint.
- The finish is dressed so it sits neatly against the stone or brick.
Preparing for the visit
- Tell us about any water getting in
- Keep pets and children clear of the area while we work
- Try not to wet indoor joints just before the visit
How to get a quote
We quote each job on its own, so the first step is telling us about yours. Just call 0345 464 0079 or email us with the details.
Related advice
Common questions in Coldharbour
Is Coldharbour within the area you cover?
Yes. Coldharbour is within the area we cover, which takes in towns, villages and rural addresses. Our work covers London and the South East. Let us know about access, parking and anything unusual about getting there when you book.
Do you work for landlords with property near Hildenborough station?
Yes. We work for landlords and agents as well as homeowners. You can ring 0345 464 0079 or send us an email with the details for a clear quote.
Is it messy?
We keep the work tidy. We protect what’s around the joints.
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 do not need to watch us work.
Are you an approved applicator?
Yes. We are an ARBOMaster approved applicator.
Is there any odour?
There can be a smell while the sealant cures. Ventilation helps.
Where is Mr Mastic based?
Mr Mastic is based in Crawley. We cover Coldharbour and the rest of Kent.
How long will you be here?
Typically it takes anything from a few hours to a full day, depending on how many windows. Bigger jobs take longer, and we’ll say how long yours will take.