Greater London · England
Sand mastic for sash & case windows in Coldharbour, Greater London
Professional sand mastic in and around Coldharbour, with every bit of old sealant taken out first and a 12-month guarantee.
- A silicone bead on a sash window that spoils the look
- Failed mastic on an exposed elevation
- Cement or filler used on old window joints that has cracked
Sand mastic in Coldharbour
Silicone on a period window often looks wrong and is not always the right material. Sand mastic gives a finish that matches the age of the house and we can swap the silicone for it. We work on sash and case windows, brick reveals and tenement windows, and people most often call us about patchy fillers round a sash window and wind and rain getting in round a sash window.
From mansion-block windows to modern glazing in new flats, London has every kind of frame. Over the years, the sealant around them shrinks, cracks and pulls away, which is when draughts and damp patches appear in homes in Coldharbour.
Big or small, you get the same 12-month guarantee in Coldharbour and across Greater London.
- Location
- Coldharbour (SE9, BR7)
- Region
- Greater London
- Cover
- A year, on every job
- Quotes
- A clear price before any work starts
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
What the job involves on each surface
Timber door frames
A neat sand mastic joint round a front door suits a period home.
Period and listed homes
Many older homes were built with sand mastic round the windows. On listed buildings, check with your planning authority first.
What happens on the day
All our tools and materials come with us in the van. Once we have agreed what’s being done, we protect the area and start. Most jobs take anything from a few hours to a full day, depending on how many windows. In Coldharbour, as in most of London, parking needs a little planning. A visitor permit or a nearby bay makes the visit run more smoothly.
- We look at the surrounds with you and agree the joints to renew.
- Old mastic and any loose material are raked out.
- Deep gaps are packed so the mastic sits at the right depth.
- We apply the mastic by hand and shape it.
- The surface is finished to suit the stone or brick.
Before we arrive
- Tell us about any water getting in
- Mention any sign-in or site rules at work premises
- Try not to wet indoor joints just before the visit
Get a quote
Quotes start with a quick conversation. Tell us what’s wrong, where it is and how much there is, and we will explain how we’d tackle it. Whenever you’re ready, call 0345 464 0079 or email us.
Related advice
Should I try it myself first?
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.
Too much sealant is as bad as too little. A heavy bead looks messy and copes badly with movement, and getting the depth right matters as much as the look.
Landlords, agents and businesses in Coldharbour
Failed sealant is one of the commonest items on a check-out report, and it’s quick to put right between tenancies. We can quote for more than one property at once.
Water getting past a failed joint can damage the building, which is a bigger problem in a rented property. Resealing at the right time is simple maintenance.
How to look after the new joints
Good habits help new joints last longer. Our tips:
- Ask us before painting near the mastic
- Have rotten timber repaired before new mastic goes in
- Avoid heavy scraping on the mastic joint
- Ask the planning authority about consent for listed or conservation-area homes
When preparing windows for paint, take care around the mastic. It can be damaged by heavy scraping.
Fine cracks show the mastic is starting to fail. Renewing it then is simpler than waiting until it falls out.
Questions from Coldharbour
Can you do sand mastic in Coldharbour?
Yes. Our work covers London and the South East, and Coldharbour is part of that. Just phone 0345 464 0079 or drop us an email with a few details of the job.
Is parking a problem for a job in Coldharbour?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. That way the visit can be planned around it.
Is it OK to seal over old sealant?
No, and we never do. It can look neat for a few weeks, but the new bead soon lifts. The old sealant has to come out completely.
Is it worth trying it myself?
You can, for simple jobs. Preparation is everything: all the old sealant out, and a clean, dry joint. We can always put it right if it fails.
Can landlords and businesses book you?
Yes, regularly. We can quote for several properties at once.
Is it messy?
Tidy work is part of the job. We protect what’s around the joints, and we clear up when we are done.
Can you work on commercial sites?
Yes. We’ve worked for hotels, offices and other businesses.
What do you put in the joint?
Quality sealants from brands including Arbo and Everbuild, chosen to suit the joint. We explain the product when we quote.
Why it’s worth doing now in Coldharbour
If you’re redecorating, renew the mastic first. Paint over cracked mastic won’t stop the gaps and traditional guidance is to leave the new mastic unpainted. In a flat in Coldharbour, failed sealant seldom stays inside your own four walls: water can reach the neighbours below, and gaps in fire-rated joints affect the whole building.
Combining jobs into one visit usually makes better use of the time than several visits, so tell us about everything that needs sealing. You’ll get one clear quote for the whole job.
Why choose Mr Mastic in Coldharbour
- Every job guaranteed for a year
- Homes, businesses and hotels
- Trusted Arbo and Everbuild sealants
- 20+ years of sealant experience
See what affects the cost and our reviews.
Frames and glazing around Coldharbour
Rainfall in the South East is lower than in much of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind. With historic houses such as Eltham Palace (about 1.1 miles north) nearby, there’s older building stock in the area around Coldharbour as well as newer homes. Where a home is older, older timber frames in brick or stone need a different approach from a modern uPVC window.
For landlords with property near Mottingham station, older sash windows in a rental need their mastic kept sound to keep the weather out. As a London address, Coldharbour can be tricky for parking: let us know about parking bays, permits or a driveway. If you live in an older home near St Alban, the joint between an old wall and a newer frame is generally the first place rain gets in.
Coldharbour is about 4 miles north-west of Orpington, in Greater London. From the centre of Coldharbour to the outskirts, sand mastic is available for homes and businesses alike, from flats and houses to offices and hotels. Coldharbour is one of 764 places in Greater London where we work for sand mastic. Our London page covers work nearby, about 8 miles away.
All of SE9 and BR7 is within our area for sand mastic, from the main roads to the quietest streets. Sand mastic is available to properties on Green Lane, Horley Road and Dorset Road and the roads around them. We also cover Mottingham (1 mile west), Chinbrook (1 mile west), New Eltham (1 mile north-east), Eltham (1 mile north) and Middle Park (1 mile north-west). Further out, we also cover London (8 miles north-west), City of Westminster (11 miles north-west), Marylebone (10 miles north-west), Kensington (12 miles north-west), St Pancras (10 miles north-west) and Shoreditch (9 miles north-west).
Around Coldharbour
Typical jobs here are in homes near Elmstead Wood and St Thomas More Catholic Comprehensive School, among other places. The nearest railway station is Mottingham station, about 0.6 miles north of the centre. A little further out are The Glades (2.4 miles south-west) and Metropolitan Police Museum (2.2 miles east). The countryside around Coldharbour includes The Tarn and Summer Hill.
How we quote for sand mastic
Every job gets its own quote. These are the things that affect it:
- How many rooms, windows or areas are involved
- Which sealant suits the joint
- How much old sealant there is and how hard it is to remove
- Whether there’s mould to deal with
We don’t show prices on the website, because the cost depends so much on the job itself. Call for a quick quote.
What to tell us for a quote
The more you tell us, the more accurate the quote. When you ask for a quote, tell us:
- If someone has resealed it before
- If it’s domestic, commercial or a hotel
- The problem you’ve noticed
- Photos by email, if that is easy
Every job is quoted individually. Simply call 0345 464 0079 or drop us an email and describe the job and send pictures if you have them.