Greater London · England
Sand Mastic in Chelsea
Sand mastic across Chelsea and nearby, with every bit of old sealant taken out first.
- Gaps between timber frames and stone or brick
- Window mastic to renew ahead of painting
- Wind and rain getting in round a sash window
Sand mastic for homes and businesses in Chelsea
Sand mastic doesn’t last for ever, leaving gaps round the window. Renewing it closes the gap and tidies the surround. Typical jobs include window mastic to renew ahead of painting and gaps where the frame meets the masonry, on period & listed homes, sash and case windows and tenement windows.
Many London homes are flats, with windows high above the street. In a converted house or block, the lease normally says who is responsible for the windows, so it’s worth checking before booking.
All our work comes with a 12-month guarantee.
- Place
- Chelsea (SW3, SW10, SW1X, SW1W)
- Wider area
- Greater London
- Cover
- 12 months on all our work
- Quotes
- A clear quote up front
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
Why deal with it now?
Not every filler suits an old window surround. Sand mastic is the like-for-like choice, which can matter on listed and conservation-area homes. In a London flat, a failed joint rarely stays your problem alone: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
Combining jobs into one visit is normally more efficient than separate visits, so tell us about everything that needs sealing. We will send you a clear quote for the lot.
Why Chelsea customers choose us
- Any old sealant cut out fully, not covered over
- Arbo and Everbuild products
- We leave the area clean and tidy
- Anti-fungal sanitary silicone in wet areas
Take a look at our cost guide or customer reviews.
What we can’t put right
To be straight with you, some problems need a different trade:
- Crumbling stone or brickwork round the window
- Whether work needs listed building consent
- Rotten sashes, sills or window boxes (a joiner’s job)
Not sure which it is? You can ring 0345 464 0079 or send us an email and we’ll tell you honestly.
Joints and surfaces we work on
- Tenement windows
- Sash and case windows
- Period & listed homes
- Brick reveals
- Stone surrounds
- Timber door frames
Chelsea: your questions answered
Is parking a problem for a job in Chelsea?
London parking needs a little planning, so let us know about permits, bays or a driveway when you book. That way the visit can be planned around it.
Can you help a landlord with a rental near London Victoria station?
Yes, we work for letting agents and landlords. Just phone 0345 464 0079 or send us an email and tell us about the property, and we’ll give you a clear price.
Where do you work from?
Mr Mastic is based in Crawley. Our applicators cover Chelsea.
Can you work on commercial sites?
Yes. We can plan bigger jobs in stages.
How long does sand mastic take to go off?
A skin forms quite soon, but full hardening takes longer. We will tell you what to expect for your job.
What do you need from me for a quote?
The location, the problem and the rough size of the job. Photos by email help too.
Does someone need to be in?
It depends on the job. Inside work needs someone to give us access, and for outside work we’ll agree access with you when we book.
Can sand mastic be painted?
Sand mastic is normally left unpainted, as guidance on traditional windows advises. Talk to us before any painting near it.
Windows and doors in Chelsea
In London conversions and blocks, the lease decides who is responsible for the frames, so check that before you book. With historic houses such as Carlyle's House (about 0.4 miles south-west) nearby, there’s older building stock in the area around Chelsea as well as newer homes. Where a home is older, older frames set in brick or stone need a sealant that suits them, and sometimes that’s traditional sand mastic.
For landlords with property near London Victoria station, any sash windows need sound mastic to keep draughts and rain out. For an older house near a landmark such as Former Welsh Congregational Church, the joint between an old wall and a newer frame is usually the first place rain gets in.
Chelsea is about 2 miles south-east of Kensington, in Greater London. Wherever you are in the SW3 postcode area, our applicators can take on sand mastic. Chelsea is one of 764 places in Greater London where we work.
All of SW3, SW10, SW1X and SW1W is within our area for sand mastic, from the main roads to the quietest streets. You will find streets such as Markham Square, Wellington Square and Tedworth Square, all of which we cover. Main roads around Chelsea include the B302 and B304, so getting to you is simple. We also cover Brompton (1 mile north), South Kensington (1 mile west), Little Chelsea (1 mile south-west), Belgravia (1 mile north-east) and World's End (1 mile south-west). Larger places within reach include London (3 miles east), St Pancras (3 miles north-east), Shoreditch (5 miles north-east), Walthamstow (9 miles north-east), Hoxton (5 miles north-east) and Whitechapel (5 miles north-east).
Around Chelsea
Around Chelsea, our work takes us to homes and buildings near Burton’s Court, St Thomas More RC Language College and Markham Arms Public House. Also close by are Natural History Museum Library and Archives (0.7 miles north-west) and Hellenic College of London (0.5 miles north). Chelsea’s nearest station is London Victoria station, about 1 mile north-east. A little further out are Baynard's Castle (3.2 miles north-east) and Harrods (0.7 miles north). Open spaces near Chelsea include Campden Hill and Battersea Park Lake.
Should I try it myself first?
Too much sealant is as bad as too little. A heavy bead looks messy and copes badly with movement, and the joint depth matters as much as the finish.
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.
What happens on the day
A visit follows a simple pattern: we look at the joints together, mask and protect the surrounding surfaces, do the work and clear up. Most jobs take a few hours for a single window, longer for several. For a job in Chelsea, parking and access are the things to plan: let us know about parking, the floor we’ll be working on and any lift or shared entrance.
- We look at the surrounds with you and agree the joints to renew.
- We remove the old, loose mastic.
- Deep gaps are packed so the mastic sits at the right depth.
- We apply the mastic by hand and shape it.
- We dress the finish so it sits neatly against the masonry.
Before we arrive
- Where the joints are inside, avoid wetting them before we arrive
- For business premises, tell us about site rules or sign-in
- Keep children and pets away from the work area
Ask for a quote
Want a quote for sand mastic? Please call 0345 464 0079 or drop us an email and tell us about the job. We will explain what we’d do and send you a clear quote before we start.
Related advice
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What affects the quote in Chelsea
For a quick quote, just ask. What matters most is:
- The number and length of the joints
- Any working-time requirements on site
- Which sealant suits the joint
- The old material and how stubborn it is
We don’t show prices on the website, because each job is priced on what it involves. Call for a quick quote.
Asking for a quote
When you contact us, it’s useful to know:
- Roughly how big the job is
- Where the job is, and your postcode
- Whether it has been sealed before
- If it’s domestic, commercial or a hotel
It all starts with a short chat. Tell us what’s wrong, where it is and how much there is, and we will talk you through what we’d do. When it suits you, call 0345 464 0079 or send us an email.
When to call us in Chelsea
Timber frames move with the seasons. The movement cracks the mastic over time.
These are the problems we are asked about most:
- Cracked mastic round a front door frame
- Weathered mastic on the most exposed windows
- Tired mastic found when preparing windows for paint
- Cement or filler used on old window joints that has cracked
For site and facilities teams at buildings such as Oratory Roman Catholic Primary School, the mastic around its windows and doors needs looking after like any other building’s.
Before you book anyone
- Whether they’re fully insured
- What the cure time is
- Who does the work, and how experienced they are
- Whether they seal over old material or remove it
Surface by surface
Tenement and terrace windows
Upper-floor windows need access planning. Let us know the floor and we’ll confirm access.
Sash and case windows
On a sash window, the mastic joint shows on the outside, so a neat, even finish matters.