Greater London · England
Sand Mastic in Swiss Cottage
Sand mastic across Swiss Cottage and nearby, with every bit of old sealant taken out first.
- Mastic that needs renewing before redecorating
- Cement or filler used on old window joints that has cracked
- Wind and rain getting in round a sash window
Sand mastic in Swiss Cottage
Silicone on a period window often looks wrong and doesn’t suit the building. Sand mastic gives a finish that matches the age of the house and we can swap the silicone for it. If you have cement or filler used on old window joints that has cracked and old sand mastic that has cracked, crumbled or fallen out, we can help, whatever the surface.
London’s Victorian and Edwardian terraces were built with timber sash windows, and many still have them or their replacements. Either way, the mastic between frame and brickwork is what stops draughts and rain getting in, in Swiss Cottage as anywhere.
You get a one-year guarantee, the same in Swiss Cottage as everywhere else we work.
- Where
- Swiss Cottage (NW3, NW8, NW6)
- Wider area
- Greater London
- Cover
- A year, on every job
- Price
- Quoted before any work starts
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
Looking after it afterwards
Simple care keeps the joints in good condition. We recommend:
- Inspect the joints round the windows every year or so
- Don’t run silicone over sand mastic
- Ask a joiner to look at soft timber first
- Avoid heavy scraping on the mastic joint
Don’t touch or press the mastic while it hardens. It forms a skin fairly soon, but takes longer to harden fully.
An open joint round the box lets weather through. The longer it’s left, the more the joint opens as more mastic falls out.
FAQs for Swiss Cottage
Can you help a landlord with a rental near South Hampstead station?
Yes, we work for landlords and agents. Just phone 0345 464 0079 or email us and tell us about the property, and we will send you a clear quote.
Is Swiss Cottage in your area for sand mastic?
Yes, Swiss Cottage is within the area we cover. Our work covers London and the South East. Just phone 0345 464 0079 or drop us an email with a few details of the job, and we’ll send you a clear quote.
Is the work guaranteed?
You get our one-year guarantee on every job.
Is it messy?
Not at all. We work neatly, protect the area around the joints and tidy up afterwards.
Do you take out the old sealant first?
Yes. All of the old material is cut out and the joint cleaned before applying anything new.
What exactly is sand mastic?
Sand plus a binder based on linseed oil. It’s built up in the joint by hand and finished to sit neatly against the masonry.
How long does sand mastic take?
Most jobs take a few hours for a single window, longer for several, including the preparation. We’ll confirm how long when we quote.
Can I choose the sealant colour?
In most cases you can choose. We will tell you which colours the right product comes in and agree one before work begins.
For landlords and businesses
We regularly work with letting and managing agents. Send the address, what’s needed and the access arrangements and we’ll give you a quote.
Whether it’s one flat or a portfolio, you get the same standard of work: old sealant fully removed, joints prepared properly and a 12-month guarantee.
What the job involves on each surface
Stone surrounds
Sand mastic sits naturally against stone. The finish blends with the masonry.
Brick reveals
An open joint at a brick reveal lets weather in. New mastic seals the gap.
How the visit works
Every visit runs the same way: we look at the joints together, mask and protect the surrounding surfaces, do the work and tidy away. It normally takes anything from a few hours to a full day, depending on how many windows. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. Mention any building rules, key holders or managing agents when you book.
- Each surround is checked first.
- We rake out the old mastic and clean the joint.
- We fill deep gaps so the new mastic is not too thick.
- New sand mastic is applied and shaped by hand.
- The finish is dressed neatly.
Before we arrive
- Mention any leaks or damp you’ve noticed
- Mention any tricky access
- For business premises, tell us about site rules or sign-in
Ask for a quote
Need a quote? Please phone 0345 464 0079 or send us an email and tell us about the job. You will know what we plan to do, and what it will cost, before any work begins.
Read more
Windows and doors in Swiss Cottage
In a converted house or block, who looks after the windows depends on the lease, so check that before booking. With historic houses such as Winfield House (about 0.9 miles south-east) nearby, there’s older building stock in the area around Swiss Cottage 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 is traditional sand mastic.
As a London address, Swiss Cottage can be tricky for parking: tell us about permits, visitor bays or off-street space when you book. If you look after a building such as The UCL Academy, its window and door frames need their mastic kept sound, just like a home’s.
Swiss Cottage is about 1 mile south of Hampstead, in Greater London. For sand mastic in and around Swiss Cottage, please phone 0345 464 0079 or send us an email for a quick quote. We’re based in Crawley and cover Greater London, Swiss Cottage included. Across Greater London, we cover 764 places, Swiss Cottage among them.
All of NW3, NW8 and NW6 is within our area for sand mastic. Whether your property is on Avenue Road, Acacia Road and Harben Road or a nearby road, our applicators can take on the job. We also cover the places around Swiss Cottage: South Hampstead (1 mile north), St John's Wood (1 mile south), Haverstock (1 mile east), Belsize Park (1 mile east) and Primrose Hill (1 mile east). Further out, we also cover London (4 miles south-east), Kensington (3 miles south-west), St Pancras (3 miles south-east), Shoreditch (4 miles east), Walthamstow (7 miles north-east) and Hoxton (4 miles east).
Local landmarks in Swiss Cottage
In Swiss Cottage, that means homes and buildings near Cafe Med pub, Holy Trinity CofE Primary School and Primrose Hill and the streets around them. You will also find Cecil Sharp House (1.1 miles east) and St. Mary's Town and Country School (under half a mile north-east). There’s a railway station in Swiss Cottage itself: South Hampstead station. Nearby you’ll also find Montfichet's Tower (3.7 miles south-east) and Isokon Gallery (0.8 miles north-east). Open spaces near Swiss Cottage include The Long Water and Primrose Hill.
Leave it or put it right?
New mastic over crumbling mastic won’t hold. Raking out and preparing the joint gives it a sound base so the new mastic stays put. Converted houses in London often have a bathroom above someone else’s living room, so a small leak from tired sealant can mean a neighbour’s ceiling and a lot of disruption. Putting it right early is much less trouble for homes in Swiss Cottage.
Every job is a little different, so each one gets its own quote. Size, access and the product the joint needs all make a difference, and we’ll explain the quote if you ask.
Why choose Mr Mastic in Swiss Cottage
- Arbo and Everbuild products
- Anti-fungal sanitary silicone in wet areas
- More than 20 years in sealant work
- 180+ five-star Google reviews
Read how sealant jobs are priced and our reviews.
Nearby places to Swiss Cottage
Other services in Swiss Cottage
DIY versus a professional finish
Not every job suits DIY: work at height, external movement joints, fire-rated sealant and large areas call for the right materials, safe access and experience.
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.
When to call us in Swiss Cottage
Rain on the window surround works into any crack and loosens it further. Windows facing the weather tend to go first.
Common reasons people contact us are:
- Mastic dropping out of the joint
- Mastic that needs renewing before redecorating
- Patchy fillers round a sash window
- Open joints round the window box
Letting a property close to South Hampstead station? Then older sash windows in a rental need their mastic kept sound to keep the weather out.
What to look for in a quote
- Is the old sealant removed completely?
- What guarantee comes with the work
- Whether VAT is included
- What the cure time is