Greater London · England
Sand mastic for sash & case windows in Greenhill, Greater London
Traditional burnt sand mastic around sash and case windows and doors in stone and brick for homeowners, landlords and businesses in Greenhill. Fully insured, ARBOMaster approved and guaranteed for a year.
- Old cement repairs round a window that have failed
- Open joints round the window box
- Failed mastic on an exposed elevation
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 matched to the joint and its conditions, and the work is guaranteed for a year.
Overfilling a joint is a classic DIY mistake. A thick, smeared bead looks untidy and does not move well, and the joint depth matters as much as the finish.
How we handle sand mastic in Greenhill
Traditional burnt sand mastic that sits naturally against stone and brick. It’s a good fit for period properties where a modern sealant bead would stand out. Typical jobs include silicone on a period window that looks wrong and wind and rain getting in round a sash window, across stone surrounds, brick reveals and timber door frames.
London’s Victorian and Edwardian terraces were built with timber sash windows, and many still have them or their replacements. Whatever is in the opening now, the joint between frame and wall is what keeps the weather out.
We guarantee the work for a year. If there’s a problem with our work within the year, let us know and we will sort it.
- Place
- Greenhill (NW3, NW6)
- Region
- Greater London
- Guarantee
- A year, on every job
- Quotes
- A clear price before work begins
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
What sand mastic looks like in Greenhill
In a converted house or block, who looks after the windows depends on the lease, so it’s worth checking before booking. Historic houses like 2 Willow Road (about 0.3 miles north-east) are a reminder that the area around Greenhill 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.
If you let a flat or house near Hampstead Heath station, cracked sand mastic around sash windows lets in the draughts tenants complain about. If you look after a building such as The Royal School, the mastic around its windows and doors needs looking after like any other building’s. Greenhill is in London, so parking needs planning: let us know about parking bays, permits or a driveway.
Greenhill is about 1 mile north-east of Hampstead, in Greater London. Wherever you are in the NW3 postcode area, we cover sand mastic for homes and businesses. Greenhill is one of 764 towns and villages in Greater London where we work.
We cover every part of the NW3 and NW6 postcode area for sand mastic and the streets around it. Sand mastic is available to properties on Back Lane, Well Road and Ornan Road and the roads around them. If you’re just outside Greenhill, we cover Hampstead (1 mile south-west), Vale of Health (1 mile north), West Hampstead (1 mile west), Fortune Green (1 mile west) and Haverstock (1 mile south-east). Further out, we also cover London (5 miles south-east), City of Westminster (3 miles south), Marylebone (3 miles south-east), Kensington (4 miles south), St Pancras (3 miles south-east) and Shoreditch (5 miles south-east).
Landmarks near Greenhill
We work in homes and buildings around Cecil Sharp House, Fitzjohn's Primary School and King William IV Public House, among other places. You will also find South Hampstead High School (0.6 miles south) and Hampstead Heath (0.7 miles north-east). Greenhill has its own railway station: Hampstead Heath station. Nearby you will also find New End Hospital (under half a mile north-west) and Montfichet's Tower (4.3 miles south-east). For a walk, there’s Belsize Wood and Parliament Hill.
Leave it or put it right?
If you’re redecorating, renew the mastic first. Painting over failed mastic doesn’t seal it, and the new mastic is traditionally left unpainted. In older London homes, water behind a failed joint soaks into brick and timber without much sign, and by the time it shows on a wall or ceiling in Greenhill, the repair is bigger than the sealant job would have been.
Instead of a standard rate, we price the job in front of us: the amount of work, the old material and the access. The price is agreed before we begin.
Why book with us
- One-year guarantee on every job
- Arbo and Everbuild products
- 180+ five-star Google reviews
- Full insurance on every job
Take a look at our cost guide or our reviews.
What the job involves on each surface
Timber door frames
Period doors in stone or brick openings are often pointed with sand mastic. The method is the same as for windows.
Tenement and terrace windows
Rows of sash windows on tenements and terraces often need renewing together. We can do one window or several.
Common questions in Greenhill
Is parking a problem for a job in Greenhill?
In much of London, parking needs planning: a visitor permit or a bay close to the door helps a lot, so mention what’s available when you book.
Do you cover Greenhill for sand mastic?
Yes. We work across London and the South East, and Greenhill is part of that. You can phone 0345 464 0079 or send us an email and tell us what needs doing, and we will give you a clear quote.
I’m a tenant. Can you help?
Of course. Check with your landlord; we can send the quote to them too.
Do you take out the old sealant first?
Yes. Sealing over old sealant is the main reason resealing fails early, so we never do it.
Do you work for landlords and businesses?
Yes. Domestic, commercial and hotel work are all part of what we do.
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 don’t need to watch us work.
Do you work for hotels and businesses?
Yes, regularly. Larger jobs can be planned room by room or area by area.
Can you seal over the old sealant?
No, and we never do. It can look neat for a few weeks, but the new bead soon lifts. Removing the old sealant completely is the only lasting way.
Nearby places to Greenhill
More services for Greenhill
Honest limits
Sealant isn’t the answer to every problem, and we will tell you before any work starts. It won’t solve:
- Timber that has rotted
- Sash cords, weights and draught-proofing of the sashes
- Planning or listed building consent (your local planning authority decides)
Not sure which it is? You can phone 0345 464 0079 or send us an email and we’ll tell you honestly before you book.
What we seal
- Stone surrounds
- Period & listed homes
- Sash and case windows
- Tenement windows
- Timber door frames
- Brick reveals
Quotes for sand mastic in Greenhill
Call for a quick quote. What matters most is:
- Whether the work is at height
- The old material and how stubborn it is
- Mould in or behind the old joints
- The number and length of the joints
What it costs depends on the size of the job, how much old material has to come out and access to the work. We give a clear quote before any work starts.
What to tell us for a quote
When you call or email, these details help:
- How many joints, rooms or windows are involved
- A few photos by email, if you can
- If someone has resealed it before
- What the problem is, such as mould, gaps, leaks or cracking
We quote each job on its own, so start by telling us what you need. Simply call 0345 464 0079 or drop us an email and describe the job and send photos if you have them.
How to look after the new joints
After the cure time, these simple habits help:
- Inspect the joints round the windows every year or so
- Find out about consent before window work on a listed home
- Do not paint over the new mastic
- Avoid patching sand mastic with silicone
Leave the new mastic alone while it firms up. It skins over quickly, but takes longer to harden fully.
Renewing mastic before redecorating saves doing it twice. Paint over cracked mastic only covers it up.
How the visit works
We work through the job in order: protect, prepare, seal, tidy. Typically it takes a few hours per window, depending on the condition of the joints, and the area is left clean. 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.
- We look at the surrounds with you and agree the joints to renew.
- Old mastic and any loose material are raked out.
- We pack any deep voids first.
- We apply the mastic by hand and shape it.
- The surface is finished to suit the stone or brick.
Preparing for the visit
- Mention any sign-in or site rules at work premises
- Mention any tricky access
- Mention if the joints have been sealed before
Getting a quote
Want a quote for sand mastic? Please phone 0345 464 0079 or send us an email with a few details. You will know what we plan to do, and what it will cost, before any work begins.