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 homes and businesses in Greenhill and across Greater London. Fully insured, ARBOMaster approved and guaranteed for a year.
- Draughty sash windows at the surround
- A silicone bead on a sash window that spoils the look
- Mastic worn away on windows facing the weather
Sand mastic in Greenhill, done properly
Sand mastic does not last for ever and gaps open up round the frame. We rake it out and renew it and tidies the surround. Typical jobs include draughty sash windows at the surround and modern sealant on a period surround, across stone surrounds, tenement windows and period & listed homes.
London homes have every kind of window, from timber sashes in period terraces to aluminium and uPVC in newer blocks. The mastic around them dries out and cracks with age, which is when draughts and damp patches appear in homes in Greenhill.
You get a one-year guarantee, the same in Greenhill as everywhere else we work.
- Place
- Greenhill (HA1, HA3, HA2)
- Region
- Greater London
- Cover
- A year, on every job
- Quote
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
The process
You don’t need to clear the whole room or building, only the area right around the joints. Everything nearby is protected, and the job takes a few hours per window, depending on the condition of the joints for a typical job. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. If the building has a concierge, managing agent or access rules, tell us when you book.
- First, we look at the surrounds with you and agree what needs doing.
- Old, loose mastic is raked out and the joint cleaned.
- Deep voids are packed so the mastic is the right thickness.
- We mix the sand mastic and apply it by hand, shaping it to the joint.
- We dress the surface so it sits neatly against the masonry.
Getting ready for the visit
- On commercial sites, let us know about site rules
- Let us know about parking restrictions
- Tell us about any previous sealing or DIY attempts
Getting a quote
We don’t publish a price list, because every job is different. Instead, your job gets its own clear quote. To arrange one, phone 0345 464 0079 or send us an email.
Read more
Keeping the joints in good condition
No joint lasts for ever, but care makes a real difference. Our tips:
- Ask us before painting near the mastic
- Look over the window mastic once a year
- Avoid heavy scraping on the mastic joint
- Ask the planning authority about consent for listed or conservation-area homes
Keep gutters and sills clear so water runs away from the surround. Constant wetting wears the mastic faster.
Crumbling mastic lets rain into the joint. That water can reach the timber frame and the wall so early renewal protects both.
Greenhill homes and the weather
The South East is one of the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. In a converted house or block, who looks after the windows depends on the lease, so check that before you book.
In the older streets around Church of St John the Baptist, frames set in older brick or stone need a sealant that suits the wall as well as the frame. For landlords with property near Harrow-on-the-Hill station, cracked sand mastic around sash windows lets in the draughts tenants complain about.
Greenhill is about 1 mile north-east of Harrow, in Greater London. From the centre of Greenhill to the outskirts, sand mastic is available for homes and businesses alike. Our Greater London coverage runs to 764 places, Greenhill among them. London is on our list too, about 12 miles from Greenhill.
We cover every part of the HA1, HA3 and HA2 postcode area for sand mastic. You’ll find streets such as Lyon Road, Hill Road and Byron Road. Nearby, we also carry out sand mastic in Wealdstone (1 mile north), Northwick Park (1 mile south-east), Harrow (1 mile south-west), Kenton (1 mile east) and Roxeth (1 mile south-west). Larger places within reach include London (12 miles south-east), City of Westminster (9 miles south-east), Marylebone (9 miles south-east), Kensington (8 miles south-east), St Pancras (10 miles south-east) and Shoreditch (12 miles east).
Landmarks near Greenhill
Locally, jobs take us to homes and businesses close to Royal Oak pub, Northwick Park and Harrow High School. Greenhill has its own railway station: Harrow-on-the-Hill station. A little further out are St. Anns (within half a mile south-west) and Hilfield Castle (4.8 miles north). For a walk, there’s Masons Field and Northala Fields.
DIY versus a professional finish
The difference is mostly in the preparation and the product. Joints are cleaned back to sound surfaces and dried, and the sealant is chosen for how the joint moves and where it is, and the work is guaranteed for a year.
Overfilling a joint is a classic DIY mistake. A thick, smeared bead looks untidy and doesn’t move well, and the joint depth matters as much as the finish.
Places near Greenhill
What else we do in Greenhill
Common problems we fix in Greenhill
Most of it is simply age. Even well-laid mastic needs renewing in time and how long it lasts depends on the weather it faces.
Common reasons people contact us are:
- Window mastic to renew ahead of painting
- Gaps where the frame meets the masonry
- Wind and rain getting in round a sash window
- Mastic worn away on windows facing the weather
Schools such as Saint Jerome Church of England Bilingual School are buildings too, and the mastic around its windows and doors needs looking after like any other building’s.
Before booking anyone
- What insurance they hold
- How long to leave it before use
- How the joint is cleaned and prepared
- How much experience the applicator has
What affects the cost of sand mastic
Call for a quick quote. What matters most is:
- Whether old sealant or filler has to be cut out
- The product the joint needs
- Any mould that needs treating
- Access and height
Leaving a failed joint usually makes the job bigger, not smaller, as water and mould keep getting in. If you’re not sure whether it needs doing, call 0345 464 0079 or email us for an honest opinion and a quote.
Asking for a quote
A few details help us give you an accurate quote. When you get in contact, it helps to mention:
- Pictures of the joints, sent by email
- Whether it has been sealed before
- What’s wrong with the joints now
- Where the job is, and your postcode
A good description makes for an accurate quote. Tell us where the job is, what’s wrong and how much there is, and email photos if that is easy.
Why deal with it now?
Replacing sash windows is a big decision for a period home and on a listed home, consent may be needed. If the frames are sound, renewing the mastic deals with gaps and draughts at the surround. 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.
Every job is a little different, so we quote each one individually. Size, access and the product the joint needs all play a part, and we’ll explain the quote if you ask.
Why us?
- Anti-fungal sanitary silicone in wet areas
- Trusted Arbo and Everbuild sealants
- We leave the area clean and tidy
- Experience in homes, commercial sites and hotels
Read our cost guide or customer reviews.
Surface by surface
Stone surrounds
Sand mastic sits naturally against stone. It finishes to look like part of the surround.
Timber door frames
Doors face weather and wear, so their mastic can fail sooner. We rake it out and renew it.
Common questions in Greenhill
Do you work for landlords with property near Harrow-on-the-Hill 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 will send you a clear quote.
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 drop us an email and tell us what needs doing.
Do the sealants smell?
Possibly a little. It fades as the sealant cures.
Is the work guaranteed?
There’s a 12-month guarantee on every job.
Do you hold any approvals?
Yes. We’re an ARBOMaster approved applicator, which is run for the Arbo sealant brand.
Do you offer different sealant colours?
Normally, yes. White, clear and grey are common, and other colours are available, and we agree the colour with you before any work starts.
What is sand mastic?
Sand mastic is a traditional material for pointing round windows and doors. It’s made with sand and a linseed-oil-based binder.
How much does sand mastic cost in Greenhill?
Size, access and the old material all affect the cost. Ask us for a quote.