Greater London · England
South Harrow Sand Mastic
Sand mastic for South Harrow, by sealant specialists with 20+ years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Mastic dropping out of the joint
- Draughty sash windows at the surround
- Old cement repairs round a window that have failed
How we handle sand mastic in South Harrow
For a listed home or one in a conservation area, ask your local planning authority if consent is needed before window work. Like-for-like sand mastic is often the preferred finish. We work on timber door frames, brick reveals and period & listed homes, and common reasons people get in touch are cement or filler used on old window joints that has cracked and modern sealant on a period surround.
Many London homes are flats, with windows high above the street. In a converted house or block, the lease usually says who is responsible for the windows, so it’s worth checking before booking, and access in South Harrow is something to talk through when you book.
We guarantee the work for a year. If something is not right with it in that time, tell us and we’ll put it right.
- Place
- South Harrow (HA2, HA1, UB5)
- Region
- Greater London
- Cover
- A year, on every job
- Price
- A clear quote up front
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
Work for landlords, hotels and businesses
We also work for property managers and facilities teams in South Harrow and across Greater London. We can quote a run of properties together.
We work for letting agents and landlords as well as householders. Resealing between tenancies keeps a property looking cared for.
Nearby places to South Harrow
More services for South Harrow
What happens on the day
There is not much for you to do on the day. Show us the job and we will take it from there. The job generally takes a few hours per window, depending on the condition of the joints from start to finish. 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.
- 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.
- Sand mastic is mixed and applied by hand, then shaped to the joint.
- The mastic is finished to sit tidily against the stone or brick.
Getting ready for the visit
- Let us know about earlier repairs to the joints
- Let us know about parking restrictions
- Keep pets and children clear of the area while we work
How to get a quote
For a quick quote, get us on the phone, or email us if that’s easier. Describe what needs sealing and we’ll talk you through the work and send you a clear quote.
Related advice
Keeping the joints in good condition
Good habits help new joints last longer. Our tips:
- Keep modern sealant off the mastic
- Make sure water runs off the sill
- Go gently near the mastic when preparing windows
- Sort the mastic before the decorators arrive
Check the mastic when you check the paintwork. Catching cracks early keeps repairs small.
Fine cracks show the mastic is starting to fail. Renewing it then is simpler than waiting until it falls out.
Can I do it myself?
What a professional job adds is preparation and the right product. We take joints back to clean, dry surfaces, and the sealant is matched to the joint and its conditions, then guaranteed for a year.
A DIY attempt does not rule out a professional job. We remove it and do the joint properly, so tell us about it when you ask for a quote.
When to call us in South Harrow
Rain on the window surround works into any crack and loosens it further. Windows facing the weather tend to go first.
The problems people normally mention when they call include:
- Patchy fillers round a sash window
- Gaps where the frame meets the masonry
- Cracked mastic round a front door frame
- A silicone bead on a sash window that spoils the look
If you look after a building such as The Welldon Park Academy, its window and door frames need their mastic kept sound, just like a home’s.
What your quote should include
- What preparation is included
- How long to leave it before use
- Which sealant they’ll use, and why
- Who turns up on the day
Surface by surface
Timber door frames
Doors face weather and wear and the mastic can crack early. We rake it out and renew it.
Stone surrounds
We take care not to mark the stone when the old mastic comes out.
What affects the cost of sand mastic
There’s no set price list, because no two jobs are the same. What we look at:
- Any working-time requirements on site
- The size of the job
- The old material and how stubborn it is
- Mould in or behind the old joints
A few things move the cost up or down: how much old sealant there is and how stubborn it is, whether mould needs treating, and whether the work is at height. We take all of that into account in your quote.
Helping us quote
You don’t need to know the technical terms. It helps if you can tell us:
- A few photos by email, if you can
- How many joints, rooms or windows are involved
- Whether it’s a home or a business
- Where the job is, and your postcode
For a quote, phone 0345 464 0079 or send us an email with the location and a short description of the problem. You’ll have a clear quote before we start.
Questions from South Harrow
Can you do sand mastic in South Harrow?
Yes, South Harrow is within the area we cover. Our work covers London and the South East. Just call 0345 464 0079 or email us with a few details of the job, and we’ll give you a clear quote.
Can parking be tricky for a visit in South Harrow?
Parking in South Harrow, as in most of London, takes a little planning: a visitor permit or a bay close to the door helps a lot, so mention what’s available when you book.
Do you do commercial work?
Yes. We have worked for hotels, offices and other businesses.
Do you have insurance?
Yes. Mr Mastic is fully insured, with over 20 years’ experience in sealant work.
Do the sealants smell?
That depends on the sealant. Some smell for a while, some hardly at all.
What sealant do you use?
It depends on the joint: anti-fungal sanitary silicone in wet areas, and other sealants where joints move or face the weather. Brands we use include Arbo and Everbuild.
How long does sand mastic take to harden?
It skins over fairly quickly but takes longer to harden fully. We will tell you what to expect for your job.
What exactly is sand mastic?
It’s the traditional filler for the joint round timber windows and doors. It combines sand with a linseed-oil-based binder.
What sand mastic looks like in South Harrow
Rainfall in the South East is lower than in much 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.
If you let a flat or house near Northolt Park station, older sash windows in a rental need their mastic kept sound to keep the weather out. As a London address, South Harrow can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
South Harrow is about 1 mile south of Harrow, in Greater London. Homes, rented property, offices and hotels in South Harrow can book us for sand mastic, old or new, large or small. The work is guaranteed for a year. We cover 764 towns and villages across Greater London, large and small. London is on our list too, around 12 miles away.
Jobs for sand mastic in HA2, HA1 and UB5 is quoted and booked the same way as anywhere else. We cover properties on Park Lane, Grange Road and Dudley Road. Other places close to South Harrow include Roxeth (1 mile north-east), Harrow (1 mile north), Harrow on the Hill (1 mile east), Rayners Lane (1 mile north-west) and Northolt (1 mile south-west). Within a short drive, we also cover London (12 miles east), City of Westminster (9 miles east), Marylebone (9 miles east), Kensington (8 miles south-east), St Pancras (10 miles east) and Shoreditch (12 miles east).
Landmarks near South Harrow
Locally, jobs take us to homes and businesses close to Orley Farm School, Northwick Park and St Dominic's Sixth Form College and the streets around them. The closest station to South Harrow is Northolt Park station, about 0.5 miles south-west. Nearby you’ll also find St. George's Shopping Centre (1.3 miles north-east) and Kodak Museum (2 miles north). The countryside around South Harrow includes Middle Lake and Northala Fields.