Greater London · England
North Harrow Sand Mastic
Traditional burnt sand mastic around sash and case windows and doors in stone and brick for householders, landlords and businesses in North Harrow. Fully insured, ARBOMaster approved and guaranteed for a year.
- Modern sealant on a period surround
- Old sand mastic that has cracked, crumbled or fallen out
- Weathered mastic on the most exposed windows
What happens on the day
There’s no need to move everything out, only the area right around the joints. We protect the rest, 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. 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
- For business premises, tell us about site rules or sign-in
- Keep pets and children clear of the area while we work
- Mention any parking rules near the property
Getting a quote
It all starts with a short chat. Tell us what’s wrong, where it is and how much there is. When it suits you, call 0345 464 0079 or send us an email.
Advice
How we handle sand mastic in North Harrow
For a listed home or one in a conservation area, ask your local planning authority whether consent is needed for work to windows. Like-for-like sand mastic is often the preferred finish. We work on stone surrounds, brick reveals and sash and case windows, and common reasons people get in touch are weathered mastic on the most exposed windows and old sand mastic that has cracked, crumbled or fallen out.
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 North Harrow as anywhere.
Each job carries a 12-month guarantee, whatever its size.
- Where
- North Harrow (HA2, HA1, HA5)
- Region
- Greater London
- Guarantee
- One year on every job
- Price
- Quoted before any work starts
- Phone
- 0345 464 0079
- Updated
- 26 October 2026
More services for North Harrow
How to look after the new joints
Looking after new joints is easy:
- Inspect the joints round the windows every year or so
- Clear gutters so water doesn’t pour onto the windows
- Avoid heavy scraping on the mastic joint
- Avoid patching sand mastic with silicone
Leave the new mastic unpainted, which is the traditional advice. Ask us before any decorating around it.
Small cracks are a sign the mastic is ageing. It’s easier to renew it before it drops out.
Leave it or put it right?
An open joint round the frame lets weather in. Left, water can reach the timber and the wall so renewing it early protects the window. In older London homes, water behind a failed joint soaks into brick and timber without much sign, and once it shows in North Harrow, the repair is bigger than a sealant job.
Some things make a job bigger or smaller: 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.
What you get with us
- Sanitary silicone with an anti-fungal additive in wet areas
- Full insurance on every job
- Arbo and Everbuild products
- Experience in homes, commercial sites and hotels
Take a look at what affects the cost and our reviews.
Can I do it myself?
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.
If you’ve already had a go yourself, that is fine. We remove it and do the joint properly, so tell us about it when you ask for a quote.
What sand mastic looks like in North Harrow
With historic houses such as Headstone Manor (about 0.8 miles north-east) nearby, there’s older building stock in the area around North Harrow as well as newer homes. In older buildings, older timber frames in brick or stone need a different approach from a modern uPVC window. In a converted house or block, who looks after the windows depends on the lease, so it’s worth checking before booking.
For site and facilities teams at buildings such as Longfield Primary School, the mastic around its windows and doors needs looking after like any other building’s. North Harrow is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
North Harrow is about 1 mile north-west of Harrow, in Greater London. Whether you’re in the middle of North Harrow or further out, we cover sand mastic for every kind of property. We cover 764 towns and villages across Greater London, from the larger towns to small villages. We also work in London, about 13 miles from North Harrow.
Jobs for sand mastic in HA2, HA1 and HA5 works the same way as everywhere else we cover. That includes homes and businesses on The Avenue, Pinner Road and Durham Road. Nearby, we also carry out sand mastic in Rayners Lane (1 mile south-west), Harrow (1 mile south-east), Roxbourne (1 mile south-west), Eastcote (1 mile west) and Greenhill (1 mile east). Larger places within reach include London (13 miles south-east), City of Westminster (10 miles south-east), Marylebone (10 miles south-east), Kensington (9 miles south-east), St Pancras (11 miles east) and Shoreditch (13 miles east).
What’s near North Harrow
Typical jobs here are in homes near Nower Hill High School, Heathfield School and Headstone Manor Recreation Ground. North Harrow’s nearest station is Harrow-on-the-Hill station, about 1.2 miles east. Other landmarks nearby include St. George's Shopping Centre (1 mile east) and Hilfield Castle (5 miles north). The countryside around North Harrow includes Northala Fields and Islip Manor Meadows.
Do you need sand mastic in North Harrow?
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.
Look out for any of the following:
- Gaps between timber frames and stone or brick
- Wind and rain getting in round a sash window
- Failed mastic on an exposed elevation
- Old cement repairs round a window that have failed
For landlords with property near Harrow-on-the-Hill station, older sash windows in a rental need their mastic kept sound to keep the weather out.
Questions to ask before booking
- How the joint is cleaned and prepared
- What guarantee comes with the work
- How long to leave it before use
- Whether they’re fully insured
Work for landlords, hotels and businesses
We work for landlords and agents as well as householders. Resealing between tenancies keeps a property looking cared for before the next move-in.
Letting agents often deal with us directly. Tell us the address, the job and how access works.
How we quote for sand mastic
We quote each job individually. These are the things that affect it:
- Any mould that needs treating
- Whether old sealant or filler has to be cut out
- Working hours on commercial sites
- The number of rooms or windows
No two jobs are quite the same, so we quote each one individually. Size, access and the product the joint needs all play a part, and we will explain the quote if you ask.
What to tell us for a quote
To make quoting easier, let us know:
- If someone has resealed it before
- What’s wrong with the joints now
- If it’s domestic, commercial or a hotel
- How we’d reach the joints
For a quick quote, get us on the phone, or send an email if you’d rather. Describe what needs sealing and we will explain what’s involved before giving you a price.
North Harrow: your questions answered
Is parking an issue for sand mastic in North Harrow?
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 do sand mastic in North Harrow?
Yes, North Harrow is within the area we cover. We work across London and the South East. You can phone 0345 464 0079 or send us an email and let us know what needs doing, and we will give you a clear quote.
How long will you be here?
Typically it takes a few hours for a single window, longer for several. Larger jobs naturally take longer, and we’ll tell you how long to expect.
Is sand mastic better than silicone for my windows?
For period timber windows in stone or brick, sand mastic is often the better fit. Modern frames normally suit a flexible sealant.
Do the sealants smell?
Sometimes, a little. It fades as the sealant cures, and ventilation helps.
Do I need permission for sand mastic on a listed building?
Yes, it’s worth checking. Your local planning authority can say if consent is needed for work on a listed home or in a conservation area.
Will you leave a mess?
Very little: the area around the joints is protected first, and we tidy up before we go.
Is it OK to seal over old sealant?
No, because it fails. The old sealant always comes out first.