Greater London · England
Sand mastic for sash & case windows in Harefield, Greater London
Professional sand mastic in and around Harefield, with every bit of old sealant taken out first and a 12-month guarantee.
- Crumbling sand mastic round a window
- A silicone bead on a sash window that spoils the look
- Cracked mastic round a front door frame
About our sand mastic in Harefield
For a listed home or one in a conservation area, ask your local planning authority if consent is needed before window work. Sand mastic is often favoured as a like-for-like material. If you are dealing with old cement repairs round a window that have failed and old sand mastic that has cracked, crumbled or fallen out, we can put it right, whatever the surface. Whether you’re looking for a mastic company, a sealant applicator or a sealant contractor in Harefield, Mr Mastic can help.
Much of London’s older housing was built with timber sash windows, some still in place and some long since replaced. Either way, the mastic between frame and brickwork is what stops draughts and rain getting in, in Harefield as anywhere.
All our work is covered by our one-year guarantee, wherever you are in Greater London.
- Place
- Harefield (UB9)
- Wider area
- Greater London
- Cover
- One year on every job
- Quote
- A clear price before any work starts
- Call
- 07833 053749
- Last updated
- 26 October 2026
DIY sealant or a professional job?
The biggest DIY mistake is sealing over old sealant. Silicone doesn’t stick to old silicone, so it lifts and traps water and mould underneath. All the old material has to come out first.
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.
Towns and villages near Harefield
Also in Harefield
Harefield: your questions answered
Do you cover Harefield for sand mastic?
Yes, Harefield is within the area we cover. Our work covers London and the South East. You can ring 07833 053749 or send us an email and tell us what needs doing, and we will give you a clear price.
Can you help a landlord with a rental near Denham station?
Yes, we work for landlords and letting agents. Just call 07833 053749 or drop us an email and tell us about the property, and we’ll send you a clear quote.
Where is Mr Mastic based?
We work from Crawley. Our applicators cover Harefield.
Are you an approved applicator?
Yes. We’re approved under the ARBOMaster scheme, which is run for the Arbo sealant brand.
How long does sand mastic take?
That depends on how much there is to do, but as a guide it takes a few hours for a single window, longer for several. We will give you a better idea when we quote.
What is sand mastic?
Sand plus a binder based on linseed oil. It’s built up in the joint by hand and shaped to suit the surround.
Do I have to be there?
That depends on where the joints are. For work indoors, someone needs to let us in, while outside work can sometimes be arranged differently.
Will you leave a mess?
No. We protect the surfaces around the joints, and we tidy up before we go.
Quotes for sand mastic in Harefield
Jobs vary more than people expect. The main factors:
- Whether old sealant or filler has to be cut out
- The number of rooms or windows
- Whether the work is at height
- The size of the job
Leaving a failed joint normally makes the job bigger, not smaller. If you’re not sure whether it needs doing, ring 07833 053749 or email us for an honest opinion and a quote.
What we need to know
When you call or email, these details help:
- How many joints, rooms or windows are involved
- Access, such as stairs, a lift or height
- Where the job is, and your postcode
- Whether it’s a home or a business
There’s no standard price list, as no two jobs are quite the same. Instead, your job gets its own clear quote. To get started, call 07833 053749 or drop us an email.
Frames and glazing around Harefield
The South East is one of the drier parts of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. With historic houses such as Ickenham Hall (about 3.4 miles south-east) nearby, there’s older building stock in the area around Harefield as well as newer homes. In older buildings, older timber frames in brick or stone need a different approach from a modern uPVC window.
Managing a site like Harefield Infant School? Then larger buildings have plenty of frames, and the mastic around each one ages. For an older house near a landmark such as Harefield Baptist Church, the joint between an old wall and a newer frame is usually the first place rain gets in.
Harefield is about 3 miles south of Rickmansworth, in Greater London. We provide sand mastic to householders, landlords and businesses in Harefield and the surrounding area, as part of our work across Greater London. Harefield is one of 786 places in Greater London where we work.
Every address in UB9 is covered for sand mastic. You will find streets such as High Street, Vernon Drive and New Park Road, and we cover them all. Other places close to Harefield include Hill End (1 mile north), Woodcock Hill (1 mile north-east), Batchworth Heath (2 miles north-east), Batchworth (2 miles north-east) and Mill End (2 miles north). We also work in nearby towns such as City of Westminster (15 miles south-east), Kensington (14 miles south-east), Hampstead (13 miles east), Ruislip (4 miles south-east), Ealing (10 miles south-east) and Hayes (7 miles south-east).
What’s near Harefield
Around Harefield, our work takes us to homes and buildings near The King's Arms Public House, The Green and The Harefield Academy, among other places. The nearest railway station is Denham station, about 2 miles south. Nearby you will also find Chiltern Open Air Museum (3.4 miles north-west) and Harefield Hospital (less than half a mile north-west). Open spaces near Harefield include Dews Farm Sand Pits and Horse Shoe Bay.
How the job changes by surface
Period and listed homes
Many older homes were built with sand mastic round the windows. If your home is listed, ask your local planning authority about consent.
Brick reveals
Gaps between frame and brick let in rain and draughts. New mastic seals the gap.
How to look after the new joints
Joint life depends on how it’s used and looked after. We suggest:
- Avoid heavy scraping on the mastic joint
- Ask us before painting near the mastic
- Ask a joiner to look at soft timber first
- Find out about consent before window work on a listed home
Do not run silicone over the new mastic. If you see a crack, ask us to take a look before trying a quick fix.
It’s best to renew mastic before painting the windows. Paint over cracked mastic only covers it up.
What we’re called out for in Harefield
Decorating can disturb tired mastic. Many people find it crumbling when they prepare the windows, which is a good time to renew it.
It’s worth asking for a quote if you see:
- Mastic worn away on windows facing the weather
- Wind and rain getting in round a sash window
- Tired mastic found when preparing windows for paint
- Gaps between timber frames and stone or brick
Harefield is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
Before you book anyone
- Whether the sealant suits the joint
- What the quote includes, VAT included or not
- What preparation is included
- Who turns up on the day
What happens on the day
We work through the job in order: protect, prepare, seal, tidy. Typically it takes anything from a few hours to a full day, depending on how many windows and we leave things clean and tidy. In Harefield, as in most of London, parking needs a little planning. It helps if you can point us to a visitor permit or a bay close to the door.
- Each surround is checked first.
- The joint is raked out and cleaned.
- 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.
Preparing for the visit
- Mention any sign-in or site rules at work premises
- Clear the area around the work
- Tell us if parking is tricky
Getting a quote
For a quick quote, get us on the phone, or email us if that is easier. Tell us about the joints that need doing and we will talk you through the work.
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For landlords and businesses
We also work for businesses, from offices to washrooms and kitchens. On commercial sites, working times can be discussed when we quote.
Letting agents often deal with us directly. Tell us the address, the job and how access works and we’ll give you a quote.