Greater London · England
Sand mastic for sash & case windows in High Barnet, Greater London
Traditional burnt sand mastic around sash and case windows and doors in stone and brick in High Barnet, with a one-year guarantee on every job. Call for a quick quote.
- Tired mastic found when preparing windows for paint
- Draughty sash windows at the surround
- Modern sealant on a period surround
Should I try it myself first?
If you are set on DIY, put the effort into preparation: take out all the old sealant, make sure the joint is clean and dry, and give it the full cure time. If it fails, we can still redo it.
A careful DIYer can reseal a simple joint, such as a straightforward joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
Sand mastic in High Barnet
Sand mastic suits most period window surrounds. On modern frames we’d normally use a flexible sealant and we will explain which is best for yours. We’re often asked to deal with a silicone bead on a sash window that spoils the look and open joints round the window box, across brick reveals, sash and case windows and tenement windows.
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, in High Barnet as anywhere.
Whatever the size of the job, it’s backed by our 12-month guarantee in High Barnet and across Greater London.
- Place
- High Barnet (EN5)
- Region
- Greater London
- Cover
- 12 months on all our work
- Quotes
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
Landlords, agents and businesses in High Barnet
In hotels, rooms out of use cost money, so we plan the work room by room. We’ve worked in hotels as well as homes and businesses.
Mouldy or split sealant often shows up at the end of a tenancy, and it’s easy to sort out between tenants. We can quote for more than one property at once.
Questions from High Barnet
I let a flat near Hadley Wood station. Can you help?
Yes, we work for letting agents and landlords. Just call 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 High Barnet for sand mastic?
Yes, High Barnet is within the area we cover. We work across London and the South East. You can ring 0345 464 0079 or email us and let us know what needs doing, and we’ll send you a clear quote.
Do I have to be there?
That depends on where the joints are. Inside work needs someone to give us access.
What information do you need?
Just the basics: the address or postcode, what’s wrong and any access issues. After that, simply phone 0345 464 0079 or send us an email.
Will the old sealant be removed?
Yes. All of the old material is cut out and the joint cleaned before resealing.
Should I try DIY first?
Sometimes. The key is preparation: remove all the old material and work on a clean, dry joint. If it does not work out, we can redo it.
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. We use products from Arbo and Everbuild.
Can you replace silicone on a period window with sand mastic?
Yes, we do this often. All the old silicone is removed first so the mastic beds in well.
Windows and doors in High Barnet
In London conversions and blocks, the lease decides who is responsible for the frames, so it’s worth checking before booking. With historic houses such as Wyllyotts Manor (about 2.9 miles north) nearby, there’s older building stock in the area around High Barnet as well as newer homes. Where a home is older, older frames set in brick or stone need a sealant that suits them, and sometimes that is traditional sand mastic.
If you live in an older home near Christ Church, frames set in older brick or stone need a sealant that suits the wall as well as the frame. For site and facilities teams at buildings such as Foulds School, the mastic around its windows and doors needs looking after like any other building’s. Rented homes near Hadley Wood station change hands often, and older sash windows in a rental need their mastic kept sound to keep the weather out.
High Barnet is about 1 mile north-west of Barnet, in Greater London. Wherever you are in the EN5 postcode area, our applicators can take on sand mastic. Our Greater London coverage runs to 764 places, and High Barnet is one of them. For nearby work, see our London page.
Postcode districts we cover here for sand mastic: EN5. Local streets include Byng Road, Park Road and Kings Road, and we cover them all. You will find High Barnet on the A1081, so it’s easy for us to get to with everything needed for sand mastic. Close by, we work in Hadley (1 mile east), Arkley (1 mile south-west), Kitts End (1 mile north), Totteridge (1 mile south) and Rowley Green (2 miles west). Larger places within reach include London (12 miles south-east), City of Westminster (10 miles south), Marylebone (10 miles south), Kensington (11 miles south), St Pancras (10 miles south-east) and Shoreditch (11 miles south-east).
What’s near High Barnet
In High Barnet, that means homes and buildings near Susi Earnshaw Theatre School, The White Lion pub and Queen Elizabeth's School and the streets around them. For rail, the closest station is Hadley Wood station, roughly 1.6 miles north-east of the centre. Nearby you will also find Spires Shopping Centre (within half a mile east) and Barnet General Hospital (0.5 miles south-west). Not far away are Barnet Countryside Centre and Darland's Lake.
Why act early in High Barnet
Not every draught comes from the sashes themselves. Open mastic joints round the box can let air in and new mastic seals them. In a London flat, a failed joint rarely stays your problem alone: water can reach the neighbours below, and gaps in fire-rated joints affect the whole building.
What it costs depends on how much there is to do, how much old material has to come out and how easy the joints are to reach. You will have a clear quote before any work starts, so you know where you stand.
Why book with us
- We’re fully insured
- An ARBOMaster approved applicator
- One-year guarantee on every job
- We never seal over old sealant
Take a look at our cost guide and our reviews.
Surface by surface
Timber door frames
Sand mastic is used round timber door frames too. The method is the same as for windows.
Stone surrounds
The stone is treated with care while raking out the old mastic.
Quotes for sand mastic in High Barnet
Jobs vary more than people expect. The main factors:
- Any mould that needs treating
- How much old sealant there is and how hard it is to remove
- When we can work, for business premises
- How easy the joints are to reach
Doing several joints on one visit is usually more efficient than separate visits, so tell us about everything that needs sealing. We’ll give you a clear price for the lot.
Helping us quote
Photos by email are helpful but not essential. Please mention:
- Pictures of the joints, sent by email
- What’s wrong with the joints now
- If it’s domestic, commercial or a hotel
- Whether it has been sealed before
There’s no standard price list. Instead, we give you a clear price for your job. To get started, ring 0345 464 0079 or email us.
Looking after it afterwards
No joint lasts for ever, but care makes a real difference. Our tips:
- Go gently near the mastic when preparing windows
- Keep modern sealant off the mastic
- Look over the window mastic once a year
- Find out about consent before window work on a listed home
Avoid sealing over the mastic with silicone. If you see a crack, ask us to take a look rather than patching it.
Small cracks are a sign the mastic is ageing. Renewing it then is simpler than waiting until it falls out.
How the visit works
All our tools and materials come with us in the van, so you don’t need to buy or prepare anything. Once we have agreed what’s being done, the area is protected and the work begins. Most jobs take anything from a few hours to a full day, depending on how many windows. For a job in High Barnet, parking and access are the things to plan: tell us about permits, visitor bays or off-street space, which floor we’re working on and whether there’s a lift.
- We check each window surround and the condition of the joint.
- The joint is raked out and cleaned.
- Large voids are packed out.
- New sand mastic is applied and shaped by hand.
- The finish is dressed neatly.
How to prepare
- For indoor joints, keep the area dry beforehand if you can
- Clear the area around the work
- Plan for the work area to be out of bounds to pets and children
Get a quote
For a quote, ring 0345 464 0079 or email us with the location and a short description of the problem. We’ll give you a clear quote before any work starts.