Greater London · England
Sand mastic for sash & case windows in Whetstone, Greater London
We cover Whetstone for traditional burnt sand mastic around sash and case windows and doors in stone and brick. Old sealant removed completely, joints prepared properly and every job guaranteed for a year.
- Cement or filler used on old window joints that has cracked
- Mastic dropping out of the joint
- Cracked mastic round a front door frame
How we handle sand mastic in Whetstone
Sand mastic skins over fairly quickly, but it takes longer to harden fully. Traditional guidance is not to paint over it, so ask us before you decorate. If you have patchy fillers round a sash window and gaps where the frame meets the masonry, we can put it right, whatever the surface.
From mansion-block windows to modern glazing in new flats, London has every kind of frame. The mastic around them dries out and cracks with age, letting in draughts and water.
The work is covered for a year after we finish. If there’s a problem with it, please call 0345 464 0079 or send us an email.
- Place
- Whetstone (N12, N20, N11)
- Wider area
- Greater London
- Cover
- 12 months on all our work
- Quotes
- A clear price before work begins
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Why act early in Whetstone
Silicone might seem the quicker option, but on period stone or brick it often looks out of place. Sand mastic is the traditional material and finishes neatly against the masonry. Converted houses in London often have a bathroom above someone else’s living room, and a slow leak from a failed seal can end up in the flat below. Putting it right early is much less trouble.
Commercial jobs are quoted on the same basis as homes: the amount of work, the access and the products needed, along with when we can work on site. Call for a quick quote and we’ll go through it with you.
Why us?
- Every job guaranteed for a year
- Approved under the ARBOMaster scheme
- Anti-fungal silicone where joints get wet
- 20+ years of sealant experience
Read how sealant jobs are priced and our reviews.
What sand mastic looks like in Whetstone
The South East is one of the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind. In a converted house or block, who looks after the windows depends on the lease, so check that before booking.
For an older house near a landmark such as Church of St John, the windows may be timber, sash or later replacements, and each needs the right sealant against the wall. If you look after a building such as Queenswell Infant & Nursery School, the mastic around its windows and doors needs looking after like any other building’s. If you let a flat or house near Oakleigh Park station, cracked sand mastic around sash windows lets in the draughts tenants complain about.
Whetstone is about 7 miles north of St Pancras, in Greater London. For sand mastic in and around Whetstone, please ring 0345 464 0079 or drop us an email for a quick quote. We are based in Crawley and cover Greater London, Whetstone included. Whetstone is one of 764 places in Greater London where we work. You can also see our page for London, about 9 miles away.
Here we cover the N12, N20 and N11 postcode area for sand mastic. Whether your property is on High Road, Swan Lane and Dene Road or a nearby road, we can help. Whetstone sits on or near the A1000. We also cover Oakleigh Park (1 mile west), North Finchley (1 mile south), Woodside Park (1 mile south-west), East Barnet (1 mile north-east) and Brunswick Park (1 mile east). We also work in nearby towns such as London (9 miles south), City of Westminster (8 miles south), Marylebone (8 miles south), Kensington (9 miles south), St Pancras (7 miles south) and Shoreditch (8 miles south-east).
Around Whetstone
We work in homes and buildings around Finchley Catholic High School, Francis Skaryna Belarusian Library and Museum and Woodhouse College and the streets around them. Other local landmarks include Three Horseshoes pub (under half a mile north-west) and Swan Lane Open Space (less than half a mile west). The nearest railway station is Oakleigh Park station, roughly 0.8 miles north. Nearby you’ll also find Grand Arcade (0.9 miles south) and Francis Skaryna Belarusian Library and Museum (0.9 miles south-west). Green spaces nearby include Highgate Hill and Barfield Allotments Nature Park.
What the job involves on each surface
Timber door frames
Door frames get knocked and soaked, so their mastic can fail sooner. We rake it out and renew it.
Tenement and terrace windows
Windows above ground floor need the right access. Tell us the height and we’ll confirm what’s needed.
Places near Whetstone
Also in Whetstone
The process
On the day, there’s very little for you to do. Show us the job and we will take it from there. The work itself 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.
- We check each window surround and the condition of the joint.
- We rake out the old mastic and clean the joint.
- Large voids are packed out.
- New sand mastic is applied and shaped by hand.
- The finish is dressed neatly.
Getting ready for the visit
- Keep children and pets away from the work area
- Move anything stored near the joints
- For business premises, tell us about site rules or sign-in
Ask for a quote
There’s no standard price list, as no two jobs are quite the same. Instead, we give you a clear quote for your job. To arrange one, phone 0345 464 0079 or drop us an email.
Read more
What affects the cost of sand mastic
Call for a quick quote. What matters most is:
- How much old sealant there is and how hard it is to remove
- The number of rooms or windows
- Whether there’s mould to deal with
- When we can work, for business premises
What it costs depends on the size of the job, how much old material has to come out and how easy the joints are to reach. You’ll have a clear quote before any work starts, so you know where you stand.
Helping us quote
A few details help us give you an accurate quote. When you ask for a quote, tell us:
- How many joints, rooms or windows are involved
- Access, such as stairs, a lift or height
- If someone has resealed it before
- Photos by email, if that is easy
For a quick quote, get us on the phone, or email us if that is easier. Describe what needs sealing and we’ll talk you through the work before giving you a price.
Landlords, agents and businesses in Whetstone
We also work for property managers and facilities teams in Whetstone and across Greater London. Several sites can be quoted together.
Letting agents often deal with us directly. Send the address, what’s needed and the access arrangements and we will give you a quote.
DIY sealant or a professional job?
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 doesn’t work out, we can still put it right.
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.
When it isn’t the sealant
Some problems need a builder, plumber or other trade rather than us:
- Decisions on consent for listed homes
- Putty and glazing repairs
- Sashes that rattle, stick or won’t open
If in doubt, phone 0345 464 0079 or drop us an email and we will say what we think.
Where we work in Whetstone
- Stone surrounds
- Brick reveals
- Timber door frames
- Tenement windows
- Sash and case windows
- Period & listed homes
Common questions in Whetstone
Is Whetstone in your area for sand mastic?
Yes, Whetstone is within the area we cover. We work across London and the South East. Just ring 0345 464 0079 or send us an email with a few details of the job, and we’ll send you a clear quote.
I let a flat near Oakleigh Park station. Can you help?
Yes. We work for landlords and agents as well as householders. Just phone 0345 464 0079 or drop us an email with the address and what needs doing, and we will send you a clear quote.
Where is Mr Mastic based?
Our base is Crawley, with over 20 years’ experience. Our area covers South East England, London and Scotland.
Can you quote for more than one area?
Of course. Doing several areas at once is normally more efficient.
What’s sand mastic made of?
Sand mastic is a traditional material for pointing round windows and doors. It combines sand with a linseed-oil-based binder.
Can sand mastic be painted?
The usual advice is to leave sand mastic unpainted. Ask us before you decorate around it and we’ll talk you through it.
Can you work on commercial sites?
Yes, regularly. We can plan bigger jobs in stages.
Can old silicone round a sash window be swapped for sand mastic?
In most cases. The silicone is cut out and the joint cleaned before the sand mastic goes in.