Greater London · England
Sand mastic for sash & case windows in Merton, Greater London
Sand mastic in Merton from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Open joints round the window box
- Cement or filler used on old window joints that has cracked
- Window mastic to renew ahead of painting
How we handle sand mastic in Merton
Silicone on a period window often looks wrong and isn’t always the right material. Sand mastic is the traditional choice, and we can replace one with the other. We work on tenement windows, timber door frames and brick reveals, and the jobs we see most are patchy fillers round a sash window and mastic dropping out of the joint.
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.
The work is covered for a year after we finish. If anything isn’t right with it, ring 0345 464 0079 or send us an email.
- Where
- Merton (SW19)
- Region
- Greater London
- Cover
- One year on every job
- Quote
- Quoted before any work starts
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
What sealant work cannot fix
We’d rather tell you now than do work that won’t last, so these are the limits:
- Sashes that need overhauling
- Whether work needs listed building consent
- Putty and glazing repairs
Not sure which it is? You can ring 0345 464 0079 or email us and we will tell you honestly before booking.
What we seal
- Timber door frames
- Brick reveals
- Tenement windows
- Sash and case windows
- Stone surrounds
- Period & listed homes
How we quote for sand mastic
Some jobs are bigger than they look, and some smaller. The main factors:
- The type of sealant required
- How many rooms, windows or areas are involved
- The size of the job
- How easy the joints are to reach
We don’t show prices on the website, because the cost depends so much on the job itself. For a quick quote, please ring 0345 464 0079 or email us and we’ll talk you through it.
What to tell us for a quote
To make quoting easier, let us know:
- The address or postcode of the job
- How many joints, rooms or windows are involved
- What the problem is, such as mould, gaps, leaks or cracking
- If it’s domestic, commercial or a hotel
Want a quote for sand mastic? Please phone 0345 464 0079 or email us and tell us about the job. You will know what we plan to do, and what it will cost, before any work begins.
How the visit works
At the end, we look at the finished work together. The visit itself usually takes anything from a few hours to a full day, depending on how many windows, depending on the size of the job. In Merton, as in most of London, parking needs a little planning. A visitor permit or a nearby bay makes the visit run more smoothly.
- We check each window surround and the condition of the joint.
- We rake out the old mastic and clean the joint.
- We fill deep gaps so the new mastic isn’t too thick.
- We point the joint with sand mastic by hand.
- The finish is dressed neatly.
Getting ready for the visit
- For business premises, tell us about site rules or sign-in
- For indoor joints, keep the area dry beforehand if you can
- Tell us about any previous sealing or DIY attempts
Getting a quote
We quote each job on its own, so start by telling us what you need. Simply phone 0345 464 0079 or drop us an email and describe the job.
Read more
Why deal with it now?
New mastic over crumbling mastic won’t hold. Raking out and preparing the joint gives it a sound base so the new work lasts. 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. Dealing with it early is far simpler.
A failed joint rarely gets cheaper to fix by waiting, because water and mould keep working on it. If you are not sure whether it needs doing, phone 0345 464 0079 or drop us an email and we’ll give you an honest view and a quote.
Why book with us
- Experience in homes, commercial sites and hotels
- Approved under the ARBOMaster scheme
- Over 20 years’ experience
- Fully insured
See what affects the cost and customer reviews.
How the job changes by surface
Brick reveals
Sand mastic is also used where timber frames meet brick. It gives a traditional finish.
Tenement and terrace windows
Rows of sash windows on tenements and terraces often need renewing together. We work on single windows or whole elevations.
Merton: your questions answered
Is Merton in your area for sand mastic?
Yes. Our work covers London and the South East, and Merton is part of that. You can ring 0345 464 0079 or email us and let us know what needs doing.
Is parking a problem for a job in Merton?
Parking in Merton, as in most of London, takes a little planning: a visitor permit or a nearby bay makes the day run more smoothly, so mention what’s available when you book.
Do you take out the old sealant first?
Yes. We cut out all the old sealant and clean the joint before resealing.
Do I need to be at home?
If the work is inside, we need someone to let us in. After that, you can carry on with your day.
What should I tell you?
A short description and the location, plus pictures if you have them. If we need more, we’ll ask.
Will there be a smell?
Possibly a little. It fades as the sealant cures, and ventilation helps.
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.
Are you an approved applicator?
Yes. ARBOMaster is the approved applicator scheme for Arbo sealants, and we’re part of it.
Merton homes and the weather
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 London conversions and blocks, the lease decides who is responsible for the frames, so it’s worth checking before booking.
If you let a flat or house near Haydons Road station, cracked sand mastic around sash windows lets in the draughts tenants complain about. Merton is in London, so parking needs planning: let us know about parking bays, permits or a driveway.
Merton is about 1 mile south-east of Wimbledon, in Greater London. From the centre of Merton to the outskirts, sand mastic is available for homes and businesses alike. Merton is one of 764 towns and villages in Greater London we cover for sand mastic. There’s also a page for London, about 7 miles away.
We work across the SW19 postcode area for sand mastic and the streets around it. If you need sand mastic at a property on High Path, Pincott Road and Hayward Close or a nearby road, we can help. Merton is on the A24, which makes it straightforward to reach with everything needed for sand mastic. Neighbouring places we cover for sand mastic include Merton Abbey (1 mile east), South Wimbledon (1 mile north-west), Colliers Wood (1 mile east), Tooting Bec (1 mile north-east) and Summerstown (1 mile north). Within a short drive, we also cover London (7 miles north-east), City of Westminster (7 miles north), Marylebone (7 miles north), Kensington (6 miles north), St Pancras (8 miles north) and Shoreditch (9 miles north-east).
Landmarks near Merton
In Merton, that means homes and buildings near The Nelson Arms, Wimbledon School of Art and Wandle Park. For rail, the closest station is Haydons Road station, roughly 0.8 miles north of the centre. Well-known places in the area include Southside Wandsworth (2.8 miles north) and St George's Hospital (1.1 miles north-east). Not far away are Henman Hill and Merton Park Green Walks.
Should I try it myself first?
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and the joint depth matters as much as the finish.
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is chosen for how the joint moves and where it is, then guaranteed for a year.
Towns and villages near Merton
More services for Merton
Common problems we fix in Merton
Shallow joints are a common cause. A thin layer doesn’t hold well so we make sure the new mastic is the right thickness.
Most people get in touch after spotting something like this:
- Mastic dropping out of the joint
- Modern sealant on a period surround
- Gaps between timber frames and stone or brick
- Draughts and rain around sash boxes
If you look after a building such as Merton Abbey Primary School, the mastic around its windows and doors needs looking after like any other building’s.
Comparing quotes
- What insurance they hold
- Whether they seal over old material or remove it
- How much experience the applicator has
- When the joint can take water or movement