Greater London · England
Sand mastic for sash & case windows in Balham, Greater London
Sand mastic across Balham and nearby, with old sealant always removed completely and a 12-month guarantee.
- Draughty sash windows at the surround
- Gaps where the frame meets the masonry
- Silicone on a period window that looks wrong
Leave it or put it right?
Silicone might seem the quicker option, but it can look wrong on a period surround. Sand mastic suits the building and blends with the stone or brick. 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.
Every job is a little different, so each one gets its own quote. Size, access and the product the joint needs all play a part.
Why choose Mr Mastic in Balham
- Neat joints and a tidy finish
- Fully insured
- 20+ years of sealant experience
- 180+ five-star Google reviews
See what affects the cost and our reviews.
Sand mastic for homes and businesses in Balham
On many period windows, sand mastic looks right and suits the building. On modern frames we’d normally use a flexible sealant and we will explain which is best for yours. If you have mastic dropping out of the joint and modern sealant on a period surround, we can help, 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.
Our work is backed for twelve months.
- Where
- Balham (SW12, SW17, SW4)
- Wider area
- Greater London
- Guarantee
- A year, on every job
- Quote
- A clear quote up front
- Call
- 0345 464 0079
- Updated
- 26 October 2026
What the job involves on each surface
Tenement and terrace windows
In shared buildings, the windows may be part of a wider repair, so check who is responsible first.
Timber door frames
Sand mastic is used round timber door frames too. The method is the same as for windows.
Windows and doors in Balham
In London conversions and blocks, the lease decides who is responsible for the frames, so it’s worth checking before booking. London and the South East are among the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
For an older house near a landmark such as Church of St Mary, the joint between an old wall and a newer frame is usually the first place rain gets in. Balham is in London, so parking needs planning: let us know about parking bays, permits or a driveway.
Balham is about 2 miles south-west of Stockwell, in Greater London. We carry out sand mastic for homeowners, landlords and businesses in Balham. Our Greater London coverage runs to 764 places, Balham among them.
Our applicators cover all of the SW12, SW17 and SW4 postcode area for sand mastic and the streets around it. If you need sand mastic at a property on Lynn Road, Weir Road and Byrne Road or a nearby road, our applicators can take on the job. Other places close to Balham include Grange Mills (1 mile north-east), Hyde farm estate (1 mile east), Clapham Park (1 mile north-east), Streatham Park (1 mile south-east) and Tooting Bec (1 mile south-west). Larger places within reach include London (5 miles north-east), City of Westminster (5 miles north), Marylebone (5 miles north), Kensington (4 miles north-west), St Pancras (6 miles north) and Shoreditch (7 miles north-east).
Near you in Balham
We work in homes and buildings around Oak Lodge School, Wandsworth Common and The Bedford pub, among other places. Balham has its own railway station: Balham station. Nearby you will also find St James' Hospital (0.5 miles west) and London Sewing Machine Museum (0.6 miles south-west). For a walk, there’s Knight's Hill and Battersea Park Lake.
What happens on the day
Every visit runs the same way: we look at the joints together, mask and protect the surrounding surfaces, do the work and tidy away. Most jobs take a few hours per window, depending on the condition of the joints. For a job in Balham, parking and access are the things to plan: let us know about parking, the floor we’ll be working on and any lift or shared entrance.
- We check the window surrounds and agree which joints need renewing.
- We rake out the old mastic and clean the joint.
- Large voids are packed out first, so the mastic is not too thick.
- We mix the sand mastic and apply it by hand, shaping it to the joint.
- We dress the surface so it sits neatly against the masonry.
Getting ready for the visit
- Where the joints are inside, avoid wetting them before we arrive
- Tell us if parking is tricky
- Mention any leaks or damp you’ve noticed
How to get a quote
Every job is quoted individually. Just call 0345 464 0079 or email us with the details and send pictures if you have them.
Read more
Quotes for sand mastic in Balham
The price is agreed before any work begins. It takes into account:
- When we can work, for business premises
- Which sealant suits the joint
- How many areas need sealing
- The number and length of the joints
The cost reflects the work involved, not guesswork. That is why we ask a few questions first and agree the price before starting.
What we need to know
Before you ask for a quote, have a think about:
- Any access issues, like height or stairs
- If someone has resealed it before
- The problem you’ve noticed
- Where the job is, and your postcode
Need a quote? Please ring 0345 464 0079 or send us an email with a few details. We will explain what we’d do and give you a clear quote before we start.
Do you need sand mastic in Balham?
Decorating can disturb tired mastic. Many people find it crumbling when they prepare the windows, which is a good time to renew it.
Look out for these signs:
- Open joints round the window box
- Mastic worn away on windows facing the weather
- Mastic dropping out of the joint
- Mastic that needs renewing before redecorating
If you look after a building such as Ravenstone Primary School, its window and door frames need their mastic kept sound, just like a home’s.
Comparing quotes
- How the joint is cleaned and prepared
- Whether you can choose the colour
- What product goes in the joint
- Whether they’re fully insured
Also in Balham
When it is not the sealant
We’ll always be straight with you, so here’s what new sealant won’t do:
- Cracked or broken glass
- Sashes that rattle, stick or will not open
- Planning or listed building consent (your local planning authority decides)
If in doubt, ring 0345 464 0079 or drop us an email and we’ll say what we think.
Surfaces we seal
- Brick reveals
- Sash and case windows
- Tenement windows
- Period & listed homes
- Stone surrounds
- Timber door frames
Balham: your questions answered
Can you do sand mastic in Balham?
Yes. Our work covers London and the South East, and Balham is part of that. Just call 0345 464 0079 or drop us an email with a few details of the job, and we will give you a clear quote.
Can you help a landlord with a rental near Balham station?
Yes, we work for landlords and letting agents. Just ring 0345 464 0079 or send us an email and tell us about the property, and we will give you a clear price.
Should I try DIY first?
Sometimes. The key is preparation: remove all the old material and work on a clean, dry joint. If it doesn’t work out, we can redo it.
Which is right for my windows, sand mastic or modern sealant?
We will help you decide. Sand mastic suits many period homes and newer frames suit modern sealant.
Will you leave a mess?
No. We protect the surfaces around the joints, and we tidy up before we go.
How long does sand mastic take to go off?
The surface skins quite quickly and it hardens fully over a longer time. The weather and joint depth both affect it.
What exactly is sand mastic?
It’s a mix of sand and a linseed-oil-based binder. It’s applied by hand and shaped to suit the surround.
Can you work on commercial sites?
Yes, regularly. Larger jobs can be planned room by room or area by area to suit the site.
Aftercare tips
Aftercare is simple, and it makes a real difference:
- Inspect the joints round the windows every year or so
- Don’t paint over the new mastic
- Keep sills and gutters clear so water drains away
- Go gently near the mastic when preparing windows
Keep paint scrapers and sanders off the mastic when redecorating. It can be damaged by heavy scraping.
Crumbling mastic lets rain into the joint. That water can reach the timber frame and the wall so early renewal protects both.