Greater London · England
Sand mastic for sash & case windows in Netherne on-the-Hill, Greater London
Traditional burnt sand mastic around sash and case windows and doors in stone and brick for homes and businesses in Netherne on-the-Hill and across Greater London. ARBOMaster approved applicators, fully insured, with a one-year guarantee.
- Gaps between timber frames and stone or brick
- Draughts and rain around sash boxes
- Mastic that needs renewing before redecorating
What happens if it’s left?
If you’re redecorating, renew the mastic first. Painting over failed mastic doesn’t seal it, and the new mastic is traditionally left unpainted. In a flat in Netherne on-the-Hill, failed sealant seldom stays inside your own four walls: water can reach the neighbours below, and gaps in fire-rated joints affect the whole building.
What you pay reflects the work, not a rough estimate. That’s why we ask about the job first and give you a clear price before work begins.
Why book with us
- We never seal over old sealant
- Sanitary silicone with an anti-fungal additive in wet areas
- Rated 4.9 stars on Google
- Neat joints and a tidy finish
See what affects the cost and our reviews.
Sand mastic in Netherne on-the-Hill
Sand mastic is the traditional way to point the gap between a timber window frame and the stone or brick around it. It’s a mix of sand and a linseed-oil-based binder and built up by hand. On older homes, it suits the building far better than silicone. We work on stone surrounds, brick reveals and period & listed homes, and people most often call us about open joints round the window box and cracked mastic round a front door frame.
London homes have every kind of window, from timber sashes in period terraces to aluminium and uPVC in newer blocks. Over the years, the sealant around them shrinks, cracks and pulls away, which is when draughts and damp patches appear in homes in Netherne on-the-Hill.
We guarantee the work for a year. If there’s a problem with our work within the year, let us know and we will sort it.
- Location
- Netherne on-the-Hill (CR5)
- Wider area
- Greater London
- Guarantee
- A year, on every job
- Quotes
- A clear quote up front
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
How the visit works
A visit follows a simple pattern: we check the joints, protect the area around them, carry out the job and tidy away. Most jobs take anything from a few hours to a full day, depending on how many windows. In Netherne on-the-Hill, 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.
- First we agree which joints need doing.
- We remove the old, loose mastic.
- We pack any deep voids first.
- We apply the mastic by hand and shape it.
- The surface is finished to suit the stone or brick.
Before we arrive
- Mention any tricky access
- Mention any leaks or damp you’ve noticed
- Let us know about earlier repairs to the joints
How to get a quote
A good description makes for an accurate quote. Tell us where the job is, what’s wrong and how much there is, and email photos if that’s easy.
Related advice
Questions from Netherne on-the-Hill
I let a flat near Coulsdon South station. Can you help?
Yes, rental work is part of what we do. Just phone 0345 464 0079 or drop us an email and tell us about the property, and we will send you a clear quote.
Is parking a problem for a job in Netherne on-the-Hill?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. That way the visit can be planned around it.
What should I tell you?
Just the basics: where it is, what you’ve noticed and how we reach it. Then call 0345 464 0079 or email us.
Should I check with the council before work on a listed or conservation-area home?
Check with your local planning authority. They’ll tell you if consent is needed.
Do you do commercial work?
Yes. Hotels, offices and other businesses use us, and we are fully insured.
Will there be a smell?
That depends on the sealant. Some smell for a while, some hardly at all.
What sealant do you use?
Products from Arbo and Everbuild, among others, picked for each joint. We will tell you what we are using and why.
Can I paint the new mastic?
It’s traditionally left unpainted, which is what traditional guidance recommends. Ask us before decorating.
Should I try it myself first?
Some jobs are best left to a professional: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.
If you do try it yourself, take your time over the preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it does not work out, we can still put it right.
What sealant work cannot fix
A few problems are outside what sealant work can do:
- Planning or listed building consent (your local planning authority decides)
- Putty and glazing repairs
- Sash cords, weights and draught-proofing of the sashes
If you’re not sure, just phone 0345 464 0079 or drop us an email and we will give you a straight answer.
Joints and surfaces we work on
- Brick reveals
- Stone surrounds
- Tenement windows
- Timber door frames
- Period & listed homes
- Sash and case windows
Netherne on-the-Hill homes and the weather
In London conversions and blocks, the lease decides who is responsible for the frames, so check that before booking. The South East is one of the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
Managing a site like Coulsdon Sixth Form College? Then its window and door frames need their mastic kept sound, just like a home’s. As a London address, Netherne on-the-Hill can be tricky for parking: let us know about parking bays, permits or a driveway.
Netherne on-the-Hill is about 2 miles south of Coulsdon, in Greater London. Our applicators cover sand mastic for householders, landlords and businesses in Netherne on-the-Hill and nearby, as part of our work across Greater London. Our area takes in 764 places across Greater London, large and small. We also work in Crawley, around 13 miles away.
Our applicators cover all of the CR5 postcode area for sand mastic. Local streets include The Village Square, Rookery Mead and Netherne Lane, all of which we cover. Neighbouring places we cover for sand mastic include Hooley (1 mile west), Merstham (2 miles south), Chaldon (2 miles south-east), South Merstham (2 miles south) and Gatton (2 miles south-west). Further out, we also cover London (14 miles north), City of Westminster (15 miles north), Kensington (15 miles north), Brompton (14 miles north), Stockwell (12 miles north) and Orpington (12 miles north-east).
What’s near Netherne on-the-Hill
Typical jobs here are in homes near Shabden Park and the streets around them. Netherne on-the-Hill’s nearest station is Coulsdon South station, roughly 1.6 miles north of the centre. Other landmarks nearby include The Belfry (3.8 miles south) and East Surrey Museum (2.9 miles east). Green spaces nearby include South London Downs National Nature Reserve and Colley Hill.
Signs you need sand mastic in Netherne on-the-Hill
Timber swells and shrinks with the weather. The movement cracks the mastic over time.
These are the problems we’re asked about most:
- Gaps round a timber door in stone or brick
- Window mastic to renew ahead of painting
- Modern sealant on a period surround
- Old sand mastic that has cracked, crumbled or fallen out
For an older house near a landmark such as Church of St Margaret, the windows may be timber, sash or later replacements, and each needs the right sealant against the wall.
Before booking anyone
- Whether they seal over old material or remove it
- The length of the guarantee
- What preparation is included
- What happens if they find a problem under the old sealant
What affects the cost of sand mastic
Every job gets its own quote. These are the things that affect it:
- The old material and how stubborn it is
- How many areas need sealing
- Working hours on commercial sites
- The amount of work
A failed joint rarely gets cheaper to fix by waiting, because water and mould keep working on it. If you’re unsure, ring 0345 464 0079 or send us an email and we will give you an honest view and a quote.
What we need to know
There’s no need for technical detail. Just tell us:
- Photos by email, if that is easy
- What the problem is, such as mould, gaps, leaks or cracking
- How many joints, rooms or windows are involved
- If someone has resealed it before
For a quote, call 0345 464 0079 or email us with the location and a short description of the problem. You will have a clear quote before work begins.
Other services in Netherne on-the-Hill
How the job changes by surface
Brick reveals
Gaps between frame and brick let in rain and draughts. New mastic seals the gap.
Stone surrounds
Stone surrounds suit sand mastic well. The finish blends with the masonry.