Greater London · England
Sand mastic for sash & case windows in Sydenham Hill, Greater London
Window and door surrounds in Sydenham Hill need attention? We cut out the old, prepare the joints and apply the right sealant.
- Draughts and rain around sash boxes
- Failed mastic on an exposed elevation
- Tired mastic found when preparing windows for paint
About our sand mastic in Sydenham Hill
Sand mastic suits most period window surrounds. Newer frames usually get a flexible sealant instead and we will explain which is best for yours. We work on brick reveals, sash and case windows and period & listed homes, and people most often call us about patchy fillers round a sash window and gaps where the frame meets the masonry.
Many London homes are flats, with windows high above the street. Who looks after the outside of the frames can depend on the lease, so check that first, and access in Sydenham Hill is something to talk through when you book.
A 12-month guarantee comes with the work, just as it does everywhere we cover.
- Where
- Sydenham Hill (SE26, SE23, SE21)
- Wider area
- Greater London
- Guarantee
- One year on every job
- Price
- Quoted before any work starts
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
Aftercare tips
Looking after new joints is easy, and it makes a real difference:
- Check the mastic when you check the paintwork
- Check with your local planning authority if your home is listed
- Ask us before painting near the mastic
- Go gently near the mastic when preparing windows
Leave the new mastic alone while it firms up. It skins over quickly but needs longer to fully harden.
Small cracks are a sign the mastic is ageing. Renewing it then is simpler than waiting until it falls out.
Nearby places to Sydenham Hill
More services for Sydenham Hill
FAQs for Sydenham Hill
Is Sydenham Hill in your area for sand mastic?
Yes. Our work covers London and the South East, and Sydenham Hill is part of that. Just call 0345 464 0079 or drop us an email with a few details of the job.
Is parking a problem for a job in Sydenham Hill?
London parking needs a little planning, so let us know about permits, bays or a driveway when you book. That way the visit can be planned around it.
Can tenants book the work?
Of course. Check with your landlord; we can send the quote to them too.
Do you take out the old sealant first?
Yes, always, and completely. New silicone does not stick to old silicone, so any old material comes out before anything new goes in.
Where is Mr Mastic based?
Our base is Crawley. Our area covers South East England, London and Scotland.
How much does sand mastic cost in Sydenham Hill?
There’s no set price, as it depends on the job: how much there is, what’s there now, how we reach it and what it needs. You will get a clear quote before work begins.
Do I need to be at home?
For indoor joints, yes, someone needs to let us in. Once we have agreed the job, you do not need to watch us work.
Can I do it myself?
It depends on the job. Work at height, movement joints, fire-rated gaps and large areas are best left to a professional.
Landlord and commercial work in Sydenham Hill
We regularly work with letting and managing agents. Send the address, what’s needed and the access arrangements.
Failed sealant is one of the commonest items on a check-out report, and it’s easy to sort out between tenants. Several properties can be quoted together.
DIY sealant or a professional job?
If you do try it yourself, take your time over the 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.
Too much sealant is as bad as too little. A heavy bead looks messy and copes badly with movement, and getting the depth right matters as much as the look.
How the job changes by surface
Timber door frames
Door frames get knocked and soaked, so their mastic can fail sooner. It’s renewed by hand.
Period and listed homes
Sand mastic is the like-for-like choice for many period homes. If your home is listed, ask your local planning authority about consent.
What we do, step by step
When we get to you, we compare the joints with what we discussed. If anything is different, we explain it before carrying on. After that, the work takes a few hours for a single window, longer for several. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. If the building has a concierge, managing agent or access rules, tell us when you book.
- 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.
- We dress the finish so it sits neatly against the masonry.
Before we arrive
- Tell us if parking is tricky
- Try not to wet indoor joints just before the visit
- Mention if the joints have been sealed before
Get a quote
For a quick quote, get us on the phone, or send an email if you’d rather. Describe what needs sealing and we will talk you through the work.
Related advice
Windows and doors in Sydenham Hill
Historic houses like Kingswood House (about 0.6 miles west) are a reminder that the area around Sydenham Hill has older buildings as well as new. In older buildings, older frames set in brick or stone need a sealant that suits them, and sometimes that is traditional sand mastic. 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 the older streets around Church of St Philip the Apostle, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. Letting a property close to Sydenham Hill station? Then older sash windows in a rental need their mastic kept sound to keep the weather out.
Sydenham Hill is about 1 mile east of West Norwood, in Greater London. We provide sand mastic to homeowners, landlords and businesses in Sydenham Hill and nearby. We cover 764 towns and villages across Greater London.
We cover every part of SE26, SE23 and SE21 for sand mastic and the streets around it. Sand mastic is available to properties on Grange Lane, Dallas Road and Lyall Avenue. Close by, we work in West Dulwich (1 mile west), Sydenham (1 mile south-east), Crystal Palace (1 mile south), Dulwich (1 mile north-west) and Gipsy Hill (1 mile south-west). We also work in nearby towns such as London (5 miles north), City of Westminster (7 miles north-west), Marylebone (7 miles north-west), Kensington (7 miles north-west), St Pancras (7 miles north) and Shoreditch (6 miles north).
Local landmarks in Sydenham Hill
Locally, jobs take us to homes and businesses close to Long Meadow, The Wood House and Sydenham School and the streets around them. For rail, the closest station is Sydenham Hill station, about 0.5 miles west. Nearby you’ll also find Horniman Museum and Gardens (0.6 miles north-east) and Lewisham Shopping Centre (3.2 miles north-east). For a walk, there’s Knight's Hill and Dulwich Upper Wood.
What we are called out for in Sydenham Hill
Decorating can disturb tired mastic. It’s often found when windows are being prepared for paint, which is a good time to renew it.
Signs it’s time to call us include:
- Weathered mastic on the most exposed windows
- Gaps where the frame meets the masonry
- Gaps round a timber door in stone or brick
- Wind and rain getting in round a sash window
As a London address, Sydenham Hill can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
Questions to ask before booking
- What the cure time is
- Whether you can choose the colour
- What preparation is included
- What happens if they find a problem under the old sealant
When it isn’t the sealant
Some problems need a builder, plumber or other trade rather than us:
- Timber that has rotted
- Sashes that need overhauling
- Decisions on consent for listed homes
Not sure which it is? You can phone 0345 464 0079 or drop us an email and we will tell you honestly.
Surfaces we seal
- Tenement windows
- Stone surrounds
- Brick reveals
- Period & listed homes
- Sash and case windows
- Timber door frames