Greater London · England
Sand mastic for sash & case windows in Streatham, Greater London
Specialist sand mastic for Streatham: careful preparation, the right product and tidy work. Call for a quick quote.
- Mastic that needs renewing before redecorating
- A silicone bead on a sash window that spoils the look
- Crumbling sand mastic round a window
Sand mastic for homes and businesses in Streatham
Our applicators renew the sand mastic around sash and case windows and doors set in stone or brick. The old mastic is raked out, and new mastic is applied and shaped by hand. If you are dealing with window mastic to renew ahead of painting and wind and rain getting in round a sash window, we can help, on timber door frames, brick reveals and period & listed homes alike.
London’s Victorian and Edwardian terraces were built with timber sash windows, and many still have them or their replacements. Whatever is in the opening now, the joint between frame and wall is what keeps the weather out.
There’s a 12-month guarantee on every job.
- Location
- Streatham (SW16, SW2, CR4, SW12)
- Region
- Greater London
- Cover
- 12 months on all our work
- Quotes
- Quoted before any work starts
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Sand mastic in Streatham: local notes
Historic houses like Kingswood House (about 2 miles east) are a reminder that the area around Streatham has older buildings as well as new. In older buildings, older timber frames in brick or stone need a different approach from a modern uPVC window. Rainfall in the South East is lower than in much of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
Streatham is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book. Managing a site like St Andrew's Catholic Primary School? Then its window and door frames need their mastic kept sound, just like a home’s. If you let a flat or house near Streatham station, cracked sand mastic around sash windows lets in the draughts tenants complain about.
Streatham is about 5 miles south of London, in Greater London. Homes, rented property, offices and hotels in Streatham can book us for sand mastic. The work is guaranteed for a year. Across Greater London, we cover 764 places, Streatham among them.
All of SW16, SW2, CR4 and SW12 is within our area for sand mastic. If you need sand mastic at a property on Stanthorpe Road, Gleneagle Mews and Madeira Road or anywhere close by, we can help. You’ll find Streatham on the A205 and A216, which makes it straightforward to reach with everything needed for sand mastic. We also cover the places around Streatham: Streatham Park (1 mile west), Furzedown (1 mile west), Streatham Hill (1 mile north), Hyde farm estate (1 mile north) and Grange Mills (1 mile north-west). Larger places within reach include London (5 miles north), City of Westminster (6 miles north), Marylebone (6 miles north), Kensington (6 miles north-west), St Pancras (7 miles north) and Shoreditch (7 miles north).
Local landmarks in Streatham
Typical jobs here are in homes near Bishop Thomas Grant Catholic Secondary School, Streatham Common and Waldorf School of South West London, among other places. There’s a railway station in Streatham itself: Streatham station. Well-known places in the area include Clockworks Museum (1.1 miles east) and Southside Wandsworth (3.3 miles north-west). Not far away are Knight's Hill and Battersea Park Lake.
Why it’s worth doing now in Streatham
Not every filler suits an old window surround. Sand mastic matches what was there and that can be important for listed homes. In a flat in Streatham, 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.
Leaving a failed joint generally makes the job bigger, not smaller. If you are unsure, call 0345 464 0079 or email us and we will give you an honest view and a quote.
Why Streatham customers choose us
- We never seal over old sealant
- We leave the area clean and tidy
- Experience in homes, commercial sites and hotels
- Full insurance on every job
Take a look at our cost guide or what customers say.
What affects the cost of sand mastic
There’s no set price list, because jobs vary so much. What we look at:
- The size of the job
- How many areas need sealing
- The product the joint needs
- How much old sealant there is and how hard it is to remove
Some things make a job bigger or smaller: the old material and how easily it comes out, whether mould needs treating, and whether the work is at height. Your quote takes all of that into account.
Asking for a quote
When you call or email, these details help:
- What’s wrong with the joints now
- Any previous sealing or DIY work
- Where the job is, and your postcode
- The rough size of the job
We quote each job on its own. Just call 0345 464 0079 or send us an email with the details.
DIY sealant or a professional job?
If you’re 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 does not work out, we can still put it right.
The biggest DIY mistake is sealing over old sealant. New silicone will not bond to old, so it peels away and traps moisture behind it. Everything old must be removed first.
How the job changes by surface
Period and listed homes
Materials matter on listed and conservation-area homes. Like-for-like sand mastic is usually favoured.
Sash and case windows
The box of a sash and case window sits in the stone or brick opening. The gap round it is pointed with sand mastic.
What we do, step by step
We bring everything the job needs with us. Once we’ve agreed what’s being done, we protect the area and start. Most jobs take a few hours for a single window, longer for several. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in Streatham. A visitor permit or a nearby bay makes the visit run more smoothly.
- We start by checking each surround and agreeing the joints to renew.
- The loose and crumbling mastic is raked out and the joint cleaned.
- Deep voids are packed so the mastic is the right thickness.
- Sand mastic is mixed and applied by hand, then shaped to the joint.
- We dress the surface so it sits neatly against the masonry.
Preparing for the visit
- Tell us if parking is tricky
- On commercial sites, let us know about site rules
- Where the joints are inside, avoid wetting them before we arrive
Ask for a quote
For a quick quote, get us on the phone, or send an email if you’d rather. Tell us about the joints that need doing and we will explain what’s involved and give you a clear price.
Read more
Looking after it afterwards
So the new joints stay in good condition:
- Ask the planning authority about consent for listed or conservation-area homes
- Look over the window mastic once a year
- Get any rot dealt with first
- Go gently near the mastic when preparing windows
Avoid painting over the new mastic, which is the traditional advice. Ask us before any decorating around it.
Small cracks are a sign the mastic is ageing. It’s easier to renew it before it drops out.
Places near Streatham
Also in Streatham
Common questions in Streatham
Do you cover Streatham for sand mastic?
Yes, Streatham is within the area we cover. Our work covers London and the South East. You can ring 0345 464 0079 or send us an email and tell us what needs doing, and we’ll give you a clear quote.
Can parking be tricky for a visit in Streatham?
Parking in Streatham, as in most of London, takes a little planning: a visitor permit or a nearby bay makes the day run more smoothly.
What sealant do you use?
It depends on the joint: sanitary silicone where it gets wet, and sealants suited to movement or weather elsewhere. Brands we use include Arbo and Everbuild.
Do you remove the old sealant?
Yes. Sealing over the old bead is the commonest cause of early failure, and it’s something we never do.
Which is right for my windows, sand mastic or modern sealant?
It depends on the window. On many period windows, sand mastic looks right and suits the building, while modern frames normally get a flexible sealant.
Should I check with the council before work on a listed or conservation-area home?
It’s best to ask your local planning authority first. Like-for-like sand mastic is often the preferred finish but the decision is theirs.
Will it make a mess?
Very little: the area around the joints is protected first, and we tidy up before we go.
What do you need from me for a quote?
A short description and the location, with photos by email if possible. If we need more, we will ask.
Work for landlords, hotels and businesses
We work for landlords and letting agents as well as householders. Resealing between tenancies is a simple way to keep a property in good order.
A neglected joint can let water reach the structure, which matters even more when someone else lives there. Resealing at the right time is simple maintenance.