Greater London · England
Sand mastic for sash & case windows in Downham, Greater London
Our applicators work in Downham on traditional burnt sand mastic around sash and case windows and doors in stone and brick. Old sealant removed completely, joints prepared properly and a 12-month guarantee.
- Cement or filler used on old window joints that has cracked
- Window mastic to renew ahead of painting
- Crumbling sand mastic round a window
The process
We keep the work tidy and contained to the joints we’re treating, so you can carry on as normal. The job generally takes a few hours per window, depending on the condition of the joints, and we tell you how long to leave it before we go. For a job in Downham, parking and access are the things to plan: tell us about permits, visitor bays or off-street space, which floor we’re working on and whether there’s a lift.
- We look at the surrounds with you and agree the joints to renew.
- We remove the old, loose mastic.
- We pack any deep voids first.
- The sand mastic is mixed and pressed into the joint by hand.
- We dress the finish so it sits neatly against the masonry.
How to prepare
- Where the joints are inside, avoid wetting them before we arrive
- Tell us about access, such as stairs, a lift or high-level joints
- Tell us about any water getting in
Getting a quote
We quote each job on its own. Simply phone 0345 464 0079 or drop us an email and describe the job, and pictures are welcome.
Advice
Sand mastic for homes and businesses in Downham
Burnt sand mastic is a traditional material that sits naturally against stone and brick. It suits period and listed homes where a modern sealant bead would stand out. We’re often asked to deal with window mastic to renew ahead of painting and wind and rain getting in round a sash window, across sash and case windows, brick reveals and tenement windows.
Many London homes are flats, with windows high above the street. In a converted house or block, the lease normally says who is responsible for the windows, so it’s worth checking before booking, and access in Downham is something to talk through when you book.
Big or small, it’s backed by our one-year guarantee in Downham and across Greater London.
- Place
- Downham (BR1, SE6, SE12)
- Region
- Greater London
- Cover
- One year on every job
- Price
- A clear price before we start
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
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 finishes neatly against the masonry. 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.
The cost reflects the work involved, not guesswork. That’s why we ask about the job first and give you a clear price before any work starts.
Why us?
- 180+ five-star Google reviews
- Trusted Arbo and Everbuild sealants
- Experience in homes, commercial sites and hotels
- We’re fully insured
Take a look at what affects the cost or customer reviews.
Questions from Downham
Is parking an issue for sand mastic in Downham?
In much of London, parking needs planning: a visitor permit or a nearby bay makes the day run more smoothly, so mention what’s available when you book.
Can you do sand mastic in Downham?
Yes. Our work covers London and the South East, and Downham is part of that. You can call 0345 464 0079 or send us an email and let us know what needs doing.
Can tenants book the work?
We can work for tenants, landlords or agents. Get your landlord’s agreement first.
How much does sand mastic cost in Downham?
It depends on the job, so we quote each one individually. For a quick quote, ring 0345 464 0079 or drop us an email with a short description of the job.
Will the old sealant be removed?
Yes, every time. New sealant will not bond properly to old, so the joint is cleaned back first.
Where are you based?
Our base is in Crawley, and we cover South East England, London and all of Scotland.
Can landlords and businesses book you?
Yes, we do. Domestic, commercial and hotel work are all part of what we do.
How long does sand mastic take?
That depends on how much there is to do, but most jobs take a few hours per window, depending on the condition of the joints. We will tell you when we quote.
Should I try it myself first?
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 fails, we can still redo it.
Some sealant jobs are within reach of a careful DIYer, like a short, easy-to-reach joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
Looking after it afterwards
Good habits help new joints last longer. A few tips:
- Avoid heavy scraping on the mastic joint
- Get any rot dealt with first
- Sort the mastic before the decorators arrive
- Keep sills and gutters clear so water drains away
Avoid sealing over the mastic with silicone. If you see a crack, ask us to take a look rather than patching it.
Once mastic starts to crumble, rain gets in. That water can reach the timber frame and the wall so early renewal protects both.
When to call us in Downham
Timber frames move with the seasons. The movement cracks the mastic little by little.
If you can see any of these, it’s time to have the joints looked at:
- Crumbling sand mastic round a window
- A silicone bead on a sash window that spoils the look
- Patchy fillers round a sash window
- Wind and rain getting in round a sash window
For site and facilities teams at buildings such as Rangefield Primary School, its window and door frames need their mastic kept sound, just like a home’s.
Before you book anyone
- Whether they seal over old material or remove it
- What happens if the job turns out different
- How the joint is cleaned and prepared
- Whether you can choose the colour
What affects the quote in Downham
You will get a clear quote before we start. It takes into account:
- How easy the joints are to reach
- Which sealant suits the joint
- When we can work, for business premises
- The size of the job
Every job is a little different, so each one gets its own quote. Size, access and the product the joint needs all make a difference, and we’ll explain the quote if you ask.
What we need to know
A few details help us give you an accurate quote. When you get in contact, it helps to mention:
- A few photos by email, if you can
- The type of property
- Roughly how big the job is
- The problem you’ve noticed
There’s no standard price list, as no two jobs are quite the same. Instead, we send you a clear quote for your job. To arrange one, ring 0345 464 0079 or drop us an email.
Surface by surface
Sash and case windows
The mastic round a sash window is on show so we finish it carefully.
Tenement and terrace windows
Upper-floor windows need access planning. Let us know the floor and we’ll confirm access.
Places near Downham
More services for Downham
What sand mastic looks like in Downham
Compared with the north and west, the South East gets less rain, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. Historic houses like Bromley Palace (about 1.7 miles south-east) are a reminder that the area around Downham 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.
As a London address, Downham can be tricky for parking: tell us about permits, visitor bays or off-street space when you book. Homes close to St Barnabas include some older properties, and the windows may be timber, sash or later replacements, and each needs the right sealant against the wall.
Downham is about 2 miles north of Bromley, in Greater London. If you need sand mastic in Downham, please call 0345 464 0079 or send us an email for a quick quote. We’re based in Crawley and cover Greater London, Downham included. Downham is one of 764 towns and villages in Greater London where we work. You can also see our page for London, about 7 miles away.
Here we cover the BR1, SE6 and SE12 postcode area for sand mastic. If you need sand mastic at a property on Shaw Road, Arcus Road and Brook Lane or anywhere close by, we can help. If you are just outside Downham, we cover Plaistow (1 mile south), Grove Park (1 mile north-east), Sundridge (1 mile south-east), Chinbrook (1 mile east) and Bellingham (1 mile west). We also work in nearby towns such as London (7 miles north-west), City of Westminster (9 miles north-west), Marylebone (9 miles north-west), Kensington (10 miles north-west), St Pancras (9 miles north-west) and Shoreditch (8 miles north-west).
What’s near Downham
Around Downham, our work takes us to homes and buildings near Holy Trinity College Bromley, Downham Fields and Bonus Pastor Catholic College. The closest station to Downham is Grove Park station, about 0.8 miles north-east. Other landmarks nearby include The Glades (1.6 miles south) and Greenwich Castle (3.6 miles north). Green spaces nearby include Summer Hill and Downham Woodland Walk.