Greater London · England
Sand mastic for sash & case windows in Northumberland Heath, Greater London
Traditional burnt sand mastic around sash and case windows and doors in stone and brick for Northumberland Heath, backed by a 12-month guarantee. Ask us for a quote.
- Open joints round the window box
- Cement or filler used on old window joints that has cracked
- Old sand mastic that has cracked, crumbled or fallen out
Should I try it myself first?
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.
Sealing over old silicone is the commonest DIY error. New silicone won’t bond to old, so it peels away and traps moisture behind it. All the old material has to come out first.
About our sand mastic in Northumberland Heath
If your home is listed or in a conservation area, check with your local planning authority whether consent is needed for work to windows. Sand mastic is often favoured as a like-for-like material. If you have tired mastic found when preparing windows for paint and old sand mastic that has cracked, crumbled or fallen out, we can help, on tenement windows, timber door frames and stone surrounds alike.
From mansion-block windows to modern glazing in new flats, London has every kind of frame. Over the years, the sealant around them shrinks, cracks and pulls away, which is when draughts and damp patches appear in homes in Northumberland Heath.
A 12-month guarantee comes as standard, so you are not left on your own once the job is done.
- Where
- Northumberland Heath (DA8, DA7)
- Region
- Greater London
- Guarantee
- One year on every job
- Quote
- Quoted before any work starts
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
Northumberland Heath: your questions answered
Is Northumberland Heath in your area for sand mastic?
Yes. Our work covers London and the South East, and Northumberland Heath is part of that. Just ring 0345 464 0079 or send us an email with a few details of the job, and we’ll send you a clear quote.
Can parking be tricky for a visit in Northumberland Heath?
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.
Is it possible to take out silicone and use sand mastic instead?
Generally, yes. Once the silicone is out and the joint prepared, sand mastic is applied by hand.
Which products do you use?
Each joint gets the product that suits it. Where it moves, gets wet or faces the weather makes a difference, and we will explain our choice.
Do you hold any approvals?
Yes. We are an ARBOMaster approved applicator, the approved applicator scheme for Arbo sealants.
Does someone need to be in?
If the work is inside, we need someone to let us in. After that, you can carry on with your day.
Should I use sand mastic or silicone?
Sand mastic normally suits period timber windows best. Modern frames normally suit a flexible sealant.
Can I do it myself?
Sometimes. The key is preparation: remove all the old material and work on a clean, dry joint. If it does not work out, we can redo it.
Aftercare tips
Joint life depends on how it’s used and looked after. We suggest:
- Avoid patching sand mastic with silicone
- Find out about consent before window work on a listed home
- Do not paint over the new mastic
- Have rotten timber repaired before new mastic goes in
Look at the mastic when you look over the windows. Small cracks are easier to deal with early.
Sound mastic protects the frame. Once it fails, water can sit against the timber and timber that stays wet can rot.
Also near Northumberland Heath
Also in Northumberland Heath
Why it’s worth doing now in Northumberland Heath
Cement-based fillers and modern sealants do not always suit a period surround. Sand mastic is the like-for-like choice and that can be important for listed homes. 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.
Commercial jobs are quoted on the same basis as homes: how much there is to do, how we reach it and what it needs. Call for a quick quote and we will go through it with you.
Why Northumberland Heath clients choose us
- Homes, businesses and hotels
- A 12-month guarantee on all work
- Trusted Arbo and Everbuild sealants
- 180+ five-star Google reviews
What we cannot put right
A few problems are outside what sealant work can do:
- Timber that has rotted
- Crumbling stone or brickwork round the window
- Putty and glazing repairs
Not sure which it is? You can phone 0345 464 0079 or email us and we’ll tell you honestly.
What we seal
- Brick reveals
- Period & listed homes
- Stone surrounds
- Tenement windows
- Timber door frames
- Sash and case windows
Sand mastic in Northumberland Heath: local notes
In a converted house or block, who looks after the windows depends on the lease, so check that before booking. Historic houses like Hall Place and Gardens (about 1.8 miles south) are a reminder that the area around Northumberland Heath has older buildings as well as new. Where a home is older, older timber frames in brick or stone need a different approach from a modern uPVC window.
In the older streets around St Paul's, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. If you look after a building such as King Henry School, the mastic around its windows and doors needs looking after like any other building’s.
Northumberland Heath is about 3 miles north-west of Dartford, in Greater London. Homes, rented property, offices and hotels in Northumberland Heath can book us for sand mastic, old or new, large or small. The work is guaranteed for a year. Our Greater London coverage runs to 764 places, Northumberland Heath among them. For nearby work, see our London page.
Our applicators cover all of DA8 and DA7 for sand mastic. We cover properties on Mill Road, Penda Road and Chalk Road. Close by, we work in Bexley Riverside (1 mile south-east), Erith (1 mile north), Barnehurst (1 mile south), Belvedere (1 mile north-west) and Lessness Heath (1 mile north-west). Larger places within reach include London (11 miles west), City of Westminster (14 miles west), Marylebone (14 miles west), St Pancras (13 miles west), Shoreditch (11 miles west) and Walthamstow (11 miles north-west).
What’s near Northumberland Heath
Locally, jobs take us to homes and businesses close to Trinity School, The Royal Oak pub and Braeburn Park and the streets around them. The closest station to Northumberland Heath is Barnehurst station, roughly 0.6 miles south-west of the centre. A little further out are Erith Museum (0.7 miles north-east) and Erith and District Hospital (within half a mile north). Not far away are Crossness Nature Reserve.
How the visit works
The work is kept neat and contained to the area we’re working on, so you can get on with your day. The job normally takes anything from a few hours to a full day, depending on how many windows. In a London area like Northumberland Heath, the main things to plan are parking and access: let us know about parking, the floor we will be working on and any lift or shared entrance.
- Each surround is checked first.
- The joint is raked out and cleaned.
- Large voids are packed out.
- We point the joint with sand mastic by hand.
- We finish the mastic to a tidy line.
Before we arrive
- Tell us about any previous sealing or DIY attempts
- Clear the area around the work
- Mention any leaks or damp you’ve noticed
Get a quote
Want a quote for sand mastic? Please phone 0345 464 0079 or drop us an email and tell us about the job. You will know what we plan to do, and what it will cost, before any work begins.
Related advice
What affects the quote in Northumberland Heath
There’s no set price list. What we look at:
- The number and length of the joints
- How many areas need sealing
- How much old sealant there is and how hard it is to remove
- Access and height
Instead of a standard rate, we look at what your job involves: the amount of work, the old material and the access. The price is agreed before we begin.
Helping us quote
The more you tell us, the more accurate the quote. When you get in contact, it helps to mention:
- What’s wrong with the joints now
- The rough size of the job
- Pictures of the joints, sent by email
- How we’d reach the joints
For a quote, ring 0345 464 0079 or drop us an email with the location and a short description of the problem. You will have a clear quote before we start.
Signs you need sand mastic in Northumberland Heath
Rain on the window surround works into any crack and loosens it further. Exposed elevations normally fail first.
The problems people usually mention when they call include:
- Tired mastic found when preparing windows for paint
- Silicone on a period window that looks wrong
- Failed mastic on an exposed elevation
- Cement or filler used on old window joints that has cracked
As a London address, Northumberland Heath can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
What your quote should include
- Who turns up on the day
- How hidden problems are handled
- Whether the sealant suits the joint
- When the joint can take water or movement