Greater London · England
Blackwall Window Mastic
Window mastic for Blackwall, by sealant specialists with 20+ years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Whistling draughts around closed windows
- Cracked sealant at the sill ends
- Rain getting in at the frame or under the sill
Should I try it myself first?
Some sealant jobs are within reach of a careful DIYer, such as a straightforward joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
Too much sealant is as bad as too little. A thick, smeared bead looks untidy and does not move well, and getting the depth right matters as much as the look.
About our window mastic in Blackwall
From a single sill to a whole house of windows, the work is priced before anything is done. Just call 0345 464 0079 or send us an email and tell us how many frames there are and how they’re reached for window mastic in Blackwall. We work on aluminium frames, patio & French doors and uPVC windows, and people most often call us about rain getting in at the frame or under the sill and gaps between the frame and the inside reveal.
London homes have every kind of window, from timber sashes in period terraces to aluminium and uPVC in newer blocks. The mastic around them dries out and cracks with age, letting in draughts and water.
Whatever the size of the job, it’s backed by our 12-month guarantee in Blackwall and across Greater London.
- Place
- Blackwall (E14, SE10, E16)
- 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
Also in Blackwall
Blackwall: your questions answered
I let a flat near Canary Wharf station. Can you help?
Yes, rental work is part of what we do. You can phone 0345 464 0079 or drop us an email with the address and a few details, and we will give you a fixed price before we start.
Is parking a problem for a job in Blackwall?
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.
Is there any odour?
That depends on the sealant. Some smell for a while, some hardly at all, and any smell fades as they cure.
Do you have insurance?
Yes. We’re fully insured.
How many windows can you do in a day?
The work takes a few hours for a few frames, or a day or more for a whole house. Access and the amount of old mastic make the biggest difference.
What does window mastic cost?
The cost depends on the size of the job, access and how much old sealant has to come out. Call for a quick quote.
How long should I leave it?
Different products cure at different speeds, so follow the cure time we give you.
Do you seal inside as well as outside?
Yes. Outside is the weather seal; inside closes the gap to the plaster. We do one or both.
Keeping the joints in good condition
So the new joints stay in good condition:
- Use gentle cleaners on frames and sealant
- Make sure the drainage slots aren’t blocked
- Keep paint and stain on wooden frames in good order
- Walk round the house once a year and look at the joints
Check the drainage slots in the frames aren’t blocked, so rain drains out rather than building up at the sealant.
A small gap around a frame only grows. As the old mastic shrinks further, more air gets through, and a cold room gets colder. Resealing closes it.
Surface by surface
uPVC windows
We clean the frame edge carefully so the plastic isn’t marked, then the sealant goes in between frame and wall and tooled smooth.
Aluminium frames
Aluminium needs a sealant that bonds to coated metal, and acetoxy silicones aren’t used, as they can attack some metals. Neutral-cure sealant is the safe choice.
Common problems we fix in Blackwall
Water runs down the glass onto the sill, so the sill ends and the joint below the frame are common leak points. When that sealant fails, water gets into the wall or under the frame.
It’s worth asking for a quote if you see:
- Black, perished sealant on frames
- Rushed sealant from a window installation
- Water coming in at the bottom corners of a door
- A bead that does not match the frame
For an older house near a landmark such as All Saints Church, frames set in older brick or stone need a sealant that suits the wall as well as the frame.
Questions to ask before you book
- How the joint is cleaned and prepared
- Are they insured?
- Whether they seal over old material or remove it
- What happens if the job turns out different
What happens if it’s left?
Working on frames from a ladder with a sealant gun isn’t easy, especially on upper floors. A professional job is cut out properly, backed where needed and finished neatly, in a sealant suited to the wall. In London conversions, one flat’s bathroom is often above another flat’s ceiling, and a slow leak from a failed seal can end up in the flat below. Putting it right early is much less trouble.
No two jobs are quite the same, so we quote each one individually. Size, access and the product the joint needs all play a part.
Why choose Mr Mastic in Blackwall
- Anti-fungal silicone where joints get wet
- 20+ years of sealant experience
- An ARBOMaster approved applicator
- 180+ five-star Google reviews
Take a look at our cost guide and our reviews.
What affects the quote in Blackwall
Every job gets its own quote. This is what makes a difference:
- Mould in or behind the old joints
- The type of sealant required
- When we can work, for business premises
- The old material and how stubborn it is
Homes and businesses are quoted the same way: the amount of work, the access and the products needed, along with when we can work on site. Ask us for a quote and we’ll explain what it covers.
What to tell us for a quote
There’s no need for technical detail. Just tell us:
- Pictures of the joints, sent by email
- Access, such as stairs, a lift or height
- Where the job is, and your postcode
- The rough size of the job
Need a quote? Please phone 0345 464 0079 or email us and tell us about the job. You will know what we plan to do, and what it will cost, before any work begins.
What window mastic looks like in Blackwall
In London conversions and blocks, the lease decides who is responsible for the frames, so it’s worth checking before booking. Historic houses like Queen's House (about 1.7 miles south) are a reminder that the area around Blackwall 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.
Managing a site like Woolmore Primary School? Then its window and door frames need their mastic kept sound, just like a home’s. As a London address, Blackwall can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
Blackwall is about 1 mile south-west of Canning Town, in Greater London. For window mastic in and around Blackwall, please phone 0345 464 0079 or drop us an email for a quick quote. We cover Greater London from our Crawley base, Blackwall included. Blackwall is one of 764 towns and villages in Greater London where we work for window mastic.
We cover every part of the E14, SE10 and E16 postcode area for window mastic. If you need window mastic at a property on Nutmeg Lane, Athol Square and Leamouth Road or a nearby road, our applicators can take on the job. Blackwall sits on or near the A102 and A1206, which makes travel easy. Nearby, we also carry out window mastic in Coldharbour (1 mile south-west), Leamouth (1 mile north-east), Limmo Peninsula (1 mile north-east), Poplar (1 mile west) and London Docklands (1 mile west). Larger places within reach include London (4 miles west), City of Westminster (6 miles west), Marylebone (6 miles west), Kensington (9 miles west), St Pancras (5 miles west) and Shoreditch (3 miles north-west).
Near you in Blackwall
We work in homes and buildings around The Gun pub, Tower Hamlets College and Bow Creek Ecology Park, among other places. For rail, the closest station is Canary Wharf station, roughly 0.6 miles west. Nearby you will also find Poplar Hospital (within half a mile north-west) and London Gas Museum (1.1 miles north). Not far away are Lavender Pond and Tower Hill.
How it works
On the day, there’s very little for you to do. Show us the job and we’ll take it from there. The work itself takes anything from an hour or two to a full day, depending on how many frames there are from start to finish. In a London area like Blackwall, the main things to plan are parking and access: let us know about parking, the floor we’ll be working on and any lift or shared entrance.
- First we look at every frame and agree the list.
- Next the failed sealant is cut away and the joint cleaned.
- Where gaps are deep, backing rod goes in first.
- New exterior sealant goes on in a matching colour and is tooled smooth.
- Finally we tidy up and check each joint.
Preparing for the visit
- Where the joints are inside, avoid wetting them before we arrive
- Keep children and pets away from the work area
- Clear the area around the work
Ask for a quote
For a quote, phone 0345 464 0079 or send us an email with the location and a short description of the problem. We’ll give you a clear price before any work starts.