Greater London · England
Belgravia Window Mastic
Specialist window mastic for Belgravia: careful preparation, the right product and tidy work. Ask us for a quick quote.
- Gaps between the frame and the inside reveal
- Draughts coming in around windows and doors
- Rain getting in at the frame or under the sill
How we handle window mastic in Belgravia
Around Belgravia we seal all kinds of frames: from uPVC casements to timber and aluminium, plus patio doors, French doors and sills. The sealant is chosen to suit the frame material and the wall. We are often asked to deal with leaking joints at the ends of sills and mastic that has split away from the wall, on aluminium frames, patio & French doors and composite doors.
Many London homes are flats, with windows high above the street. In a converted house or block, the lease generally says who is responsible for the windows, so it’s worth checking before booking, and access in Belgravia is something to talk through when you book.
Big or small, you get the same one-year guarantee.
- Where
- Belgravia (SW3, SW1X, SW1W)
- Region
- Greater London
- Cover
- A year, on every job
- Quotes
- A clear price before any work starts
- Phone
- 0345 464 0079
- Last updated
- 26 October 2026
How the job changes by surface
Window sills
The end joints of a sill tend to fail before the rest. We reseal them so rain cannot run into the wall.
Aluminium frames
Aluminium moves with heat, and the frames are often slimmer than uPVC. A neat, narrow bead in a colour to match keeps the clean look.
Landlord and commercial work in Belgravia
A neglected joint can let water reach the structure, which matters even more when someone else lives there. Keeping joints in good order is simple maintenance that we can handle for you.
Letting agents often deal with us directly. Send the address, what’s needed and the access arrangements and we’ll quote.
Can I do it myself?
The biggest DIY mistake is sealing over old sealant. New silicone won’t bond to old, so it lifts and traps water and mould underneath. All the old material has to come out first.
Not every job suits DIY: work at height, external movement joints, fire-rated sealant and large areas call for the right materials, safe access and experience.
What window mastic looks like in Belgravia
In London conversions and blocks, the lease decides who is responsible for the frames, so it’s worth checking before booking. The South East is one of the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
In the older streets around St Peter's Church, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. As a London address, Belgravia can be tricky for parking: let us know about parking bays, permits or a driveway. Schools such as Holy Trinity CofE Primary School are buildings too, and larger buildings have plenty of frames, and the mastic around each one ages.
Belgravia is about 1 mile south of City of Westminster, in Greater London. If you need window mastic in Belgravia, please call 0345 464 0079 or email us for a quick quote. We’re based in Crawley and cover Greater London. 764 places in Greater London are on our list, from the larger towns to small villages.
All of SW3, SW1X and SW1W is within our area for window mastic. Whether your property is on Hans Road, Eaton Lane and Gerald Road or a nearby road, our applicators can take on the job. You will find Belgravia on the A3214 and A3217, so it’s easy for us to get to with everything needed for window mastic. If you are just outside Belgravia, we cover Brompton (1 mile south-west), Victoria (1 mile south-east), Chelsea (1 mile south-west), Pimlico (1 mile south-east) and Westminster (1 mile east). We also work in nearby towns such as London (3 miles east), St Pancras (3 miles north-east), Shoreditch (4 miles north-east), Walthamstow (8 miles north-east), Hoxton (4 miles north-east) and Whitechapel (4 miles east).
Around Belgravia
Typical jobs here are in homes near Saint Thomas More Language College, Green Park and Natural History Museum Library and Archives and the streets around them. You will also find Star Tavern (less than half a mile north-west) and Inchbald School of Design (under half a mile south). For rail, the closest station is London Victoria station, about 0.5 miles south-east. A little further out are Health Exhibition Centre (less than half a mile south-east) and Harrods (less than half a mile west). Open spaces near Belgravia include Campden Hill and Serpentine.
What we do, step by step
Before we leave, we go over the finished joints with you and tell you how long to leave it. The work normally takes most of a day for a typical house, less for a few frames, depending on the amount of work. In a London area like Belgravia, the main things to plan are parking and access: tell us about permits, visitor bays or off-street space, which floor we’re working on and whether there’s a lift.
- First, we go round the frames with you and agree the list.
- We remove the old mastic and clean the frame edge and wall.
- Deep gaps get closed-cell backing rod to set the depth.
- The new sealant goes on in white, brown, anthracite grey, black or clear to suit.
- Every joint is tooled smooth and checked before we leave.
Before we arrive
- Plan for the work area to be out of bounds to pets and children
- Tell us if parking is tricky
- Where the joints are inside, avoid wetting them before we arrive
Ask for a quote
The more we know about the job, the more useful the quote. Tell us where the job is, what’s wrong and how much there is.
Related advice
When something else is needed
Sealant is not the answer to every problem, and we’d rather say so up front. It won’t solve:
- A door that needs adjusting, rehanging or new seals
- Penetrating damp from a failed cavity tray or render
- Condensation trapped between the panes
If in doubt, ring 0345 464 0079 or send us an email and we will say what we think before booking.
Joints and surfaces we work on
- Aluminium frames
- Patio & French doors
- Window sills
- uPVC windows
- Composite doors
- Timber windows & doors
Nearby places to Belgravia
More services for Belgravia
Belgravia questions
Is parking an issue for window mastic in Belgravia?
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.
Can you help a landlord with a rental near London Victoria station?
Yes, landlords and agents are among the people we work for, and several properties can be quoted together. Just call 0345 464 0079 or send us an email with the address and what needs doing, and we will give you a clear quote.
Will you leave a mess?
Not at all. The area is protected while we work and cleaned up afterwards.
Does someone need to be in?
For indoor joints, yes, someone needs to let us in. After that, you can carry on with your day.
Do you take out the old sealant first?
Always. Sealing over the old bead is the commonest cause of early failure, and it’s something we never do.
Where is Mr Mastic based?
Mr Mastic is based in Crawley. Our applicators cover Belgravia, along with the rest of our area.
What information do you need?
Just the basics: the address or postcode, what’s wrong and any access issues. Then phone 0345 464 0079 or drop us an email.
Can you do the inside joint as well?
Yes. Draughts often come through the inside gap too, so it can be worth sealing both.
What affects the cost of window mastic
Call for a quick quote. The main things that affect it are:
- The old material and how stubborn it is
- How many rooms, windows or areas are involved
- The type of sealant required
- Access and height
Doing several joints on one visit normally makes better use of the time than several visits, so it’s worth mentioning everything you’d like done. We’ll give you a clear price for the lot.
What to tell us for a quote
To make quoting easier, please include:
- The problem you’ve noticed
- If someone has resealed it before
- Whether it’s a home or a business
- How we’d reach the joints
To get a quote, ring 0345 464 0079 or email us and tell us where the job is and what the problem looks like. You will have a clear quote before any work starts.
How to look after the new joints
How long the joints last depends on use and care. We suggest:
- Keep drainage slots and sill grooves clear
- Wipe condensation off the frames
- Use gentle cleaners on frames and sealant
- Avoid harsh chemicals near the mastic
A yearly look round the frames is enough. Small splits are simple to catch before they leak.
Look out for the warning signs: cracks in the mastic, gaps you can see light through, damp on the reveal or mould around the inside of the frame. Any of these is worth a call.