Greater London · England
City of Westminster External Mastic
Sealing brickwork movement joints, render, cladding and façade joints in City of Westminster, with a 12-month guarantee on every job. Call for a quick quote.
- Joints pointed up with cement by mistake
- Joints with sealant missing in places
- Gaps where render, brick and frames meet
What happens if it’s left?
It often makes sense to reseal all the failing joints on an elevation together. Joints of the same age tend to fail together and it means sorting access once. In a flat in City of Westminster, 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.
No two jobs are quite the same, so each one gets its own quote. The number of joints, how easy they are to reach and the sealant needed all make a difference, and we will explain the quote if you ask.
What you get with us
- White, clear, grey or coloured to suit, where the product allows
- A sealant colour to suit the surroundings
- We are fully insured
- Neat joints and a tidy finish
Take a look at what affects the cost and what customers say.
External mastic for homes and businesses in City of Westminster
Joints between dissimilar materials, like brick against render or concrete against a steel frame, see movement from both sides. A flexible sealant bridges the two where mortar or filler would crack. We work on façade panels, joints between brick and frames and concrete & block, and the jobs we see most are brick movement joints where the sealant has split and moss and dirt in joints with no sealant left.
Outside work in London starts with access: side passages, upper floors and where to park. For a home in City of Westminster, tell us how high the joints are and how to reach the back of the building.
The work is covered for a year after we finish. If there’s a problem with it, please ring 0345 464 0079 or send us an email.
- Place
- City of Westminster (W2, NW8, W9, SW1V)
- Region
- Greater London
- Cover
- One year on every job
- Quotes
- A clear price before we start
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
Places near City of Westminster
Other services in City of Westminster
External mastic in City of Westminster: local notes
Compared with the north and west, the South East gets less rain, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind. With historic houses such as Handel Hendrix House (about 0.3 miles east) nearby, there’s older building stock in the area around City of Westminster as well as newer homes. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material.
City of Westminster is in London, so parking needs planning: let us know about parking bays, permits or a driveway. If you live in an older home near St Mark's, an extension built onto an older house moves differently, and the joint between them takes the strain. For site and facilities teams at buildings such as St Vincent's Catholic Primary School, larger buildings have long runs of movement joint that eventually need resealing.
City of Westminster is about 3 miles west of London, in Greater London. Jobs in City of Westminster get the same care as everywhere else we work: old sealant removed completely, careful preparation and a 12-month guarantee. Across Greater London, we cover 764 places, and City of Westminster is one of them.
Here we cover the W2, NW8, W9 and SW1V postcode area for external mastic. If you need external mastic at a property on Portman Square, Grosvenor Square and Cavendish Square or a nearby road, our applicators can take on the job. City of Westminster is on the A4 and A5, so it’s easy for us to get to with everything needed for external mastic. If you are just outside City of Westminster, we cover Marylebone (1 mile north-east), Mayfair (1 mile south-east), Tyburn (1 mile west), Burlington Estate (1 mile south-east) and Connaught Village (1 mile west). Within a short drive, we also cover London (3 miles south-east), Shoreditch (3 miles east), Walthamstow (7 miles north-east), Hoxton (3 miles north-east), Whitechapel (4 miles east) and Hampstead (3 miles north-west). Being one of Greater London’s larger places, City of Westminster has homes, rented property and businesses of every kind.
Local landmarks in City of Westminster
Around City of Westminster, our work takes us to homes and buildings near LITE Regal International School, Royal Society of Medicine Library and Devonshire Arms and the streets around them. Other local landmarks include The St Marylebone CofE School (0.5 miles north) and Hyde Park (0.6 miles south-west). City of Westminster has its own railway station: Bond Street station. Other landmarks nearby include Dunhill Museum & Archive (within half a mile north) and Kingly Court (0.6 miles east). Not far away are Serpentine and Primrose Hill.
What affects the cost of external mastic
There’s no set price list. What we look at:
- Which sealant suits the joint
- Mould in or behind the old joints
- When we can work, for business premises
- The size of the job
A failed joint rarely gets cheaper to fix by waiting. If you are not sure whether it needs doing, phone 0345 464 0079 or send us an email and we’ll give you an honest view and a quote.
What we need to know
What to tell us when you ask for a quote:
- How we’d reach the joints
- Where the property is
- Any previous sealing or DIY work
- Photos by email, if that is easy
It all starts with a short chat. Tell us what’s wrong, where it is and how much there is, and we’ll talk you through what we’d do. When it suits you, ring 0345 464 0079 or drop us an email.
City of Westminster questions
Do you work for landlords with property near Bond Street station?
Yes, we work for letting agents and landlords. Just ring 0345 464 0079 or drop us an email and tell us about the property, and we’ll give you a clear price.
Is City of Westminster in your area for external mastic?
Yes, City of Westminster is within the area we cover. We work across London and the South East. Just ring 0345 464 0079 or drop us an email with a few details of the job, and we will give you a clear price.
Which products do you use?
Quality sealants from brands including Arbo and Everbuild, chosen to suit the joint. We’ll tell you what we are using and why.
Will you leave a mess?
No. We work neatly, protect the area around the joints and tidy up afterwards.
How much does external mastic cost in City of Westminster?
Size, access and the old material all affect the cost. Call for a quick quote.
Do the sealants smell?
It depends on the product. Some smell for a while, some hardly at all, and any smell fades as they cure.
How long should I leave it?
That depends on the sealant used, so follow the cure time we give you.
What is backing rod for?
Closed-cell backing rod sets the depth of the sealant and stops it sticking to the back of the joint. Then the sealant bonds to two faces and can move.
What happens on the day
Once we are on site, we check the joints match what you told us. If we find something unexpected, we talk it through with you first. Most jobs then take anything from a few hours to several days, depending on the building. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. Mention any building rules, key holders or managing agents when you book.
- We start by checking each joint, agreeing the ones to redo and how we’ll reach them.
- The old mastic and anything lodged in the joint is removed.
- The joint faces are cleaned and primed where the sealant needs it.
- Backing rod goes in next, setting the depth and keeping the sealant off the back of the joint.
- We gun in a flexible exterior sealant in a colour that suits the wall and tool it neatly.
How to prepare
- Tell us about access, such as stairs, a lift or high-level joints
- For business premises, tell us about site rules or sign-in
- Keep children and pets away from the work area
How to get a quote
The more we know about the job, the more useful the quote. Let us know the location, the problem and roughly how many joints.
Advice
For landlords and businesses
For anyone letting property in or around City of Westminster, several properties can go on one quote. Send us the addresses and the work at each.
Mouldy or split sealant often shows up at the end of a tenancy, and it’s easy to sort out between tenants. Several properties can go on one quote.
When it isn’t the sealant
We won’t take on work that won’t last, so here’s what sealant can’t put right:
- Structural movement, which needs a surveyor or engineer
- Render that is blown, hollow or coming away
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
If you are not sure, just call 0345 464 0079 or email us and we’ll give you a straight answer before you book.
Joints and surfaces we work on
- Render & cladding joints
- Joints between brick and frames
- Façade panels
- Brickwork movement joints
- Copings & trims
- Concrete & block
Looking after it afterwards
Good habits help new joints last longer. Our tips:
- Ask before painting over external sealant
- Tell anyone working on the walls about the movement joints
- Have failed joints looked at early
- Keep soil, plants and ivy away from the joints
Make sure anyone working on the wall later knows where the movement joints are. They must stay as flexible joints, never rendered or pointed over.
Leave a failed movement joint and water keeps getting into the wall. That can lead to damp patches, staining and frost damage, all bigger jobs than a reseal.
DIY sealant or a professional job?
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.
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.