Greater London · England
External & façade joints in Clapham, Greater London
External mastic across Clapham and nearby, with old sealant always removed completely.
- Joints where the bead has come unstuck
- Movement joints filled with mortar instead of sealant
- Weathered mastic that no longer stretches
Looking after it afterwards
Good habits help new joints last longer. A few tips:
- Leave the joints unpainted unless we have said otherwise
- Fix overflowing gutters above sealed joints
- Never let anyone fill a movement joint with mortar
- Look over the joints every year, ideally after winter
Don’t paint over the new sealant unless we’ve said the product is paintable. Many exterior sealants aren’t designed to be painted.
Leave a failed movement joint and water keeps getting into the wall. That can lead to damp patches, staining and frost damage which cost more to put right than the joint.
External mastic in Clapham
A movement joint is a deliberate break that lets a wall expand and contract. Its sealant has to flex with the building, season after season, and when it fails, the wall takes the strain and water finds a way in. Common call-outs are for weeds or debris growing in open joints and movement joints filled with mortar instead of sealant, on render & cladding joints, brickwork movement joints and façade panels.
In London terraces and converted houses, gutters and walls are often shared with the house next door, so one failed joint can cause damp for more than one household. For a flat in Clapham, check the lease for who looks after the outside.
All our work comes with our one-year guarantee, wherever you are in Greater London.
- Location
- Clapham (SW4, SW8, SW9)
- Wider area
- Greater London
- Cover
- 12 months on all our work
- Quote
- A clear quote up front
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
Can I do it myself?
If you do try it yourself, take your time over the preparation: take out all the old sealant, make sure the joint is clean and dry, and give it the full cure time. If it fails, we can still redo it.
Some jobs are best left to a professional: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.
Clapham buildings and the weather
London and the South East are among the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind. London terraces and converted houses often share gutters, downpipes and walls, so check who is responsible for the outside before booking.
In the older streets around St Paul's Church, the joints between older walls, newer extensions and the roofline need a sealant that can move. Clapham is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
Clapham is about 3 miles north of Streatham, in Greater London. Clapham gets the same service as everywhere we cover: old sealant removed completely, careful preparation and a one-year guarantee. Clapham is one of 764 places in Greater London we cover.
Jobs for external mastic in SW4, SW8 and SW9 is quoted and booked the same way as anywhere else. External mastic is available to properties on Grafton Square, Clapham High Street and Houghton Square and the roads around them. Main roads around Clapham include the B224 and B303, so getting to you is simple. Close by, we work in Stockwell (1 mile east), Little Portugal (1 mile north-east), Clapham Park (1 mile south), South Lambeth (1 mile north-east) and Brixton (1 mile south-east). Larger places within reach include London (3 miles north-east), City of Westminster (3 miles north), Marylebone (4 miles north), Kensington (4 miles north-west), St Pancras (4 miles north) and Shoreditch (5 miles north-east).
Landmarks near Clapham
We work in homes and buildings around Lambeth Academy, Larkhall Park and Trinity Academy. Clapham has its own railway station: Clapham High Street station. Other landmarks nearby include Baynard's Castle (3.5 miles north-east) and Harrods (2.6 miles north-west). Green spaces nearby include Battersea Park Lake and Knight's Hill.
How the visit works
When we arrive, we look over the joints with you first, so you know exactly what we are doing. We protect the surfaces around the joints before any work begins. Most jobs take anything from a few hours to several days, depending on the building. In Clapham, flats, stairs and shared entrances are part of the routine. Mention any building rules, key holders or managing agents when you book.
- Each joint is checked and the colour of the new sealant agreed.
- Failed sealant is removed back to clean, sound faces.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
Getting ready for the visit
- Mention any leaks or damp you’ve noticed
- Tell us if parking is tricky
- Let us know about earlier repairs to the joints
Getting a quote
If you’re in Clapham and need external mastic, phone 0345 464 0079 or email us. A short description of the job and where it is helps us quote, and we will agree the price before any work begins.
Related advice
How the job changes by surface
Concrete and blockwork
Wide joints in concrete need the depth controlling carefully. Backing rod sized to the joint sets it and keep the sealant to the right depth.
Brickwork movement joints
Clay brickwork grows slightly over its life and moves with the weather. That movement goes into the joint, so its sealant has to stay flexible.
Why deal with it now?
The longer a joint stays open, the more water the wall takes in. In cold weather, frost can damage wet brick and render, so the problem grows beyond the joint itself. In a flat in Clapham, 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.
We do not show prices on the website, because each job is priced on what it involves. Call for a quick quote and we’ll talk you through it.
Why Clapham customers choose us
- White, clear, grey or coloured to suit, where the product allows
- Neat joints and a tidy finish
- 4.9 on Google from 180+ five-star reviews
- Domestic, commercial and hotel work
Take a look at how sealant jobs are priced or customer reviews.
For landlords and businesses
From a single let to a portfolio, the work is the same standard: old sealant fully removed, joints prepared properly and a one-year guarantee.
We regularly work with letting and managing agents. Send the address, what’s needed and the access arrangements and we’ll quote.
Signs you need external mastic in Clapham
Weeds, moss and debris in a joint are a sign the sealant has gone. Roots and dirt hold water against the wall and make things worse.
The problems people generally mention when they call are:
- Brick movement joints where the sealant has split
- Hard, crazed mastic that has stopped moving
- Damp patches traced to an open external joint
- Rigid filler in a joint that should flex
Schools such as Clapham Manor Primary School are buildings too, and movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
What your quote should include
- Whether the sealant suits the joint
- What guarantee comes with the work
- Who turns up on the day
- Whether VAT is included
Questions from Clapham
Can you do external mastic in Clapham?
Yes. We work across London and the South East, and Clapham is part of that. You can ring 0345 464 0079 or drop us an email and let us know what needs doing.
Is parking a problem for a job in Clapham?
In much of London, parking needs planning: a visitor permit or a bay close to the door helps a lot, so mention what’s available when you book.
Will there be a smell?
That depends on the sealant. Some smell for a while, some hardly at all.
What do you need from me for a quote?
Where the job is, what the problem is and roughly how big it is. Photos by email help too.
Do you work at height?
It depends on the building. Send us photos and a rough idea of the height and we will confirm how they can be reached safely.
Are you fully insured?
Yes. We’re fully insured.
How long will you be here?
A typical job takes anything from a few hours to several days, depending on the building, including the preparation. We will confirm how long when we quote.
What colours does the sealant come in?
The sealant colour is picked to suit the wall. There’s a wide choice of exterior colours.