Greater London · England
Southwark External Mastic
Sealing brickwork movement joints, render, cladding and façade joints in Southwark, with a one-year guarantee on every job. Call for a quick quote.
- Panel joints letting water in
- Movement joints with cracked, split or missing sealant
- Joints pointed up with cement by mistake
The process
At the end, we look at the finished work together and tell you how long to leave it. The visit itself usually takes anything from a few hours to several days, depending on the building, depending on the amount of work. 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 walking round the building and agreeing the joints and the access.
- We cut out the old mastic and rake out anything in the joint.
- The faces are brushed clean and primed where the product requires it.
- We fit closed-cell backing rod to control the depth.
- We apply the sealant, tool it and check the whole run.
Preparing for the visit
- For indoor joints, keep the area dry beforehand if you can
- Let us know if you’ve seen damp or leaks
- Mention any sign-in or site rules at work premises
Ask for a quote
Call for a quick quote, or email us if that’s easier. Tell us about the joints that need doing and we’ll talk you through the work before giving you a price.
Related advice
External mastic in Southwark
Where two different materials meet, such as brick and render or blockwork and metal, they move at different rates. A flexible sealant bridges the two where mortar or filler would crack. If you’re dealing with weathered mastic that no longer stretches and weeds or debris growing in open joints, we can help, whatever the surface.
In London terraces and converted houses, gutters and walls are often shared with the house next door, so a leaking gutter joint or failed wall joint can affect more than one home. In a converted house in Southwark, it’s worth checking who is responsible for the outside before booking.
You get a one-year guarantee, the same in Southwark as everywhere else we work.
- Location
- Southwark (SE1, SE11)
- Wider area
- Greater London
- Cover
- One year on every job
- Quote
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
External mastic in Southwark: local notes
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. London terraces and converted houses often share gutters, downpipes and walls, so check who is responsible for the outside before booking.
If you look after a building such as Charles Dickens Primary School, larger buildings have long runs of movement joint that eventually need resealing. Homes close to Borough Welsh Congregational Chapel include some older properties, and the joints between older walls, newer extensions and the roofline need a sealant that can move.
Southwark is about 0 miles north-west of London, in Greater London. Every kind of property in Southwark can book us for external mastic, old or new, large or small. The work is guaranteed for a year. Southwark is one of 764 towns and villages in Greater London we cover.
Every address in SE1 and SE11 is covered for external mastic, from the main roads to the quietest streets. If you need external mastic at a property on Borough Square, Trinity Church Square and Merrick Square or anywhere close by, we can help. Southwark is on the A300 and B240, which makes it straightforward to reach. We also cover the places around Southwark: Tower Hill (1 mile north-east), City of London (1 mile north), Aldgate (1 mile north-east), Bishopsgate (1 mile north-east) and Barbican Estate (1 mile north). Further out, we also cover City of Westminster (3 miles west), Kensington (5 miles west), Walthamstow (7 miles north-east), Hampstead (5 miles north-west), Ruislip (14 miles west) and Brompton (3 miles west).
Near you in Southwark
In Southwark, that means homes and buildings near London School of Musical Theatre, Little Dorrit's Playground and St Mary-at-Hill. Nearby too are Ark Globe Academy (under half a mile south-east), The BFI Reuben Library (0.9 miles north-west) and The Gladstone Arms (under half a mile north-east). For rail, the closest station is Elephant & Castle station, about 0.5 miles south of the centre. Other landmarks nearby include Gabriel's Wharf (0.7 miles north-west) and Baynard's Castle (0.8 miles north). Not far away are Ludgate Hill and Bellenden Road Nature Garden.
Also near Southwark
What else we do in Southwark
For landlords and businesses
From a single let to a portfolio, you get the same standard of work: old sealant fully removed, joints prepared properly and a 12-month guarantee.
We also work for businesses, from offices to washrooms and kitchens. For commercial premises, we can talk through working times when we quote.
Why act early in Southwark
Water gets in through a failed movement joint, behind render and cladding. Dealing with it early keeps the repair to the joint, instead of the wall and finishes around it. Damp from a failed joint spreads quietly in older London brickwork and timber, and by the time it shows on a wall or ceiling in Southwark, the repair is bigger than the sealant job would have been.
No two jobs are quite the same, so we quote each one individually. The number of joints, how easy they are to reach and the sealant needed all make a difference.
What you get with us
- 180+ five-star Google reviews
- 12-month guarantee on every job
- 20+ years of sealant experience
- Old sealant always removed completely
Take a look at our cost guide or our reviews.
Quotes for external mastic in Southwark
For a quick quote, just ask. The main things that affect it are:
- The number and length of the joints
- Whether old sealant or filler has to be cut out
- When we can work, for business premises
- Whether the work is at height
The cost depends on how much there is to do, how much old material has to come out and access to the work. You’ll have a clear quote before any work starts.
Asking for a quote
Before you ask for a quote, have a think about:
- If it’s domestic, commercial or a hotel
- Photos by email, if that is easy
- If someone has resealed it before
- What the problem is, such as mould, gaps, leaks or cracking
To get a quote, call 0345 464 0079 or drop us an email with the location and a short description of the problem. We will give you a clear price before any work starts.
Keeping the joints in good condition
A little care helps the new joints last. Our advice:
- Tell anyone working on the walls about the movement joints
- Look over the joints every year, ideally after winter
- Fix overflowing gutters above sealed joints
- Clear growth from the base of walls and joints
Have a quick look at the joints each spring. Watch for splits, edges coming away or growth in the joint.
Once a joint cannot move, the wall finds another way, generally as cracking in the brickwork or render nearby. Resealing it early helps prevent that.
Signs you need external mastic in Southwark
Sunlight, wet weather and frost wear exterior sealant down. In time it goes hard, crazes on the surface and stops stretching, so the next time the wall moves, it splits or pulls away.
Any of these means the joints need attention:
- Joints with sealant missing in places
- Damp patches traced to an open external joint
- Failed seals between different materials
- Joints pointed up with cement by mistake
Southwark is in London, so parking needs planning: let us know about parking bays, permits or a driveway.
Questions to ask before you book
- Whether they seal over old material or remove it
- What insurance they hold
- What happens if they find a problem under the old sealant
- Which colour the sealant will be
Surface by surface
Joints between dissimilar materials
Where a frame or panel meets masonry, water often finds a way in. The old joint is removed and a sealant that bonds to both sides goes in.
Render joints
Water behind render can lead to blown patches. Resealing the joints early keeps water out.
Your questions about external mastic in Southwark
Can parking be tricky for a visit in Southwark?
Parking in Southwark, as in most of London, takes a little planning: a visitor permit or a bay close to the door helps a lot.
Can you help a landlord with a rental near Elephant & Castle station?
Yes, rental work is part of what we do. Just call 0345 464 0079 or send us an email and tell us about the property, and we’ll give you a clear quote.
Where are you based?
We work from Crawley. We cover Southwark and the rest of Greater London, along with the rest of our area.
Can a movement joint be filled with mortar?
No. A mortar-filled joint cannot move, so the movement cracks the wall elsewhere. Use a flexible sealant with backing rod.
Are you fully insured?
Yes. Mr Mastic is fully insured, and we have been doing sealant work for more than 20 years.
Is the work guaranteed?
Yes. Every job comes with our one-year guarantee.
How long will you be here?
A typical job takes anything from a few hours to several days, depending on the building. Your quote will say how long we expect yours to take.
Are you an approved applicator?
Yes. We hold ARBOMaster approved applicator status, and we’re fully insured.