City of London · England
External Mastic in City of London
Sealing brickwork movement joints, render, cladding and façade joints for homes and businesses in City of London. Fully insured, ARBOMaster approved and guaranteed for a year.
- Panel joints letting water in
- Rigid filler in a joint that should flex
- Joints where the bead has come unstuck
External mastic in City of London, done properly
Ground-floor and low-level joints are straightforward to reach. For joints higher up, give us some details of the building and we will confirm what access is needed. If you have joints pointed up with cement by mistake and sealant that has lost its bond to the brick or render, we can help, whatever the surface.
London’s terraces and conversions often share walls, gutters and downpipes with their neighbours, so a leaking gutter joint or failed wall joint can affect more than one home. For a flat in City of London, check the lease for who looks after the outside.
The work is covered for a year after we finish. If there’s a problem with it, please call 0345 464 0079 or send us an email.
- Location
- City of London (EC4V, EC1A, EC2M, EC2Y)
- Region
- City of London
- Cover
- A year, on every job
- Quote
- A clear quote up front
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
Aftercare tips
A little care helps the new joints last. We recommend:
- Have failed joints looked at early
- Check the sealant is paintable before painting near it
- Avoid pressure-washing directly into sealant joints
- Do not let climbing plants root in the sealant
Don’t let soil, plants or ivy build up against the new joints. Anything that holds water against the joint wears it out sooner.
Act while the splits are small. Then it’s a straightforward cut-out and reseal.
Honest limits
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
- Rising or penetrating damp from elsewhere in the wall
- Adding movement joints to masonry that has none
If in doubt, phone 0345 464 0079 or send us an email and we’ll say what we think before booking.
Joints and surfaces we work on
- Joints between brick and frames
- Brickwork movement joints
- Façade panels
- Concrete & block
- Render & cladding joints
- Copings & trims
City of London: your questions answered
Is parking a problem for a job in City of London?
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.
Is City of London in your area for external mastic?
Yes. We work across London and the South East, and City of London is part of that. Just ring 0345 464 0079 or send us an email with a few details of the job.
Where are you based?
We are based in Crawley, West Sussex, and we cover South East England, London and all of Scotland.
Can you do several jobs on one visit?
Of course. Combining jobs makes good use of the visit.
How do I get a quote for external mastic in City of London?
Every job is different, so each one gets its own quote. To get one, call 0345 464 0079 or send us an email and tell us what needs doing and where.
Can a movement joint be filled with mortar?
No. Cement or mortar can’t stretch, so the joint stops doing its job. Where a joint has been mortared, it can often be raked out and sealed properly.
Why is there a gap in my brick wall?
A vertical gap in a long brick wall is normally a movement joint. It lets the bricks expand without cracking, and it should be sealed with a flexible sealant.
Are you fully insured?
Yes, we’re fully insured.
City of London buildings and the weather
Rainfall in the South East is lower than in much of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. In terraces and conversions, gutters and walls are often shared with the neighbours, so check who is responsible for the outside before booking.
City of London is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book. For an older house near a landmark such as St Olave Old Jewry, an extension built onto an older house moves differently, and the joint between them takes the strain.
City of London is about 1 mile north of London, in City of London. From the centre of City of London to the outskirts, external mastic is available for homes and businesses alike, from flats and houses to offices and hotels.
We work across EC4V, EC1A, EC2M and EC2Y for external mastic. You’ll find streets such as Aldermanbury Square, Monkwell Square and Paternoster Square, all of which we cover. Being close to the A1 and A3, City of London is simple for us to get to for external mastic. If you’re just outside City of London, we cover Barbican Estate (1 mile north), Bishopsgate (1 mile east), Finsbury (1 mile north), Aldgate (1 mile east) and St Luke's (1 mile north).
Local landmarks in City of London
Typical jobs here are in homes near St Mary-at-Hill, Prior Weston Primary School and Children's Centre and Golden Fleece pub, among other places. Other local landmarks include Central Foundation Boys' School (0.8 miles north), Barts Health Archives (within half a mile north-west) and St Alphage Garden (less than half a mile north). City of London has its own railway station: London Cannon Street station. A little further out are Gabriel's Wharf (0.8 miles south-west) and London Mithraeum (less than half a mile south). For a walk, there’s St. James's Park Lake and Barnsbury Wood.
When to call us in City of London
A lot of failed joints come down to preparation: dusty or wet faces, no primer where one was needed, or old sealant left in. The new sealant then lets go long before it should.
Signs it’s time to call us include:
- Cracked joints where brick meets render or frames
- Leaking joints around cladding and façade panels
- Movement joints with cracked, split or missing sealant
- Rain getting behind render or cladding at a joint
For site and facilities teams at buildings such as Fashion Retail Academy, larger buildings have long runs of movement joint that eventually need resealing.
What to look for in a quote
- Who turns up on the day
- Which colour the sealant will be
- Whether the sealant suits the joint
- Whether all the old sealant comes out first
Also near City of London
Also in City of London
DIY versus a professional finish
A careful DIYer can reseal a simple joint, such as a straightforward joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
Some jobs are best left to a professional: work at height, external movement joints, fire-rated sealant and large areas need the right product, the right access and the right method.
What affects the quote in City of London
For a quick quote, just ask. The main things that affect it are:
- The type of sealant required
- Working hours on commercial sites
- The number and length of the joints
- How many areas need sealing
There are no prices on our website, because the cost depends so much on the job itself. Call for a quick quote and we’ll talk you through it.
Helping us quote
To help us quote quickly, let us know:
- How we’d reach the joints
- The problem you’ve noticed
- Where the property is
- Pictures of the joints, sent by email
Want a quote for external mastic? Please call 0345 464 0079 or drop us an email with a few details. You will know what we plan to do, and what it will cost, before any work begins.
What the job involves on each surface
Copings and trims
Copings expand and contract through the day, so a flexible sealant suits them best year round.
Concrete and blockwork
Concrete faces can be dusty and porous, so cleaning and priming matter. A primer goes on where the product requires one before sealing.
What we do, step by step
On the day, there’s very little for you to do. Show us the job and we will take it from there. The work itself takes a few hours to a few days, depending on the length of joint and the access. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. If the building has a concierge, managing agent or access rules, tell us when you book.
- First, the joints are inspected and the access agreed.
- 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.
- The exterior sealant is applied, tooled and checked along its length.
Before we arrive
- Mention any leaks or damp you’ve noticed
- Tell us about access, such as stairs, a lift or high-level joints
- Tell us about any previous sealing or DIY attempts
How to get a quote
For external mastic in City of London, ring 0345 464 0079 or send us an email. Tell us what the problem is and where, and we will agree the price before any work begins.