Greater London · England
St Luke's External Mastic
Movement joints in St Luke's need attention? We remove the old material, prepare the joints and seal them properly.
- Rigid filler in a joint that should flex
- Cracked joints where brick meets render or frames
- Hard, crazed mastic that has stopped moving
About our external mastic in St Luke's
External mastic is a job where short cuts show quickly. New sealant over old, joints packed with mortar and beads with no backing all tend to fail early. We strip the joint back and start again. We work on render & cladding joints, brickwork movement joints and concrete & block, and people most often call us about hard, crazed mastic that has stopped moving and weeds or debris growing in open joints.
Newer London blocks are built with movement joints in brick and render, and with cladding joints sealed with mastic. Older terraces have their own weak points: gutter joints, roofline trims and the joint where an extension meets the original wall, and both kinds of building are found across London.
The work is guaranteed for twelve months. If something is not right with it in that time, tell us and we will put it right.
- Place
- St Luke's (N1, EC1V, EC2A)
- Region
- Greater London
- Cover
- A year, on every job
- Quote
- A clear quote up front
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
When something else is needed
We won’t take on work that won’t last, so these are the limits:
- Walls that need new movement joints cut into them
- Subsidence or other structural problems
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
If you’re not sure, just call 0345 464 0079 or email us and we will give you a straight answer before booking.
Joints and surfaces we work on
- Concrete & block
- Copings & trims
- Joints between brick and frames
- Render & cladding joints
- Brickwork movement joints
- Façade panels
St Luke's questions
Do you work for landlords with property near Old Street station?
Yes, rental work is part of what we do. Just ring 0345 464 0079 or email us and tell us about the property, and we will send you a clear quote.
Is St Luke's in your area for external mastic?
Yes. We work across London and the South East, and St Luke's is part of that. Just call 0345 464 0079 or email us with a few details of the job, and we’ll give you a clear quote.
Can a movement joint be filled with mortar?
No, not where the gap is a movement joint. Filling it with mortar defeats its purpose and can lead to cracking. We will reseal it with a flexible sealant.
Which products do you use?
The product depends on the job: anti-fungal sanitary silicone in wet areas, and other sealants where joints move or face the weather. We use products from Arbo and Everbuild.
Is it OK to seal over old sealant?
No, it won’t last. It may look fine at first, but the new bead soon lifts. The old sealant has to come out completely.
How long should I leave it?
Cure times vary by product and the conditions. Before we leave, we’ll tell you the cure time.
Do you have insurance?
Yes. We are fully insured for domestic and commercial work.
Is there any odour?
Some sealants have a smell while they cure. Opening a window helps.
Also near St Luke's
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Why it’s worth doing now in St Luke's
The longer a joint stays open, the more water the wall takes in. Wet masonry is more easily damaged by frost near the open joint, so the damage spreads beyond the joint. In a London flat, a failed joint rarely stays your problem alone: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
Homes and businesses are quoted the same way: the amount of work, the access and the products needed, plus any working-time requirements on site. Call for a quick quote and we will explain what it covers.
Why choose Mr Mastic in St Luke's
- One-year guarantee on every job
- Domestic, commercial and hotel work
- Full insurance on every job
- 180+ five-star Google reviews
Read how sealant jobs are priced and our reviews.
Surface by surface
Render joints
The face of render can be soft, so a sealant that stretches easily protects the edges. We prime where the product needs it.
Brickwork movement joints
Brick walls have vertical movement joints to absorb expansion. We reseal them with a low-modulus sealant over backing rod in a colour to suit the brick.
How it works
On the day, there’s very little for you to do. Show us the job and we’ll take it from there. The work itself takes a few hours for a handful of joints, longer for a whole elevation, including the tidy-up. For a job in St Luke's, parking and access are the things to plan: tell us about permits, visitor bays or off-street space, which floor we’re working on and whether there’s a lift.
- We inspect the joints and agree which need resealing and how they’ll be reached.
- We cut out the failed sealant and rake out any dirt or growth.
- The joint faces are cleaned and primed where the sealant needs it.
- Closed-cell backing rod is fitted to set the depth and stop three-sided bonding.
- We gun in a flexible exterior sealant in a colour that suits the wall and tool it neatly.
How to prepare
- Tell us about any previous sealing or DIY attempts
- Let us know about stairs, lifts or work at height
- Keep children and pets away from the work area
Get a quote
For a quick quote, get us on the phone, or email us if that’s easier. Describe what needs sealing and we will explain what’s involved and send you a clear quote.
Read more
St Luke's buildings and the weather
With historic houses such as Mansion House (about 0.8 miles south) nearby, there’s older building stock in the area around St Luke's as well as newer homes. In older buildings, older walls and rooflines need a sealant that moves with them and suits the material. 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.
As a London address, St Luke's can be tricky for parking: tell us about permits, visitor bays or off-street space when you book. If you live in an older home near Jewin Welsh Presbyterian Chapel, the joints between older walls, newer extensions and the roofline need a sealant that can move. For site and facilities teams at buildings such as St Luke's CofE Primary School, its movement joints, gutters and trims need looking after like any other building’s.
St Luke's is about 2 miles north of London, in Greater London. Our applicators cover external mastic for homeowners, landlords and businesses in St Luke's and the surrounding area, as part of our work across Greater London. 764 places in Greater London are on our list, large and small.
Postcode districts we cover here for external mastic: N1, EC1V and EC2A. Whether your property is on Long Lane, City Road and Moor Lane or anywhere close by, our applicators can take on the job. St Luke's sits on or near the A1 and A501, which makes travel easy. Neighbouring places we cover for external mastic include Finsbury (1 mile south), Barbican Estate (1 mile south), Shoreditch (1 mile east), Hoxton (1 mile north-east) and City of London (1 mile south). Further out, we also cover City of Westminster (3 miles west), Kensington (5 miles west), Walthamstow (5 miles north-east), Hampstead (4 miles north-west), Ruislip (14 miles west) and Brompton (4 miles south-west).
Around St Luke's
We work in homes and buildings around Barts Health Archives, Charterhouse Square School and The Masque Haunt pub and the streets around them. Nearby too are St Mary-at-Hill (1.1 miles south), Central Foundation Boys' School (within half a mile east) and Artillery Ground (under half a mile south-east). St Luke's has its own railway station: Old Street station. Nearby you will also find Gabriel's Wharf (1.3 miles south-west) and Montfichet's Tower (0.9 miles south-west). The countryside around St Luke's includes St. James's Park Lake and Barnsbury Wood.
Keeping the joints in good condition
To keep the joints looking good and working properly:
- Deal with leaking gutters that soak the joints below
- Avoid pressure-washing directly into sealant joints
- Get split or bare joints resealed while the damage is small
- Ask before painting over external sealant
Look over the joints once a year, ideally after winter. Splits, gaps at the edges or plants in the joint are early warning signs.
Leaks behind façade panels and render often go unseen. By the time there’s a damp patch, the damage can be well established so early resealing is worth it.
Should I try it myself 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.
Sealing over old silicone is the commonest DIY error. Silicone does not stick to old silicone, so it peels away and traps moisture behind it. All the old material has to come out first.
Landlord and commercial work in St Luke's
Failed sealant is one of the commonest items on a check-out report. We can quote for more than one property at once.
Letting agents often deal with us directly. Tell us the address, the job and how access works and we will quote.