Greater London · England
External Mastic in Islington
External mastic for Islington, by sealant specialists with 20+ years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Failed seals between different materials
- Old sealant gone brittle and cracked
- Sealant that has lost its bond to the brick or render
External mastic for homes and businesses in Islington
As ARBOMaster approved applicators, we choose exterior sealants to suit the joint and the surfaces. Some surfaces need a primer before sealing, and we do not skip that step. We work on render & cladding joints, concrete & block and copings & trims, and people most often call us about moss and dirt in joints with no sealant left and failed sealant between panels on a façade.
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 Islington, it’s worth checking who is responsible for the outside before booking.
A 12-month guarantee comes with the work, just as it does everywhere we cover.
- Location
- Islington (N1, N7, NW1, EC1V)
- Region
- Greater London
- Cover
- A year, on every job
- Quotes
- A clear quote up front
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
Should I try it myself first?
If you are set on DIY, put the effort into preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it fails, we can still redo it.
A careful DIYer can reseal a simple joint, like a short, easy-to-reach joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
Towns and villages near Islington
What else we do in Islington
Work for landlords, hotels and businesses
In hotels, rooms out of use cost money, so the work can be planned room by room. We have worked in hotels as well as homes and businesses.
We work for letting agents and landlords as well as homeowners. Sealant work between tenants keeps a property looking cared for.
How it works
Our applicators work methodically: protect, prepare, seal, tidy. For most jobs that takes a few hours to a few days, depending on the length of joint and the access, and the area is left clean. In Islington, flats, stairs and shared entrances are part of the routine. If the building has a concierge, managing agent or access rules, tell us when you book.
- First we look over the joints with you, agree which to renew and talk through access.
- The old mastic and anything lodged in the joint is removed.
- The joint faces are cleaned and primed where the sealant needs it.
- We push in closed-cell backing rod so the sealant is the right depth and bonds to the sides only.
- The new sealant, chosen to suit the brick or render, is applied and tooled to a neat finish.
Getting ready for the visit
- Plan for the work area to be out of bounds to pets and children
- Mention if the joints have been sealed before
- Mention any parking rules near the property
Get a quote
For a quick quote, get us on the phone, or send an email if you’d rather. Tell us about the joints that need doing and we’ll explain what’s involved and give you a clear price.
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Islington questions
Is Islington in your area for external mastic?
Yes, Islington is within the area we cover. Our work covers London and the South East. Just phone 0345 464 0079 or drop us an email with a few details of the job.
Do you work for landlords with property near Essex Road station?
Yes. We work for landlords and agents as well as householders. Just phone 0345 464 0079 or email us with the address and what needs doing, and we will give you a clear quote.
Can you do several jobs on one visit?
Yes. Tell us about everything you’d like done and we’ll quote it together.
Are you ARBOMaster approved?
Yes. ARBOMaster is the approved applicator scheme for Arbo sealants, and we are part of it.
Can new sealant go over the old?
No. Fresh sealant doesn’t stick to old sealant, and anything trapped underneath, including mould and water, stays there. It all has to come out first.
Can you seal joints between render and window frames?
Yes. Materials like render, brick, metal and uPVC all move differently, so a flexible sealant is needed where they meet. We choose one that suits both surfaces.
Can you work on commercial sites?
Yes. We have worked for hotels, offices and other businesses.
Do you remove the old sealant?
Yes, every time. New silicone doesn’t stick to old silicone, so the joint is cleaned back first.
Surface by surface
Concrete and blockwork
Blockwork and concrete shrink over time and move with the seasons. Their movement joints are sealed over backing rod with a flexible sealant.
Copings and trims
Coping joints that leak let water straight down into the wall. Sealing them early saves the wall below.
How we quote for external mastic
Jobs vary more than people expect. What affects the quote:
- How many areas need sealing
- Access and height
- The type of sealant required
- Whether there’s mould to deal with
A few things move the cost up or down: the old material and how easily it comes out, any mould to treat, and whether the work is at height. Your quote takes all of that into account.
Helping us quote
When you contact us, these details help:
- Roughly how big the job is
- How we’d reach the joints
- If someone has resealed it before
- Where the job is, and your postcode
A good description makes for an accurate quote. Tell us where the job is, what’s wrong and how much there is, and add photos by email if you can.
Islington buildings and the weather
London terraces and converted houses often share gutters, downpipes and walls, so it’s worth agreeing who is responsible before work starts. Rainfall in the South East is lower than in much of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
For landlords with property near Essex Road station, split movement joints are easy to miss on a rental until damp shows inside. In the older streets around St Mary's Church, an extension built onto an older house moves differently, and the joint between them takes the strain.
Islington is about 3 miles north-east of City of Westminster, in Greater London. Jobs in Islington get the same care as everywhere else we work: old sealant removed completely, careful preparation and a 12-month guarantee. 764 places in Greater London are on our list.
Work in N1, N7, NW1 and EC1V works the same way as everywhere else we cover. Local streets include Gibson Square, Old Royal Free Square and Cloudesley Square, and we cover them all. You will find Islington on the B515 and A5203, which makes it straightforward to reach with everything needed for external mastic. We also cover Pentonville (1 mile south), Angel (1 mile south), Barnsbury (1 mile north-west), Clerkenwell (1 mile south) and Lower Holloway (1 mile north-west). Further out, we also cover London (3 miles south), City of Westminster (3 miles south-west), Kensington (5 miles south-west), Walthamstow (5 miles north-east), Hampstead (3 miles west) and Ruislip (13 miles west).
Near you in Islington
We work in homes and buildings around Islington Green School, The King's Head Public House and Pilsudski Institute of London, among other places. Nearby too are Barnard Park (under half a mile south-west) and St Mary's CofE Primary School (under half a mile east). There’s a railway station in Islington itself: Essex Road station. Other landmarks nearby include King's College Hospital Charity (0.7 miles north-west) and Montfichet's Tower (1.7 miles south). Open spaces near Islington include Barnsbury Wood and Ludgate Hill.
Aftercare tips
Good habits help new joints last longer. Our tips:
- Make sure movement joints aren’t pointed over
- Keep water from gutters off the wall
- Avoid pressure-washing directly into sealant joints
- Show decorators and builders where the movement joints are
Have a quick look at the joints each spring. Splits, gaps at the edges or plants in the joint are early warning signs.
Water getting behind cladding or render can go unnoticed for a long time. When it finally shows inside, the joint may have been open for years so early resealing is worth it.
Signs you need external mastic in Islington
Poor preparation causes many early failures: joint faces that were dusty or damp, unprimed where they needed it, or still carrying old sealant. The sealant never bonds properly.
If you can see any of these, it’s time to have the joints looked at:
- Damp patches traced to an open external joint
- Rigid filler in a joint that should flex
- Leaking joints around cladding and façade panels
- Movement joints with cracked, split or missing sealant
As a London address, Islington can be tricky for parking: let us know about parking bays, permits or a driveway.
Questions to ask before booking
- What preparation is included
- What product goes in the joint
- What happens if they find a problem under the old sealant
- Whether VAT is included