Greater London · England
External Mastic in Hornsey
External mastic in Hornsey from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Movement joints filled with mortar instead of sealant
- Sealant pulling away from one side of the joint
- Panel joints letting water in
What happens if it’s left?
Pointing a movement joint with mortar might seem a neat fix, but it stops the joint moving. The wall then cracks somewhere else. A flexible sealant over backing rod is what the joint needs. 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 Hornsey, 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.
Why Hornsey clients choose us
- Anti-fungal silicone where joints get wet
- One-year guarantee on every job
- Any old sealant cut out fully, not covered over
- 180+ five-star Google reviews
Read our cost guide and our reviews.
External mastic in Hornsey, done properly
For buildings in Hornsey, we reseal external joints of all kinds, from brick movement joints to cladding panels. The preparation is the same whatever the wall: clean joint faces and the right depth. Common call-outs are for joints pointed up with cement by mistake and gaps where render, brick and frames meet, on render & cladding joints, façade panels and copings & trims.
Newer London blocks are built with movement joints in brick and render, and with cladding joints sealed with mastic. Period houses have different weak points, such as gutter joints, trims and the line where an extension meets the old wall.
Big or small, it’s backed by our one-year guarantee in Hornsey and across Greater London.
- Location
- Hornsey (N8, N22)
- Wider area
- Greater London
- Cover
- A year, on every job
- Price
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
Places near Hornsey
What else we do in Hornsey
How it works
We keep the work tidy and contained to the area we are working on. Expect the work to take a few hours for a handful of joints, longer for a whole elevation, and we tell you how long to leave it before we go. In Hornsey, as in most of London, parking needs a little planning. It helps if you can point us to a visitor permit or a bay close to the door.
- We start by walking round the building and agreeing the joints and the access.
- Every bit of old sealant and any mortar or debris is cut out.
- 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.
Getting ready for the visit
- Clear items away from the joints we are working on
- Tell us about access, such as stairs, a lift or high-level joints
- Mention any sign-in or site rules at work premises
Getting a quote
Every job is quoted individually, so the first step is telling us about yours. Just call 0345 464 0079 or email us with the details, and pictures are welcome.
Advice
External mastic in Hornsey: local notes
Historic houses like Bruce Castle (about 2 miles north-east) are a reminder that the area around Hornsey has older buildings as well as new. 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, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day.
Managing a site like St Mary's CofE Primary School? Then its movement joints, gutters and trims need looking after like any other building’s. Hornsey is in London, so parking needs planning: let us know about parking bays, permits or a driveway.
Hornsey is about 3 miles east of Finchley, in Greater London. For external mastic in and around Hornsey, it’s easy to get a quote: please call 0345 464 0079 or email us. We cover Greater London from our Crawley base, Hornsey included. Our area takes in 764 places across Greater London. Our London page covers work nearby (6 miles or so).
All of N8 and N22 is within our area for external mastic, from the main roads to the quietest streets. Whether your property is on High Street, Brandon Place and Cross Lane or anywhere close by, our applicators can take on the job. We also cover the places around Hornsey: Turnpike Lane (1 mile east), Crouch End (1 mile south-west), Stroud Green (1 mile south-east), Wood Green (1 mile north-east) and Noel Park (1 mile north-east). Within a short drive, we also cover London (6 miles south), City of Westminster (5 miles south), Marylebone (5 miles south), Kensington (7 miles south-west), St Pancras (4 miles south) and Shoreditch (5 miles south).
Near you in Hornsey
Locally, jobs take us to homes and businesses close to Great Northern Railway pub, Priory Park and Greek Secondary School of London. Hornsey has its own railway station: Hornsey station. Other landmarks nearby include Hornsey Central Hospital (0.7 miles west) and Broomfield House Museum (2 miles north). Green spaces nearby include Darland's Lake and Highgate Hill.
Keeping the joints in good condition
Looking after new joints is easy, and it makes a real difference:
- Check external joints each spring
- Leave the joints unpainted unless we’ve said otherwise
- Keep soil, plants and ivy away from the joints
- Get split or bare joints resealed while the damage is small
If you have more work done on the wall, such as new render, cladding or an opening, show the contractor the movement joints. They should be kept open and resealed, not filled.
If you can see gaps, plants or bare sections in a joint, have it checked. Early work is quicker and leaves a better finish.
Common problems we fix in Hornsey
Weeds, moss and debris in a joint are a sign the sealant has gone. Dirt and roots then trap moisture in the joint.
The problems people usually mention when they call include:
- Brick movement joints where the sealant has split
- Rain getting behind render or cladding at a joint
- Failed sealant between panels on a façade
- Sealant pulling away from one side of the joint
Letting a property close to Hornsey station? Then outside joints that have cracked can let damp into a rental, so check them between lets.
Questions to ask before you book
- Who does the work, and how experienced they are
- Is the old sealant removed completely?
- The length of the guarantee
- Whether you can choose the colour
How we quote for external mastic
There’s no set price list, because jobs vary so much. What we look at:
- When we can work, for business premises
- The old material and how stubborn it is
- Whether there’s mould to deal with
- How many areas need sealing
Commercial jobs are quoted on the same basis as homes: how much there is to do, how we reach it and what it needs, plus any working-time requirements on site. Call for a quick quote and we’ll explain what it covers.
What we need to know
What to tell us when you ask for a quote:
- If it’s domestic, commercial or a hotel
- Roughly how big the job is
- Where the property is
- Pictures of the joints, sent by email
If you are in Hornsey and need external mastic, call 0345 464 0079 or send us an email. Tell us what the problem is and where, and you will get a clear quote before any work starts.
Landlords, agents and businesses in Hornsey
From a single let to a portfolio, you get the same standard of work: the old material taken out, careful preparation and a 12-month guarantee.
We work for landlords and letting agents as well as homeowners. Resealing between tenancies is a simple way to keep a property in good order.
What the job involves on each 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.
Concrete and blockwork
Concrete and block walls shrink as they dry and move with temperature. Their movement joints are sealed over backing rod with a flexible sealant.
Hornsey: your questions answered
Is Hornsey in your area for external mastic?
Yes, Hornsey 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.
Can you help a landlord with a rental near Hornsey station?
Yes. We work for landlords and letting agents as well as homeowners. Just ring 0345 464 0079 or email us with the address and what needs doing, and we will send you a clear quote.
Will the old sealant be removed?
Always. Sealing over the old bead is the commonest cause of early failure, so we never do it.
How do you reach high-level joints?
That depends on how high the joints are and the ground below. Low-level joints are straightforward; for higher work, tell us about the building and we’ll confirm what’s needed.
Is it OK to seal over old sealant?
No. Fresh sealant does not stick to old sealant, and anything trapped underneath, including mould and water, stays there. It all has to come out first.
Do you do commercial work?
Yes. Commercial and hotel work is a large part of what we do, as well as homes. We can talk about working times when we quote.
Where is Mr Mastic based?
We work from Crawley. We cover Hornsey and the rest of Greater London, along with the rest of our area.
Is it OK to fill a movement joint with cement?
No. Cement or mortar cannot stretch, so the joint stops doing its job. If it has already been filled, we can normally cut it out and reseal it.