Greater London · England
External Mastic in Fortis Green
External mastic in Fortis Green from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Failed sealant between panels on a façade
- Rain getting behind render or cladding at a joint
- Cracked joints where brick meets render or frames
How we handle external mastic in Fortis Green
Movement joints let brickwork, render and cladding expand and shrink without cracking. The sealant in it has to stretch and squeeze for years, so once it splits or hardens, the joint stops working and water gets in. If you’re dealing with joints pointed up with cement by mistake and plants rooting in failed movement joints, we can put it right, whatever the surface.
Modern London flats rely on sealed movement joints and cladding joints. Older terraces have their own weak points: gutter joints, roofline trims and the joint where an extension meets the original wall.
We stand behind the work with a one-year guarantee, so you’re not left on your own once the job is done.
- Place
- Fortis Green (N10, N2, N6)
- Region
- Greater London
- Guarantee
- A year, on every job
- Quote
- A clear quote up front
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
Your questions about external mastic in Fortis Green
Can you help a landlord with a rental near Alexandra Palace station?
Yes, landlords and agents are among the people we work for. Just ring 0345 464 0079 or drop us an email with the address and what needs doing, and we will give you a clear quote.
Do you cover Fortis Green for external mastic?
Yes. Our work covers London and the South East, and Fortis Green 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.
Is it messy?
Very little: the area around the joints is protected first, and we tidy up before we go.
Is the work guaranteed?
Yes: twelve months. If anything isn’t right with the work within the year, let us know and we will sort it.
Can I do it myself?
That depends on the joint. High-level, external movement and fire-rated joints are professional jobs, while a short indoor joint may be within reach.
Does someone need to be in?
We need access to the joints, so we will agree that with you when we book. Indoors, that generally means someone at home.
Do you have insurance?
Yes. We are fully insured, and we can confirm the details when we quote.
Why do you put foam in the joint first?
Backing rod goes into deeper joints as a matter of course. It sets the sealant depth and prevents three-sided bonding.
What affects the quote in Fortis Green
Your quote is based on your job. We take into account:
- The type of sealant required
- Access and height
- Any mould that needs treating
- The number and length of the joints
Combining jobs into one visit is normally more efficient than separate visits, so it’s worth mentioning everything you’d like done. You’ll get one clear quote for the whole job.
What to tell us for a quote
You do not need to know the technical terms. Just tell us:
- What the problem is, such as mould, gaps, leaks or cracking
- The type of property
- Pictures of the joints, sent by email
- The address or postcode of the job
For external mastic in Fortis Green, call 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.
Places near Fortis Green
More services for Fortis Green
What we do, step by step
All our tools and materials come with us in the van, so you do not need to buy or prepare anything. Once we’ve agreed what’s being done, we protect the area and start. It normally takes anything from a few hours to several days, depending on the building. In a London area like Fortis Green, the main things to plan are parking and access: let us know about parking, the floor we will be working on and any lift or shared entrance.
- We start by checking each joint, agreeing the ones to redo and how we will reach them.
- We cut out the failed sealant and rake out any dirt or growth.
- We clean both faces of the joint and prime them where the product calls for it.
- Backing rod goes in next, setting the depth and keeping the sealant off the back of the joint.
- A flexible exterior sealant is applied and tooled in a colour to suit the wall.
Preparing for the visit
- Clear items away from the joints we’re working on
- Try not to wet indoor joints just before the visit
- Tell us if parking is tricky
Get a quote
The more we know about the job, the more useful the quote. Tell us where the job is, what’s wrong and how much there is, and add photos by email if you can.
Read more
Do you need external mastic in Fortis Green?
Sometimes a movement joint was filled with mortar or a rigid filler by mistake. With the joint locked solid, the movement turns into cracks elsewhere in the wall.
People normally contact us when they notice something like this:
- Joints with sealant missing in places
- Weathered mastic that no longer stretches
- Sealant that has lost its bond to the brick or render
- Movement joints filled with mortar instead of sealant
Managing a site like Fortismere School? Then movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
What your quote should include
- How the joint is cleaned and prepared
- Who does the work, and how experienced they are
- How long to leave it before use
- What product goes in the joint
Landlord and commercial work in Fortis Green
We also work for businesses, from offices to washrooms and kitchens. On commercial sites, working times can be discussed when we quote.
Mouldy or split sealant often shows up at the end of a tenancy, and it’s easy to sort out between tenants. We can quote for more than one property at once.
What the job involves on each surface
Copings and trims
Coping and trim joints face rain and sun head on. Each is resealed with a weatherproof, flexible sealant.
Brickwork movement joints
Brick movement joints are often mistaken for a missing mortar line. Where one has been mortared, we cut it out and reseal it with sealant if the joint can be cleared.
What external mastic looks like in Fortis Green
Historic houses like Heath Hall (about 1.4 miles south-west) are a reminder that the area around Fortis Green has older buildings as well as new. Where a home is older, older brick and stone need a sealant that suits them, at the right joint depth. London terraces and converted houses often share gutters, downpipes and walls, so check who is responsible for the outside before booking.
For an older house near a landmark such as United Reformed Church, the joints between older walls, newer extensions and the roofline need a sealant that can move. Rented homes near Alexandra Palace station change hands often, and split movement joints are easy to miss on a rental until damp shows inside.
Fortis Green is about 1 mile south-east of Finchley, in Greater London. Every kind of property in Fortis Green can book us for external mastic. Every job comes with our one-year guarantee. 764 places in Greater London are on our list, from the larger towns to small villages. We also work in London, around 7 miles away.
Every address in N10, N2 and N6 is covered for external mastic, from the main roads to the quietest streets. If you need external mastic at a property on Hill Road, Durham Road and Steeds Road or anywhere close by, we can help. You’ll find Fortis Green on the A504, so it’s easy for us to get to with everything needed for external mastic. Other places close to Fortis Green include Muswell Hill (1 mile east), East Finchley (1 mile west), Highgate (1 mile south), Crouch End (1 mile south-east) and Hampstead Garden Suburb (2 miles south-west). Further out, we also cover London (7 miles south), City of Westminster (5 miles south), Marylebone (5 miles south), Kensington (7 miles south), St Pancras (5 miles south) and Shoreditch (6 miles south-east).
Local landmarks in Fortis Green
Around Fortis Green, our work takes us to homes and buildings near Tollington School, Cherry Tree Wood and The Clissold Arms. For rail, the closest station is Alexandra Palace station, about 1.4 miles east of the centre. Well-known places in the area include Kenwood House (1.6 miles south-west) and Grand Arcade (1.8 miles north-west). For a walk, there’s Highgate Hill and Glebelands Local Nature Reserve.
Leave it or put it right?
Low-modulus sealants stretch easily, so they put less strain on the joint edges. That matters on brick, render and concrete, which can be weaker at the face. Too stiff a sealant can pull at the edges and break them. In a flat in Fortis Green, failed sealant seldom stays inside your own four walls: water can reach the neighbours below, and gaps in fire-rated joints affect the whole building.
A failed joint rarely gets cheaper to fix by waiting, as water and mould keep getting in. If you are unsure, ring 0345 464 0079 or email us for an honest opinion and a quote.
What you get with us
- 4.9 on Google from 180+ five-star reviews
- Anti-fungal silicone where joints get wet
- Sealant colour chosen to suit
- A choice of colours where the product allows
See our cost guide or customer reviews.
Honest limits
It helps to know what we cannot do too:
- Cracks in the bricks or render themselves, away from the joints
- Structural movement, which needs a surveyor or engineer
- Adding movement joints to masonry that has none
If you are not sure, just ring 0345 464 0079 or send us an email and we’ll give you a straight answer.
What we seal
- Brickwork movement joints
- Render & cladding joints
- Concrete & block
- Copings & trims
- Joints between brick and frames
- Façade panels