Greater London · England
External & façade joints in Friern Barnet, Greater London
External mastic across Friern Barnet and nearby, with old sealant always removed completely.
- Rain getting behind render or cladding at a joint
- Joints with sealant missing in places
- Failed seals between different materials
DIY sealant or a professional job?
Sealing over old silicone is the commonest DIY error. New silicone won’t bond to old, so it lifts and traps water and mould underneath. Everything old must be removed first.
What a professional job adds is preparation and the right product. We take joints back to clean, dry surfaces, and the sealant is matched to the joint and its conditions, then guaranteed for a year.
External mastic for homes and businesses in Friern Barnet
A movement joint is a deliberate break that lets a wall expand and contract. The sealant in it has to stretch and squeeze for years, and when it fails, the wall takes the strain and water finds a way in. Common call-outs are for old sealant gone brittle and cracked and failed seals between different materials, across façade panels, joints between brick and frames and copings & trims.
In London terraces and converted houses, gutters and walls are often shared with the house next door, so one failed joint can cause damp for more than one household. For a flat in Friern Barnet, check the lease for who looks after the outside.
Each job carries a 12-month guarantee, large or small.
- Location
- Friern Barnet (N11, N12, N10, N20)
- Region
- Greater London
- Guarantee
- One year on every job
- Price
- A clear quote up front
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Nearby places to Friern Barnet
Other services in Friern Barnet
Surface by surface
Render joints
Water behind render can lead to blown patches. A sound joint keeps the render dry behind and protects the render itself.
Cladding and façade panels
Cladding and façade panels are generally separated by sealed joints. Each joint gets a sealant that suits the panel and its movement.
Why deal with it now?
Pointing a movement joint with mortar might seem a neat fix, but it stops the joint moving. The wall then cracks somewhere else. The correct repair is a flexible sealant with the right backing. 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.
Some things make a job bigger or smaller: the old material and how easily it comes out, whether mould needs treating, and whether we need extra access for height. Your quote takes all of that into account.
Why us?
- An ARBOMaster approved applicator
- Experience in homes, commercial sites and hotels
- Any old sealant cut out fully, not covered over
- Full insurance on every job
Read what affects the cost and what customers say.
External mastic in Friern Barnet: local notes
London and the South East are among the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. Historic houses like Heath Hall (about 2.7 miles south) are a reminder that the area around Friern Barnet 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.
Letting a property close to New Southgate station? Then outside joints that have cracked can let damp into a rental, so check them between lets. For site and facilities teams at buildings such as Holly Park Primary School, movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
Friern Barnet is about 2 miles north-east of Finchley, in Greater London. Across the N11 area, we can carry out external mastic at your property. We cover 764 towns and villages across Greater London. There’s also a page for London, roughly 8 miles from Friern Barnet.
Every address in N11, N12, N10 and N20 is within our area for external mastic. That includes homes and businesses on Martock Gardens, Shapwick Close and Radstock Close and the roads around them. Main roads around Friern Barnet include the A406 and B550, which makes travel easy. If you are just outside Friern Barnet, we cover New Southgate (1 mile east), Brunswick Park (1 mile north), North Finchley (1 mile west), Arnos Grove (1 mile east) and Whetstone (1 mile north-west). Further out, we also cover London (8 miles south), City of Westminster (7 miles south), Marylebone (7 miles south), Kensington (8 miles south), St Pancras (6 miles south) and Shoreditch (7 miles south-east).
Landmarks near Friern Barnet
Locally, jobs take us to homes and businesses close to Francis Skaryna Belarusian Library and Museum, Friary Park and Friern Barnet School and the streets around them. There’s a railway station in Friern Barnet itself: New Southgate station. Other landmarks nearby include Francis Skaryna Belarusian Library and Museum (1.4 miles west) and Grand Arcade (1 mile west). Not far away are Highgate Hill and Darland's Lake.
What we are called out for in Friern Barnet
Joints sealed without backing rod, or far too deep, rarely last. If the sealant sticks to the back as well as the sides, it can’t stretch and tears as soon as the joint widens.
It’s worth asking for a quote if you see:
- Failed sealant between panels on a façade
- Weathered mastic that no longer stretches
- Weeds or debris growing in open joints
- Movement joints with cracked, split or missing sealant
As a London address, Friern Barnet can be tricky for parking: let us know about parking bays, permits or a driveway.
What your quote should include
- How the surfaces are prepared before sealing
- When the joint can take water or movement
- Whether VAT is included
- What insurance they hold
How it works
There isn’t much for you to do on the day. Point us to the joints and we’ll get on with it. The job generally takes a few hours to a few days, depending on the length of joint and the access, including the tidy-up. In a London area like Friern Barnet, the main things to plan are parking and access: let us know about parking, the floor we’ll be working on and any lift or shared entrance.
- 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.
- Joint faces are cleaned back and primed if the sealant needs it.
- Backing rod sized to the joint goes in to set the depth.
- The exterior sealant is applied, tooled and checked along its length.
How to prepare
- Where the joints are inside, avoid wetting them before we arrive
- Tell us about any water getting in
- Mention any tricky access
Ask for a quote
There’s no standard price list, as no two jobs are quite the same. Instead, we give you a clear price for your job. To get started, phone 0345 464 0079 or send us an email.
Advice
Looking after it afterwards
A little care helps the new joints last. We recommend:
- Leave the joints unpainted unless we have said otherwise
- Have failed joints looked at early
- Fix overflowing gutters above sealed joints
- Tell anyone working on the walls about the movement joints
Give the sealant the cure time we tell you before anything rubs against it. Most exterior sealants skin fast but take longer to cure right through.
Gaps, plants or missing sealant in a joint are worth getting looked at. Earlier resealing means a smaller job and a better result.
Quotes for external mastic in Friern Barnet
For a quick quote, just ask. What matters most is:
- The number of rooms or windows
- Which sealant suits the joint
- The size of the job
- Any working-time requirements on site
We do not show prices on the website, because the cost depends so much on the job itself. Call for a quick quote.
Asking for a quote
There’s no need for technical detail. Just tell us:
- The type of property
- Pictures of the joints, sent by email
- Where the property is
- What’s wrong with the joints now
It all starts with a short chat. Tell us what’s wrong, where it is and how much there is. Whenever you are ready, call 0345 464 0079 or send us an email.
Your questions about external mastic in Friern Barnet
I let a flat near New Southgate station. Can you help?
Yes. We work for landlords and agents as well as homeowners. Just call 0345 464 0079 or send us an email with the address and what needs doing, and we will send you a clear quote.
Is parking an issue for external mastic in Friern Barnet?
In much of London, parking needs planning: a visitor permit or a nearby bay makes the day run more smoothly, so mention what’s available when you book.
How long does external mastic take?
A typical job takes anything from a few hours to several days, depending on the building. Your quote will say how long we expect yours to take.
Can you quote for more than one area?
Yes. More than one area can be quoted together.
Are you an approved applicator?
Yes. We’re approved under the ARBOMaster scheme.
Can I do it myself?
That depends on the joint. High-level, external movement and fire-rated joints are professional jobs.
What do you need from me for a quote?
Tell us what needs doing and where, with pictures by email if possible. If we need more, we will ask.
What does external mastic cost?
The cost depends on the size of the job, access and how much old sealant has to come out. Ask us for a quote and we’ll talk you through it.