Greater London · England
Barnet External Mastic
Movement joints in Barnet need attention? We cut out the old, prepare the joints and apply the right sealant, and the work is guaranteed for a year.
- Joints pointed up with cement by mistake
- Movement joints with cracked, split or missing sealant
- Damp patches traced to an open external joint
External mastic in Barnet, done properly
Low-level joints can usually be done from the ground. Where joints are higher up, tell us about the building when you get in touch and we will confirm what access is needed. We work on façade panels, render & cladding joints and joints between brick and frames, and people most often call us about sealant pulling away from one side of the joint and joints with sealant missing in places.
Working on the outside of a London home means planning access: shared paths, upper floors and parking. In Barnet, joints up high may need ladders or other access, which is worth talking through when you book.
We guarantee the work for a year. If something isn’t right with it in that time, tell us and we’ll put it right.
- Place
- Barnet (EN5, EN4, N20, N11)
- Region
- Greater London
- Guarantee
- A year, on every job
- Quotes
- A clear quote up front
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
What happens on the day
All our tools and materials come with us in the van. Once we’ve agreed what’s being done, we protect the area and start. It normally takes a few hours for a handful of joints, longer for a whole elevation. In a London area like Barnet, 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 look at every joint and agree a colour to suit the wall.
- Failed sealant is removed back to clean, sound faces.
- Backing rod goes in so the sealant can stretch between the two faces.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
Before we arrive
- Where the joints are inside, avoid wetting them before we arrive
- Let us know about stairs, lifts or work at height
- Mention if the joints have been sealed before
Get a quote
We quote each job on its own, so start by telling us what you need. Simply ring 0345 464 0079 or drop us an email and describe the job and send pictures if you have them.
Related advice
Nearby places to Barnet
Other services in Barnet
What we can’t put right
Some problems need a builder, plumber or other trade rather than us:
- Cutting new joints into brickwork, which is building work rather than sealant work
- Cracks in the bricks or render themselves, away from the joints
- Structural movement, which needs a surveyor or engineer
Not sure which it is? You can phone 0345 464 0079 or email us and we’ll tell you honestly before booking.
Surfaces we seal
- Copings & trims
- Render & cladding joints
- Joints between brick and frames
- Brickwork movement joints
- Façade panels
- Concrete & block
What we are called out for in Barnet
UV, rain and frost all age exterior sealant. In time it goes hard, crazes on the surface and stops stretching, so the next time the wall moves, it splits or pulls away.
Most people get in touch when they notice something like this:
- Joints with sealant missing in places
- Moss and dirt in joints with no sealant left
- Rain getting behind render or cladding at a joint
- Gaps where render, brick and frames meet
Barnet is in London, so parking needs planning: let us know about parking bays, permits or a driveway.
Questions to ask before you book
- How hidden problems are handled
- Whether the sealant suits the joint
- What insurance they hold
- How the joint is cleaned and prepared
Leave it or put it right?
Sealing over the top of old mastic does not hold for long. New sealant does not bond well to old, weathered sealant, so we always take the old sealant out. In a flat in Barnet, 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.
What you pay reflects the work, not a rough estimate. That’s why we ask about the job first.
What you get with us
- Any old sealant cut out fully, not covered over
- ARBOMaster approved applicator
- Colour picked to suit the job
- Anti-fungal sanitary silicone in wet areas
Take a look at what affects the cost or what customers say.
Barnet buildings and the weather
Rainfall in the South East is lower than in much of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. London terraces and converted houses often share gutters, downpipes and walls, so it’s worth agreeing who is responsible before work starts.
For site and facilities teams at buildings such as Grasvenor Avenue Infant School, movement joints, cladding joints and gutters on larger buildings need the same care as a house’s. Letting a property close to New Barnet station? Then outside joints that have cracked can let damp into a rental, so check them between lets.
Barnet is about 9 miles east of Watford, in Greater London. Jobs in Barnet get the same care as everywhere else we work: old sealant removed completely, careful preparation and a 12-month guarantee. We cover 764 towns and villages across Greater London, from the larger towns to small villages. London is on our list too, about 11 miles from Barnet.
Here we cover the EN5, EN4, N20 and N11 postcode area for external mastic. If you need external mastic at a property on Station Road, High Street and Sambroke Square or a nearby road, our applicators can take on the job. Main roads around Barnet include the B193 and A1081. Other places close to Barnet include Underhill (1 mile west), New Barnet (1 mile east), Monken Hadley (1 mile north-west), Hadley Wood (1 mile north-east) and Cockfosters (1 mile east). Larger places within reach include London (11 miles south), City of Westminster (9 miles south), Marylebone (9 miles south), Kensington (10 miles south), St Pancras (9 miles south) and Shoreditch (10 miles south-east).
What’s near Barnet
Locally, jobs take us to homes and businesses close to Queen Elizabeth's Girls' School, The Railway Tavern and Highlands Gardens, among other places. The nearest railway station is New Barnet station, about 0.6 miles east. Well-known places in the area include Barnet General Hospital (1.2 miles west) and Francis Skaryna Belarusian Library and Museum (2.1 miles south). For a walk, there’s Darland's Lake and Greenhill Gardens.
Keeping the joints in good condition
How long the joints last depends on use and care. Here’s what we suggest:
- Ask before painting over external sealant
- Fix overflowing gutters above sealed joints
- Act on the first splits you see
- Keep movement joints as flexible joints, not mortar
Keep the joints clear of soil, plants and climbing growth. Anything that holds water against the joint wears it out sooner.
Leave a failed movement joint and water keeps getting into the wall. Over time it can mean damp inside, stained render or frost-damaged brick, all bigger jobs than a reseal.
Barnet questions
Do you work for landlords with property near New Barnet station?
Yes, landlords and agents are among the people we work for, and several properties can go on one quote. Just call 0345 464 0079 or send us an email with the address and what needs doing, and we will give you a clear price.
Is Barnet in your area for external mastic?
Yes. Our work covers London and the South East, and Barnet is part of that. You can call 0345 464 0079 or drop us an email and tell us what needs doing, and we will give you a clear quote.
When is the sealant fully cured?
That depends on the sealant used, so follow the cure time we give you when we finish.
Is the work guaranteed?
Yes. All our work carries our 12-month guarantee.
Will you leave a mess?
No. We work neatly, protect the area around the joints and tidy up afterwards.
How do I get a quote for external mastic in Barnet?
Size, access and the old material all affect the cost. Ask us for a quote.
Do the sealants smell?
It depends on the product. Some products have a noticeable smell, others very little.
Can you match the colour of my brickwork?
We choose a sealant colour to suit the brick, stone or render. Exterior sealants come in a good range of colours.
For landlords and businesses
We also work for businesses, from offices to washrooms and kitchens. For commercial premises, we can talk through working times when we quote.
Housing providers, facilities teams and property managers book us too. We can quote a run of properties together.
DIY sealant or a professional job?
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.
If you do try it yourself, take your time over the 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.