Greater London · England
High Barnet External Mastic
We cover High Barnet for sealing brickwork movement joints, render, cladding and façade joints. Old material cut out, joints cleaned and sealed neatly and every job guaranteed for a year.
- Moss and dirt in joints with no sealant left
- Damp patches traced to an open external joint
- Weathered mastic that no longer stretches
External mastic in High Barnet: local notes
Historic houses like Wyllyotts Manor (about 2.9 miles north) are a reminder that the area around High Barnet 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. In terraces and conversions, gutters and walls are often shared with the neighbours, so it’s worth agreeing who is responsible before work starts.
Schools such as Foulds School are buildings too, and movement joints, cladding joints and gutters on larger buildings need the same care as a house’s. As a London address, High Barnet can be tricky for parking: let us know about parking bays, permits or a driveway.
High Barnet is about 1 mile north-west of Barnet, in Greater London. Across the EN5 area, our applicators can take on external mastic. We cover 764 towns and villages across Greater London. Our London page covers work nearby, about 12 miles away.
We work across EN5 for external mastic and the streets around it. External mastic is available to properties on Byng Road, Park Road and Kings Road and the roads around them. High Barnet is on the A1081, so it’s easy for us to get to. Neighbouring places we cover for external mastic include Hadley (1 mile east), Arkley (1 mile south-west), Kitts End (1 mile north), Totteridge (1 mile south) and Rowley Green (2 miles west). Within a short drive, we also cover London (12 miles south-east), City of Westminster (10 miles south), Marylebone (10 miles south), Kensington (11 miles south), St Pancras (10 miles south-east) and Shoreditch (11 miles south-east).
Near you in High Barnet
Typical jobs here are in homes near Susi Earnshaw Theatre School, The White Lion pub and Queen Elizabeth's School. The nearest railway station is Hadley Wood station, about 1.6 miles north-east of the centre. Nearby you will also find Spires Shopping Centre (within half a mile east) and Barnet General Hospital (0.5 miles south-west). For a walk, there’s Barnet Countryside Centre and Darland's Lake.
External mastic in High Barnet
Short cuts in external joints show up within a season or two. Overfilled joints, missing backing rod and sealant laid over old sealant all tend to fail early. We strip the joint back and start again. We work on copings & trims, concrete & block and render & cladding joints, and the jobs we see most are joints where the bead has come unstuck and old sealant gone brittle and cracked.
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, and both kinds of building are found across London.
You are covered for a year from the day we finish. If there’s a problem with it, please call 0345 464 0079 or send us an email.
- Place
- High Barnet (EN5)
- Wider area
- Greater London
- Guarantee
- A year, on every job
- Quote
- A clear quote up front
- Call
- 0345 464 0079
- Updated
- 26 October 2026
Towns and villages near High Barnet
Other services in High Barnet
What affects the quote in High Barnet
You’ll get a clear quote before any work starts. It’s based on:
- How easy the joints are to reach
- Whether there’s mould to deal with
- The number and length of the joints
- Working hours on commercial sites
A failed joint rarely gets cheaper to fix by waiting, because water and mould keep working on it. If you are not sure whether it needs doing, phone 0345 464 0079 or send us an email and we’ll give you an honest view and a quote.
What we need to know
To make quoting easier, let us know:
- The type of property
- Whether it has been sealed before
- What the problem is, such as mould, gaps, leaks or cracking
- Any access issues, like height or stairs
Call for a quick quote, or email us if that’s easier. Describe what needs sealing and we’ll explain what’s involved.
Why it’s worth doing now in High Barnet
Sealing over the top of old mastic doesn’t hold for long. New sealant doesn’t bond well to old, weathered sealant, so the old joint is cut out fully first. Converted houses in London often have a bathroom above someone else’s living room, so a small leak from tired sealant can mean a neighbour’s ceiling and a lot of disruption. Dealing with it early is far simpler for homes in High Barnet.
The cost reflects the work involved, not guesswork. That’s why we ask about the job first.
Why choose Mr Mastic in High Barnet
- Rated 4.9 stars on Google
- 20+ years of sealant experience
- We are fully insured
- You choose the colour before work begins
Landlords, agents and businesses in High Barnet
Letting agents often deal with us directly. Send the address, what’s needed and the access arrangements.
Failed sealant is one of the commonest items on a check-out report, and it’s easy to sort out between tenants. Several properties can go on one quote.
DIY versus a professional finish
Too much sealant is as bad as too little. A thick, smeared bead looks untidy and does not move well, and getting the depth right matters as much as the look.
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is matched to the joint and its conditions.
How it works
There’s no need to move everything out before we come, only the area right around the joints. Everything nearby is protected, and the work takes anything from a few hours to several days, depending on the building for a typical job. In High Barnet, 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 inspect the joints and agree which need resealing and how they’ll be reached.
- We cut out the failed sealant and rake out any dirt or growth.
- Both sides are cleaned back to sound material and primed if needed.
- Closed-cell backing rod is fitted to set the depth and stop three-sided bonding.
- We gun in a flexible exterior sealant in a colour that suits the wall and tool it neatly.
Preparing for the visit
- Mention any tricky access
- Clear the area around the work
- Plan for the work area to be out of bounds to pets and children
Ask for a quote
If you’re in High Barnet and need external mastic, ring 0345 464 0079 or email us. A short description of the job and where it is helps us quote, and we will agree the price before any work begins.
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Signs you need external mastic in High Barnet
UV, rain and frost all age exterior sealant. In time it goes hard, crazes on the surface and stops stretching, so the joint eventually tears or comes away from one side.
Keep an eye out for these signs:
- Joints where the bead has come unstuck
- Rain getting behind render or cladding at a joint
- Weathered mastic that no longer stretches
- Weeds or debris growing in open joints
If you live in an older home near Christ Church, the joints between older walls, newer extensions and the roofline need a sealant that can move.
Before you book anyone
- What the cure time is
- Which colour the sealant will be
- Whether they seal over old material or remove it
- Whether the sealant suits the joint
High Barnet questions
Can parking be tricky for a visit in High Barnet?
In much of London, parking needs planning: a visitor permit or a bay close to the door helps a lot.
I let a flat near Hadley Wood station. Can you help?
Yes, rental work is part of what we do. Just ring 0345 464 0079 or send us an email and tell us about the property, and we will give you a clear price.
Do you have insurance?
Yes. Mr Mastic is fully insured.
Do you work in High Barnet?
Yes. We are based in Crawley and work across South East England, London and Scotland.
What is backing rod for?
That’s backing rod, a closed-cell foam. It keeps the sealant at the right depth and bonded to the sides only so it can flex with the joint.
Will the new joint stand out?
The sealant colour is picked to suit the wall. Exterior sealants come in a good range of colours.
Do I need to be at home?
For indoor joints, yes, someone needs to let us in. Once we have agreed the job, you do not need to watch us work.
What sealant do you use?
Each joint gets the product that suits it. Where it moves, gets wet or faces the weather makes a difference, and we’ll explain our choice.
Different surfaces, different methods
Cladding and façade panels
Where a cladding system has its own specified sealant, we follow it or an approved alternative. Send us any details you have about the façade.
Brickwork movement joints
Brick walls have vertical movement joints to absorb expansion. They’re resealed over backing rod with a low-modulus sealant coloured to suit the wall.