Greater London · England
External Mastic in Hendon
Sealing brickwork movement joints, render, cladding and façade joints for Hendon, backed by a one-year guarantee. Call for a quick quote.
- Rain getting behind render or cladding at a joint
- Joints pointed up with cement by mistake
- Failed seals between different materials
How we handle external mastic in Hendon
Movement joints let brickwork, render and cladding expand and shrink without cracking. 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. If you’re dealing with damp patches traced to an open external joint and weathered mastic that no longer stretches, we can put it right, whatever the surface.
Working on the outside of a London home means planning access: shared paths, upper floors and parking. For a home in Hendon, tell us how high the joints are and how to reach the back of the building.
A 12-month guarantee comes as standard, so you’re covered after we’ve gone.
- Where
- Hendon (NW4, NW9, NW2, NW11)
- Region
- Greater London
- Guarantee
- One year on every job
- Quotes
- A clear quote up front
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
FAQs for Hendon
Is parking a problem for a job in Hendon?
In much of London, parking needs planning: a visitor permit or a bay close to the door helps a lot.
Do you work for landlords with property near Hendon station?
Yes, we work for letting agents and landlords. Just phone 0345 464 0079 or drop us an email and tell us about the property, and we will give you a clear price.
What colours does the sealant come in?
Exterior sealants are made in a range of colours, from greys and browns to whites and stone shades. We choose the closest to your brick or render so it doesn’t stand out.
Can you quote for more than one area?
Yes. Tell us about everything you’d like done.
Are you insured?
Yes. Mr Mastic is fully insured.
Can a movement joint be filled with mortar?
No, not if it’s a movement joint. Pointing it stops it working, and the wall may crack nearby. A flexible sealant is the right fill.
How long does external mastic last?
That depends on the wall, the weather and the movement. Signs to watch for are cracking, hardening and gaps at the edges.
Can you reach joints on upper floors?
It depends on the building. Tell us the height, the number of joints and what’s below them.
What happens on the day
Our applicators work methodically: protect, prepare, seal, tidy. For most jobs that takes a few hours for a handful of joints, longer for a whole elevation and we leave things clean and tidy. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in Hendon. It helps if you can point us to a visitor permit or a bay close to the door.
- First we look over the joints with you, agree which to renew and talk through access.
- Old sealant and any debris are cut and raked out.
- The joint faces are cleaned and primed where the sealant needs it.
- We push in closed-cell backing rod so the sealant is the right depth and bonds to the sides only.
- We gun in a flexible exterior sealant in a colour that suits the wall and tool it neatly.
Preparing for the visit
- Mention any sign-in or site rules at work premises
- Let us know about earlier repairs to the joints
- Move anything stored near the joints
Getting a quote
Getting a quote is simple: let us know what needs doing and where. Photos by email help us understand the job.
Read more
Surface by surface
Joints between dissimilar materials
Where a frame or panel meets masonry, water often finds a way in. We cut out the old sealant and reseal with a product suited to both surfaces.
Render joints
Cracks along render joints let water in behind the coat. Resealing the joints early keeps water out and helps it last.
Nearby places to Hendon
Also in Hendon
When something else is needed
We will not take on work that won’t last, so here’s what sealant cannot put right:
- Movement that is more than a sealant joint can take
- Failed render or damaged cladding panels
- Cracks in the bricks or render themselves, away from the joints
If you’re not sure, just call 0345 464 0079 or send us an email and we will give you a straight answer before booking.
Joints and surfaces we work on
- Concrete & block
- Façade panels
- Brickwork movement joints
- Joints between brick and frames
- Render & cladding joints
- Copings & trims
How we quote for external mastic
Your quote is based on your job. We look at:
- Working hours on commercial sites
- How many areas need sealing
- Whether old sealant or filler has to be cut out
- The size of the job
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 play a part, and we’ll explain the quote if you ask.
What to tell us for a quote
What to tell us when you ask for a quote:
- Roughly how big the job is
- Access, such as stairs, a lift or height
- The problem you’ve noticed
- Photos by email, if that’s easy
If you’re in Hendon and need external mastic, ring 0345 464 0079 or send us an email. A short description of the job and where it is helps us quote, and you’ll get a clear quote before work begins.
Aftercare tips
A little care helps the new joints last. We recommend:
- Keep water from gutters off the wall
- Leave the joints unpainted unless we have said otherwise
- Do not let climbing plants root in the sealant
- Never let anyone fill a movement joint with mortar
Do not paint over the new sealant unless we have said the product is paintable. Paint can crack on a flexible joint.
An open movement joint lets rain into the wall every time it pours. Over time it can mean damp inside, stained render or frost-damaged brick which cost more to put right than the joint.
Common problems we fix in Hendon
Weeds, moss and debris in a joint are a sign the sealant has gone. Dirt and roots then trap moisture in the joint and make things worse.
Keep an eye out for these signs:
- Leaking joints around cladding and façade panels
- Hard, crazed mastic that has stopped moving
- Cracked joints where brick meets render or frames
- Water getting into walls through failed joints
As a London address, Hendon can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
Questions to ask before booking
- The length of the guarantee
- Whether you can choose the colour
- What happens if the job turns out different
- What the quote includes, VAT included or not
What happens if it’s left?
Done well, a resealed joint is a neat, straight line that suits the wall. A rushed bead with no backing looks untidy and doesn’t last, so it pays to do it properly once. In a flat in Hendon, failed sealant seldom stays inside your own four walls: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
Rather than a set price list, we price the job in front of us: the amount of work, the old material and the access. The price is agreed before we begin.
Why us?
- Fully insured
- Colour agreed with you before work begins
- We leave the area clean and tidy
- White, clear, grey or coloured to suit, where the product allows
Take a look at our cost guide or our reviews.
Hendon buildings and the weather
London terraces and converted houses often share gutters, downpipes and walls, so it’s worth agreeing who is responsible before work starts. Rainfall in the South East is lower than in much of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
If you let a flat or house near Hendon station, failed wall and movement joints let damp in, so they’re worth checking between tenancies. If you look after a building such as Hendon School, its movement joints, gutters and trims need looking after like any other building’s.
Hendon is about 3 miles north-west of Hampstead, in Greater London. Wherever you are in the NW4 postcode area, our applicators can take on external mastic. Across Greater London, we cover 764 places, Hendon among them. Our London page covers work nearby.
All of NW4, NW9, NW2 and NW11 is within our area for external mastic, from the main roads to the quietest streets. External mastic is available to properties on Church Road, Station Road and Sydney Grove. With the A5 and A41 close by, Hendon is simple for us to get to. Other places close to Hendon include The Burroughs (1 mile north-west), Brent Cross (1 mile south), Staples Corner (1 mile south), West Hendon (1 mile west) and The Hyde (1 mile west). Further out, we also cover London (8 miles south-east), City of Westminster (6 miles south-east), Marylebone (6 miles south-east), Kensington (6 miles south), St Pancras (6 miles south-east) and Shoreditch (7 miles south-east).
Local landmarks in Hendon
We work in homes and buildings around Hasmonean Primary School, The White Bear pub and Kisharon College, among other places. Hendon’s nearest station is Hendon station, roughly 0.7 miles south-west of the centre. Other landmarks nearby include Brent Cross Shopping Centre (0.5 miles south) and St Andrew's Hospital (1.6 miles south). Green spaces nearby include Darland's Lake and Parliament Hill.