Greater London · England
External Mastic in Northwick Park
External mastic in Northwick Park from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Old sealant gone brittle and cracked
- Movement joints with cracked, split or missing sealant
- Weeds or debris growing in open joints
Honest limits
We’d rather tell you now than do work that won’t last, so here’s what sealant cannot put right:
- Movement that is more than a sealant joint can take
- Cracks in the bricks or render themselves, away from the joints
- Rising or penetrating damp from elsewhere in the wall
Not sure which it is? You can call 0345 464 0079 or drop us an email and we’ll tell you honestly.
Surfaces we seal
- Concrete & block
- Façade panels
- Joints between brick and frames
- Render & cladding joints
- Copings & trims
- Brickwork movement joints
External mastic for homes and businesses in Northwick Park
On houses, flats and commercial buildings across Northwick Park, we reseal joints in brickwork, render, cladding and façade panels. The preparation is the same whatever the wall: clean joint faces and the right depth. We work on joints between brick and frames, façade panels and brickwork movement joints, and the jobs we see most are rigid filler in a joint that should flex 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.
A one-year guarantee comes as standard, so you are covered after we’ve gone.
- Place
- Northwick Park (HA1, HA3, HA0)
- Region
- Greater London
- Cover
- One year on every job
- Price
- A clear price before we start
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
FAQs for Northwick Park
Can you do external mastic in Northwick Park?
Yes, Northwick Park is within the area we cover. We work across London and the South East. You can call 0345 464 0079 or drop us an email and tell us what needs doing.
Can you help a landlord with a rental near Kenton station?
Yes. We work for landlords and agents as well as homeowners. You can ring 0345 464 0079 or send us an email with the details for a clear quote.
Are you an approved applicator?
Yes. We hold ARBOMaster approved applicator status and we are fully insured too.
Are you insured?
Yes. We are fully insured.
Can a movement joint be filled with mortar?
No, not where the gap is a movement joint. Pointing it stops it working. A flexible sealant is the right fill.
Can you seal joints between render and window frames?
Yes. We cut out the old sealant, prepare both faces and reseal with a flexible exterior product. The colour is chosen to suit.
When will the joints need doing again?
That varies with the weather the wall faces, how much it moves and the sealant used. Treat it as a maintenance item and look at it yearly and renew it when it starts to fail.
What do you put in the joint?
It depends on the joint: anti-fungal sanitary silicone in wet areas, and other sealants where joints move or face the weather. We use products from Arbo and Everbuild.
Places near Northwick Park
More services for Northwick Park
How the job changes by surface
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.
Joints between dissimilar materials
Each side of the joint may need its own preparation. Both surfaces are cleaned and primed as the product requires.
The process
On the day, we start by going over the job with you. We protect the surfaces around the joints before any work begins. The work normally takes a few hours to a few days, depending on the length of joint and the access. For a job in Northwick Park, parking and access are the things to plan: tell us about permits, visitor bays or off-street space, which floor we are working on and whether there’s a lift.
- 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.
Preparing for the visit
- Let us know about earlier repairs to the joints
- Clear the area around the work
- Mention any tricky access
Ask for a quote
It all starts with a short chat. Tell us what’s wrong, where it is and how much there is, and we will talk you through what we’d do. Whenever you are ready, ring 0345 464 0079 or drop us an email.
Advice
Signs you need external mastic in Northwick Park
If plants are growing out of a joint, the sealant has usually failed or was never there. Dirt and roots then trap moisture in the joint.
The problems people normally mention when they call are:
- Joints where the bead has come unstuck
- Cracked joints where brick meets render or frames
- Old sealant gone brittle and cracked
- Weeds or debris growing in open joints
Managing a site like Harrow High School? Then its movement joints, gutters and trims need looking after like any other building’s.
Questions to ask before you book
- Whether all the old sealant comes out first
- What the cure time is
- How hidden problems are handled
- How the joint is cleaned and prepared
Outside joints around Northwick Park
In terraces and conversions, gutters and walls are often shared with the neighbours, so it’s worth agreeing who is responsible before work starts. Compared with the north and west, the South East gets less rain, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
For an older house near a landmark such as Saint Cuthberts Church, an extension built onto an older house moves differently, and the joint between them takes the strain. As a London address, Northwick Park can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
Northwick Park is about 1 mile south-west of Kenton, in Greater London. For external mastic in and around Northwick Park, please call 0345 464 0079 or email us for a quick quote. We cover Greater London from our Crawley base. Northwick Park is one of 764 places in Greater London we cover for external mastic. For nearby work, see our London page, about 11 miles away.
All of HA1, HA3 and HA0 is within our area for external mastic, from the main roads to the quietest streets. That includes homes and businesses on Lyon Road, Manor Road and Gayton Road and the roads around them. Main roads around Northwick Park include the A404. Other places close to Northwick Park include Greenhill (1 mile north-west), Harrow on the Hill (1 mile south-west), South Kenton (1 mile east), Kenton (1 mile north-east) and Harrow (1 mile west). Larger places within reach include London (11 miles south-east), City of Westminster (9 miles south-east), Marylebone (9 miles south-east), Kensington (7 miles south-east), St Pancras (10 miles east) and Shoreditch (11 miles east).
Landmarks near Northwick Park
In Northwick Park, that means homes and buildings near St Anselm's Catholic Primary School, Orley Farm School and Preston Park. The nearest railway station is Kenton station, roughly 0.6 miles north-east. Other landmarks nearby include Northwick Park Hospital (under half a mile north-east) and Kodak Museum (1.5 miles north-west). For a walk, there’s Masons Field and Northala Fields.
Why it’s worth doing now in Northwick Park
Running new sealant over the old bead rarely lasts. The new layer can’t bond properly to old, weathered material, so we always take the old sealant out. In a London flat, a failed joint rarely stays your problem alone: water can reach the neighbours below, and gaps in fire-rated joints affect the whole building.
What you pay reflects the work, not guesswork. That’s why we ask about the job first.
Why choose Mr Mastic in Northwick Park
- Anti-fungal silicone where joints get wet
- We agree the colour with you first
- Trusted Arbo and Everbuild sealants
- Neat joints and a tidy finish
Read how sealant jobs are priced or our reviews.
DIY versus a professional finish
Some jobs are best left to a professional: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.
What a professional job adds is preparation and the right product. Joints are cleaned back to sound surfaces and dried, and the sealant is chosen for how the joint moves and where it is, then guaranteed for a year.
Work for landlords, hotels and businesses
Failed sealant is one of the commonest items on a check-out report, and it’s quick to put right between tenancies. We can quote for more than one property at once.
Hotels need rooms back in use, so the work can be planned room by room. Hotel work is part of what we do, alongside homes and businesses.