Greater London · England
External Mastic in South Harrow
Sealing brickwork movement joints, render, cladding and façade joints for homeowners, landlords and businesses in South Harrow. Fully insured, ARBOMaster approved and guaranteed for a year.
- Weeds or debris growing in open joints
- Cracked joints where brick meets render or frames
- Rigid filler in a joint that should flex
South Harrow: your questions answered
Can you do external mastic in South Harrow?
Yes. Our work covers London and the South East, and South Harrow is part of that. You can phone 0345 464 0079 or send us an email and let us know what needs doing.
Can parking be tricky for a visit in South Harrow?
Parking in South Harrow, as in most of London, takes a little planning: a visitor permit or a nearby bay makes the day run more smoothly.
Is there a guarantee?
Yes: twelve months. If there’s a problem with our work in that time, tell us and we will put it right.
How long will you be here?
That depends on how much there is to do, but as a guide it takes anything from a few hours to several days, depending on the building. We will tell you when we quote.
Do I have to be there?
It depends on the job. Inside work needs someone to give us access, while outside work can sometimes be arranged differently.
I rent my home. Can I book you?
We are happy to deal with the tenant, landlord or agent. Get your landlord’s agreement first.
Will the new joint stand out?
We choose a sealant colour to suit the brick, stone or render. Exterior sealants come in a good range of colours.
Do you seal joints where cladding meets other materials?
Yes. Different materials move at different rates, so the joint between them must be flexible. We choose one that suits both surfaces.
How we handle external mastic in South Harrow
Ground-floor and low-level joints are straightforward to reach. Where joints are higher up, tell us about the building when you get in touch and we will confirm what’s needed to reach them safely. We work on joints between brick and frames, copings & trims and concrete & block, and the jobs we see most are moss and dirt in joints with no sealant left and cracked joints where brick meets render or frames.
Working on the outside of a London home means planning access: shared paths, upper floors and parking. In South Harrow, joints up high may need ladders or other access, which is worth talking through when you book.
All our work is covered by a one-year guarantee, wherever you are in Greater London.
- Where
- South Harrow (HA2, HA1, UB5)
- Wider area
- Greater London
- Guarantee
- A year, on every job
- Quote
- A clear quote up front
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
Surface by surface
Joints between dissimilar materials
Each side of the joint may need its own preparation. Both surfaces are cleaned and primed as the product requires.
Cladding and façade panels
If the façade has a specified sealant, that’s what we use. Send us any details you have about the façade.
Why it’s worth doing now in South Harrow
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. 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 South Harrow.
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 will explain the quote if you ask.
Why us?
- 4.9 on Google from 180+ five-star reviews
- We are fully insured
- Old sealant always removed completely
- A sealant colour to suit the surroundings
What we do, step by step
A visit follows a simple pattern: we look at the joints together, protect the area around them, carry out the job and tidy away. It generally takes anything from a few hours to several days, depending on the building. In South Harrow, 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 start by checking each joint, agreeing the ones to redo and how we’ll reach them.
- The old mastic and anything lodged in the joint is removed.
- The joint faces are cleaned and primed where the sealant needs it.
- Closed-cell backing rod is fitted to set the depth and stop three-sided bonding.
- A flexible exterior sealant is applied and tooled in a colour to suit the wall.
How to prepare
- Let us know if you’ve seen damp or leaks
- Mention any parking rules near the property
- Plan for the work area to be out of bounds to pets and children
Get a quote
To get a quote, phone 0345 464 0079 or send us an email with the location and a short description of the problem. We will send you a clear quote before any work starts.
Read more
DIY sealant or a professional job?
The biggest DIY mistake is sealing over old sealant. Silicone doesn’t stick to old silicone, so it peels away and traps moisture behind it. Everything old must be removed first.
If you are set on DIY, put the effort into preparation: take out all the old sealant, make sure the joint is clean and dry, and give it the full cure time. If it doesn’t work out, we can still put it right.
Do you need external mastic in South Harrow?
Sometimes a movement joint was filled with mortar or a rigid filler, often by someone who didn’t know what it was for. With the joint locked solid, the movement turns into cracks elsewhere in the wall.
It’s worth asking for a quote if you see:
- Panel joints letting water in
- Hard, crazed mastic that has stopped moving
- Failed seals between different materials
- Joints where the bead has come unstuck
Homes close to Parish Church of St Paul include some older properties, and the joints between older walls, newer extensions and the roofline need a sealant that can move.
What to look for in a quote
- What preparation is included
- How hidden problems are handled
- What the quote includes, VAT included or not
- How much experience the applicator has
When it isn’t the sealant
New sealant cannot fix everything, and we will tell you before work begins. It will not solve:
- Cracked brickwork or render that needs a builder or plasterer
- Failed render or damaged cladding panels
- Adding movement joints to masonry that has none
If in doubt, phone 0345 464 0079 or drop us an email and we’ll say what we think.
Surfaces we seal
- Render & cladding joints
- Concrete & block
- Joints between brick and frames
- Copings & trims
- Façade panels
- Brickwork movement joints
External mastic in South Harrow: local notes
With historic houses such as Northolt Manor (about 1.5 miles south-west) nearby, there’s older building stock in the area around South Harrow as well as newer homes. Where a home is older, older brick and stone need a sealant that suits them, at the right joint depth. The South East is one of the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
If you look after a building such as The Welldon Park Academy, larger buildings have long runs of movement joint that eventually need resealing. As a London address, South Harrow can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
South Harrow is about 1 mile south of Harrow, in Greater London. From the centre of South Harrow to the outskirts, we cover external mastic for every kind of property. South Harrow is one of 764 towns and villages in Greater London we cover for external mastic. Our London page covers work nearby (12 miles or so).
Work in HA2, HA1 and UB5 is quoted and booked the same way as anywhere else. Local streets include Park Lane, Grange Road and Dudley Road, all of which we cover. If you’re just outside South Harrow, we cover Roxeth (1 mile north-east), Harrow (1 mile north), Harrow on the Hill (1 mile east), Rayners Lane (1 mile north-west) and Northolt (1 mile south-west). We also work in nearby towns such as London (12 miles east), City of Westminster (9 miles east), Marylebone (9 miles east), Kensington (8 miles south-east), St Pancras (10 miles east) and Shoreditch (12 miles east).
Local landmarks in South Harrow
In South Harrow, that means homes and buildings near Orley Farm School, Northwick Park and St Dominic's Sixth Form College and the streets around them. South Harrow’s nearest station is Northolt Park station, roughly 0.5 miles south-west of the centre. Nearby you’ll also find St. George's Shopping Centre (1.3 miles north-east) and Kodak Museum (2 miles north). Green spaces nearby include Middle Lake and Northala Fields.
For landlords and businesses
A neglected joint can let water reach the structure, which is a bigger problem in a rented property. Keeping joints in good order is simple maintenance.
We work for landlords and letting agents as well as householders. Resealing between tenancies is a simple way to keep a property in good order before the next move-in.