Greater London · England
Window Mastic in Harlesden
Window and door frames in Harlesden need attention? We cut out the old, prepare the joints and apply the right sealant.
- White mastic on grey or black frames
- Gaps left after new windows were fitted
- Mastic that has split away from the wall
Questions from Harlesden
Is parking an issue for window mastic in Harlesden?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. The visit is then planned around what’s available.
Is Harlesden in your area for window mastic?
Yes. Our work covers London and the South East, and Harlesden is part of that. Just ring 0345 464 0079 or send us an email with a few details of the job, and we’ll send you a clear quote.
I rent my home. Can I book you?
Yes, though it’s best to check with your landlord first. Landlords are often happy for the work to be arranged.
What should I tell you?
Tell us what needs doing and where. We’ll ask anything else we need to know.
Can I paint over the new sealant?
Not normally, if it’s silicone. We choose the product with your decorating in mind, so mention it when you book.
Can you do the inside joint as well?
Yes, we do both. Indoors, we seal between the frame and the plaster or reveal.
Where is Mr Mastic based?
We work from Crawley. Our applicators cover Harlesden.
Do you do commercial work?
Yes. We can plan bigger jobs in stages.
Window mastic in Harlesden, done properly
Mr Mastic’s applicators have more than 20 years’ experience with window and door sealants. We’re ARBOMaster approved and fully insured, and we give a 12-month guarantee on the work. We are often asked to deal with cracked or shrunken mastic around the frame and draughts coming in around windows and doors, across window sills, aluminium frames and uPVC windows.
Many London homes are flats, with windows high above the street. In a converted house or block, the lease usually says who is responsible for the windows, so it’s worth checking before booking.
The work is guaranteed for twelve months. If something isn’t right with it in that time, tell us and we’ll put it right.
- Place
- Harlesden (NW10, W3, NW26)
- Region
- Greater London
- Cover
- One year on every job
- Price
- A clear price before work begins
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Places near Harlesden
Also in Harlesden
DIY sealant or a professional job?
A DIY attempt doesn’t rule out a professional job. We cut it out and start again, so just mention it when you contact us.
What a professional job adds is preparation and the right product. We take joints back to clean, dry surfaces, and the sealant is matched to the joint and its conditions.
How to look after the new joints
Good habits help new joints last longer. A few tips:
- Don’t aim a pressure washer at the joints
- Clear any debris from frame drain holes
- Clean frames with a soft cloth and soapy water
- Avoid harsh chemicals near the mastic
Have a look at the joints once a year, ideally after winter. Small splits are simple to catch before they leak.
Water trapped behind a failed joint can start rot in timber frames and sills. Once wood has rotted, it needs repair before it can be sealed, so early resealing is worth it.
Harlesden homes and the weather
In a converted house or block, who looks after the windows depends on the lease, so check that before you book. With historic houses such as Pitzhanger Manor (about 3.1 miles south-west) nearby, there’s older building stock in the area around Harlesden as well as newer homes. Where a home is older, older frames set in brick or stone need a sealant that suits them, and sometimes that’s traditional sand mastic.
Rented homes near Willesden Junction station change hands often, and renewing tired window mastic between tenants heads off draught and damp complaints. Managing a site like John Keble CofE Primary School? Then larger buildings have plenty of frames, and the mastic around each one ages. As a London address, Harlesden can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
Harlesden is about 4 miles west of City of Westminster, in Greater London. Our applicators cover window mastic for homes and businesses in Harlesden and nearby, as part of our work across Greater London. Harlesden is one of 764 places in Greater London where we work for window mastic. For nearby work, see our London page, about 7 miles away.
Here we cover the NW10, W3 and NW26 postcode area for window mastic. That includes homes and businesses on Fry Road, Wood Road and Park Road and the roads around them. We also cover College Park (1 mile south-east), Old Oak Common (1 mile south), Church End (1 mile north), Stonebridge (1 mile north-west) and Willesden Green (1 mile north-east). We also work in nearby towns such as London (7 miles east), City of Westminster (4 miles east), Marylebone (5 miles east), Kensington (3 miles south-east), St Pancras (6 miles east) and Shoreditch (7 miles east).
Around Harlesden
Around Harlesden, our work takes us to homes and buildings near St Claudine's Catholic School for Girls, Royal Oak Inn and Roundwood Park, among other places. There’s a railway station in Harlesden itself: Willesden Junction station. Other landmarks nearby include Central Middlesex Hospital (1 mile west) and Brent Museum and Archives (1.1 miles north-east). The countryside around Harlesden includes Castlebar Hill and The Long Water.
Landlord and commercial work in Harlesden
From a single let to a portfolio, you get the same standard of work: the old material taken out, careful preparation and a 12-month guarantee.
We regularly work with letting and managing agents. Tell us the address, the job and how access works and we will give you a quote.
Leave it or put it right?
Failed mastic isn’t a reason to replace sound windows. If the frames and glass are in good order, resealing the joints is often all that’s needed. If we find failed glass units or worn seals, we’ll tell you. In a London flat, a failed joint rarely stays your problem alone: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
What it costs depends on the size of the job, how much old material has to come out and how easy the joints are to reach. We give a clear quote before work begins, so you know where you stand.
Why Harlesden clients choose us
- Approved under the ARBOMaster scheme
- Full insurance on every job
- Colour picked to suit the job
- Every job guaranteed for a year
How we quote for window mastic
You’ll get a clear quote before we start. It takes into account:
- Mould in or behind the old joints
- The number and length of the joints
- When we can work, for business premises
- Which sealant suits the joint
Rather than a set price list, we look at what your job involves: how many joints, what’s in them now and how we reach them. You will know the price before we begin.
Helping us quote
The more you tell us, the more accurate the quote. When you ask for a quote, tell us:
- Any previous sealing or DIY work
- Photos by email, if that is easy
- Whether it’s a home or a business
- The rough size of the job
For a quote, ring 0345 464 0079 or email us and tell us where the job is and what the problem looks like. We will give you a clear quote before any work starts.
The process
Every visit runs the same way: we check the joints, mask and protect the surrounding surfaces, do the work and clear up. It normally takes a morning for a couple of windows and a door. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. Mention any building rules, key holders or managing agents when you book.
- We check how each frame can be reached safely.
- All the failed sealant is cut away.
- Frame and wall are cleaned and must be dry before sealing.
- Deep voids are backed, then the sealant is gunned in.
- We tool the joint so water runs off, then clear up.
Preparing for the visit
- For indoor joints, keep the area dry beforehand if you can
- Move anything stored near the joints
- Mention if the joints have been sealed before
Ask for a quote
If you’re in Harlesden and need window mastic, call 0345 464 0079 or send us an email. A short description of the job and where it is helps us quote, and we will agree the price before any work begins.
Advice
Surface by surface
uPVC windows
uPVC expands and contracts noticeably with temperature, so the joint needs a low-modulus sealant that stays flexible. White is the usual colour, with brown, anthracite grey and black for coloured frames.
Window sills
Stone and concrete sills have their own joints, and the joint under the frame can let rain run behind. We seal those with a sealant suited to masonry.