Greater London · England
Window & door mastic in Harmondsworth, Greater London
Window mastic in Harmondsworth from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Cracked or shrunken mastic around the frame
- Black, perished sealant on frames
- Rushed sealant from a window installation
How we handle window mastic in Harmondsworth
Every window and door frame has a gap around it, and mastic is what closes it. When it cracks, hardens or pulls away, draughts and rain get in. The old mastic is removed and the joint resealed with a flexible exterior sealant. If you’re dealing with untidy mastic left by window fitters and mastic that has split away from the wall, we can put it right, on aluminium frames, uPVC windows and timber windows & doors alike.
Much of London’s older housing was built with timber sash windows, some still in place and some long since replaced. Either way, the mastic between frame and brickwork is what stops draughts and rain getting in.
Whatever the size of the job, it’s backed by our one-year guarantee.
- Location
- Harmondsworth (UB7, TW6)
- Wider area
- Greater London
- Cover
- 12 months on all our work
- Quotes
- Quoted before any work starts
- Phone
- 0345 464 0079
- Updated
- 26 October 2026
What affects the cost of window mastic
Call for a quick quote. What matters most is:
- Whether there’s mould to deal with
- The number and length of the joints
- Any working-time requirements on site
- How much old sealant there is and how hard it is to remove
Every job is a little different, so each one gets its own quote. Size, access and the product the joint needs all play a part, and we’ll explain the quote if you ask.
Asking for a quote
There’s no need for technical detail. Just tell us:
- Whether it’s a home or a business
- Whether it has been sealed before
- The problem you’ve noticed
- Where the property is
For window mastic in Harmondsworth, ring 0345 464 0079 or drop us an email. A short description of the job and where it is helps us quote, and you’ll get a clear quote before we start.
How to look after the new joints
How long the joints last depends on use and care. We suggest:
- Avoid blasting the frames with a pressure washer
- Do not paint over the silicone
- Look round the frames every year or so
- Air rooms to keep condensation down around windows
Wipe the frames with soapy water when you clean the windows, and keep solvents and harsh chemicals off the joint.
On timber windows, water behind the joint can lead to rot. Rotten timber needs a joiner, not a sealant, so it pays to reseal before that happens.
What we cannot put right
It helps to know what we can’t do too:
- Condensation trapped between the panes
- Damp problems in the wall away from the window
- Draughts through the window seals rather than the frame
Not sure which it is? You can call 0345 464 0079 or send us an email and we’ll tell you honestly.
What we seal
- uPVC windows
- Timber windows & doors
- Patio & French doors
- Composite doors
- Aluminium frames
- Window sills
How it works
We work through the job in order: protect, prepare, seal, tidy. Typically it takes anything from an hour or two to a full day, depending on how many frames there are and we leave things clean and tidy. In Harmondsworth, flats, stairs and shared entrances are part of the routine. Mention any building rules, key holders or managing agents when you book.
- We check how each frame can be reached safely.
- Old, cracked mastic is removed completely, along with any loose debris.
- The surfaces are cleaned and left dry, and primed where the sealant calls for it.
- Backing rod fills deep voids and the sealant goes in on top.
- We tool the joint so water runs off, then clear up.
Getting ready for the visit
- Tell us about any water getting in
- Keep pets and children clear of the area while we work
- Tell us about any previous sealing or DIY attempts
Ask for a quote
Getting a quote is simple: let us know the job and the location, and roughly how big it is. A few photos by email make the job easier to understand, and we will come back to you with a quote.
Advice
Questions from Harmondsworth
Is parking a problem for a job in Harmondsworth?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. That way the visit can be planned around it.
Do you work for landlords with property near Heathrow Terminal 5 Rail station?
Yes, we work for landlords and letting agents. Just call 0345 464 0079 or email us and tell us about the property, and we’ll give you a clear quote.
Do you work on first-floor windows?
Yes, if safe access is possible. For high or awkward windows, we’ll tell you what access is needed.
Are you fully insured?
Yes. We are fully insured, with over 20 years’ experience in sealant work.
Is there any odour?
It depends on the product. Some smell for a while, some hardly at all, and any smell fades as they cure.
Will it make a mess?
No. We protect the surfaces around the joints, and we clear up the old sealant and our materials before we leave.
Do you work in Harmondsworth?
We do. Our applicators work in Harmondsworth.
Do you hold any approvals?
Yes. We are an ARBOMaster approved applicator.
What we’re called out for in Harmondsworth
Joints that are too thin or too deep fail early. A thin smear across a wide gap has nothing to it, and a gap filled solid can’t flex. That’s what backing rod is for.
Look out for any of the following:
- Black, perished sealant on frames
- Leaking joints at the ends of sills
- A bead that doesn’t match the frame
- Gaps between the frame and the inside reveal
Schools such as Harmondsworth Primary School are buildings too, and larger buildings have plenty of frames, and the mastic around each one ages.
Before you book anyone
- Are they insured?
- What guarantee comes with the work
- What happens if the job turns out different
- Whether you can choose the colour
Landlord and commercial work in Harmondsworth
Water getting past a failed joint can damage the building, which is a bigger problem in a rented property. Keeping joints in good order is simple maintenance.
Businesses can book us for washrooms, kitchens, offices and more. For commercial premises, we can talk through working times when we quote.
DIY sealant or a professional job?
The biggest DIY mistake is sealing over old sealant. New silicone will not bond to old, so it lifts and traps water and mould underneath. Everything old must be removed first.
A careful DIYer can reseal a simple joint, like a short, easy-to-reach joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
Places near Harmondsworth
What else we do in Harmondsworth
Harmondsworth homes and the weather
Rainfall in the South East is lower than in much of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. In a converted house or block, who looks after the windows depends on the lease, so check that before you book.
In the older streets around Church of St Mary, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. Harmondsworth is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
Harmondsworth is about 1 mile south-west of West Drayton, in Greater London. For window mastic in and around Harmondsworth, please call 0345 464 0079 or drop us an email for a quick quote. We are based in Crawley and cover Greater London. Our Greater London coverage runs to 764 places, Harmondsworth among them. We also work in London, around 17 miles away.
We cover every part of the UB7 and TW6 postcode area for window mastic and the streets around it. That includes homes and businesses on Moor Lane, Hatch Lane and High Street and the roads around them. We also cover Longford (1 mile south-west), Sipson (1 mile north-east), Heathrow (2 miles south-east), Harlington (2 miles east) and Stanwell (2 miles south). We also work in nearby towns such as City of Westminster (14 miles east), Marylebone (14 miles east), Kensington (12 miles east), Hampstead (14 miles east), Ruislip (7 miles north-east) and Brompton (14 miles east).
Around Harmondsworth
Locally, jobs take us to homes and businesses close to Harlington Community School and The Five Bells Inn, among other places. The nearest railway station is Heathrow Terminal 5 Rail station, roughly 1 mile south of the centre. A little further out are British Airways Heritage Collection (3.5 miles north) and Harlington (1.4 miles east). Open spaces near Harmondsworth include Crane Meadows and Staines Reservoirs.