Greater London · England
Window Mastic in Harrow Weald
Mastic around window and door frames, sills and patio doors in Harrow Weald, with a one-year guarantee on every job. Ask us for a quote.
- Gaps between the frame and the inside reveal
- Rain getting in at the frame or under the sill
- Hard, cracked sealant around windows
Window mastic for homes and businesses in Harrow Weald
Over two decades of sealing frames has taught us which products suit which walls. We are ARBOMaster approved and fully insured, and every job is covered by a 12-month guarantee. We’re often asked to deal with water coming in at the bottom corners of a door and cracked internal joints between frame and plaster, on timber windows & doors, patio & French doors and composite doors.
Much of London’s older housing was built with timber sash windows, some still in place and some long since replaced. Whatever is in the opening now, the joint between frame and wall is what keeps the weather out, in Harrow Weald as anywhere.
A one-year guarantee comes with the work, just as it does everywhere we cover.
- Location
- Harrow Weald (HA3, HA7, HA1)
- Region
- Greater London
- Cover
- 12 months on all our work
- Quote
- A clear price before any work starts
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
What affects the cost of window mastic
There’s no set price list, because no two jobs are the same. The quote depends on:
- The old material and how stubborn it is
- How many areas need sealing
- Any working-time requirements on site
- How easy the joints are to reach
Combining jobs into one visit usually makes better use of the time than several visits. We will send you a clear quote for the lot.
What to tell us for a quote
When you contact us, these details help:
- Photos by email, if that’s easy
- What the problem is, such as mould, gaps, leaks or cracking
- Whether it has been sealed before
- If it’s domestic, commercial or a hotel
If you are in Harrow Weald and need window mastic, call 0345 464 0079 or email us. A short description of the job and where it is helps us quote, and you’ll get a clear quote before work begins.
Surface by surface
Window sills
Stone and concrete sills have their own joints, and the joint under the frame can let rain run behind. Those are sealed with a product suited to stone or concrete.
Timber windows & doors
On period timber windows, traditional sand mastic is sometimes the better choice. We will tell you which suits your home.
What happens on the day
You don’t need to clear the whole room or building before we come, just the space around the work. We protect the rest, and the work takes a few hours for a few frames, or a day or more for a whole house for a typical job. In a London area like Harrow Weald, the main things to plan are parking and access: let us know about parking, the floor we will be working on and any lift or shared entrance.
- We start by checking each window and door with you.
- The old mastic is cut out and the surfaces cleaned back.
- Where gaps are deep, backing rod goes in first.
- We apply a weatherproof sealant to match the frame and tool it neatly.
- Finally we tidy up and check each joint.
Preparing for the visit
- Mention any parking rules near the property
- Try not to wet indoor joints just before the visit
- Clear items away from the joints we are working on
Get a quote
Getting a quote is simple: let us know the job and the location and its rough size. A few pictures by email make the job easier to understand, and we will come back to you with a quote.
Related advice
What we can’t put right
We will not take on work that will not last, so these are the limits:
- Faulty window hardware
- A failed sealed unit that has misted up
- A frame that has rotted at the joint
If you are not sure, just call 0345 464 0079 or drop us an email and we’ll give you a straight answer before you book.
Surfaces we seal
- Patio & French doors
- uPVC windows
- Aluminium frames
- Composite doors
- Timber windows & doors
- Window sills
Common questions in Harrow Weald
I let a flat near Headstone Lane station. Can you help?
Yes. We work for landlords and letting agents as well as householders. You can call 0345 464 0079 or send us an email with the details for a clear quote.
Can parking be tricky for a visit in Harrow Weald?
Parking in Harrow Weald, as in most of London, takes a little planning: a visitor permit or a nearby bay makes the day run more smoothly.
Will you leave a mess?
Not at all. We work neatly, protect the area around the joints and tidy up afterwards.
Do you come to Harrow Weald?
Yes. From our base in Crawley, we cover South East England, London and all of Scotland.
Can you get sealant to suit coloured frames?
Yes, we choose a colour to suit the frame. Grey and black frames get grey or black sealant, and wood-effect frames generally suit brown.
What does window mastic cost?
The cost depends on the size of the job, access and how much old sealant has to come out. Ask us for a quote.
Can I add another job to the visit?
Yes. Just list everything you need.
Can new sealant go over the old?
No. Fresh sealant doesn’t stick to old sealant, and anything trapped underneath, including mould and water, stays there. We remove it all first.
Towns and villages near Harrow Weald
Also in Harrow Weald
Looking after it afterwards
A little care helps the new joints last. We recommend:
- Keep drainage slots and sill grooves clear
- Repaint timber before it’s bare
- Do not paint over the silicone
- Keep solvents and bleach off the sealant
Try not to touch the new joint while it cures, for as long as we advise. Keep jet washers away from the frames.
Look out for the warning signs: split or missing mastic, gaps, damp patches inside or black mould on the reveal. If you notice one, it’s time to get the joint looked at.
Why it’s worth doing now in Harrow Weald
Redecorating is a good moment to renew the mastic. A clean new bead makes new paint or render look finished, and it’s easier while the walls are being worked on anyway. In older London homes, water behind a failed joint soaks into brick and timber without much sign, and once it shows in Harrow Weald, the repair is bigger than a sealant job.
Instead of a standard rate, we price the job in front of us: how many joints, what’s in them now and how we reach them. You’ll know the price before we begin.
Why book with us
- 180+ five-star Google reviews
- Every job guaranteed for a year
- More than 20 years in sealant work
- Neat joints and a tidy finish
Read our cost guide and what customers say.
DIY sealant or a professional job?
A careful DIYer can reseal a simple joint, like a short, easy-to-reach joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is chosen for how the joint moves and where it is, then guaranteed for a year.
Frames and glazing around Harrow Weald
With historic houses such as Headstone Manor (about 0.9 miles south-west) nearby, there’s older building stock in the area around Harrow Weald as well as newer homes. In older buildings, older timber frames in brick or stone need a different approach from a modern uPVC window. 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.
Letting a property close to Headstone Lane station? Then cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets. If you live in an older home near St Michael & All Angels, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. As a London address, Harrow Weald can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
Harrow Weald is about 2 miles west of Stanmore, in Greater London. Homes, rented property, offices and hotels in Harrow Weald can book us for window mastic, old or new, large or small. Every job comes with our one-year guarantee. Our Greater London coverage runs to 764 places, Harrow Weald among them. We also work in London, about 13 miles from Harrow Weald.
Our applicators cover all of HA3, HA7 and HA1 for window mastic. If you need window mastic at a property on High Road, Elms Road and Tudor Road or anywhere close by, our applicators can take on the job. You will find Harrow Weald on the A409, which makes it straightforward to reach. We also cover Belmont (1 mile east), Headstone (1 mile west), Hatch End (2 miles west), Stanmore (2 miles east) and Bushey Heath (2 miles north). Further out, we also cover London (13 miles south-east), City of Westminster (10 miles south-east), Marylebone (10 miles south-east), Kensington (9 miles south-east), St Pancras (11 miles south-east) and Shoreditch (12 miles south-east).
Landmarks near Harrow Weald
Around Harrow Weald, our work takes us to homes and buildings near The Duck in the Pond pub, Weald Rise Primary School and Headstone Manor Recreation Ground, among other places. The nearest railway station is Headstone Lane station, roughly 0.8 miles west of the centre. Nearby you’ll also find Northwick Park Hospital (2.1 miles south) and Cat Museum (within half a mile south). Not far away are Harrow Weald Common and Northala Fields.