Greater London · England
Window & door mastic in Harrow on the Hill, Greater London
Window mastic for Harrow on the Hill, by sealant specialists with 20+ years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Cold air getting in at the frame edge
- Gaps where the sill meets the wall
- Gaps left after new windows were fitted
What we’re called out for in Harrow on the Hill
On timber frames, paint and putty build up around the joint. Old mastic gets painted over and cracks under the paint, and the wood moves with damp as well as heat.
It’s worth asking for a quote if you see:
- Gaps where the sill meets the wall
- Draughty joints inside around the window
- Sealant in the wrong colour for the frame
- Mastic that’s falling out in pieces
Managing a site like St George’s Primary Catholic Voluntary Academy? Then larger buildings have plenty of frames, and the mastic around each one ages.
Before booking anyone
- What the cure time is
- Who does the work, and how experienced they are
- Whether VAT is included
- Whether they seal over old material or remove it
Window mastic for homes and businesses in Harrow on the Hill
Behind a thin line of old mastic there’s sometimes a deep void. Filling it with sealant alone leaves a joint that cannot move properly, so we fit backing rod to set the right depth. That way the new bead bonds to the frame and the wall only. If you are dealing with water coming in at the bottom corners of a door and draughts coming in around windows and doors, we can put it right.
London has a lot of flats and conversions, where windows are often on upper floors. In a converted house or block, the lease usually says who is responsible for the windows, so it’s worth checking before booking.
A one-year guarantee comes as standard.
- Place
- Harrow on the Hill (HA1, HA0, HA2)
- Region
- Greater London
- Cover
- A year, on every job
- Price
- A clear price before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
What window mastic looks like in Harrow on the Hill
In a converted house or block, who looks after the windows depends on the lease, so check that before you book. 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.
Harrow on the Hill is in London, so parking needs planning: let us know about parking bays, permits or a driveway. If you live in an older home near Christ Church, frames set in older brick or stone need a sealant that suits the wall as well as the frame.
Harrow on the Hill is about 1 mile south-east of Harrow, in Greater London. Harrow on the Hill gets the same service as everywhere we cover: old sealant removed completely, careful preparation and a 12-month guarantee. Our Greater London coverage runs to 764 places, Harrow on the Hill among them. There’s also a page for London, roughly 11 miles from Harrow on the Hill.
Our applicators cover all of HA1, HA0 and HA2 for window mastic. Whether your property is on New Road, Amery Road and London Road or a nearby road, we can help. Neighbouring places we cover for window mastic include Roxeth (1 mile west), Northwick Park (1 mile north-east), South Harrow (1 mile west), Harrow (1 mile north-west) and Sudbury (1 mile south-east). Within a short drive, we also cover London (11 miles south-east), City of Westminster (9 miles south-east), Marylebone (9 miles east), Kensington (7 miles south-east), St Pancras (10 miles east) and Shoreditch (11 miles east).
What’s near Harrow on the Hill
We work in homes and buildings around Northwick Park, St Dominic's Sixth Form College and Orley Farm School. Harrow on the Hill’s nearest station is Sudbury Hill Harrow station, about 0.5 miles south. Other landmarks nearby include Kodak Museum (2 miles north) and Clementine Churchill Hospital (less than half a mile south-east). For a walk, there’s Middle Lake and Northala Fields.
FAQs for Harrow on the Hill
Do you cover Harrow on the Hill for window mastic?
Yes, Harrow on the Hill is within the area we cover. We work across London and the South East. You can call 0345 464 0079 or email us and let us know what needs doing.
Do you work for landlords with property near Sudbury Hill Harrow station?
Yes. We work for landlords and agents as well as householders. You can call 0345 464 0079 or send us an email with the details for a clear quote.
Can I add another job to the visit?
Yes, we can. Several rooms, windows or areas can go on one quote.
Are you an approved applicator?
Yes. We are approved under the ARBOMaster scheme, the approved applicator scheme for Arbo sealants.
Do you seal inside as well as outside?
Yes. Plenty of draughts come through the inside joint as well as the outside, so sealing both is often worthwhile.
Can you get sealant to suit coloured frames?
Yes, we choose a colour to suit the frame. Anthracite grey, black, brown and white cover most frames, with clear as an option.
Do I need to be at home?
We need access to the joints, so we’ll agree that with you when we book. Indoors, that normally means someone at home.
Is it OK to seal over old sealant?
No, and we never do. It may look fine at first, but the new layer lifts away from the old one. The old sealant has to come out completely.
Looking after it afterwards
A little care helps the new joints last. We recommend:
- Clear any debris from frame drain holes
- Paint up to the joint, not over it
- Keep jet washers away from the mastic
- Avoid harsh chemicals near the mastic
Timber frames need their paint kept up, since wood that gets wet swells and shrinks more. Paint up to the joint, not over the silicone.
Signs to watch for: cracks in the mastic, gaps you can see light through, damp on the reveal or mould around the inside of the frame. Any of these is worth a call.
When it isn’t the sealant
Before you book, it’s worth knowing the limits:
- Rotten timber, which needs a joiner first
- Damp problems in the wall away from the window
- Worn gaskets, brush seals or a door that has dropped
If in doubt, phone 0345 464 0079 or send us an email and we will say what we think.
Joints and surfaces we work on
- Patio & French doors
- Window sills
- Aluminium frames
- Timber windows & doors
- Composite doors
- uPVC windows
Nearby places to Harrow on the Hill
Also in Harrow on the Hill
For landlords and businesses
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.
Letting agents often deal with us directly. Tell us the address, the job and how access works and we will quote.
Should I try it myself 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 fails, we can still redo it.
Some sealant jobs are within reach of a careful DIYer, such as a straightforward joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
What happens if it’s left?
Failed mastic isn’t a reason to replace sound windows. Where the frames are sound, new mastic usually deals with draughts and leaks at the edges. Problems with the glass or gaskets are for a window company, and we’ll say so. In older London homes, water behind a failed joint soaks into brick and timber without much sign, and once it shows in Harrow on the Hill, the repair is bigger than a sealant job.
Doing several joints on one visit is usually more efficient than separate visits, so it’s worth mentioning everything you’d like done. We’ll give you a clear price for the lot.
Why Harrow on the Hill customers choose us
- A sealant colour to suit the surroundings
- You choose the colour before work begins
- Fully insured
- More than 20 years in sealant work
Read what affects the cost or what customers say.
What we do, step by step
The work is kept neat and contained to the area we are working on, so you can get on with your day. Expect the work to take a few hours for a few frames, or a day or more for a whole house, and we explain the cure time before we leave. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in Harrow on the Hill. It helps if you can point us to a visitor permit or a bay close to the door.
- Each frame is looked over and we agree which ones need resealing.
- The old mastic is cut out and scraped back to clean surfaces.
- Deep gaps get closed-cell backing rod to set the depth.
- A flexible exterior sealant is applied in a colour to suit the frame.
- Every joint is tooled smooth and checked before we leave.
How to prepare
- Mention any tricky access
- Keep children and pets away from the work area
- Let us know if you’ve seen damp or leaks
How to get a quote
Need a quote? Please phone 0345 464 0079 or email us with a few details. We’ll explain what we’d do and send you a clear quote before work begins.