Greater London · England
Westerham Window Mastic
Window mastic in Westerham from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Hard, cracked sealant around windows
- Cracked sealant at the sill ends
- Water coming in at the bottom corners of a door
Window mastic for homes and businesses in Westerham
Most frames have an outside joint and an inside one. The external joint is the weather seal; inside, the joint between frame and plaster stops draughts and tidies the reveal. Either or both can be done. We work on patio & French doors, uPVC windows and composite doors, and people most often call us about cold air getting in at the frame edge and white mastic on grey or black frames.
From mansion-block windows to modern glazing in new flats, London has every kind of frame. Over the years, the sealant around them shrinks, cracks and pulls away, letting in draughts and water.
Whatever the size of the job, it’s backed by our 12-month guarantee.
- Location
- Westerham (TN16)
- Region
- Greater London
- Guarantee
- One year on every job
- Price
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
What happens on the day
There is not much for you to do on the day. Show us the job and we’ll take it from there. The job generally takes most of a day for a typical house, less for a few frames. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in Westerham. It helps if you can point us to a visitor permit or a bay close to the door.
- We start by checking each window and door with you.
- The old mastic is cut out and the surfaces cleaned back.
- Deep gaps are filled with backing rod to set the depth.
- New exterior sealant goes on in a matching colour and is tooled smooth.
- Every joint is checked before we leave.
Preparing for the visit
- Tell us about any water getting in
- Mention any tricky access
- On commercial sites, let us know about site rules
Get a quote
Every job is quoted individually, so the first step is telling us about yours. Just phone 0345 464 0079 or send us an email with the details.
Read more
How to look after the new joints
Simple care keeps the joints in good condition. We recommend:
- Avoid blasting the frames with a pressure washer
- Walk round the house once a year and look at the joints
- Keep solvents and bleach off the sealant
- Ventilate rooms so frames do not stay wet inside
On timber frames, keep the paintwork in good order, because bare, wet timber moves more and pulls at the joint. Paint up to the joint, not over the silicone.
Leaks usually show up in wet, windy weather, but resealing works best in dry conditions. Sorting cracked mastic early means the joint is sound before the bad weather.
Landlords, agents and businesses in Westerham
Letting agents often deal with us directly. Tell us the address, the job and how access works and we will quote.
Housing providers, facilities teams and property managers book us too in Westerham and across Greater London. We can quote a run of properties together.
Towns and villages near Westerham
Also in Westerham
DIY sealant or a professional job?
Not every job suits DIY: work at height, external movement joints, fire-rated sealant and large areas need the right product, the right access and the right method.
Sealing over old silicone is the commonest DIY error. New silicone will not bond to old, so it lifts and traps water and mould underneath. All the old material has to come out first.
Westerham: your questions answered
Is Westerham in your area for window mastic?
Yes. Our work covers London and the South East, and Westerham is part of that. Just ring 0345 464 0079 or email us with a few details of the job.
I let a flat near Hurst Green station. Can you help?
Yes, landlords and agents are among the people we work for. You can ring 0345 464 0079 or drop us an email with the details for a clear quote.
Will it make a mess?
Tidy work is part of the job. Nearby surfaces are protected.
Where do you work from?
We’re a Crawley-based firm, with over 20 years’ experience. We work across South East England, London and Scotland.
Can I do it myself?
Some simple jobs can be done by a careful DIYer. The usual mistakes are sealing over old sealant, sealing a damp joint and using too much.
Can you reach windows above the ground floor?
Yes, where it’s safe. For high or awkward windows, we will tell you what access is needed.
Can you seal the gap between the frame and the plaster indoors?
Yes. Indoors, we seal between the frame and the plaster or reveal, using a paintable sealant if you want to decorate.
Is it OK to seal over old sealant?
No. New silicone will not bond to old silicone, and it traps any mould or water underneath. We remove it all first.
Why deal with it now?
A cracked joint around a frame lets rain into the wall. Over time that can mean damp patches, damaged plaster and rotting timber. A reseal is a much smaller job. Converted houses in London often have a bathroom above someone else’s living room, and a slow leak from a failed seal can end up in the flat below. Putting it right early is much less trouble for homes in Westerham.
The cost reflects the work involved, not guesswork. That is why we ask about the job first and give you a clear price before any work starts.
Why us?
- Homes, businesses and hotels
- We never seal over old sealant
- 180+ five-star Google reviews
- ARBOMaster approved applicator
See our cost guide or customer reviews.
Frames and glazing around Westerham
Historic houses like Quebec House (about 0.2 miles south-east) are a reminder that the area around Westerham has older buildings as well as new. 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. Compared with the north and west, the South East gets less rain, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
Rented homes near Hurst Green station change hands often, and 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 Church of St Mary the Virgin, frames set in older brick or stone need a sealant that suits the wall as well as the frame.
Westerham is about 5 miles west of Sevenoaks, in Greater London. Westerham gets the same service as everywhere we cover: old sealant removed completely, careful preparation and a one-year guarantee. We cover 764 towns and villages across Greater London, large and small. We also work in Crawley, around 16 miles away.
Work in TN16 is quoted and booked the same way as anywhere else. We cover properties on Market Square, London Road and High Street. With the A25 and B2024 close by, Westerham is easy for our applicators to reach. Nearby, we also carry out window mastic in Force Green (1 mile north), Moorhouse Bank (1 mile south-west), Goodley Stock (2 miles south), The Chart (2 miles south-west) and South Street (2 miles north-west). Larger places within reach include Orpington (8 miles north), New Cross (15 miles north), Thornton Heath (12 miles north-west), Croydon (10 miles north-west), East Dulwich (15 miles north-west) and Plumstead (15 miles north).
Around Westerham
Typical jobs here are in homes near The Olde House At Home Public House and the streets around them. The nearest railway station is Hurst Green station, roughly 3.4 miles south-west of the centre. Well-known places in the area include Tandridge Priory (2.2 miles south-west). For a walk, there’s Betsom's Hill and Dryhill Nature Reserve.
What sealant work can’t fix
Sealant isn’t the answer to every problem, and we’d rather say so up front. It will not solve:
- Condensation trapped between the panes
- Draughts through the window seals rather than the frame
- A sash or casement that will not close properly
If in doubt, phone 0345 464 0079 or email us and we’ll say what we think before booking.
Surfaces we seal
- Timber windows & doors
- uPVC windows
- Patio & French doors
- Window sills
- Composite doors
- Aluminium frames
Signs you need window mastic in Westerham
Older frames were often sealed with products that set hard. Once it has hardened, the frame’s movement tears it from the wall, and a gap opens along one edge.
If you can see any of these, it’s time to have the joints looked at:
- Cracked or shrunken mastic around the frame
- Leaking joints at the ends of sills
- Black, perished sealant on frames
- Draughts coming in around windows and doors
As a London address, Westerham can be tricky for parking: let us know about parking bays, permits or a driveway.
Questions to ask before booking
- Which sealant they’ll use, and why
- What insurance they hold
- The length of the guarantee
- Is VAT in the price?