Greater London · England
Window Mastic in Cannon Hill
Mastic around window and door frames, sills and patio doors in Cannon Hill, with a 12-month guarantee on every job. Call for a quick quote.
- A bead that does not match the frame
- Cracked sealant at the sill ends
- Old mastic that has gone black or come away
How we handle window mastic in Cannon Hill
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. If you have water coming in at the bottom corners of a door and hard, cracked sealant around windows, we can help, on timber windows & doors, composite doors and patio & French doors alike.
Many London homes are flats, with windows high above the street. Who looks after the outside of the frames can depend on the lease, so check that first, and access in Cannon Hill is something to talk through when you book.
Every job is covered by our one-year guarantee.
- Place
- Cannon Hill (SW20, SM4, KT3)
- Region
- Greater London
- Cover
- One year on every job
- Quotes
- Quoted before any work starts
- Phone
- 0345 464 0079
- Last updated
- 26 October 2026
Should I try it myself first?
What a professional job adds is preparation and the right product. Joints are cleaned back to sound surfaces and dried, and the sealant is matched to the joint and its conditions, then guaranteed for a year.
Not every job suits DIY: high-level joints, fire-rated gaps, external movement joints and big jobs call for the right materials, safe access and experience.
Keeping the joints in good condition
After the cure time, these simple habits help:
- Make sure the drainage slots aren’t blocked
- Look round the frames every year or so
- Wipe condensation off the frames
- Don’t paint over the silicone
Keep the new mastic undisturbed while it cures, following the cure time we give you. Don’t point a pressure washer at the joints.
Water gets in quietly when mastic fails. You might not see it until plaster blows or a damp patch appears inside. Early resealing stops it reaching that point.
Windows and doors in Cannon Hill
With historic houses such as Southside House (about 1.2 miles north-west) nearby, there’s older building stock in the area around Cannon Hill as well as newer homes. In older buildings, older frames set in brick or stone need a sealant that suits them, and sometimes that is traditional sand mastic. In a converted house or block, who looks after the windows depends on the lease, so it’s worth checking before booking.
For site and facilities teams at buildings such as Hillcross Primary School, larger buildings have plenty of frames, and the mastic around each one ages. As a London address, Cannon Hill can be tricky for parking: let us know about parking bays, permits or a driveway. Letting a property close to South Merton station? Then sound mastic around windows and doors keeps out the draughts and damp that tenants notice first.
Cannon Hill is about 1 mile north-west of Morden, in Greater London. Jobs in Cannon Hill get the same care as everywhere else we work: the old material taken out, joints prepared properly and a 12-month guarantee. 764 places in Greater London are on our list, large and small. There’s also a page for London, roughly 9 miles from Cannon Hill.
Every address in SW20, SM4 and KT3 is within our area for window mastic, from the main roads to the quietest streets. If you need window mastic at a property on Aylward Road, Camborne Road and Botsford Road or a nearby road, our applicators can take on the job. Other places close to Cannon Hill include Bushey Mead (1 mile north-west), Raynes Park (1 mile west), Wimbledon Chase (1 mile north), West Barnes (1 mile west) and Merton Park (1 mile north-east). Further out, we also cover London (9 miles north-east), City of Westminster (8 miles north), Marylebone (9 miles north), Kensington (7 miles north), St Pancras (10 miles north-east) and Shoreditch (11 miles north-east).
Landmarks near Cannon Hill
Locally, jobs take us to homes and businesses close to The Edward Rayne pub, Cannon Hill Common and Harris Academy Wimbledon, among other places. For rail, the closest station is South Merton station, roughly 0.5 miles north-east. Nearby you will also find St. Anthony's Hospital (1.5 miles south) and Wimbledon Museum (1.6 miles north). Not far away are Cherry Wood and Henman Hill.
Also near Cannon Hill
More services for Cannon Hill
Cannon Hill questions
Is parking a problem for a job in Cannon Hill?
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.
Can you help a landlord with a rental near South Merton station?
Yes, landlords and agents are among the people we work for. You can phone 0345 464 0079 or email us with the details for a clear quote.
What should I tell you?
Just the basics: the address or postcode, what’s wrong and any access issues. Then call 0345 464 0079 or email us.
Will the old sealant be removed?
Always. Sealing over the old bead is the commonest cause of early failure, so we never do it.
Can new sealant go over the old?
No. New silicone won’t bond to old silicone, and anything trapped underneath, including mould and water, stays there. We remove it all first.
Do you work on first-floor windows?
Yes, if safe access is possible. For high or awkward windows, we will tell you what access is needed.
Do you work in Cannon Hill?
Yes, we do. Cannon Hill is part of the area we cover, and the service is the same as everywhere else.
Do you have insurance?
Yes. We’re fully insured.
When something else is needed
We will not take on work that will not last, so here’s what sealant cannot put right:
- Damp coming through the wall itself rather than the frame joint
- Misting between the panes of a double-glazed unit (that needs a new unit)
- A sash or casement that won’t close properly
If in doubt, ring 0345 464 0079 or drop us an email and we will say what we think.
Surfaces we seal
- Window sills
- uPVC windows
- Timber windows & doors
- Aluminium frames
- Patio & French doors
- Composite doors
Different surfaces, different methods
Timber windows & doors
Soft or rotten wood cannot be sealed successfully. If we find rot, we will tell you before going ahead, as that is a job for a joiner.
Patio & French doors
The joints around patio doors run a long way, top, sides and threshold. The threshold and the bottom corners take the most water, so we pay close attention there.
What happens if it’s left?
Draughts and leaks don’t always mean new windows. Where the frames are sound, new mastic normally 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 a flat in Cannon Hill, failed sealant seldom stays inside your own four walls: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
Commercial jobs are quoted on the same basis as homes: the amount of work, the access and the products needed, along with when we can work on site. Ask us for a quote and we’ll explain what it covers.
Why Cannon Hill clients choose us
- Sanitary silicone with an anti-fungal additive in wet areas
- Experience in homes, commercial sites and hotels
- 20+ years of sealant experience
- Neat joints and a tidy finish
Read our cost guide and what customers say.
How we quote for window mastic
There’s no set price list, because jobs vary so much. What we look at:
- Working hours on commercial sites
- The number and length of the joints
- Which sealant suits the joint
- Whether old sealant or filler has to be cut out
Every job is a little different, so we quote each one individually. Size, access and the product the joint needs all play a part, and we will explain the quote if you ask.
Helping us quote
To help us quote quickly, let us know:
- Photos by email, if that is easy
- The type of property
- The rough size of the job
- If someone has resealed it before
Asking for a quote is easy: tell us what needs doing and where. A few pictures by email make the job easier to understand, and we’ll take it from there.
What happens on the day
Our applicators work methodically: protection first, then preparation, sealing and a tidy-up. Typically it takes a few hours for a handful of frames, longer for a whole house and we leave things clean and tidy. For a job in Cannon Hill, parking and access are the things to plan: let us know about parking, the floor we’ll be working on and any lift or shared entrance.
- Each frame is looked over and we agree which ones need resealing.
- We remove the old mastic and clean the frame edge and wall.
- Where the gap is deep, backing rod goes in first.
- The new sealant goes on in white, brown, anthracite grey, black or clear to suit.
- Every joint is tooled smooth and checked before we leave.
Preparing for the visit
- Plan for the work area to be out of bounds to pets and children
- Mention any tricky access
- Clear the area around the work
Getting a quote
We don’t publish a price list. Instead, your job gets its own clear quote. To arrange one, ring 0345 464 0079 or drop us an email.