Greater London · England
Window & door mastic in Forest Hill, Greater London
Mastic around window and door frames, sills and patio doors in Forest Hill, with a 12-month guarantee on every job. Call for a quick quote.
- Draughts coming in around windows and doors
- Hard, cracked sealant around windows
- Old mastic that has gone black or come away
How we handle window mastic in Forest Hill
A cold draught around a closed window often comes from the frame edge. Resealing that joint can make a room feel noticeably less draughty and quietens the whistle on windy days. If the draught is through the window seals instead, we’ll tell you. We work on uPVC windows, aluminium frames and window sills, and the jobs we see most are rain getting in at the frame or under the sill and gaps left after new windows were fitted.
London homes have every kind of window, from timber sashes in period terraces to aluminium and uPVC in newer blocks. Over the years, the sealant around them shrinks, cracks and pulls away, letting in draughts and water.
Our work is backed for twelve months, and the guarantee is the same wherever you are.
- Where
- Forest Hill (SE23, SE22, SE26)
- Wider area
- Greater London
- Guarantee
- A year, on every job
- Price
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
When to call us in Forest Hill
Some failures date back to when the windows were fitted. Mastic laid onto dusty, damp or crumbling surfaces didn’t grip properly, so it comes away long before its time.
It’s worth asking for a quote if you see:
- Mastic that has split away from the wall
- Rushed sealant from a window installation
- A bead that doesn’t match the frame
- Draughts coming in around windows and doors
Schools such as Fairlawn Primary School are buildings too, and larger buildings have plenty of frames, and the mastic around each one ages.
Questions to ask before you book
- What guarantee comes with the work
- Whether VAT is included
- How hidden problems are handled
- Are they insured?
For landlords and businesses
Failed sealant is one of the commonest items on a check-out report. Several properties can be quoted together.
If you manage several properties in or around Forest Hill, several properties can go on one quote. Send us the addresses and the work at each.
DIY versus a professional finish
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and getting the depth right matters as much as the look.
Some sealant jobs are within reach of a careful DIYer, 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.
How we quote for window mastic
Every job gets its own quote. This is what makes a difference:
- Any working-time requirements on site
- Whether old sealant or filler has to be cut out
- Whether the work is at height
- How many rooms, windows or areas are involved
Leaving a failed joint normally makes the job bigger, not smaller, as water and mould keep getting in. If you’re not sure whether it needs doing, phone 0345 464 0079 or drop us an email for an honest opinion and a quote.
What we need to know
The more you tell us, the more accurate the quote. When you ask for a quote, tell us:
- What the problem is, such as mould, gaps, leaks or cracking
- How many joints, rooms or windows are involved
- Pictures of the joints, sent by email
- Any previous sealing or DIY work
The more we know about the job, the more useful the quote. Tell us where the job is, what’s wrong and how much there is, and email photos if that is easy.
Nearby places to Forest Hill
Other services in Forest Hill
Your questions about window mastic in Forest Hill
Is parking an issue for window mastic in Forest Hill?
Parking in Forest Hill, as in most of London, takes a little planning: a visitor permit or a bay close to the door helps a lot, so mention what’s available when you book.
I let a flat near Honor Oak Park station. Can you help?
Yes, we work for letting agents and landlords. Just ring 0345 464 0079 or send us an email and tell us about the property, and we’ll give you a clear price.
Do you guarantee window mastic?
Yes, with our one-year guarantee. A yearly look at the joints helps them last.
Where do you work from?
Mr Mastic is based in Crawley. Our applicators cover Forest Hill.
How long will my window job take?
Allow most of a day for a typical house, less for a few frames. Access and how stubborn the old mastic is affect the time most.
Will it make a mess?
We keep the work tidy. Nearby surfaces are protected.
Will the old sealant be removed?
Yes, every time. New silicone does not stick to old silicone, so the joint is cleaned back first.
Can new window sealant be painted?
That depends on the product. Silicone is not paintable, but some hybrid sealants are. Mention any painting plans before any work starts.
When something else is needed
To be straight with you, there are a few things sealant won’t fix:
- A door that needs adjusting, rehanging or new seals
- Misting between the panes of a double-glazed unit (that needs a new unit)
- Faulty window hardware
Not sure which it is? You can ring 0345 464 0079 or send us an email and we will tell you honestly before you book.
Joints and surfaces we work on
- Composite doors
- Timber windows & doors
- Aluminium frames
- Patio & French doors
- uPVC windows
- Window sills
What window mastic looks like in Forest Hill
London and the South East are among the drier parts 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 it’s worth checking before booking.
Homes close to Honor Oak Christian Fellowship Centre include some older properties, and replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. Forest Hill is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
Forest Hill is about 2 miles south-east of East Dulwich, in Greater London. Forest Hill 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.
Every address in SE23, SE22 and SE26 is within our area for window mastic, from the main roads to the quietest streets. That includes homes and businesses on Ewart Road, London Road and Rojack Road and the roads around them. Neighbouring places we cover for window mastic include Honor Oak (1 mile north), Perry Vale (1 mile south-east), Brockley (1 mile north-east), Crofton Park (1 mile north-east) and Dulwich (1 mile west). We also work in nearby towns such as London (4 miles north-west), City of Westminster (6 miles north-west), Marylebone (6 miles north-west), Kensington (7 miles north-west), St Pancras (6 miles north-west) and Shoreditch (6 miles north).
Near you in Forest Hill
We work in homes and buildings around Allenby Tutorial Trust, Capitol Cinema pub and Harris Girls' Academy East Dulwich, among other places. Forest Hill’s nearest station is Honor Oak Park station, about 0.5 miles north-east. Nearby you will also find Greenwich Castle (3.1 miles north-east) and Horniman Museum and Gardens (0.5 miles south-west). Not far away are One Tree Hill and Knight's Hill.
How the visit works
There’s no need to move everything out before we come, only the area right around the joints. We protect the rest, and the work takes a few hours for a handful of frames, longer for a whole house for a typical job. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in Forest Hill. It helps if you can point us to a visitor permit or a bay close to the door.
- We check each frame and agree which ones need doing.
- The old mastic is cut out and the surfaces cleaned back.
- Deep gaps are filled with backing rod to set the depth.
- A flexible, weatherproof sealant is applied in a colour to suit the frame.
- Finally we tidy up and check each joint.
How to prepare
- Mention if the joints have been sealed before
- Where the joints are inside, avoid wetting them before we arrive
- Mention any leaks or damp you’ve noticed
Ask for a quote
If you’re in Forest Hill and need window mastic, call 0345 464 0079 or drop us an email. Tell us what the problem is and where, and you’ll get a clear quote before work begins.
Related advice
Surface by surface
Window sills
Every drop off the glass ends up on the sill, so the joints at each end and underneath matter. They’re cut out and resealed with exterior sealant.
Timber windows & doors
Older timber windows in stone or brick can suit sand mastic rather than modern sealant. We will tell you which suits your home.