Greater London · England
Longlands Window Mastic
We cover Longlands for mastic around window and door frames, sills and patio doors. Old material cut out, joints cleaned and sealed neatly and a one-year guarantee.
- Black, perished sealant on frames
- Cracked internal joints between frame and plaster
- Leaking joints at the ends of sills
How we handle window mastic in Longlands
Colour matters on a frame. White, brown, anthracite grey, black and clear sealants are all available, so the line suits the frame instead of standing out. If you have draughts coming in around windows and doors and a bead that doesn’t match the frame, we can help, whatever the surface.
Much of London’s older housing was built with timber sash windows, some still in place and some long since replaced. Either way, the mastic between frame and brickwork is what stops draughts and rain getting in, in Longlands as anywhere.
We guarantee the work for a year. If there’s a problem with our work within the year, let us know and we’ll sort it.
- Place
- Longlands (DA15, DA14, SE9)
- Wider area
- Greater London
- Guarantee
- A year, on every job
- Price
- A clear price before any work starts
- Call
- 0345 464 0079
- Updated
- 26 October 2026
How we quote for window mastic
There’s no set price list, because no two jobs are the same. The quote depends on:
- How much there is to do
- Whether the work is at height
- The old material and how stubborn it is
- How many rooms, windows or areas are involved
What it costs depends on the size of the job, how much old material has to come out and how easy the joints are to reach. You’ll have a clear quote before any work starts, so you know where you stand.
Asking for a quote
Photos by email are helpful but not essential. Try to tell us:
- Pictures of the joints, sent by email
- The rough size of the job
- If it’s domestic, commercial or a hotel
- Where the property is
A good description makes for an accurate quote. Let us know the location, the problem and roughly how many joints, and email photos if that’s easy.
The process
Once we are on site, we compare the joints with what we discussed. If we find something unexpected, we talk it through with you first. Most jobs then take a morning for a couple of windows and a door. In a London area like Longlands, the main things to plan are parking and access: tell us about permits, visitor bays or off-street space, which floor we are working on and whether there’s a lift.
- We start by checking each window and door with you.
- The old mastic is cut out and the surfaces cleaned back.
- We fit backing rod in deep gaps so the sealant is the right depth.
- We apply a weatherproof sealant to match the frame and tool it neatly.
- We clear up and check every joint is fully closed.
Before we arrive
- Keep children and pets away from the work area
- Let us know about earlier repairs to the joints
- Mention any leaks or damp you’ve noticed
Ask for a quote
There’s no standard price list. Instead, we give you a clear quote for your job. To arrange one, phone 0345 464 0079 or send us an email.
Advice
Landlords, agents and businesses in Longlands
Whether it’s one flat or a portfolio, you get the same standard of work: the old material taken out, careful preparation and a 12-month guarantee.
Hotels need rooms back in use, so we plan the work room by room. We have worked in hotels as well as homes and businesses.
DIY sealant or a professional job?
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.
Not every job suits DIY: work at height, external movement joints, fire-rated sealant and large areas call for the right materials, safe access and experience.
Honest limits
We will not take on work that will not last, so these are the limits:
- Damp problems in the wall away from the window
- Rotten timber, which needs a joiner first
- Faulty window hardware
If in doubt, call 0345 464 0079 or send us an email and we’ll say what we think.
Joints and surfaces we work on
- Patio & French doors
- Composite doors
- Window sills
- Aluminium frames
- uPVC windows
- Timber windows & doors
What happens if it’s left?
Failed mastic isn’t a reason to replace sound windows. If the frames and glass are in good order, resealing the joints is often all that’s needed. Problems with the glass or gaskets are for a window company, and we will say so. In London conversions, one flat’s bathroom is often above another flat’s ceiling, and a slow leak from a failed seal can end up in the flat below. Putting it right early is much less trouble.
What you pay reflects the work, not a rough estimate. That’s why we ask about the job first and agree the price before starting.
Why Longlands customers choose us
- Sanitary silicone with an anti-fungal additive in wet areas
- White, clear, grey or coloured to suit, where the product allows
- Any old sealant cut out fully, not covered over
- More than 20 years in sealant work
See our cost guide and customer reviews.
Nearby places to Longlands
What else we do in Longlands
Looking after it afterwards
Simple care keeps the joints in good condition. Our advice:
- Keep drainage slots and sill grooves clear
- Keep timber frames painted
- Walk round the house once a year and look at the joints
- Keep jet washers away from the mastic
Have a look at the joints once a year, ideally after winter. Small splits are simple to catch before they leak.
Water gets in quietly when mastic fails. Often the first sign is a damp patch inside or flaking paint on the reveal. Catching it early keeps the fix to a reseal.
What window mastic looks like in Longlands
Historic houses like Eltham Palace (about 2 miles north-west) are a reminder that the area around Longlands 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.
As a London address, Longlands can be tricky for parking: let us know about parking bays, permits or a driveway. If you look after a building such as Longlands Primary School, the mastic around its windows and doors needs looking after like any other building’s. For an older house near a landmark such as Christ Church, the windows may be timber, sash or later replacements, and each needs the right sealant against the wall.
Longlands is about 1 mile west of Sidcup, in Greater London. Every kind of property in Longlands is covered for window mastic, old or new, large or small. The work is guaranteed for a year. Our Greater London coverage runs to 764 places, and Longlands is one of them. There’s also a page for London, about 9 miles away.
All of DA15, DA14 and SE9 is within our area for window mastic, from the main roads to the quietest streets. That includes homes and businesses on Main Road, Alder Road and Sidcup Road and the roads around them. With the A211 close by, Longlands is simple for us to get to. We also cover the places around Longlands: Foxbury (1 mile south), New Eltham (1 mile north-west), Chislehurst (1 mile south-west), Coldharbour (1 mile west) and Blackfen (1 mile north). We also work in nearby towns such as London (9 miles north-west), City of Westminster (12 miles north-west), Marylebone (12 miles north-west), Kensington (13 miles west), St Pancras (11 miles north-west) and Shoreditch (10 miles north-west).
What’s near Longlands
We work in homes and buildings around Waring Park, Chislehurst School for Girls and Ye Olde Black Horse Inn, among other places. The nearest railway station is New Eltham station, roughly 0.8 miles north-west of the centre. Nearby you will also find Queen Mary's Hospital (1 mile south-east) and Greenwich Castle (5 miles north-west). Open spaces near Longlands include Summer Hill and The Tarn.
Questions from Longlands
Is parking an issue for window mastic in Longlands?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. That way the visit can be planned around it.
Is Longlands in your area for window mastic?
Yes. Our work covers London and the South East, and Longlands is part of that. You can phone 0345 464 0079 or drop us an email and let us know what needs doing.
Can you seal over the old sealant?
No, it will not last. It may look fine at first, but the new layer lifts away from the old one. The old sealant has to come out completely.
Where is Mr Mastic based?
We work from Crawley. We cover Longlands and the rest of Greater London, along with the rest of our area.
Will there be a smell?
It depends on the product. Some products have a noticeable smell, others very little, and any smell fades as they cure.
How long does it take to reseal the windows on a house?
A few frames take a few hours. You will get a timescale with the quote.
Can you seal the gap between the frame and the plaster indoors?
Yes. Inside, the joint between frame and plaster is sealed neatly.
Are you insured?
Yes. Full insurance covers our work.