Greater London · England
Window & door mastic in Sydenham, Greater London
We cover Sydenham 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.
- A bead that does not match the frame
- Black, perished sealant on frames
- Cracked internal joints between frame and plaster
How to look after the new joints
No joint lasts for ever, but care makes a real difference. Our tips:
- Ventilate rooms so frames do not stay wet inside
- Walk round the house once a year and look at the joints
- Clean frames with a soft cloth and soapy water
- Do not paint over the silicone
Timber frames need their paint kept up, because bare, wet timber moves more and pulls at the joint. Keep paint off the silicone itself.
A failed joint lets water into the wall a little at a time. You might not see it until plaster blows or a damp patch appears inside. Catching it early keeps the fix to a reseal.
How we handle window mastic in Sydenham
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. Typical jobs include white mastic on grey or black frames and mastic that’s falling out in pieces, across aluminium frames, composite doors and window sills.
Much of London’s older housing was built with timber sash windows, some still in place and some long since replaced. Whatever is in the opening now, the joint between frame and wall is what keeps the weather out.
Every job is covered by our 12-month guarantee.
- Place
- Sydenham (SE26, SE20, SE23)
- Wider area
- Greater London
- Guarantee
- 12 months on all our work
- Quotes
- A clear price before we start
- Call
- 0345 464 0079
- Updated
- 26 October 2026
Places near Sydenham
More services for Sydenham
Why deal with it now?
Once mastic fails, rain can get between the frame and the wall. Left long enough, it can stain inside walls, spoil plaster and rot wooden frames. Resealing now is a small job by comparison. 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. Dealing with it early is far simpler.
Commercial jobs are quoted on the same basis as homes: the amount of work, the access and the products needed. Call for a quick quote and we’ll explain what it covers.
Why Sydenham clients choose us
- Sealant colour chosen to suit
- Approved under the ARBOMaster scheme
- Any old sealant cut out fully, not covered over
- Rated 4.9 stars on Google
See our cost guide or customer reviews.
What affects the quote in Sydenham
The price is agreed before any work begins. It takes into account:
- The amount of work
- Access and height
- Any working-time requirements on site
- Whether there’s mould to deal with
A failed joint rarely gets cheaper to fix by waiting. If you’re unsure, call 0345 464 0079 or email us for an honest opinion and a quote.
What we need to know
To make quoting easier, let us know:
- Access, such as stairs, a lift or height
- The problem you’ve noticed
- If it’s domestic, commercial or a hotel
- The address or postcode of the job
If you are in Sydenham and need window mastic, ring 0345 464 0079 or drop us an email. Tell us what the problem is and where, and you’ll get a clear quote before we start.
What we do, step by step
Most of a good job is in the preparation, so that is where we spend the time. Joints are cleaned back and dried before anything new goes in. All told, the work takes a few hours for a few frames, or a day or more for a whole house. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. Mention any building rules, key holders or managing agents when you book.
- We check each frame and agree which ones need doing.
- Next the failed sealant is cut away and the joint cleaned.
- Where gaps are deep, backing rod goes in first.
- We apply a weatherproof sealant to match the frame and tool it neatly.
- Finally we tidy up and check each joint.
Preparing for the visit
- Where the joints are inside, avoid wetting them before we arrive
- Mention any tricky access
- Mention any parking rules near the property
Ask for a quote
Getting a quote is simple: tell us what needs doing and where. Photos by email help us understand the job.
Related advice
When to call us in Sydenham
Frames are never completely still. Sun on a frame makes it expand, and it contracts again overnight, while the masonry beside it stays put. If the sealant cannot stretch, it splits.
People usually contact us after spotting one of these:
- Untidy mastic left by window fitters
- Draughty joints inside around the window
- Black, perished sealant on frames
- Damp patches on the reveal after heavy rain
Sydenham is in London, so parking needs planning: let us know about parking bays, permits or a driveway.
What your quote should include
- How long the guarantee is
- How the surfaces are prepared before sealing
- Is the old sealant removed completely?
- What the quote includes, VAT included or not
Questions from Sydenham
Can you help a landlord with a rental near Sydenham station?
Yes, rental work is part of what we do. Just ring 0345 464 0079 or send us an email and tell us about the property, and we’ll give you a clear price.
Can you do window mastic in Sydenham?
Yes, Sydenham is within the area we cover. Our work covers London and the South East. You can call 0345 464 0079 or email us and tell us what needs doing.
Does the work come with a guarantee?
Yes. Our 12-month guarantee covers every job, inside or out.
Do I need to be at home?
If the work is inside, we need someone to let us in. Once we’ve agreed the job, you do not need to watch us work.
Can you do the inside joint as well?
Yes, we do both. Inside, the joint between frame and plaster is sealed neatly, using a paintable sealant if you want to decorate.
Will there be a smell?
There can be a smell while the sealant cures, which fades as it sets. Opening a window helps.
Can you match the sealant to my frames?
Yes. Anthracite grey, black, brown and white cover most frames, with clear as an option.
Can you do upstairs windows?
Yes, where it’s safe. For high or awkward windows, we will tell you what access is needed.
Windows and doors in Sydenham
Compared with the north and west, the South East gets less rain, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind. Historic houses like Kingswood House (about 1.2 miles west) are a reminder that the area around Sydenham has older buildings as well as new. In older buildings, older frames set in brick or stone need a sealant that suits them, and sometimes that’s traditional sand mastic.
If you live in an older home near Church of St Bartholomew, the joint between an old wall and a newer frame is generally the first place rain gets in. If you let a flat or house near Sydenham station, cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets.
Sydenham is about 3 miles south-east of East Dulwich, in Greater London. Homes, rented property, offices and hotels in Sydenham can book us for window mastic, old or new, large or small. The work is guaranteed for a year. Sydenham is one of 764 towns and villages in Greater London where we work.
Work in SE26, SE20 and SE23 is quoted and booked the same way as anywhere else. Streets in the area include Byne Road, Lucas Road and Cator Road. Close by, we work in Penge (1 mile south), Crystal Palace (1 mile south-west), Sydenham Hill (1 mile north-west), Perry Vale (1 mile north-east) and Anerley (1 mile south-west). Within a short drive, we also cover London (5 miles north), City of Westminster (7 miles north-west), Marylebone (8 miles north-west), Kensington (8 miles north-west), St Pancras (7 miles north) and Shoreditch (7 miles north).
Around Sydenham
In Sydenham, that means homes and buildings near St Bartholomews's Church of England Primary School, Sydenham High School and Mayow Park and the streets around them. There’s a railway station in Sydenham itself: Sydenham station. Other landmarks nearby include Greenwich Castle (4.3 miles north-east) and Crystal Palace Museum (1 mile west). Not far away are Dacres Wood and Knight's Hill.
When something else is needed
Sealant isn’t the answer to every problem, and we will tell you before we start. Sealant will not put right:
- Faulty window hardware
- A frame that has rotted at the joint
- Draughts through the window seals rather than the frame
If in doubt, phone 0345 464 0079 or drop us an email and we’ll say what we think.
Surfaces we seal
- uPVC windows
- Patio & French doors
- Window sills
- Composite doors
- Timber windows & doors
- Aluminium frames
How the job changes by surface
Timber windows & doors
Where timber has rotted at the joint, it needs repairing first. We’ll point out any rot we find, as a joiner will need to deal with it.
Patio & French doors
Door frames take knocks and movement every time the doors are used. The sealant must cope with it without cracking.