Greater London · England
Lewisham Window Mastic
Specialist window mastic for Lewisham: the right sealant, proper preparation and a neat finish. Ask us for a quick quote.
- Cracked sealant at the sill ends
- Draughty joints inside around the window
- Sealant in the wrong colour for the frame
About our window mastic in Lewisham
The mastic around a window or door seals the gap between the frame and the wall. When it cracks, hardens or pulls away, draughts and rain get in. Our applicators cut it out and replace it with a flexible, weatherproof sealant. We work on composite doors, aluminium frames and uPVC windows, and people most often call us about mastic that has split away from the wall and white mastic on grey or black frames.
London has a lot of flats and conversions, where windows are often on upper floors. Who looks after the outside of the frames can depend on the lease, so check that first.
Our work is backed for twelve months, and the guarantee is the same wherever you are.
- Where
- Lewisham (SE13, SE8, SE6)
- Wider area
- Greater London
- Guarantee
- A year, on every job
- Quote
- A clear quote up front
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Should I try it myself first?
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and the joint depth matters as much as the finish.
If you do try it yourself, take your time over the preparation: take out all the old sealant, make sure the joint is clean and dry, and give it the full cure time. If it fails, we can still redo it.
Window mastic in Lewisham: local notes
In London conversions and blocks, the lease decides who is responsible for the frames, so check that before booking. Historic houses like Queen's House (about 1.4 miles north) are a reminder that the area around Lewisham has older buildings as well as new. Where a home is older, older timber frames in brick or stone need a different approach from a modern uPVC window.
In the older streets around St Stephen's Church, the windows may be timber, sash or later replacements, and each needs the right sealant against the wall. Lewisham is in London, so parking needs planning: let us know about parking bays, permits or a driveway. For landlords with property near Lewisham station, cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets.
Lewisham is about 3 miles west of Eltham, in Greater London. Wherever you are in the SE13 postcode area, our applicators can take on window mastic. Lewisham is one of 764 towns and villages in Greater London where we work for window mastic.
Here we cover the SE13, SE8 and SE6 postcode area for window mastic. Local streets include Station Road, Lewisham High Street and Lewis Grove. You’ll find Lewisham on the B220, which makes it straightforward to reach. Nearby, we also carry out window mastic in Ladywell (1 mile south-west), St Johns (1 mile north-west), Hither Green (1 mile south-east), Blackheath (1 mile north-east) and Lee (1 mile south-east). Further out, we also cover London (4 miles north-west), City of Westminster (7 miles north-west), Marylebone (7 miles north-west), Kensington (9 miles west), St Pancras (6 miles north-west) and Shoreditch (5 miles north-west).
Landmarks near Lewisham
Around Lewisham, our work takes us to homes and buildings near St Joseph's Academy, Ladywell Fields and The Watch House and the streets around them. Lewisham has its own railway station: Lewisham station. Nearby you will also find Greenwich Castle (1.2 miles north) and Fan Museum (1.2 miles north). Open spaces near Lewisham include Knight's Hill and Brookmill Road Local Nature Reserve.
Surface by surface
Composite doors
If the door itself is draughty, the issue may be the door seals or hinges rather than the frame mastic. We’ll tell you if that is what we find.
Aluminium frames
Bi-fold and sliding aluminium doors have long frame joints, and the bottom joint sees the most water. We prepare and reseal every joint, backing the deep ones.
Landlords, agents and businesses in Lewisham
We work for landlords and agents as well as householders. Sealant work between tenants is a simple way to keep a property in good order before the next move-in.
A neglected joint can let water reach the structure, which matters even more when someone else lives there. Resealing at the right time is simple maintenance.
Questions from Lewisham
I let a flat near Lewisham station. Can you help?
Yes. We work for landlords and letting agents as well as householders, and several properties can be quoted together. Just ring 0345 464 0079 or send us an email with the address and what needs doing, and we will give you a clear quote.
Is Lewisham in your area for window mastic?
Yes, Lewisham is within the area we cover. We work across London and the South East. Just ring 0345 464 0079 or drop us an email with a few details of the job.
Do you work for hotels and businesses?
Yes. Hotels, offices and other businesses use us, and we are fully insured.
Do you have insurance?
Yes. We are fully insured, and we’ve been doing sealant work for more than 20 years.
What does window mastic cost?
We don’t publish prices, because the cost depends on the job: how much there is, what’s there now, how we reach it and what it needs. We agree the price before any work begins.
How many windows can you do in a day?
The work takes anything from an hour or two to a full day, depending on how many frames there are. Access and how stubborn the old mastic is affect the time most.
When is the sealant fully cured?
Most sealants are touch-dry well before they’re fully cured. We’ll give you the cure time for the product we used.
Can you match the sealant to my frames?
Generally, yes. Mention the frame colour when you ask for a quote and we’ll match it as closely as we can.
What we can’t put right
Before booking, it’s worth knowing the limits too:
- Damp coming through the wall itself rather than the frame joint
- Condensation trapped between the panes
- A frame that has rotted at the joint
If in doubt, ring 0345 464 0079 or email us and we’ll say what we think.
Joints and surfaces we work on
- uPVC windows
- Aluminium frames
- Composite doors
- Patio & French doors
- Window sills
- Timber windows & doors
Looking after it afterwards
After the cure time, these simple habits help:
- Clear any debris from frame drain holes
- Keep paint off silicone joints
- Don’t aim a pressure washer at the joints
- Walk round the house once a year and look at the joints
Keep sill grooves and drainage slots clear, so rain drains out rather than building up at the sealant.
Signs to watch for: split or missing mastic, gaps, damp patches inside or black mould on the reveal. If you notice one, it’s time to get the joint looked at.
The process
When we arrive, we start by going over the job with you, so there are no surprises. We protect the surfaces around the joints before any work begins. Most jobs take a few hours for a few frames, or a day or more for a whole house. In a London area like Lewisham, 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.
- First, we go round the frames with you and agree the list.
- 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.
- We tool each bead neatly and check every joint is closed.
How to prepare
- Mention if the joints have been sealed before
- On commercial sites, let us know about site rules
- Move anything stored near the joints
Ask for a quote
There’s no standard price list. Instead, your job gets its own clear quote. To get started, ring 0345 464 0079 or drop us an email.
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How we quote for window mastic
Every job gets its own quote. These are the things that affect it:
- The number of rooms or windows
- Whether the work is at height
- When we can work, for business premises
- How much old sealant there is and how hard it is to remove
The cost reflects the work involved, not a rough estimate. That is why we ask a few questions first.
What to tell us for a quote
To help us quote quickly, please include:
- Photos by email, if that is easy
- The type of property
- What the problem is, such as mould, gaps, leaks or cracking
- Whether it has been sealed before
Call for a quick quote, or send an email if you’d rather. Describe what needs sealing and we’ll talk you through the work before giving you a price.