Greater London · England
St Luke's Window Mastic
Window mastic for St Luke's, by sealant specialists with 20+ years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Gaps between the frame and the inside reveal
- Leaking joints at the ends of sills
- Rushed sealant from a window installation
How we handle window mastic in St Luke's
Every window and door frame has a gap around it, and mastic is what closes it. When it cracks, hardens or pulls away, draughts and rain get in. The old mastic is removed and the joint resealed with a flexible exterior sealant. If you have untidy mastic left by window fitters and old mastic that has gone black or come away, we can put it right.
From mansion-block windows to modern glazing in new flats, London has every kind of frame. Over the years, the sealant around them shrinks, cracks and pulls away, which is when draughts and damp patches appear in homes in St Luke's.
There’s a 12-month guarantee on every job, large or small.
- Location
- St Luke's (N1, EC1V, EC2A)
- Wider area
- Greater London
- Guarantee
- One year on every job
- Quote
- A clear price before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
When it is not the sealant
We will always be straight with you, so here’s what new sealant won’t do:
- Damp coming through the wall itself rather than the frame joint
- Broken hinges, locks or handles
- A failed sealed unit that has misted up
If in doubt, ring 0345 464 0079 or drop us an email and we’ll say what we think before booking.
Surfaces we seal
- Timber windows & doors
- uPVC windows
- Window sills
- Composite doors
- Aluminium frames
- Patio & French doors
What window mastic looks like in St Luke's
In London conversions and blocks, the lease decides who is responsible for the frames, so check that before you book. London and the South East are among the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
For site and facilities teams at buildings such as St Luke's CofE Primary School, its window and door frames need their mastic kept sound, just like a home’s. Homes close to Jewin Welsh Presbyterian Chapel include some older properties, and the windows may be timber, sash or later replacements, and each needs the right sealant against the wall.
St Luke's is about 2 miles north of London, in Greater London. Anywhere in N1, we can carry out window mastic at your property. St Luke's is one of 764 places in Greater London where we work for window mastic.
Here we cover the N1, EC1V and EC2A postcode area for window mastic. Streets in the area include Long Lane, City Road and Moor Lane. Being close to the A1 and A501, St Luke's is simple for us to get to for window mastic. Nearby, we also carry out window mastic in Finsbury (1 mile south), Barbican Estate (1 mile south), Shoreditch (1 mile east), Hoxton (1 mile north-east) and City of London (1 mile south). Larger places within reach include City of Westminster (3 miles west), Kensington (5 miles west), Walthamstow (5 miles north-east), Hampstead (4 miles north-west), Ruislip (14 miles west) and Brompton (4 miles south-west).
Around St Luke's
In St Luke's, that means homes and buildings near Barts Health Archives, Charterhouse Square School and The Masque Haunt pub. Nearby too are St Mary-at-Hill (1.1 miles south), Central Foundation Boys' School (within half a mile east) and Artillery Ground (less than half a mile south-east). There’s a railway station in St Luke's itself: Old Street station. Nearby you will also find Gabriel's Wharf (1.3 miles south-west) and Montfichet's Tower (0.9 miles south-west). The countryside around St Luke's includes St. James's Park Lake and Barnsbury Wood.
How to look after the new joints
How long the joints last depends on use and care. We suggest:
- Keep jet washers away from the mastic
- Keep solvents and bleach off the sealant
- Keep timber frames painted
- Keep drainage slots and sill grooves clear
On timber frames, keep the paintwork in good order, since wood that gets wet swells and shrinks more. Paint up to the joint, not over the silicone.
Leaks generally show up in wet, windy weather, but resealing works best in dry conditions. Sorting cracked mastic early means the joint is sound before the bad weather.
What affects the cost of window mastic
You will get a clear quote before we start. It’s based on:
- The old material and how stubborn it is
- How many rooms, windows or areas are involved
- Any mould that needs treating
- The number and length of the joints
Commercial jobs are quoted on the same basis as homes: how much there is to do, how we reach it and what it needs, plus any working-time requirements on site. Ask us for a quote and we’ll explain what it covers.
Asking for a quote
A few details help us give you an accurate quote. When you ask for a quote, tell us:
- The problem you’ve noticed
- How many joints, rooms or windows are involved
- The type of property
- How we’d reach the joints
To get a quote, call 0345 464 0079 or send us an email and tell us where the job is and what the problem looks like. You’ll have a clear quote before work begins.
Common questions in St Luke's
Can you help a landlord with a rental near Old Street station?
Yes, we work for landlords and agents. Just phone 0345 464 0079 or email us and tell us about the property, and we will give you a clear price.
Is parking an issue for window mastic in St Luke's?
London parking needs a little planning, so let us know about permits, bays or a driveway when you book. That way the visit can be planned around it.
Can I paint over the new sealant?
Not generally, if it’s silicone. We choose the product with your decorating in mind, so mention it when you book.
Are you insured?
Yes, we’re fully insured for every job we do.
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.
What do you put in the joint?
Quality sealants from brands including Arbo and Everbuild, picked for each joint. We’ll tell you what we’re using and why.
Does the work come with a guarantee?
Yes. All our work carries a 12-month guarantee, and we are ARBOMaster approved applicators.
What does window mastic cost?
Size, access and the old material all affect the cost. Call for a quick quote and we’ll talk you through it.
How the visit works
A visit follows a simple pattern: we look at the joints together, protect the area around them, do the work and tidy away. Most jobs take a few hours for a handful of frames, longer for a whole house. In St Luke's, flats, stairs and shared entrances are part of the routine. Mention any building rules, key holders or managing agents when you book.
- First, we confirm safe access to each frame.
- Old, cracked mastic is removed completely, along with any loose debris.
- Frame and wall are cleaned and must be dry before sealing.
- Deep voids are backed, then the sealant is gunned in.
- We tool the joint so water runs off, then clear up.
How to prepare
- Let us know about earlier repairs to the joints
- Clear the area around the work
- Let us know if you’ve seen damp or leaks
Getting a quote
There’s no standard price list, because every job is different. Instead, your job gets its own clear quote. To arrange one, phone 0345 464 0079 or email us.
Read more
Signs you need window mastic in St Luke's
On timber frames, paint and putty build up around the joint. Mastic painted over many times cracks with the paint, and the wood moves with damp as well as heat.
It’s worth asking for a quote if you see:
- Draughts coming in around windows and doors
- Damp patches on the reveal after heavy rain
- Mastic that has split away from the wall
- Mastic that is falling out in pieces
As a London address, St Luke's can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
Questions to ask before booking
- How long the guarantee is
- Which colour the sealant will be
- How much experience the applicator has
- How long to leave it before use
Should I try it myself first?
Sealing over old silicone is the commonest DIY error. Silicone doesn’t stick to old silicone, so it lifts and traps water and mould underneath. Everything old must be removed first.
Too much sealant is as bad as too little. A thick, smeared bead looks untidy and does not move well, and the joint depth matters as much as the finish.
Nearby places to St Luke's
What else we do in St Luke's
Work for landlords, hotels and businesses
We regularly work with letting and managing agents. Send the address, what’s needed and the access arrangements and we will quote.
A neglected joint can let water reach the structure, which is a bigger problem in a rented property. Keeping joints in good order is simple maintenance that we can handle for you.