Greater London · England
Window Mastic in St James's
Mastic around window and door frames, sills and patio doors in St James's, with a one-year guarantee on every job. Ask us for a quote.
- Untidy mastic left by window fitters
- Water coming in at the bottom corners of a door
- Gaps where the sill meets the wall
Window mastic in St James's
Whether it’s one leaking patio door or every frame on the house, you will get a clear quote before we start. Just call 0345 464 0079 or drop us an email and tell us how many frames there are and how they’re reached for window mastic in St James's. If you’re dealing with leaking joints at the ends of sills and cracked or shrunken mastic around the frame, we can put it right, on timber windows & doors, patio & French doors and window sills alike.
London homes have every kind of window, from timber sashes in period terraces to aluminium and uPVC in newer blocks. The mastic around them dries out and cracks with age, letting in draughts and water.
Every job is covered by a 12-month guarantee.
- Location
- St James's (W1F, W1D, W1J)
- Region
- Greater London
- Guarantee
- 12 months on all our work
- Price
- A clear quote up front
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
Landlord and commercial work in St James's
For anyone letting property in or around St James's, jobs at different addresses can be quoted together. Send us the addresses and the work at each.
Hotels need rooms back in use, so we plan the work room by room around your bookings where we can. Hotel work is part of what we do, alongside homes and businesses.
How to look after the new joints
To keep the joints looking good and working properly:
- Check the mastic once a year
- Don’t use solvent cleaners on the joint
- Air rooms to keep condensation down around windows
- Keep timber frames painted
Most silicone sealants won’t take paint, so if you’re planning to paint the frames or walls, tell us beforehand. We can use a paintable sealant where that matters.
Look out for the warning signs: 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.
What happens if it’s left?
A quick bead over the top of old mastic looks like an easy fix, but new sealant cannot bond to old, crumbling mastic. It soon lifts and the leak carries on behind it. Proper resealing starts with removing the old joint. Damp from a failed joint spreads quietly in older London brickwork and timber, and by the time it shows on a wall or ceiling in St James's, the repair is bigger than the sealant job would have been.
Leaving a failed joint normally makes the job bigger, not smaller. If you are unsure, phone 0345 464 0079 or drop us an email and we will give you an honest view and a quote.
What you get with us
- We agree the colour with you first
- 180+ five-star Google reviews
- We’re fully insured
- Approved under the ARBOMaster scheme
Read what affects the cost or customer reviews.
St James's homes and the weather
The South East is one of the drier parts of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. With historic houses such as Marlborough House (about 0.3 miles south-west) nearby, there’s older building stock in the area around St James's as well as newer homes. In older buildings, older frames set in brick or stone need a sealant that suits them, and sometimes that is traditional sand mastic.
Rented homes near London Charing Cross station change hands often, and cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets. In the older streets around St James’s Church, frames set in older brick or stone need a sealant that suits the wall as well as the frame. If you look after a building such as Soho Parish CofE Primary School, larger buildings have plenty of frames, and the mastic around each one ages.
St James's is about 1 mile south-east of City of Westminster, in Greater London. Wherever you are in the W1F postcode area, our applicators can take on window mastic. Across Greater London, we cover 764 places, and St James's is one of them.
Jobs for window mastic in W1F, W1D and W1J is quoted and booked the same way as anywhere else. Window mastic is available to properties on Duck Lane, Bruton Lane and Bridle Lane. With the A4 and A400 close by, St James's is simple for us to get to. Other places close to St James's include Chinatown (1 mile north), Charing Cross (1 mile east), Soho (1 mile north), West End (1 mile north-east) and Burlington Estate (1 mile west). Within a short drive, we also cover Kensington (3 miles west), Shoreditch (3 miles north-east), Walthamstow (7 miles north-east), Hoxton (3 miles north-east), Whitechapel (3 miles east) and Hampstead (4 miles north-west).
Near you in St James's
Locally, jobs take us to homes and businesses close to LITE Regal International School, Tom Cribb pub and London Library. Also close by are Harris Westminster Sixth Form (0.6 miles south) and St Anne's Churchyard (less than half a mile north). There’s a railway station in St James's itself: London Charing Cross station. A little further out are The Museum of Practical Geology (less than half a mile north-west) and Montfichet's Tower (1.4 miles east). Not far away are St. James's Park Lake and Ludgate Hill.
When it isn’t the sealant
Sealant is not the answer to every problem, and we’ll tell you before we start. Sealant won’t put right:
- Worn gaskets, brush seals or a door that has dropped
- A frame that has rotted at the joint
- Faulty window hardware
If in doubt, phone 0345 464 0079 or drop us an email and we will say what we think before you book.
Joints and surfaces we work on
- uPVC windows
- Composite doors
- Timber windows & doors
- Window sills
- Patio & French doors
- Aluminium frames
Places near St James's
What else we do in St James's
St James's: your questions answered
Can you do window mastic in St James's?
Yes. We work across London and the South East, and St James's is part of that. Just phone 0345 464 0079 or drop us an email with a few details of the job.
Can parking be tricky for a visit in St James's?
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.
Will resealing my frames help with draughts?
Yes, if the air is getting in around the frame. If it’s through the window’s own seals or a hinge, that is a different fix, and we’ll say so.
Are you an approved applicator?
Yes. We’re an ARBOMaster approved applicator, which is run for the Arbo sealant brand.
What information do you need?
A short description and the location, with pictures by email if possible. We will ask anything else we need to know.
Where are you based?
Mr Mastic is based in Crawley. We cover St James's and the rest of Greater London.
Do you seal inside as well as outside?
Yes. Outside is the weather seal; inside closes the gap to the plaster. We can do either or both.
Do I have to be there?
We need access to the joints, so we will agree that with you when we book. Indoors, that generally means someone at home.
How the visit works
At the end, we look at the finished work together and tell you how long to leave it. The work normally takes most of a day for a typical house, less for a few frames, depending on the size of the job. For a job in St James's, parking and access are the things to plan: let us know about parking, the floor we’ll be working on and any lift or shared entrance.
- First, we go round the frames with you and agree the list.
- We remove the old mastic and clean the frame edge and wall.
- Deep gaps get closed-cell backing rod to set the depth.
- 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
- Let us know about stairs, lifts or work at height
- Mention any sign-in or site rules at work premises
- Move anything stored near the joints
How to get a quote
Need a quote? Please ring 0345 464 0079 or email us with a few details. We’ll explain what we’d do and give you a clear price before we start.
Read more
What the job involves on each surface
Aluminium frames
Bi-fold and sliding aluminium doors have long frame joints, and the threshold joint takes a lot of water. Each is cleaned, backed where deep and resealed.
Composite doors
A composite door normally sits in a plastic outer frame, and the joint around it is sealed like a window. We match the colour to the frame.
Quotes for window mastic in St James's
Jobs vary more than people expect. What affects the quote:
- The old material and how stubborn it is
- The amount of work
- How many areas need sealing
- Access and height
Commercial jobs are quoted on the same basis as homes: the amount of work, how we reach it and what it needs, plus any working-time requirements on site. Call for a quick quote and we will explain what it covers.
Asking for a quote
A few details help us give you an accurate quote. When you get in contact, it helps to mention:
- Where the job is, and your postcode
- A few pictures by email, if you can
- Whether it has been sealed before
- Access, such as stairs, a lift or height
For window mastic in St James's, call 0345 464 0079 or send us an email. Tell us what the problem is and where, and you will get a clear quote before any work starts.