Greater London · England
St James's New Build Mastic
We cover St James's for plot mastic for developers and snagging failed sealant in new homes. Old sealant removed completely, joints prepared properly and every job guaranteed for a year.
- Cracked caulk along new skirting
- Cracked sealant around new window and door frames
- Cracks appearing as a new home settles
New build mastic for homes and businesses in St James's
For builders and developers, we work through plots to the schedule you give us. Bathrooms, en suites, kitchens, frames and skirting are sealed ready for handover. If you are dealing with joints pulling apart as timber shrinks and sealant that never bonded to the surface, we can put it right, whatever the surface.
London homes range from new-build flats to period conversions with new floors laid over old boards. Every joint between floor, skirting and threshold has to cope with some movement, in St James's 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
- St James's (W1F, W1D, W1J)
- Wider area
- Greater London
- Guarantee
- 12 months on all our work
- Quotes
- A clear price before any work starts
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
New build mastic around St James's
Rainfall in the South East is lower than in much of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind. Much of London’s new housing is flats in larger developments, where snagging may go through the developer or managing agent.
For new homes near London Charing Cross station, it’s worth checking the sealant early, while snags are still fresh. As a London address, St James's can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
St James's is about 1 mile south-east of City of Westminster, in Greater London. Wherever you are in the W1F postcode area, we cover new build mastic for homes and businesses. Our area takes in 764 places across Greater London, from the larger towns to small villages.
All of W1F, W1D and W1J is within our area for new build mastic. Streets in the area include Duck Lane, Bruton Lane and Bridle Lane. St James's is on the A4 and A400, which makes it straightforward to reach. 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). Larger places within reach include 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).
Local landmarks in St James's
We work in homes and buildings around LITE Regal International School, Tom Cribb pub and London Library, among other places. Other local landmarks include Harris Westminster Sixth Form (0.6 miles south) and St Anne's Churchyard (within half a mile north). St James's has its own railway station: 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). For a walk, there’s St. James's Park Lake and Ludgate Hill.
St James's: your questions answered
Do you work for landlords with property near London Charing Cross station?
Yes, we work for landlords and letting agents. You can ring 0345 464 0079 or email us with the address and a few details, and we will give you a fixed price before we start.
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.
Should I wait before resealing?
It depends on whether water is getting through. A leaking shower or bath seal should be redone straight away, while small cosmetic gaps can wait a while.
Do you guarantee your work?
Yes, always. There’s a 12-month guarantee on every job, large or small.
Can you do plot mastic on a new development?
Yes. We carry out plot mastic and second-fix sealing for builders and developers. Send the schedule and any specification and we will give you a quote.
Do you remove the old sealant?
Yes. We cut out all the old sealant and clean the joint before resealing.
Can I send you my snagging list?
Yes. Send the list and a few photos of the sealant items, and we will quote. We will tell you if anything on it isn’t a sealant job.
Do I have to be there?
Access is agreed with you when the job is booked. Indoors, that generally means someone at home.
How it works
We keep the work tidy and contained to the area we are working on, so you can get on with your day. Expect the work to take a few hours in a single home. In St James's, flats, stairs and shared entrances are part of the routine. If the building has a concierge, managing agent or access rules, tell us when you book.
- We look at why each joint failed, including any movement.
- We remove the failed sealant and clean the joints.
- Joints are dried and primed where the product calls for it.
- New sealant goes in, with baths filled first so they’re at their heaviest.
- We check every joint and leave you with the cure times.
Preparing for the visit
- On commercial sites, let us know about site rules
- Let us know about earlier repairs to the joints
- Let us know if you’ve seen damp or leaks
How to get a quote
Need a quote? Please phone 0345 464 0079 or send us an email with a few details. You’ll know what we plan to do, and what it will cost, before any work begins.
Advice
Different surfaces, different methods
Skirting and floors
Gaps under skirting are one of the most common new-build snags. We seal it with a flexible sealant that copes with the movement.
Show homes
We can refresh show-home sealant that has discoloured or been knocked. The old bead comes out and a clean new one goes in.
Aftercare tips
So the new joints stay in good condition:
- Check bath and shower seals every few months as the house settles
- Don’t wait for the house to settle if water is getting through
- Avoid scourers and strong chemicals on sealant
- Avoid running a DIY bead over the old one
Keep an eye on the joints over the first couple of years. Hairline gaps can open as timber and plaster dry, and they’re simple to reseal once movement has slowed.
Leave a failed new-build seal and water can reach the floor and the ceiling below. Early resealing keeps the job small.
Quotes for new build mastic in St James's
You’ll get a clear quote before any work starts. It takes into account:
- Mould in or behind the old joints
- How many rooms, windows or areas are involved
- How easy the joints are to reach
- Any working-time requirements on site
No two jobs are quite the same, so each one gets its own quote. Size, access and the product the joint needs all make a difference.
What we need to know
A few details help us give you an accurate quote. When you get in contact, it helps to mention:
- Any previous sealing or DIY work
- Pictures of the joints, sent by email
- If it’s domestic, commercial or a hotel
- Roughly how big the job is
We quote each job on its own. Simply call 0345 464 0079 or email us and describe the job.
DIY sealant or a professional job?
Sealing over old silicone is the commonest DIY error. Silicone does not stick to old silicone, so it lifts and traps water and mould underneath. Everything old must be removed first.
If you’re set on DIY, put the effort into 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.
For landlords and businesses
Housing providers, facilities teams and property managers book us too in St James's and across Greater London. Several sites can go on one quote, and we are fully insured for the work.
A neglected joint can let water reach the structure, which is a bigger problem in a rented property. Resealing at the right time is simple maintenance.
When it isn’t the sealant
We’d rather tell you now than do work that will not last, so here’s what sealant can’t put right:
- Leaks from pipes, valves or wastes, which need a plumber
- Your warranty claim itself, which is between you and the builder
- Cracked trays, tiles or worktops
If in doubt, call 0345 464 0079 or send us an email and we will say what we think.
What we seal
- Kitchens
- Show homes
- Skirting & floors
- Plot handovers
- Windows & doors
- Bathrooms & en suites