Greater London · England
St Luke's New Build Mastic
Plot mastic for developers and snagging failed sealant in new homes for St Luke's, backed by a one-year guarantee. Ask us for a quote.
- Sealant that never bonded to the surface
- Cracks appearing as a new home settles
- Smeared, uneven beads picked up at snagging
What sealant work can’t fix
We won’t take on work that will not last, so here’s what sealant can’t put right:
- Cracking that points to a structural problem
- Leaks from pipes, valves or wastes, which need a plumber
- Movement caused by a poorly fitted tray or bath
Not sure which it is? You can ring 0345 464 0079 or drop us an email and we will tell you honestly before booking.
What we seal
- Plot handovers
- Show homes
- Kitchens
- Windows & doors
- Bathrooms & en suites
- Skirting & floors
How we handle new build mastic in St Luke's
Developers send us the plot schedule and we work through it. We seal bathrooms, kitchens, windows, doors and skirting so plots are ready to hand over with a sealant suited to each area. We work on windows & doors, kitchens and plot handovers, and the jobs we see most are new-build shower sealant that has already split and plot mastic for developers ahead of handover.
Much of London’s new housing is flats in larger developments. Snagging there often goes through the developer or managing agent, and shower seals that fail early, skirting joints that open up and gaps at thresholds are all common snags.
Every job comes with a 12-month guarantee, wherever you are in Greater London.
- Location
- St Luke's (N1, EC1V, EC2A)
- Region
- Greater London
- Cover
- 12 months on all our work
- Quote
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
Different surfaces, different methods
Show homes
Show homes need sealant that looks right from day one. We lay neat, even beads in colours to suit the finishes.
Bathrooms and en suites
Baths, showers, basins and trays in new bathrooms are the most common new-build reseal. We cut out the failed bead, clean and prime, and reseal with anti-fungal sanitary silicone.
How it works
Good joint work is mostly preparation, and we do not rush it. Every joint is cleaned and dried before new material goes in. In total, it normally takes a few hours for most snagging lists, longer for a run of plots. 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, the list of joints is agreed from your snagging sheet or plot schedule.
- Every bit of the old builder’s sealant is cut out.
- Joints are vacuumed and cleaned of building dust.
- We prime where needed and apply a sealant suited to each joint.
- We tool every joint neatly and tell you when each area can be used.
Getting ready for the visit
- Let us know about earlier repairs to the joints
- For indoor joints, keep the area dry beforehand if you can
- Mention any leaks or damp you’ve noticed
Ask for a quote
There’s no standard price list, because every job is different. Instead, we give you a clear price for your job. To arrange one, ring 0345 464 0079 or email us.
Related advice
Places near St Luke's
Other services in St Luke's
Can I do it myself?
Sealing over old silicone is the commonest DIY error. Silicone does not stick to old silicone, so it peels away and traps moisture behind it. All the old material has to come out first.
Not every job suits DIY: work at height, external movement joints, fire-rated sealant and large areas call for the right materials, safe access and experience.
Why act early in St Luke's
Sealant done properly at handover means fewer callbacks. Snagging visits for failed sealant cost time on every plot, and they’re avoidable with good preparation. In a London flat, a failed joint rarely stays your problem alone: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
Homes and businesses are quoted the same way: the amount of work, the access and the products needed. Call for a quick quote and we will go through it with you.
Why St Luke's customers choose us
- ARBOMaster approved applicator
- 180+ five-star Google reviews
- We leave the area clean and tidy
- Sealant colour chosen to suit
See what affects the cost and customer reviews.
Aftercare tips
Good habits help new joints last longer. A few tips:
- Do not seal over failed sealant yourself
- Use the extractor fan every time you shower
- Don’t wait for the house to settle if water is getting through
- Keep pictures and emails about snagging items
Keep the bathroom ventilated, especially in the first year. Use the extractor fan or open a window after showers.
If a shower tray or bath seal splits in the first year, look for movement. Getting it resealed properly, and any movement checked, stops it recurring.
New build mastic around St Luke's
Compared with the north and west, the South East gets less rain, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. Many of London’s new homes are flats in bigger developments, where snagging may go through the developer or managing agent.
St Luke's is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
St Luke's is about 2 miles north of London, in Greater London. Anywhere in N1, we can carry out new build mastic at your property. 764 places in Greater London are on our list, large and small.
Every address in N1, EC1V and EC2A is covered for new build mastic, from the main roads to the quietest streets. We cover properties on Long Lane, City Road and Moor Lane. St Luke's is on the A1 and A501, so it’s easy for us to get to. Neighbouring places we cover for new build mastic include 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). We also work in nearby towns such as 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).
Near you in St Luke's
Typical jobs here are in homes near Barts Health Archives, Charterhouse Square School and The Masque Haunt pub and the streets around them. Also close by are St Mary-at-Hill (1.1 miles south), Central Foundation Boys' School (within half a mile east) and Artillery Ground (within half a mile south-east). St Luke's has its own railway station: Old Street station. Nearby you’ll also find Gabriel's Wharf (1.3 miles south-west) and Montfichet's Tower (0.9 miles south-west). For a walk, there’s St. James's Park Lake and Barnsbury Wood.
Signs you need new build mastic in St Luke's
If plaster or screed was still damp when it was sealed, the bond suffers. On a busy site, joints aren’t always given time to dry.
If you can see any of these, it’s time to have the joints looked at:
- Messy sealant that spoils new finishes
- Sealant work across a run of new homes
- Shower seals failing in the first year or two
- Gaps between new skirting and floors
For new homes near Old Street station, it’s worth checking the sealant early, while snags are still fresh.
Comparing quotes
- What the quote includes, VAT included or not
- Whether all the old sealant comes out first
- How the colour is chosen
- What preparation is included
St Luke's questions
Can you help a landlord with a rental near Old Street station?
Yes. We work for letting agents and landlords as well as homeowners. Just ring 0345 464 0079 or drop us an email with the address and what needs doing, and we will send you a clear quote.
Can parking be tricky for a visit in St Luke's?
Parking in St Luke's, as in most of London, takes a little planning: a visitor permit or a bay close to the door helps a lot, so mention what’s available when you book.
Can I add another job to the visit?
Yes. Several rooms, windows or areas can go on one quote.
What sealant do you use?
It depends on the joint: sanitary silicone where it gets wet, and sealants suited to movement or weather elsewhere. Brands we use include Arbo and Everbuild.
Will it make a mess?
No. We protect the surfaces around the joints, and we tidy up before we go.
When is the sealant fully cured?
It depends on the product and the temperature. Before we leave, we will tell you the cure time.
Do you take out the old sealant first?
Yes. All of the old material is cut out and the joint cleaned.
Is it worth trying it myself?
That depends on the joint. Work at height, movement joints, fire-rated gaps and large areas are best left to a professional.