Greater London · England
New-build mastic & snagging in St Johns, Greater London
Plot mastic for developers and snagging failed sealant in new homes for homeowners, landlords and businesses in St Johns. Fully insured, ARBOMaster approved and guaranteed for a year.
- Leaking shower tray seals in a new home
- Smeared, uneven beads picked up at snagging
- Frame joints opening as the plaster dries
Common problems we fix in St Johns
On many sites, sealant goes on in the final rush before handover. Dusty, unprimed joints are common, so the bead never bonds properly.
Any of these means the joints need attention:
- Gaps between new skirting and floors
- Messy sealant that spoils new finishes
- Sealant applied over dusty or wet surfaces
- Joints pulling apart as timber shrinks
For new homes near St Johns station, it’s worth checking the sealant early, while snags are still fresh.
What to look for in a quote
- Whether VAT is included
- How long the guarantee is
- Whether they seal over old material or remove it
- What product goes in the joint
How we handle new build mastic in St Johns
We never seal over a failed new-build bead. New silicone won’t bond to old silicone, so it all comes out before we clean, dry and reseal. If you are dealing with beads laid onto grit and dust from the build and cracks appearing as a new home settles, we can put it right, on windows & doors, plot handovers and bathrooms & en suites alike.
New flats are going up across London, many of them in larger developments. In a new development, snags are often reported through the developer or the managing agent, and shower seals that fail early, skirting joints that open up and gaps at thresholds are all common snags.
All of our work is guaranteed for twelve months.
- Where
- St Johns (SE13, SE10, SE8)
- Wider area
- Greater London
- Cover
- One year on every job
- Price
- A clear quote up front
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Questions from St Johns
Can parking be tricky for a visit in St Johns?
In much of London, parking needs planning: a visitor permit or a nearby bay makes the day run more smoothly.
Do you cover St Johns for new build mastic?
Yes. Our work covers London and the South East, and St Johns is part of that. Just ring 0345 464 0079 or send us an email with a few details of the job.
Will the old sealant be removed?
Yes, always, and completely. New sealant won’t bond properly to old, so any old material comes out before anything new goes in.
Can I add another job to the visit?
Of course. Combining jobs makes good use of the visit.
Do you work for hotels and businesses?
Yes. We work in offices, washrooms, hotels and other commercial premises. Working times can be discussed when we quote.
Do you take on second-fix sealing for builders?
Yes. We carry out plot mastic and second-fix sealing for builders and developers. Send us the plot schedule and we will quote.
Can tenants book the work?
Of course. Check with your landlord; we can send the quote to them too.
Where do you work from?
We are a Crawley-based firm. We work across South East England, London and Scotland.
What we cannot put right
We will not take on work that won’t last, so here’s what sealant can’t put right:
- Cracking that points to a structural problem
- Cracked trays, tiles or worktops
- Deciding who is responsible under a builder’s warranty
Not sure which it is? You can call 0345 464 0079 or email us and we will tell you honestly before booking.
Joints and surfaces we work on
- Bathrooms & en suites
- Windows & doors
- Show homes
- Plot handovers
- Kitchens
- Skirting & floors
How the visit works
Good joint work is mostly preparation, so that’s where we spend the time. 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 Johns, as in most of London, parking needs a little planning. It helps if you can point us to a visitor permit or a bay close to the door.
- We start by going through the snagging items or plot schedule with you.
- The failed sealant is removed completely, with no layer left behind.
- Joints are vacuumed and cleaned of building dust.
- We prime where needed and apply a sealant suited to each joint.
- Each bead is tooled and the cure times explained.
Before we arrive
- Let us know about stairs, lifts or work at height
- Plan for the work area to be out of bounds to pets and children
- Tell us about any water getting in
Get a quote
We don’t publish a price list, because every job is different. Instead, we give you a clear price for your job. To get started, ring 0345 464 0079 or drop us an email.
Advice
How to look after the new joints
To keep the joints looking good and working properly:
- Watch for new gaps as the house dries out
- Avoid running a DIY bead over the old one
- Use the extractor fan every time you shower
- Get a leaking seal dealt with straight away
Leave the sealant for the cure time we give you before showering or bathing. Silicone is normally left for about a day.
The sooner you deal with untidy or cracking sealant, the less there is to put right. Left alone, a small crack can become a leak.
How the job changes by surface
Kitchens
Sink joints are wet all the time. We use a sealant suited to kitchens, food-safe where it’s needed.
Windows and doors
Draughts around new frames are often a sealant gap. We look at the joints and reseal where needed.
More services for St Johns
Joints and finishes in St Johns homes
Many of London’s new homes are flats in bigger developments, where snags may need reporting through the developer or the managing agent. Compared with the north and west, the South East gets less rain, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
St Johns is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
St Johns is about 4 miles south-east of London, in Greater London. We carry out new build mastic for homes and businesses in St Johns and nearby. St Johns is one of 764 towns and villages in Greater London where we work for new build mastic.
Every address in SE13, SE10 and SE8 is within our area for new build mastic, from the main roads to the quietest streets. Local streets include Avon Road, Mill Lane and Clare Road, all of which we cover. Being close to the A2210 and A2211, St Johns is simple for us to get to for new build mastic. If you’re just outside St Johns, we cover New Cross (1 mile west), Deptford (1 mile north), Lewisham (1 mile south-east), Telegraph Hill (1 mile west) and Ladywell (1 mile south). Larger places within reach include London (4 miles north-west), City of Westminster (6 miles north-west), Marylebone (6 miles north-west), Kensington (8 miles west), St Pancras (6 miles north-west) and Shoreditch (5 miles north-west).
Local landmarks in St Johns
We work in homes and buildings around Wickham Arms, Brookmill Park and Addey and Stanhope School and the streets around them. You will also find St. Paul's (0.7 miles north) and Laban Centre (0.8 miles north). There’s a railway station in St Johns itself: St Johns station. Well-known places in the area include Fan Museum (0.9 miles north-east) and Lewisham Shopping Centre (0.7 miles south-east). For a walk, there’s Brookmill Road Local Nature Reserve and Tower Hill.
How we quote for new build mastic
Your quote is based on your job. We look at:
- How easy the joints are to reach
- The size of the job
- The number of rooms or windows
- Any mould that needs treating
We do not show prices on the website, because the cost depends so much on the job itself. Call for a quick quote and we’ll talk you through it.
What to tell us for a quote
You don’t need to know the technical terms. Just tell us:
- Any access issues, like height or stairs
- The address or postcode of the job
- The problem you’ve noticed
- Whether it has been sealed before
We quote each job on its own, so the first step is telling us about yours. Just phone 0345 464 0079 or email us with the details and send pictures if you have them.
DIY versus a professional finish
A DIY attempt doesn’t rule out a professional job. We cut it out and start again, so just mention it when you contact us.
The biggest DIY mistake is sealing over old sealant. Silicone doesn’t stick to old silicone, so it peels away and traps moisture behind it. All the old material has to come out first.