Greater London · England
New Build Mastic in Belsize Park
Our applicators work in Belsize Park on plot mastic for developers and snagging failed sealant in new homes. Old sealant removed completely, joints prepared properly and a one-year guarantee.
- Joints pulling apart as timber shrinks
- Second-fix sealing on new plots
- Internal frame sealant that has split
New build mastic in Belsize Park, done properly
Dust is the enemy of new-build sealant. We clean every joint thoroughly and prime where the surface and product need it, so the new bead bonds properly instead of bonding to the dust. We work on bathrooms & en suites, windows & doors and skirting & floors, and people most often call us about plot mastic for developers ahead of handover and joints pulling apart as timber shrinks.
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 failed shower seals, open skirting joints and gaps at thresholds are typical.
There’s a 12-month guarantee on every job.
- Place
- Belsize Park (NW3, NW5, NW1)
- Region
- Greater London
- Cover
- A year, on every job
- Quotes
- Quoted before any work starts
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
DIY sealant or a professional job?
A careful DIYer can reseal a simple joint, such as a straightforward joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
If you’re set on DIY, put the effort into preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it does not work out, we can still put it right.
What the job involves on each surface
Show homes
In a show home, the sealant is on display. We lay neat, even beads in colours to suit the finishes.
Skirting and floors
Floors and skirting move as the house dries and the heating runs. We use a flexible product rather than caulk.
Looking after it afterwards
So the new joints stay in good condition:
- Watch for new gaps as the house dries out
- Keep water off fresh sealant until it has cured
- Ventilate bathrooms well, especially in the first year
- Resist patching a failed seal with a tube from the DIY shop
Ventilation matters in a new home, which is still drying out. Run the fan or open a window after bathing to help keep mould away.
Mould takes hold quickly in sealant that has gaps or lifted edges. Dealing with it before it goes black keeps the job straightforward.
Quotes for new build mastic in Belsize Park
We quote each job individually. This is what makes a difference:
- The type of sealant required
- Mould in or behind the old joints
- The number and length of the joints
- The number of rooms or windows
What it costs depends on the amount of work, how hard the old material is to remove and access to the work. You will have a clear quote before any work starts.
Helping us quote
To help us quote quickly, please include:
- Photos by email, if that’s easy
- How we’d reach the joints
- How many joints, rooms or windows are involved
- If someone has resealed it before
To get a quote, ring 0345 464 0079 or drop us an email with the location and a short description of the problem. We’ll give you a clear quote before any work starts.
Why act early in Belsize Park
A failed shower or bath seal in a new home lets water into floors and walls that are still drying out. Dealing with it early keeps the damage away from ceilings, floors and finishes. In older London homes, water behind a failed joint soaks into brick and timber without much sign, and by the time it shows on a wall or ceiling in Belsize Park, the repair is bigger than the sealant job would have been.
A failed joint rarely gets cheaper to fix by waiting. If you are unsure, call 0345 464 0079 or email us for an honest opinion and a quote.
Why book with us
- ARBOMaster approved applicator
- Rated 4.9 stars on Google
- Sanitary silicone with an anti-fungal additive in wet areas
- Old sealant always removed completely
See what affects the cost and our reviews.
What new build mastic looks like in Belsize Park
Many of London’s new homes are flats in bigger developments, where snags may need reporting through the developer or the managing agent. 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.
If you’ve bought a new home near South Hampstead station, the sealant around baths, showers and frames is worth checking in the first year or two. Belsize Park is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
Belsize Park is about 1 mile south-east of Hampstead, in Greater London. We provide new build mastic to homes and businesses in Belsize Park and nearby, as part of our work across Greater London. 764 places in Greater London are on our list.
Postcode districts we cover here for new build mastic: NW3, NW5 and NW1. Whether your property is on Eton Road, Lawn Road and Ornan Road or anywhere close by, our applicators can take on the job. We also cover the places around Belsize Park: Haverstock (1 mile north), Primrose Hill (1 mile south), South Hampstead (1 mile west), Swiss Cottage (1 mile west) and Chalk Farm (1 mile east). We also work in nearby towns such as London (4 miles south-east), Kensington (4 miles south-west), Shoreditch (4 miles east), Walthamstow (7 miles north-east), Hoxton (3 miles east) and Whitechapel (4 miles south-east).
What’s near Belsize Park
Typical jobs here are in homes near The Washington pub, Primrose Hill and St. Mary's Town and Country School, among other places. You will also find Cecil Sharp House (0.8 miles south-east) and St Paul's Church of England Primary School (less than half a mile south). Belsize Park’s nearest station is South Hampstead station, roughly 0.7 miles west. A little further out are Wellington Hospital (0.9 miles south-west) and O2 Centre (0.8 miles west). Open spaces near Belsize Park include Adelaide Nature Reserve and The Long Water.
Belsize Park: your questions answered
Can parking be tricky for a visit in Belsize Park?
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.
Do you work for landlords with property near South Hampstead station?
Yes. We work for letting agents and landlords as well as homeowners. Just ring 0345 464 0079 or send us an email with the address and what needs doing, and we’ll send you a clear quote.
Are you insured?
Yes. We’re fully insured, and we have been doing sealant work for more than 20 years.
When is the best time to reseal in a new build?
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.
Is it normal for sealant to crack in a new home?
It’s common, and there are normally two reasons: movement as the house dries and settles, and sealant laid onto dust without primer. A proper reseal deals with both.
Do you remove the old sealant?
Yes, every time. New silicone doesn’t stick to old silicone, so any old material comes out before anything new goes in.
Will you leave a mess?
We keep the work tidy. We protect what’s around the joints, and we clear up when we’re done.
Will you just run a new bead over the existing one?
No. Over-sealing traps mould and water and soon fails. All the old sealant comes out before any work starts.
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How it works
You do not need to clear the whole room or building, only the area right around the joints. Everything nearby is protected, and the work takes a few hours in a single home in most cases. Many London jobs are in flats, so we come ready for stairs, narrow hallways and shared entrances. Mention any building rules, key holders or managing agents when you book.
- Each joint is checked for movement before work begins.
- 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.
- The finished joints are checked and the cure times given.
Getting ready for the visit
- Let us know if you’ve seen damp or leaks
- Tell us if parking is tricky
- Clear items away from the joints we’re working on
Get a quote
If you’re in Belsize Park and need new build mastic, phone 0345 464 0079 or send us an email. A short description of the job and where it is helps us quote, and you’ll get a clear quote before any work starts.
Related advice
What we can’t put right
We’d rather tell you now than do work that won’t last, so these are the limits:
- Cracked trays, tiles or worktops
- Your warranty claim itself, which is between you and the builder
- Plumbing faults behind the sealant
Not sure which it is? You can call 0345 464 0079 or email us and we will tell you honestly before booking.
Surfaces we seal
- Show homes
- Bathrooms & en suites
- Plot handovers
- Kitchens
- Skirting & floors
- Windows & doors