Greater London · England
New-build mastic & snagging in Underhill, Greater London
Plot mastic for developers and snagging failed sealant in new homes in Underhill, with a one-year guarantee on every job. Ask us for a quote.
- Sealant work across a run of new homes
- Beads laid onto grit and dust from the build
- Leaking shower tray seals in a new home
About our new build mastic in Underhill
Snagging sealant properly means taking the failed bead out completely. Fresh silicone cannot bond to the old layer, so it all comes out before we clean, dry and reseal. We work on windows & doors, kitchens and skirting & floors, and the jobs we see most are messy sealant that spoils new finishes and new-build shower sealant that has already split.
Much of London’s new housing is flats 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.
Our work is backed for twelve months.
- Location
- Underhill (EN5, N20)
- Wider area
- Greater London
- Cover
- A year, on every job
- Quotes
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
Landlords, agents and businesses in Underhill
Landlords and agents in Underhill can book us as well as householders. Resealing between tenancies is a simple way to keep a property in good order.
For anyone letting property in or around Underhill, jobs at different addresses can be quoted together. Send us the addresses and the work at each.
When to call us in Underhill
When the heating goes on in the first winter, the house dries fast. Gaps open along skirting, frames and worktops and cracked sealant shows up.
These are the problems we are asked about most:
- Cracked sealant around new window and door frames
- Leaking shower tray seals in a new home
- Sealant applied over dusty or wet surfaces
- Cracked caulk along new skirting
As a London address, Underhill can be tricky for parking: tell us about permits, visitor bays or off-street space when you book.
What your quote should include
- Who does the work, and how experienced they are
- How the joint is cleaned and prepared
- The length of the guarantee
- How long to leave it before use
Different surfaces, different methods
Skirting and floors
Gaps under skirting are one of the most common new-build snags. A flexible sealant closes it without cracking like caulk.
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.
New build mastic in Underhill: local notes
Many of London’s new homes are flats in bigger developments, where snagging may go through the developer or managing agent. London and the South East are among the drier parts of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day.
If you’ve bought a new home near New Barnet station, the sealant around baths, showers and frames is worth checking in the first year or two.
Underhill is about 1 mile west of Barnet, in Greater London. Homes, rented property, offices and hotels in Underhill can book us for new build mastic, old or new, large or small. The work is guaranteed for a year. Our Greater London coverage runs to 764 places, Underhill among them. Our London page covers work nearby.
Work in EN5 and N20 works the same way as everywhere else we cover. Local streets include Park Road, May's Lane and Manor Road. Other places close to Underhill include Barnet (1 mile east), New Barnet (1 mile east), Monken Hadley (1 mile north), Hadley Wood (1 mile north-east) and Cockfosters (2 miles east). We also work in nearby towns such as London (11 miles south-east), City of Westminster (9 miles south), Marylebone (9 miles south), Kensington (10 miles south), St Pancras (9 miles south) and Shoreditch (10 miles south-east).
Landmarks near Underhill
Typical jobs here are in homes near Susi Earnshaw Theatre School, Highlands Gardens and The Red Lion pub, among other places. The nearest railway station is New Barnet station, roughly 1 mile east of the centre. Other landmarks nearby include Francis Skaryna Belarusian Library and Museum (2.2 miles south) and Barnet General Hospital (0.9 miles west). The countryside around Underhill includes Greenhill Gardens and Darland's Lake.
Towns and villages near Underhill
Other services in Underhill
Honest limits
We’ll always be straight with you, so here’s what new sealant won’t do:
- Leaking fittings rather than failed sealant
- A tray or bath that isn’t properly supported, until it’s fixed
- Damaged fittings that need replacing
If you’re not sure, just ring 0345 464 0079 or email us and we’ll give you a straight answer before you book.
Joints and surfaces we work on
- Bathrooms & en suites
- Kitchens
- Plot handovers
- Skirting & floors
- Show homes
- Windows & doors
Why it’s worth doing now in Underhill
DIY kits don’t solve the main problems with new-build sealant: grit, unprimed surfaces and old layers underneath. Cutting out, cleaning and priming are what make the difference. In London conversions, one flat’s bathroom is often above another flat’s ceiling, and a slow leak from a failed seal can end up in the flat below. Dealing with it early is far simpler for homes in Underhill.
Some things make a job bigger or smaller: how much old sealant there is and how stubborn it is, any mould to treat, and whether the work is at height. We take all of that into account in your quote.
Why book with us
- We agree the colour with you first
- An ARBOMaster approved applicator
- Experience in homes, commercial sites and hotels
- 4.9 on Google from 180+ five-star reviews
Take a look at how sealant jobs are priced or what customers say.
Quotes for new build mastic in Underhill
You will get a clear quote before work begins. It takes into account:
- The number of rooms or windows
- Whether old sealant or filler has to be cut out
- Any mould that needs treating
- The number and length of the joints
Homes and businesses are quoted the same way: the amount of work, the access and the products needed, along with when we can work on site. Ask us for a quote and we will explain what it covers.
What to tell us for a quote
What to tell us when you ask for a quote:
- How we’d reach the joints
- A few photos by email, if you can
- If someone has resealed it before
- Where the property is
For a quote, ring 0345 464 0079 or email us with the location and a short description of the problem. You will have a clear quote before any work starts.
What we do, step by step
On the day, there’s very little for you to do. Point us to the joints and we’ll get on with it. The work itself takes a few hours for most snagging lists, longer for a run of plots from start to finish. In a London area like Underhill, the main things to plan are parking and access: let us know about parking, the floor we will be working on and any lift or shared entrance.
- We start by going through the snagging items or plot schedule with you.
- The failed sealant is removed completely.
- We clean out the dust and grit left from the build.
- Primer goes on where the surface and product need it, then the new sealant.
- We tool every joint neatly and tell you when each area can be used.
Before we arrive
- Clear items away from the joints we are working on
- Tell us about any previous sealing or DIY attempts
- Tell us about any water getting in
Get a quote
There’s no standard price list. Instead, we send you a clear quote for your job. To get started, phone 0345 464 0079 or send us an email.
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Underhill questions
I let a flat near New Barnet station. Can you help?
Yes. We work for letting agents and landlords as well as homeowners. You can phone 0345 464 0079 or send us an email with the details for a clear quote.
Is parking a problem for a job in Underhill?
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 take out the old sealant first?
Yes. Sealing over the old bead is the commonest cause of early failure, and it’s something we never do.
Will you just run a new bead over the existing one?
No. The old sealant is cut out fully, the joint cleaned and primed where needed, before resealing.
How long will you be here?
As a guide, most jobs take a few hours in a single home. Bigger jobs take longer, and we’ll tell you how long to expect.
Are you fully insured?
Yes, we’re fully insured.
Can you work from my snagging list?
Yes. Snagging lists are a common starting point for us. We will go through the sealant items and agree what we’ll do.
Do you use white or clear sealant?
White and clear are the most common, but other colours are available. We choose one to suit the room and agree it with you.