Greater London · England

New-build mastic & snagging in Roundshaw, Greater London

New build mastic for Roundshaw, by sealant specialists with 20+ years’ experience. Rated 4.9 on Google from 180+ five-star reviews.

  • Frame joints opening as the plaster dries
  • Joints pulling apart as timber shrinks
  • Gaps between new skirting and floors

Trusted new build mastic in Roundshaw

Joints and finishes in Roundshaw homes

Many of London’s new homes are flats in bigger developments, where snagging may go through the developer or managing agent. Rainfall in the South East is lower than in much of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.

Roundshaw is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book. For new homes near Wallington station, it’s worth checking the sealant early, while snags are still fresh.

Roundshaw is about 2 miles south-west of Croydon, in Greater London. If you need new build mastic in Roundshaw, please ring 0345 464 0079 or send us an email for a quick quote. We cover Greater London from our Crawley base, Roundshaw included. We cover 764 towns and villages across Greater London, large and small. London is on our list too, around 10 miles away.

Work in SM6, CR8 and CR0 works the same way as everywhere else we cover. If you need new build mastic at a property on Link Lane, Milton Road and Redwing Road or anywhere close by, we can help. Neighbouring places we cover for new build mastic include Russell Hill (1 mile east), Bandonhill (1 mile north), Peaks Hill (1 mile south), Waddon (1 mile north-east) and Wallington (1 mile north-west). Within a short drive, we also cover London (10 miles north), City of Westminster (11 miles north), Marylebone (11 miles north), Kensington (11 miles north), St Pancras (12 miles north) and Shoreditch (12 miles north).

Local landmarks in Roundshaw

We work in homes and buildings around Wilson's School, Waddon Ponds and The John Fisher School. The closest station to Roundshaw is Wallington station, about 0.9 miles north-west. Nearby you’ll also find Purley War Memorial Hospital (1.2 miles south-east) and Croydon Airport Visitor Centre (0.6 miles east). Not far away are Roundshaw Downs and Duppas Hill.

Map of Roundshaw © OpenStreetMap contributors

How we handle new build mastic in Roundshaw

We carry out plot mastic and second-fix sealing for builders, and snagging reseals for new-home owners. Both get the same care over preparation, because that is what rushed new-build sealant normally lacks. Typical jobs include joints pulling apart as timber shrinks and gaps behind new kitchen upstands, across plot handovers, windows & doors and show homes.

Much of London’s new housing is flats in larger developments. Snagging there often goes through the developer or managing agent, and failed shower seals, open skirting joints and gaps at thresholds are typical.

Every job comes with a 12-month guarantee.

Place
Roundshaw (SM6, CR8, CR0)
Region
Greater London
Cover
A year, on every job
Quotes
A clear quote up front
Telephone
0345 464 0079
Page updated
26 October 2026
Mr Mastic applicator sealing the vertical joint between a glass shower screen and tiled wall

Why act early in Roundshaw

Sealant done properly at handover means fewer callbacks. Every return visit for a failed seal takes time and most come down to preparation. Converted houses in London often have a bathroom above someone else’s living room, so a small leak from tired sealant can mean a neighbour’s ceiling and a lot of disruption. Dealing with it early is far simpler.

Doing several joints on one visit usually makes better use of the time than several visits, so tell us about everything that needs sealing. You will get one clear quote for the whole job.

Why choose Mr Mastic in Roundshaw

  • Anti-fungal silicone where joints get wet
  • We agree the colour with you first
  • Quality sealants from Arbo and Everbuild
  • Fully insured

Take a look at what affects the cost and what customers say.

Questions from Roundshaw

Is Roundshaw in your area for new build mastic?

Yes, Roundshaw is within the area we cover. We work across London and the South East. You can ring 0345 464 0079 or send us an email and tell us what needs doing.

Can you help a landlord with a rental near Wallington station?

Yes, landlords and agents are among the people we work for, and several properties can go on one quote. You can call 0345 464 0079 or email us with the details for a clear quote.

Is it normal for sealant to crack in a new home?

New homes dry out and move in their first couple of years, and sealant is often rushed onto dusty, unprimed surfaces. Both lead to early failure.

Does someone need to be in?

If the work is inside, we need someone to let us in. Once we’ve agreed the job, you don’t need to watch us work.

Can you work on commercial sites?

Yes. We’ve worked for hotels, offices and other businesses, and we’re fully insured.

Will the old sealant be removed?

Yes. Sealing over the old bead is the commonest cause of early failure, so we never do it.

Do you guarantee your work?

Yes. Every job comes with a 12-month guarantee.

Can you reseal over the builder’s sealant?

No. New silicone won’t bond to old silicone, so it soon lifts and traps water. The old sealant always comes out first.

Keeping the joints in good condition

Once the sealant has cured, a few habits help it last:

  • Avoid scourers and strong chemicals on sealant
  • Ventilate bathrooms well, especially in the first year
  • Check bath and shower seals every few months as the house settles
  • Raise failed sealant with the developer while you are covered

Keep the bathroom ventilated, especially in the first year. Use the extractor fan or open a window after showers.

Lifting sealant traps moisture and mould behind it. Resealing before mould gets in keeps the job straightforward.

Surface by surface

Show homes

Bathrooms, kitchens and frames in show homes are sealed or resealed to a neat finish to a tidy standard. Tell us when the home is open so we can plan around it.

Skirting and floors

Wet-area floor joints need a flexible seal. They get a flexible, water-resistant sealant.

How we quote for new build mastic

Every job gets its own quote. This is what makes a difference:

  • Which sealant suits the joint
  • How many areas need sealing
  • Access and height
  • The amount of work

Some things make a job bigger or smaller: the old material and how easily it comes out, any mould to treat, and whether we need extra access for height. We take all of that into account in your quote.

What to tell us for a quote

Photos by email are helpful but not essential. Please mention:

  • The rough size of the job
  • Access, such as stairs, a lift or height
  • Where the job is, and your postcode
  • A few photos by email, if you can

A good description makes for an accurate quote. Let us know the location, the problem and roughly how many joints.

Should I try it myself first?

The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is matched to the joint and its conditions, then guaranteed for a year.

If you do try it yourself, take your time over the preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it fails, we can still redo it.

What we can’t put right

Before you book, it’s worth knowing the limits too:

  • Plumbing faults behind the sealant
  • Disputes or warranty claims with your builder
  • Settlement cracks that need a surveyor

Not sure which it is? You can ring 0345 464 0079 or send us an email and we will tell you honestly.

Joints and surfaces we work on

  • Skirting & floors
  • Show homes
  • Plot handovers
  • Windows & doors
  • Kitchens
  • Bathrooms & en suites

What we do, step by step

A visit follows a simple pattern: we check the joints, protect the area around them, carry out the job and clear up. It normally takes a few hours in a single home. In Roundshaw, 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.

  1. We look at why each joint failed, including any movement.
  2. We remove the failed sealant and clean the joints.
  3. We make sure the joints are dry and prime them if needed.
  4. New sealant goes in, with baths filled first so they’re at their heaviest.
  5. We check every joint and leave you with the cure times.

Preparing for the visit

  • Let us know if you’ve seen damp or leaks
  • Let us know about parking restrictions
  • Mention any sign-in or site rules at work premises

Ask for a quote

Want a quote for new build mastic? Please call 0345 464 0079 or drop us an email and tell us about the job. We’ll explain what we’d do and give you a clear price before work begins.

Get a price

Advice

20+ yearsMastic and sealant specialists
ARBOMaster approvedApproved applicator for Arbo sealants
Fully insuredDomestic, commercial and hotels
One-year guaranteeOn every job