Greater London · England
St Helier External Mastic
Sealing brickwork movement joints, render, cladding and façade joints for St Helier, backed by a 12-month guarantee. Ask us for a quote.
- Old sealant gone brittle and cracked
- Gaps where render, brick and frames meet
- Damp patches traced to an open external joint
About our external mastic in St Helier
We cut out failed sealant, set the joint depth with closed-cell backing rod and reseal with a low-modulus exterior sealant. We pick a colour that sits well with the wall so the joint does not stand out. Common call-outs are for rigid filler in a joint that should flex and joints where the bead has come unstuck, on copings & trims, joints between brick and frames and concrete & block.
Working on the outside of a London home means planning access: shared paths, upper floors and parking. For a home in St Helier, tell us how high the joints are and how to reach the back of the building.
We guarantee the work for a year. If there’s a problem with our work within the year, let us know and we will sort it.
- Place
- St Helier (SM5, SM4, SM1)
- Wider area
- Greater London
- Guarantee
- One year on every job
- Quotes
- A clear price before work begins
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
Landlord and commercial work in St Helier
Housing providers, facilities teams and property managers book us too. Several sites can be quoted together, and we’re fully insured for the work.
Mouldy or split sealant often shows up at the end of a tenancy, and it’s quick to put right between tenancies. Several properties can be quoted together.
Why deal with it now?
Water gets in through a failed movement joint. Resealing early keeps the job to the joint itself, instead of the wall and finishes around it. In a London flat, a failed joint rarely stays your problem alone: water can reach the neighbours below, and gaps in fire-rated joints affect the whole building.
What you pay reflects the work, not a rough estimate. That is why we ask about the job first and send you a clear quote before work begins.
What you get with us
- Fully insured
- Trusted Arbo and Everbuild sealants
- A sealant colour to suit the surroundings
- Every job guaranteed for a year
Take a look at how sealant jobs are priced or what customers say.
St Helier questions
Can parking be tricky for a visit in St Helier?
London parking needs a little planning, so let us know about permits, bays or a driveway when you book. The visit is then planned around what’s available.
Can you help a landlord with a rental near Sutton Common station?
Yes, we work for landlords and letting agents. Just phone 0345 464 0079 or email us and tell us about the property, and we will give you a clear quote.
Is it worth trying it myself?
You can, for simple jobs. The key is preparation: remove all the old material and work on a clean, dry joint. If it doesn’t work out, we can redo it.
What is backing rod for?
That’s backing rod, a closed-cell foam. It stops the sealant going in too deep and bonding to three sides, which would stop it stretching.
When will the joints need doing again?
It depends on the exposure, the movement and the product. Sealant is a maintenance item, so check the joints once a year.
Is there a guarantee?
Yes. There’s a 12-month guarantee on every job, wherever you are.
Can I add another job to the visit?
Of course. Doing several areas at once is usually more efficient.
How long does the job take?
It depends on the size of the job, but most jobs take a few hours to a few days, depending on the length of joint and the access. We’ll tell you when we quote.
St Helier buildings and the weather
In terraces and conversions, gutters and walls are often shared with the neighbours, so check who is responsible for the outside before booking. With historic houses such as Nonsuch Mansion (about 2.6 miles south-west) nearby, there’s older building stock in the area around St Helier as well as newer homes. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material.
For site and facilities teams at buildings such as Tweeddale Primary School, larger buildings have long runs of movement joint that eventually need resealing. If you live in an older home near St Peter's Church, an extension built onto an older house moves differently, and the joint between them takes the strain.
St Helier is about 3 miles south-east of Wimbledon, in Greater London. Homes, rented property, offices and hotels in St Helier is covered for external mastic, old or new, large or small. Every job comes with our 12-month guarantee. St Helier is one of 764 places in Greater London we cover for external mastic. Our London page covers work nearby (9 miles or so).
All of SM5, SM4 and SM1 is covered for external mastic, from the main roads to the quietest streets. External mastic is available to properties on Kelso Road, Wrythe Lane and Whitby Road. We also cover the places around St Helier: Rosehill (1 mile north-east), Benhilton (1 mile south-west), The Wrythe (1 mile south-east), Carshalton (1 mile south-east) and Sutton (1 mile south). We also work in nearby towns such as London (9 miles north-east), City of Westminster (9 miles north), Marylebone (9 miles north), Kensington (8 miles north), St Pancras (10 miles north) and Shoreditch (11 miles north-east).
Near you in St Helier
Around St Helier, our work takes us to homes and buildings near Greenshaw High School, The Cricketers Inn and Merton College. The nearest railway station is Sutton Common station, roughly 0.8 miles south-west of the centre. Nearby you will also find St Helier Hospital (less than half a mile south) and Chessington Castle Hill (5 miles west). Green spaces nearby include Bennett's Hole and Duppas Hill.
Also near St Helier
Other services in St Helier
What affects the quote in St Helier
For a quick quote, just ask. The main things that affect it are:
- Whether there’s mould to deal with
- Any working-time requirements on site
- How many rooms, windows or areas are involved
- The number and length of the joints
There are no prices on our website, because each job is priced on what it involves. For a quick quote, please call 0345 464 0079 or drop us an email and we will talk you through it.
Asking for a quote
A few details help us give you an accurate quote. When you get in contact, it helps to mention:
- Access, such as stairs, a lift or height
- What’s wrong with the joints now
- Any previous sealing or DIY work
- A few pictures by email, if you can
For external mastic in St Helier, phone 0345 464 0079 or send us an email. Tell us what the problem is and where, and you’ll get a clear quote before we start.
What happens on the day
There’s no need to move everything out, just the space around the work. Everything nearby is protected, and the work takes a few hours for a handful of joints, longer for a whole elevation in most cases. In St Helier, flats, stairs and shared entrances are part of the routine. Mention any building rules, key holders or managing agents when you book.
- Each joint is checked and the colour of the new sealant agreed.
- Failed sealant is removed back to clean, sound faces.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
Preparing for the visit
- Clear items away from the joints we’re working on
- Mention any tricky access
- Mention any leaks or damp you’ve noticed
How to get a quote
Quotes start with a quick conversation. Tell us what’s wrong, where it is and how much there is, and we will talk you through what we’d do. Whenever you are ready, call 0345 464 0079 or send us an email.
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What we’re called out for in St Helier
If plants are growing out of a joint, the sealant has normally failed or was never there. Dirt and roots then trap moisture in the joint and make things worse.
These are the problems we’re asked about most:
- Weeds or debris growing in open joints
- Joints where the bead has come unstuck
- Failed sealant between panels on a façade
- Joints pointed up with cement by mistake
Rented homes near Sutton Common station change hands often, and failed wall and movement joints let damp in, so they’re worth checking between tenancies.
What to look for in a quote
- Who does the work, and how experienced they are
- How long the guarantee is
- Whether they’re fully insured
- What the quote includes, VAT included or not
Looking after it afterwards
To keep the joints looking good and working properly:
- Keep movement joints as flexible joints, not mortar
- Keep soil, plants and ivy away from the joints
- Point out the joints to other trades
- Leave the joints unpainted unless we’ve said otherwise
Have a quick look at the joints each spring. Splits, gaps at the edges or plants in the joint are early warning signs.
If you can see gaps, plants or bare sections in a joint, have it checked. Early work is quicker and leaves a better finish.
Should I try it myself first?
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 fails, we can still redo it.
Sealing over old silicone is the commonest DIY error. Silicone doesn’t stick to old silicone, so it peels away and traps moisture behind it. Everything old must be removed first.