Greater London · England
Chelsea Harbour External Mastic
External mastic in Chelsea Harbour from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Panel joints letting water in
- Joints pointed up with cement by mistake
- Moss and dirt in joints with no sealant left
External mastic in Chelsea Harbour, done properly
Joints between dissimilar materials, like brick against render or concrete against a steel frame, see movement from both sides. A flexible sealant bridges the two where mortar or filler would crack. We work on render & cladding joints, joints between brick and frames and concrete & block, and people most often call us about movement joints filled with mortar instead of sealant and panel joints letting water in.
Outside work in London starts with access: side passages, upper floors and where to park. In Chelsea Harbour, joints up high may need ladders or other access, which is worth talking through when you book.
We stand behind the work with a one-year guarantee, so you are covered after we’ve gone.
- Where
- Chelsea Harbour (SW6, SW11, SW10)
- Region
- Greater London
- Guarantee
- 12 months on all our work
- Price
- A clear quote up front
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
What the job involves on each surface
Copings and trims
Coping and trim joints face rain and sun head on. We reseal them with an exterior sealant suited to the material.
Render joints
Render has movement joints and stop beads that need sealing. They’re resealed in a sealant that suits the render.
Nearby places to Chelsea Harbour
What else we do in Chelsea Harbour
Why act early in Chelsea Harbour
Water gets in through a failed movement joint, behind render and cladding. Resealing early keeps the job to the joint itself, rather than the wall around it. 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.
Homes and businesses are quoted the same way: how much there is to do, how we reach it and what it needs, plus any working-time requirements on site. Ask us for a quote and we will explain what it covers.
Why choose Mr Mastic in Chelsea Harbour
- 12-month guarantee on every job
- We agree the colour with you first
- Domestic, commercial and hotel work
- Fully insured
Read what affects the cost or our reviews.
What happens on the day
Before we leave, we go over the finished joints with you. The visit itself generally takes a few hours for a handful of joints, longer for a whole elevation, depending on the size of the job. In Chelsea Harbour, 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.
- First, the joints are inspected and the access agreed.
- Every bit of old sealant and any mortar or debris is cut out.
- Joint faces are cleaned back and primed if the sealant needs it.
- Backing rod sized to the joint goes in to set the depth.
- We apply the sealant, tool it and check the whole run.
Preparing for the visit
- Mention any leaks or damp you’ve noticed
- Let us know about parking restrictions
- Keep pets and children clear of the area while we work
Get a quote
Call for a quick quote, or send an email if you’d rather. Tell us about the joints that need doing and we’ll talk you through the work.
Advice
Can I do it myself?
Some jobs are best left to a professional: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.
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.
Signs you need external mastic in Chelsea Harbour
Every building moves. Clay bricks expand slightly over their life, concrete and block shrink, and everything moves with temperature and wet. The sealant in the movement joints takes that strain.
People normally contact us when they notice one of these:
- Old sealant gone brittle and cracked
- Leaking joints around cladding and façade panels
- Brick movement joints where the sealant has split
- Weeds or debris growing in open joints
For an older house near a landmark such as St Mary's Church, old and new materials meet at the roofline and walls, which is where sealant earns its keep.
Questions to ask before you book
- How the surfaces are prepared before sealing
- How hidden problems are handled
- What guarantee comes with the work
- Which sealant they’ll use, and why
Outside joints around Chelsea Harbour
In terraces and conversions, gutters and walls are often shared with the neighbours, so it’s worth agreeing who is responsible before work starts. Rainfall in the South East is lower than in much of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day.
Chelsea Harbour is in London, so parking needs planning: let us know about parking bays, permits or a driveway. Schools such as Chelsea Academy are buildings too, and its movement joints, gutters and trims need looking after like any other building’s.
Chelsea Harbour is about 2 miles south-east of Kensington, in Greater London. Jobs in Chelsea Harbour get the same care as everywhere else we work: the old material taken out, joints prepared properly and a 12-month guarantee. Our area takes in 764 places across Greater London.
Postcode districts we cover here for external mastic: SW6, SW11 and SW10. You will find streets such as Ann Lane, York Road and Lots Road, all of which we cover. If you’re just outside Chelsea Harbour, we cover Sands End (1 mile south), Walham Green (1 mile north-west), World's End (1 mile north), Little Chelsea (1 mile north) and Parsons Green (1 mile west). Larger places within reach include London (4 miles north-east), City of Westminster (3 miles north-east), Marylebone (3 miles north-east), St Pancras (4 miles north-east), Shoreditch (6 miles north-east) and Walthamstow (10 miles north-east).
Landmarks near Chelsea Harbour
We work in homes and buildings around Heatherley School of Fine Art, Lots Road pub and Imperial Park and the streets around them. You will also find Langford Primary School (less than half a mile south-west) and Natural History Museum Library and Archives (1.5 miles north). There’s a railway station in Chelsea Harbour itself: Imperial Wharf station. Other landmarks nearby include Baynard's Castle (4.3 miles north-east) and Chelsea Stadium Tour And Museum (0.6 miles north-west). The countryside around Chelsea Harbour includes WWT London Wetland Centre and Battersea Park Lake.
How to look after the new joints
Aftercare is simple:
- Deal with leaking gutters that soak the joints below
- Avoid pressure-washing directly into sealant joints
- Never let anyone fill a movement joint with mortar
- Look over the joints every year, ideally after winter
Make sure anyone working on the wall later knows where the movement joints are. They must stay as flexible joints, never rendered or pointed over.
Water getting behind cladding or render can go unnoticed for a long time. When it finally shows inside, the joint may have been open for years, so it’s worth resealing at the first signs.
Chelsea Harbour: your questions answered
Can you do external mastic in Chelsea Harbour?
Yes. Our work covers London and the South East, and Chelsea Harbour is part of that. You can phone 0345 464 0079 or email us and tell us what needs doing, and we’ll give you a clear quote.
Is parking a problem for a job in Chelsea Harbour?
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 I add another job to the visit?
Yes. Just list everything you need and we will quote it together.
Will the old sealant be removed?
Yes, every time. New silicone does not stick to old silicone, so the joint is cleaned back first.
When is the sealant fully cured?
Different products cure at different speeds, so follow the cure time we give you when we finish.
Can landlords and businesses book you?
Yes. As well as homeowners, we work for landlords, agents, businesses and hotels.
How long does the job take?
A typical job takes anything from a few hours to several days, depending on the building. We will confirm how long when we quote.
When will the joints need doing again?
That depends on the wall, the weather and the movement. Look for splits, hardening or edges coming away, and reseal at that point.
Work for landlords, hotels and businesses
Mouldy or split sealant often shows up at the end of a tenancy. We can quote for more than one property at once.
Whether it’s one flat or a portfolio, you get the same standard of work: the old material taken out, careful preparation and a 12-month guarantee.