Greater London · England
External Mastic in Streatham Park
External mastic for Streatham Park and the surrounding area: the right sealant, proper preparation and a neat finish. Call for a quick quote.
- Hard, crazed mastic that has stopped moving
- Movement joints filled with mortar instead of sealant
- Sealant pulling away from one side of the joint
How we handle external mastic in Streatham Park
Where two different materials meet, such as brick and render or blockwork and metal, they move at different rates. A flexible sealant bridges the two where a rigid filler would soon crack. We work on render & cladding joints, joints between brick and frames and façade panels, and people most often call us about movement joints filled with mortar instead of sealant and joints with sealant missing in places.
Newer London blocks are built with movement joints in brick and render, and with cladding joints sealed with mastic. Period houses have different weak points, such as gutter joints, trims and the line where an extension meets the old wall, and both kinds of building are found across London.
Our work is backed for twelve months, and the guarantee is the same wherever you are.
- Where
- Streatham Park (SW16, SW17, SW12)
- Region
- Greater London
- Guarantee
- 12 months on all our work
- Price
- A clear price before any work starts
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
When it isn’t the sealant
To be straight with you, there are a few things sealant won’t fix:
- Render that is blown, hollow or coming away
- Movement that’s more than a sealant joint can take
- Cutting new joints into brickwork, which is building work rather than sealant work
Not sure which it is? You can call 0345 464 0079 or send us an email and we will tell you honestly before you book.
Where we work in Streatham Park
- Concrete & block
- Façade panels
- Copings & trims
- Brickwork movement joints
- Joints between brick and frames
- Render & cladding joints
What happens on the day
There’s no need to move everything out, just the space around the work. We protect the rest, and the work takes a few hours to a few days, depending on the length of joint and the access for a typical job. 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.
- First, the joints are inspected and the access agreed.
- Every bit of old sealant and any mortar or debris is cut out.
- The faces are brushed clean and primed where the product requires it.
- Backing rod sized to the joint goes in to set the depth.
- The exterior sealant is applied, tooled and checked along its length.
Preparing for the visit
- Where the joints are inside, avoid wetting them before we arrive
- Clear the area around the work
- Let us know if you’ve seen damp or leaks
Get a quote
If you are in Streatham Park and need external mastic, call 0345 464 0079 or email us. Tell us what the problem is and where, and we’ll agree the price before any work begins.
Read more
Streatham Park buildings and the weather
Historic houses like Kingswood House (about 2.6 miles east) are a reminder that the area around Streatham Park has older buildings as well as new. In older buildings, older brick and stone need a sealant that suits them, at the right joint depth. London terraces and converted houses often share gutters, downpipes and walls, so it’s worth agreeing who is responsible before work starts.
For site and facilities teams at buildings such as St Leonard's Church of England Primary School, larger buildings have long runs of movement joint that eventually need resealing. Rented homes near Streatham station change hands often, and split movement joints are easy to miss on a rental until damp shows inside.
Streatham Park is about 1 mile west of Streatham, in Greater London. Across the SW16 area, our applicators can take on external mastic. Our area takes in 764 places across Greater London.
Work in SW16, SW17 and SW12 is quoted and booked the same way as anywhere else. External mastic is available to properties on Lewin Road, Rydal Road and Natal Road. Other places close to Streatham Park include Furzedown (1 mile south-west), Streatham (1 mile east), Tooting (1 mile west), Tooting Bec (1 mile west) and Hyde farm estate (1 mile north). We also work in nearby towns such as London (5 miles north), City of Westminster (6 miles north), Marylebone (6 miles north), Kensington (6 miles north-west), St Pancras (7 miles north) and Shoreditch (7 miles north).
Near you in Streatham Park
Locally, jobs take us to homes and businesses close to Furzedown Secondary School, Streatham Common and Graveney School. Streatham Park’s nearest station is Streatham station, roughly 0.5 miles east of the centre. Other landmarks nearby include London Sewing Machine Museum (0.9 miles north-west) and Southside Wandsworth (2.9 miles north-west). Not far away are Battersea Park Lake and Knight's Hill.
What we’re called out for in Streatham Park
Joints sealed without backing rod, or far too deep, rarely last. Sealant bonded to three sides has nowhere to go and rips as the joint opens.
The problems people usually mention when they call are:
- Movement joints filled with mortar instead of sealant
- Cracked joints where brick meets render or frames
- Weathered mastic that no longer stretches
- Moss and dirt in joints with no sealant left
Streatham Park is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
Before you book anyone
- How the joint is cleaned and prepared
- Is VAT in the price?
- Whether they seal over old material or remove it
- What insurance they hold
For landlords and businesses
Businesses can book us for washrooms, kitchens, offices and more. For commercial premises, we can talk through working times when we quote.
We regularly work with letting and managing agents. Tell us the address, the job and how access works.
How the job changes by surface
Render joints
Render has movement joints and stop beads that need sealing. They’re resealed in a sealant that suits the render.
Joints between dissimilar materials
Brick against render, concrete against metal, stone against timber: every change of material is a joint. We seal the joint with a flexible exterior sealant so neither cracks the other.
Nearby places to Streatham Park
Also in Streatham Park
How to look after the new joints
Aftercare is simple, and it makes a real difference:
- Point out the joints to other trades
- Walk round the building once a year and look at the joints
- Keep water from gutters off the wall
- Keep high-pressure jets off the joints
Follow the cure time we give you before the joint is knocked or disturbed. The surface skins over quickly, but full cure takes longer.
Water getting behind cladding or render can go unnoticed for a long time. By the time there’s a damp patch, the damage can be well established, so it’s worth resealing at the first signs.
Questions from Streatham Park
Can you do external mastic in Streatham Park?
Yes. We work across London and the South East, and Streatham Park is part of that. Just call 0345 464 0079 or email us with a few details of the job, and we will send you a clear quote.
Can you help a landlord with a rental near Streatham station?
Yes, landlords and agents are among the people we work for, and several properties can go on one quote. Just call 0345 464 0079 or send us an email with the address and what needs doing, and we will give you a clear price.
Why is there a gap in my brick wall?
Brickwork, render and cladding all move a little, and planned joints take up that movement. It’s closed with backing rod and a flexible sealant.
Is there a guarantee?
Yes: twelve months. If there’s a problem with our work in that time, tell us and we will put it right.
Do I have to be there?
If the work is inside, we need someone to let us in. After that, you can carry on with your day.
How long before the joint can be used?
Most sealants are touch-dry well before they’re fully cured. We will give you the cure time for the product we used before we leave.
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.
Should I point up the gap in my brickwork?
No. A mortar-filled joint can’t move, so the wall cracks somewhere else instead. Use a flexible sealant with backing rod.
Why deal with it now?
It often makes sense to reseal all the failing joints on an elevation together. They’ve weathered the same way. In London conversions, one flat’s bathroom is often above another flat’s ceiling, 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.
Some things make a job bigger or smaller: how much old sealant there is and how stubborn it is, whether mould needs treating, and whether we need extra access for height. Your quote takes all of that into account.
Why Streatham Park clients choose us
- Old sealant always removed completely
- 4.9 on Google from 180+ five-star reviews
- One-year guarantee on every job
- We leave the area clean and tidy
Read our cost guide or our reviews.