Greater London · England
Blendon External Mastic
External mastic for Blendon, by sealant specialists with 20+ years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Brick movement joints where the sealant has split
- Sealant pulling away from one side of the joint
- Rigid filler in a joint that should flex
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.
Failed sealant is one of the commonest items on a check-out report, and it’s quick to put right between tenancies. We can quote for more than one property at once.
How we handle external mastic in Blendon
A movement joint is only as good as its depth. Closed-cell backing rod sets the depth and stops the sealant sticking to the back, so it bonds to the two sides only and can stretch. We work on façade panels, copings & trims and concrete & block, and people most often call us about joints where the bead has come unstuck and gaps where render, brick and frames meet.
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.
Big or small, it’s backed by our 12-month guarantee.
- Location
- Blendon (DA5, DA15, DA6)
- Wider area
- Greater London
- Guarantee
- 12 months on all our work
- Quotes
- Quoted before any work starts
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
How it works
The work is kept neat and contained to the area we’re working on, so you can get on with your day. Expect the work to take a few hours for a handful of joints, longer for a whole elevation, and we explain the cure time before we leave. In Blendon, flats, stairs and shared entrances are part of the routine. If the building has a concierge, managing agent or access rules, tell us when you book.
- Each joint is checked and the colour of the new sealant agreed.
- Failed sealant is removed back to clean, sound faces.
- Backing rod goes in so the sealant can stretch between the two faces.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
How to prepare
- Mention any tricky access
- Clear the area around the work
- Tell us if parking is tricky
Getting a quote
We quote each job on its own. Just phone 0345 464 0079 or drop us an email with the details.
Advice
What the job involves on each surface
Copings and trims
Copings expand and contract through the day, so the joints need a sealant that stays flexible.
Concrete and blockwork
Wide joints in concrete need the depth controlling carefully. We size the backing rod to the gap and keep the sealant to the right depth.
Looking after it afterwards
So the new joints stay in good condition:
- Keep high-pressure jets off the joints
- Keep movement joints as flexible joints, not mortar
- Leave the joints unpainted unless we have said otherwise
- Fix overflowing gutters above sealed joints
Do not paint over the new sealant unless we’ve said the product is paintable. Many exterior sealants aren’t designed to be painted, and paint can crack as the joint moves.
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.
Why deal with it now?
Pointing a movement joint with mortar might seem a neat fix, but it locks the joint solid. The wall then cracks somewhere else. The correct repair is a flexible sealant with the right backing. In a London flat, a failed joint rarely stays your problem alone: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
Rather than a set price list, we price the job in front of us: the amount of work, the old material and the access. You’ll know the price before we begin.
What you get with us
- We agree the colour with you first
- White, clear, grey or coloured to suit, where the product allows
- Sealant colour chosen to suit
- We leave the area clean and tidy
Read what affects the cost or what customers say.
What external mastic looks like in Blendon
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. Historic houses like Danson House (about 0.7 miles north) are a reminder that the area around Blendon has older buildings as well as new. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material.
As a London address, Blendon can be tricky for parking: tell us about permits, visitor bays or off-street space when you book. For an older house near a landmark such as St James the Great, the joints between older walls, newer extensions and the roofline need a sealant that can move.
Blendon is about 1 mile south-east of Welling, in Greater London. From the centre of Blendon to the outskirts, external mastic is available for homes and businesses alike. Blendon is one of 764 towns and villages in Greater London where we work for external mastic. For nearby work, see our London page (10 miles or so).
All of DA5, DA15 and DA6 is covered for external mastic, from the main roads to the quietest streets. External mastic is available to properties on Penn Lane, Hurst Road and Brook Lane. Being close to the A221, Blendon is simple for us to get to. Neighbouring places we cover for external mastic include Bexley (1 mile south-east), Crook Log (1 mile north), Welling (1 mile north-west), Upton (1 mile north-east) and Bexleyheath (1 mile north-east). We also work in nearby towns such as London (10 miles west), City of Westminster (13 miles west), Marylebone (13 miles north-west), Kensington (14 miles west), St Pancras (12 miles north-west) and Shoreditch (10 miles north-west).
Near you in Blendon
Locally, jobs take us to homes and businesses close to Danson Park, The Royal Oak Public House and Hurst Primary School. The closest station to Blendon is Albany Park station, about 0.8 miles south. Other landmarks nearby include Metropolitan Police Museum (1.3 miles south-west) and Bexley Hospital (0.8 miles north-east). Not far away are Wansunt Pit and Summer Hill.
More services for Blendon
Signs you need external mastic in Blendon
Many joints fail because they were sealed too deep or with nothing behind them. If the sealant sticks to the back as well as the sides, it cannot stretch and rips as the joint opens.
These are the problems we are asked about most:
- Weeds or debris growing in open joints
- Joints where the bead has come unstuck
- Movement joints filled with mortar instead of sealant
- Hard, crazed mastic that has stopped moving
If you let a flat or house near Albany Park station, failed wall and movement joints let damp in, so they’re worth checking between tenancies.
What to look for in a quote
- What preparation is included
- What the cure time is
- How long the guarantee is
- What insurance they hold
What affects the quote in Blendon
Jobs vary more than people expect. The main factors:
- The number and length of the joints
- Any mould that needs treating
- How many rooms, windows or areas are involved
- Any working-time requirements on site
Some things make a job bigger or smaller: the old material and how easily it comes out, whether mould needs treating, and whether we need extra access for height. We take all of that into account in your quote.
Helping us quote
You don’t need to know the technical terms. It helps if you can tell us:
- Photos by email, if that is easy
- The rough size of the job
- If it’s domestic, commercial or a hotel
- The address or postcode of the job
We don’t publish a price list, as no two jobs are quite the same. Instead, we give you a clear price for your job. To get started, phone 0345 464 0079 or send us an email.
Your questions about external mastic in Blendon
Do you cover Blendon for external mastic?
Yes, Blendon is within the area we cover. We work across London and the South East. You can call 0345 464 0079 or drop us an email and let us know what needs doing, and we will send you a clear quote.
Can parking be tricky for a visit in Blendon?
Parking in Blendon, as in most of London, takes a little planning: a visitor permit or a nearby bay makes the day run more smoothly.
Do I have to be there?
We need access to the joints, so we’ll agree that with you when we book. For inside work, that normally means someone being in.
Why is there a gap in my brick wall?
A vertical gap in a long brick wall is generally a movement joint. It gives the wall room to move, and it should be sealed with a flexible sealant.
What is backing rod for?
We fit closed-cell backing rod wherever the joint depth needs controlling. It sets the sealant depth and prevents three-sided bonding, so the joint can move.
Can you seal joints between render and window frames?
Yes. Where different materials meet is one of the most common joints we seal. We use a flexible sealant suited to both surfaces, primed where needed.
Can you reach joints on upper floors?
Each building is different. Tell us the height, the number of joints and what’s below them, and we’ll confirm what access is needed.
How long will you be here?
Most jobs take a few hours for a handful of joints, longer for a whole elevation, including preparation and clearing up. Your quote will say how long we expect yours to take.