Greater London · England
Nunhead External Mastic
External mastic in Nunhead from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Cracked joints where brick meets render or frames
- Rain getting behind render or cladding at a joint
- Joints where the bead has come unstuck
About our external mastic in Nunhead
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. If you’re dealing with gaps where render, brick and frames meet and moss and dirt in joints with no sealant left, we can help.
Working on the outside of a London home means planning access: shared paths, upper floors and parking. For a home in Nunhead, tell us how high the joints are and how to reach the back of the building.
A 12-month guarantee comes as standard, so you are not left on your own once the job is done.
- Location
- Nunhead (SE15, SE4, SE14)
- Region
- Greater London
- Cover
- 12 months on all our work
- Quote
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
Aftercare tips
So the new joints stay in good condition:
- Show decorators and builders where the movement joints are
- Avoid pressure-washing directly into sealant joints
- Check external joints each spring
- Ask before painting over external sealant
Avoid pressure-washing straight into the joints. A strong jet can damage the edges of the bead and let water in behind.
Gaps, plants or missing sealant in a joint are worth getting looked at. Early work is quicker and leaves a better finish.
Walls and rooflines in Nunhead
With historic houses such as Queen's House (about 2.4 miles north-east) nearby, there’s older building stock in the area around Nunhead 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. In terraces and conversions, gutters and walls are often shared with the neighbours, so it’s worth agreeing who is responsible before work starts.
Homes close to Saint Antony with Saint Silas include some older properties, and the joints between older walls, newer extensions and the roofline need a sealant that can move. Nunhead is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
Nunhead is about 1 mile south-west of New Cross, in Greater London. Anywhere in SE15, our applicators can take on external mastic. Our area takes in 764 places across Greater London, large and small.
Our applicators cover all of SE15, SE4 and SE14 for external mastic. Whether your property is on Rye Road, Nash Road and Kitto Road or anywhere close by, our applicators can take on the job. Other places close to Nunhead include Telegraph Hill (1 mile north-east), Honor Oak (1 mile south), Peckham (1 mile north-west), New Cross (1 mile north-east) and Brockley (1 mile south-east). Larger places within reach include London (3 miles north-west), City of Westminster (6 miles north-west), Marylebone (6 miles north-west), Kensington (7 miles west), St Pancras (5 miles north-west) and Shoreditch (5 miles north).
Around Nunhead
In Nunhead, that means homes and buildings near The Ivy House, Peckham Rye and Allenby Tutorial Trust and the streets around them. Nunhead has its own railway station: Nunhead station. Nearby you’ll also find Greenwich Castle (2.4 miles north-east) and Lewisham Shopping Centre (1.7 miles east). For a walk, there’s Knight's Hill and One Tree Hill.
Work for landlords, hotels and businesses
We regularly work with letting and managing agents. Send the address, what’s needed and the access arrangements and we will give you a quote.
A neglected joint can let water reach the structure, which is a bigger problem in a rented property. Resealing at the right time is simple maintenance that we can handle for you.
Why deal with it now?
A properly done movement joint is an even line in a colour that suits the wall. A rushed bead with no backing looks untidy and does not last so it’s worth doing right. 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.
What it costs depends on the size of the job, how hard the old material is to remove and access to the work. You’ll have a clear quote before any work starts.
Why Nunhead customers choose us
- 20+ years of sealant experience
- Rated 4.9 stars on Google
- We leave the area clean and tidy
- Every job guaranteed for a year
Read our cost guide or customer reviews.
Also near Nunhead
Also in Nunhead
How the visit works
Most of a good job is in the preparation, so that is where we spend the time. Every joint is cleaned and dried before new material goes in. All told, the work takes a few hours to a few days, depending on the length of joint and the access. 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 we look over the joints with you, agree which to renew and talk through access.
- The old mastic and anything lodged in the joint is removed.
- Both sides are cleaned back to sound material and primed if needed.
- Closed-cell backing rod is fitted to set the depth and stop three-sided bonding.
- A flexible exterior sealant is applied and tooled in a colour to suit the wall.
Getting ready for the visit
- Plan for the work area to be out of bounds to pets and children
- Let us know about parking restrictions
- Mention any sign-in or site rules at work premises
Ask for a quote
A good description makes for an accurate quote. Let us know the location, the problem and roughly how many joints, and add photos by email if you can.
Related advice
Should I try it myself first?
Some sealant jobs are within reach of a careful DIYer, like a short, easy-to-reach joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
The biggest DIY mistake is sealing over old sealant. New silicone will not bond to old, so it lifts and traps water and mould underneath. Everything old must be removed first.
Signs you need external mastic in Nunhead
Joints sealed without backing rod, or far too deep, rarely last. 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:
- Movement joints with cracked, split or missing sealant
- Joints where the bead has come unstuck
- Gaps where render, brick and frames meet
- Weeds or debris growing in open joints
If you look after a building such as Ivydale Primary School, its movement joints, gutters and trims need looking after like any other building’s.
What to look for in a quote
- Which sealant they’ll use, and why
- Whether they seal over old material or remove it
- What preparation is included
- How hidden problems are handled
Questions from Nunhead
I let a flat near Nunhead station. Can you help?
Yes, landlords and agents are among the people we work for, and several properties can be quoted together. You can call 0345 464 0079 or send us an email with the details for a clear quote.
Can parking be tricky for a visit in Nunhead?
Parking in Nunhead, as in most of London, takes a little planning: a visitor permit or a nearby bay makes the day run more smoothly.
Where are you based?
Mr Mastic is based in Crawley. Our applicators cover Nunhead.
Can you seal joints between two different materials?
Yes. Where different materials meet is one of the most common joints we seal. The sealant is chosen to bond to both sides with primer where required.
Do you guarantee your work?
Yes, always. There’s a 12-month guarantee on every job, large or small.
How do you reach high-level joints?
It depends on the height and the site. Ground-floor joints are simple; for higher work, tell us about the building and we’ll confirm what’s needed.
Do you work in Nunhead?
Yes. We are based in Crawley and work across South East England, London and Scotland.
Do you hold any approvals?
Yes. ARBOMaster is the approved applicator scheme for Arbo sealants, and we are part of it.
Quotes for external mastic in Nunhead
Jobs vary more than people expect. The main factors:
- Mould in or behind the old joints
- Which sealant suits the joint
- Working hours on commercial sites
- The old material and how stubborn it is
What you pay reflects the work, not guesswork. That’s why we ask a few questions first and give you a clear quote before work begins.
What we need to know
When you call or email, these details help:
- How we’d reach the joints
- Whether it has been sealed before
- The type of property
- Where the property is
We quote each job on its own, so the first step is telling us about yours. Just call 0345 464 0079 or email us with the details.