Greater London · England
New Eltham External Mastic
External mastic for New Eltham, by sealant specialists with 20+ years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Sealant that has lost its bond to the brick or render
- Plants rooting in failed movement joints
- Brick movement joints where the sealant has split
About our external mastic in New Eltham
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’re often asked to deal with rain getting behind render or cladding at a joint and brick movement joints where the sealant has split, on concrete & block, joints between brick and frames and copings & trims.
Outside work in London starts with access: side passages, upper floors and where to park. For a home in New Eltham, tell us how high the joints are and how to reach the back of the building.
A one-year guarantee comes as standard, so you’re not left on your own once the job is done.
- Location
- New Eltham (SE9, DA15, BR7)
- Region
- Greater London
- Cover
- One year on every job
- Quote
- A clear quote up front
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
How we quote for external mastic
Your quote is based on your job. We look at:
- How easy the joints are to reach
- How much old sealant there is and how hard it is to remove
- Any mould that needs treating
- The number and length of the joints
Instead of a standard rate, we price the job in front of us: the amount of work, the old material and the access. You will know the price before we begin.
Helping us quote
When you contact us, these details help:
- Where the property is
- If it’s domestic, commercial or a hotel
- Access, such as stairs, a lift or height
- How many joints, rooms or windows are involved
We do not publish a price list, as no two jobs are quite the same. Instead, we give you a clear quote for your job. To get started, call 0345 464 0079 or drop us an email.
Common questions in New Eltham
Can you do external mastic in New Eltham?
Yes, New Eltham is within the area we cover. Our work covers London and the South East. Just phone 0345 464 0079 or drop us an email with a few details of the job, and we will send you a clear quote.
Is parking a problem for a job in New Eltham?
In much of London, parking needs planning: a visitor permit or a bay close to the door helps a lot.
How much does external mastic cost in New Eltham?
Size, access and the old material all affect the cost. Ask us for a quote and we’ll talk you through it.
How often do external joints need resealing?
That depends on the wall, the weather and the movement. Look for splits, hardening or edges coming away.
Can a movement joint be filled with mortar?
No. Rigid materials can’t move with the wall and the joint fails. Where a joint has been mortared, it can often be raked out and sealed properly.
Should I try DIY first?
For a simple, easy-to-reach joint, a careful DIYer can do a reasonable job. The usual mistakes are sealing over old sealant, sealing a damp joint and using too much.
What colours does the sealant come in?
There’s a good range of exterior colours, including greys, browns, whites and stone tones. We choose the closest to your brick or render so the joint doesn’t draw the eye.
Is it messy?
Very little: the area around the joints is protected first, and we clear up the old sealant and our materials before we leave.
Towns and villages near New Eltham
What else we do in New Eltham
How it works
On the day, there’s very little for you to do. Show us the job and we’ll take it from there. The job generally takes anything from a few hours to several days, depending on the building, including the tidy-up. For a job in New Eltham, parking and access are the things to plan: tell us about permits, visitor bays or off-street space, which floor we are working on and whether there’s a lift.
- 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.
How to prepare
- For business premises, tell us about site rules or sign-in
- Tell us about any water getting in
- Tell us about any previous sealing or DIY attempts
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 will explain what’s involved.
Read more
How the job changes by surface
Render joints
Cracks along render joints let water in behind the coat. A sound joint keeps the render dry behind and helps it last.
Concrete and blockwork
Blockwork and concrete shrink over time and move with the seasons. Their movement joints are sealed over backing rod with a flexible sealant.
Why deal with it now?
Low-modulus sealants stretch easily, so they put less strain on the joint edges. That matters on brick, render and concrete, which can be weaker at the face. Too stiff a sealant can pull at the edges and break them. 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.
We don’t show prices on the website, because the cost depends so much on the job itself. For a quick quote, please ring 0345 464 0079 or send us an email.
Why choose Mr Mastic in New Eltham
- White, clear, grey or coloured to suit, where the product allows
- 20+ years of sealant experience
- 4.9 on Google from 180+ five-star reviews
- A 12-month guarantee on all work
See what affects the cost and what customers say.
For landlords and businesses
If you manage several properties in or around New Eltham, jobs at different addresses can be quoted together. Just tell us the addresses and what each one needs.
In hotels, rooms out of use cost money, so we plan the work room by room around your bookings where we can. We’ve worked in hotels as well as homes and businesses.
Aftercare tips
Once the sealant has cured, a few habits help it last:
- Keep soil, plants and ivy away from the joints
- Wash walls gently around the sealant
- Fix overflowing gutters above sealed joints
- Check the sealant is paintable before painting near it
Give the sealant the cure time we tell you before anything rubs against it. The surface skins over quickly, but full cure takes longer.
Small splits are the time to act. At that stage it’s a simple cut out and reseal.
Can I do it myself?
A careful DIYer can reseal a simple joint, 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. Silicone doesn’t stick to old silicone, so it peels away and traps moisture behind it. Everything old must be removed first.
Walls and rooflines in New Eltham
London and the South East are among the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. London terraces and converted houses often share gutters, downpipes and walls, so it’s worth agreeing who is responsible before work starts.
Managing a site like Wyborne Primary School? Then its movement joints, gutters and trims need looking after like any other building’s. As a London address, New Eltham can be tricky for parking: let us know about parking bays, permits or a driveway. Letting a property close to New Eltham station? Then split movement joints are easy to miss on a rental until damp shows inside.
New Eltham is about 1 mile south-east of Eltham, in Greater London. Jobs in New Eltham get the same care as everywhere else we work: the old material taken out, joints prepared properly and a 12-month guarantee. Across Greater London, we cover 764 places, New Eltham among them. Our London page covers work nearby, about 8 miles away.
Every address in SE9, DA15 and BR7 is covered for external mastic, from the main roads to the quietest streets. External mastic is available to properties on Green Lane, Gerda Road and Novar Road. Close by, we work in Eltham (1 mile north-west), Longlands (1 mile south-east), Coldharbour (1 mile south-west), Avery Hill (1 mile north) and Blackfen (1 mile north-east). Within a short drive, we also cover London (8 miles north-west), City of Westminster (11 miles north-west), Marylebone (11 miles north-west), Kensington (13 miles west), St Pancras (10 miles north-west) and Shoreditch (9 miles north-west).
Landmarks near New Eltham
In New Eltham, that means homes and buildings near Elmstead Wood and St Thomas More Catholic Comprehensive School and the streets around them. New Eltham has its own railway station: New Eltham station. A little further out are Metropolitan Police Museum (1.4 miles east) and Eltham Community Hospital (1.1 miles north-west). Not far away are Summer Hill and The Tarn.