Greater London · England
External & façade joints in Derry Downs, Greater London
Our applicators work in Derry Downs on sealing brickwork movement joints, render, cladding and façade joints. Old material cut out, joints cleaned and sealed neatly and every job guaranteed for a year.
- Water getting into walls through failed joints
- Weathered mastic that no longer stretches
- Plants rooting in failed movement joints
About our external mastic in Derry Downs
A movement joint is a deliberate break that lets a wall expand and contract. The sealant in it has to stretch and squeeze for years, and when it fails, the wall takes the strain and water finds a way in. We work on joints between brick and frames, copings & trims and façade panels, and people most often call us about movement joints with cracked, split or missing sealant and old sealant gone brittle and cracked.
London’s terraces and conversions often share walls, gutters and downpipes with their neighbours, so a leaking gutter joint or failed wall joint can affect more than one home. In a converted house in Derry Downs, it’s worth checking who is responsible for the outside before booking.
All our work is covered by our 12-month guarantee.
- Where
- Derry Downs (BR5, BR6)
- Region
- Greater London
- Cover
- 12 months on all our work
- Quotes
- Quoted before any work starts
- Call
- 0345 464 0079
- Updated
- 26 October 2026
Can I do it myself?
A careful DIYer can reseal a simple joint, such as a straightforward joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
If you do try it yourself, take your time over the preparation: take out all the old sealant, make sure the joint is clean and dry, and give it the full cure time. If it fails, we can still redo it.
Also near Derry Downs
More services for Derry Downs
When to call us in Derry Downs
A lot of failed joints come down to preparation: dusty or wet faces, no primer where one was needed, or old sealant left in. The sealant never bonds properly.
Most people get in touch when they notice one of these:
- Failed sealant between panels on a façade
- Damp patches traced to an open external joint
- Movement joints filled with mortar instead of sealant
- Hard, crazed mastic that has stopped moving
Schools such as St Philomena's Primary School are buildings too, and its movement joints, gutters and trims need looking after like any other building’s.
Before you book anyone
- Is VAT in the price?
- Are they insured?
- Which colour the sealant will be
- How the joint is cleaned and prepared
FAQs for Derry Downs
Can you do external mastic in Derry Downs?
Yes. Our work covers London and the South East, and Derry Downs is part of that. You can call 0345 464 0079 or drop us an email and tell us what needs doing, and we will give you a clear price.
I let a flat near St Mary Cray station. Can you help?
Yes, we work for landlords and letting agents. You can call 0345 464 0079 or email us with the address and a few details, and we will give you a fixed price before any work starts.
Do you remove the old sealant?
Yes. All of the old material is cut out and the joint cleaned before applying anything new.
Will the new joint stand out?
There’s a good range of exterior colours, including greys, browns, whites and stone tones. We pick the one that suits your wall best.
Which products do you use?
The product depends on the job: sanitary silicone where it gets wet, and sealants suited to movement or weather elsewhere. Brands we use include Arbo and Everbuild.
Are you ARBOMaster approved?
Yes. ARBOMaster is the approved applicator scheme for Arbo sealants, and we are part of it.
Should I point up the gap in my brickwork?
No. Rigid materials cannot move with the wall and the joint fails. Where a joint has been mortared, it can often be raked out and sealed properly.
Are you insured?
Yes. Full insurance covers our work.
Surface by surface
Render joints
Cracks along render joints let water in behind the coat. Resealing the joints early keeps water out.
Concrete and blockwork
Concrete faces can be dusty and porous, so cleaning and priming matter. A primer goes on where the product requires one.
How it works
A visit follows a simple pattern: we look at the joints together, protect the area around them, do the work and clear up. It normally takes anything from a few hours to several days, depending on the building. 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.
- We start by checking each joint, agreeing the ones to redo and how we will reach them.
- Old sealant and any debris are cut and raked out.
- Both sides are cleaned back to sound material and primed if needed.
- We push in closed-cell backing rod so the sealant is the right depth and bonds to the sides only.
- The new sealant, chosen to suit the brick or render, is applied and tooled to a neat finish.
Before we arrive
- For business premises, tell us about site rules or sign-in
- Let us know about stairs, lifts or work at height
- Tell us about any water getting in
Getting a quote
For a quick quote, get us on the phone, or email us if that is easier. Describe what needs sealing and we will talk you through the work and send you a clear quote.
Related advice
Walls and rooflines in Derry Downs
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. With historic houses such as Lullingstone Castle (about 3.9 miles south-east) nearby, there’s older building stock in the area around Derry Downs as well as newer homes. Where a home is older, older brick and stone need a sealant that suits them, at the right joint depth.
Letting a property close to St Mary Cray station? Then failed wall and movement joints let damp in, so they’re worth checking between tenancies. In the older streets around St Andrew's, the joints between older walls, newer extensions and the roofline need a sealant that can move.
Derry Downs is about 1 mile east of Orpington, in Greater London. From the centre of Derry Downs to the outskirts, external mastic is available for homes and businesses alike, from flats and houses to offices and hotels. Our Greater London coverage runs to 764 places, and Derry Downs is one of them. There’s also a page for London, about 12 miles away.
We cover every part of BR5 and BR6 for external mastic. We cover properties on Kent Road, Park Road and Cross Road. Main roads around Derry Downs include the A224, so getting to you is simple. Neighbouring places we cover for external mastic include Orpington (1 mile west), St Mary Cray (1 mile north-west), Poverest (1 mile north-west), Kevington (1 mile east) and St Paul's Cray (1 mile north). Further out, we also cover London (12 miles north-west), City of Westminster (15 miles north-west), Marylebone (15 miles north-west), St Pancras (14 miles north-west), Shoreditch (13 miles north-west) and Walthamstow (15 miles north-west).
Near you in Derry Downs
Locally, jobs take us to homes and businesses close to Harris Academy Orpington, The Priory School and The Royal Albert pub, among other places. For rail, the closest station is St Mary Cray station, about 0.8 miles north-west of the centre. Nearby you’ll also find London Borough of Bromley Museum (0.7 miles south-west) and Lullingstone Castle (3.9 miles south-east). Green spaces nearby include The Warren and Summer Hill.
What sealant work can’t fix
It helps to know what we can’t do too:
- Render that’s blown, hollow or coming away
- Rising or penetrating damp from elsewhere in the wall
- Structural movement, which needs a surveyor or engineer
Not sure which it is? You can phone 0345 464 0079 or drop us an email and we’ll tell you honestly.
Where we work in Derry Downs
- Joints between brick and frames
- Concrete & block
- Brickwork movement joints
- Render & cladding joints
- Copings & trims
- Façade panels
For landlords and businesses
In hotels, rooms out of use cost money, so we plan the work room by room. Hotel work is part of what we do, alongside homes and businesses.
From a single let to a portfolio, the work is the same standard: old sealant fully removed, joints prepared properly and a 12-month guarantee.
Keeping the joints in good condition
Once the sealant has cured, a few habits help it last:
- Avoid pressure-washing directly into sealant joints
- Get split or bare joints resealed while the damage is small
- Keep soil, plants and ivy away from the joints
- Keep water from gutters off the wall
Do not let soil, plants or ivy build up against the new joints. Damp material against the sealant shortens its life.
Gaps, plants or missing sealant in a joint are worth getting looked at. Early work is quicker and leaves a better finish.