Greater London · England
External & façade joints in Forest Hill, Greater London
Sealing brickwork movement joints, render, cladding and façade joints for homes and businesses in Forest Hill and across Greater London. Fully insured, ARBOMaster approved and guaranteed for a year.
- Weathered mastic that no longer stretches
- Weeds or debris growing in open joints
- Gaps where render, brick and frames meet
External mastic in Forest Hill, done properly
Low-level joints can normally be done from the ground. For joints higher up, give us some details of the building and we’ll confirm what’s needed to reach them safely. Typical jobs include joints pointed up with cement by mistake and failed sealant between panels on a façade, on joints between brick and frames, brickwork movement joints and render & cladding joints.
Working on the outside of a London home means planning access: shared paths, upper floors and parking. In Forest Hill, joints up high may need ladders or other access, which is worth talking through when you book.
Your job is guaranteed for a year, as with all our work.
- Where
- Forest Hill (SE23, SE22, SE26)
- Region
- Greater London
- Cover
- 12 months on all our work
- Price
- A clear price before we start
- Phone
- 0345 464 0079
- Last updated
- 26 October 2026
Aftercare tips
After the cure time, these simple habits help:
- Keep water from gutters off the wall
- Keep movement joints as flexible joints, not mortar
- Clear growth from the base of walls and joints
- Wash walls gently around the sealant
Look over the joints once a year, ideally after winter. Splits, gaps at the edges or plants in the joint are early warning signs.
Act while the splits are small. Then it’s a straightforward cut-out and reseal before water has had years to get in.
What we do, step by step
On the day, we start by going over the job with you. Surfaces next to the work are protected before work begins. The work normally takes a few hours for a handful of joints, longer for a whole elevation. Parking in much of London is by permit or pay-and-display, so it helps to know what’s near you in Forest Hill. A visitor permit or a nearby bay makes the visit run more smoothly.
- We inspect the joints and agree which need resealing and how they’ll be reached.
- We cut out the failed sealant and rake out any dirt or growth.
- The joint faces are cleaned and primed where the sealant needs it.
- Backing rod goes in next, setting the depth and keeping the sealant off the back of the joint.
- We gun in a flexible exterior sealant in a colour that suits the wall and tool it neatly.
How to prepare
- On commercial sites, let us know about site rules
- Mention any parking rules near the property
- Mention any tricky access
Getting a quote
Quotes start with a quick conversation. Tell us what’s wrong, where it is and how much there is, and we’ll explain how we’d tackle it. When it suits you, ring 0345 464 0079 or send us an email.
Related advice
What affects the cost of external mastic
You will get a clear quote before we start. It takes into account:
- The amount of work
- The old material and how stubborn it is
- The number of rooms or windows
- The product the joint needs
What it costs depends on the size of the job, how hard the old material is to remove and how easy the joints are to reach. You’ll have a clear quote before any work starts.
Helping us quote
To make quoting easier, let us know:
- What the problem is, such as mould, gaps, leaks or cracking
- Where the job is, and your postcode
- Roughly how big the job is
- Any access issues, like height or stairs
Getting a quote is simple: tell us what needs doing and where and its rough size. Photos by email help us understand the job, and we will take it from there.
Walls and rooflines in Forest Hill
In terraces and conversions, gutters and walls are often shared with the neighbours, so it’s worth agreeing who is responsible before work starts. Compared with the north and west, the South East gets less rain, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
As a London address, Forest Hill can be tricky for parking: let us know about parking bays, permits or a driveway. For site and facilities teams at buildings such as Fairlawn Primary School, larger buildings have long runs of movement joint that eventually need resealing. If you let a flat or house near Honor Oak Park station, split movement joints are easy to miss on a rental until damp shows inside.
Forest Hill is about 2 miles south-east of East Dulwich, in Greater London. For external mastic in and around Forest Hill, please phone 0345 464 0079 or send us an email for a quick quote. We cover Greater London from our Crawley base. We cover 764 towns and villages across Greater London, from the larger towns to small villages.
Work in SE23, SE22 and SE26 works the same way as everywhere else we cover. We cover properties on Ewart Road, London Road and Rojack Road. Nearby, we also carry out external mastic in Honor Oak (1 mile north), Perry Vale (1 mile south-east), Brockley (1 mile north-east), Crofton Park (1 mile north-east) and Dulwich (1 mile west). Larger places within reach include London (4 miles north-west), City of Westminster (6 miles north-west), Marylebone (6 miles north-west), Kensington (7 miles north-west), St Pancras (6 miles north-west) and Shoreditch (6 miles north).
Near you in Forest Hill
We work in homes and buildings around Allenby Tutorial Trust, Capitol Cinema pub and Harris Girls' Academy East Dulwich. Forest Hill’s nearest station is Honor Oak Park station, about 0.5 miles north-east. A little further out are Greenwich Castle (3.1 miles north-east) and Horniman Museum and Gardens (0.5 miles south-west). Not far away are One Tree Hill and Knight's Hill.
Can I do it myself?
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is matched to the joint and its conditions.
A careful DIYer can reseal a simple joint, such as a straightforward joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
What happens if it’s left?
An open joint keeps letting water into the wall with every downpour. Wet masonry is more easily damaged by frost near the open joint, so the problem grows beyond the joint itself. 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.
Some things make a job bigger or smaller: the old material and how easily it comes out, any mould to treat, and whether the work is at height. Your quote takes all of that into account.
Why us?
- Any old sealant cut out fully, not covered over
- ARBOMaster approved applicator
- A sealant colour to suit the surroundings
- Sanitary silicone with an anti-fungal additive in wet areas
Take a look at what affects the cost or our reviews.
FAQs for Forest Hill
Do you cover Forest Hill for external mastic?
Yes, Forest Hill is within the area we cover. Our work covers London and the South East. Just phone 0345 464 0079 or email us with a few details of the job, and we’ll give you a clear quote.
Is parking an issue for external mastic in Forest Hill?
Parking in Forest Hill, as in most of London, takes a little planning: a visitor permit or a nearby bay makes the day run more smoothly.
Can you reach joints on upper floors?
It depends on the building. Send us photos and a rough idea of the height, and we’ll confirm what access is needed.
Can a movement joint be filled with mortar?
No. Cement or mortar cannot stretch and the joint fails. If it has already been filled, we can generally cut it out and reseal it.
Do you use backing rod?
Backing rod controls the sealant depth and keeps it off the back of the joint. Then the sealant bonds to two faces and can move.
Can you match the colour of my brickwork?
There’s a good range of exterior colours, including greys, browns, whites and stone tones. We pick the one that suits your wall best so it does not stand out.
Are you an approved applicator?
Yes. We are approved under the ARBOMaster scheme, which is run for the Arbo sealant brand.
What should I tell you?
A short description and the location. If we need more, we’ll ask.
Surface by surface
Copings and trims
Metal and stone copings both move with temperature, so a flexible sealant suits them best in all weathers.
Render joints
Render is weaker at the surface than brick, so a low-modulus sealant is kinder to the joint edges. Priming is done where the sealant calls for it.
Also near Forest Hill
Other services in Forest Hill
When it is not the sealant
It helps to know what we cannot do:
- Cutting new joints into brickwork, which is building work rather than sealant work
- Rising or penetrating damp from elsewhere in the wall
- Cracking across the wall rather than at a joint
Not sure which it is? You can phone 0345 464 0079 or drop us an email and we will tell you honestly.
What we seal
- Copings & trims
- Render & cladding joints
- Brickwork movement joints
- Façade panels
- Joints between brick and frames
- Concrete & block