Hertfordshire · England
External Mastic in South Mimms
External mastic in South Mimms from a team with over 20 years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Rain getting behind render or cladding at a joint
- Cracked joints where brick meets render or frames
- Moss and dirt in joints with no sealant left
How we quote for external mastic
Every job gets its own quote. This is what makes a difference:
- How much old sealant there is and how hard it is to remove
- Whether there’s mould to deal with
- How many rooms, windows or areas are involved
- Any working-time requirements on site
Leaving a failed joint usually makes the job bigger, not smaller, because water and mould keep working on it. If you’re unsure, ring 0345 464 0079 or email us and we’ll give you an honest view and a quote.
What to tell us for a quote
When you contact us, it’s useful to know:
- The rough size of the job
- Any previous sealing or DIY work
- Where the job is, and your postcode
- Whether it’s a home or a business
To get a quote, phone 0345 464 0079 or send us an email with the location and a short description of the problem. We will give you a clear price before any work starts.
How we handle external mastic in South Mimms
Getting the depth right is half the job. 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 joints between brick and frames, façade panels and brickwork movement joints, and people most often call us about brick movement joints where the sealant has split and leaking joints around cladding and façade panels.
Outside joints can only be sealed when they’re dry, so work in South Mimms is booked around the forecast. Let us know about access to every wall, plus any garages or outbuildings.
We guarantee the work for a year. If something is not right with it in that time, tell us and we will put it right.
- Place
- South Mimms (EN6)
- Region
- Hertfordshire
- Cover
- 12 months on all our work
- Price
- A clear quote up front
- Phone
- 0345 464 0079
- Updated
- 26 October 2026
Places near South Mimms
What else we do in South Mimms
What happens if it’s left?
Pointing a movement joint with mortar might seem a neat fix, but it locks the joint solid. The wall then cracks somewhere else. A flexible sealant over backing rod is what the joint needs. Where a wall is exposed, as many are in small places like South Mimms, wind-driven rain gets into any failed joint, and older walls, once damp, take a long time to dry.
Commercial jobs are quoted on the same basis as homes: the amount of work, how we reach it and what it needs, along with when we can work on site. Ask us for a quote and we’ll explain what it covers.
Why South Mimms customers choose us
- 4.9 on Google from 180+ five-star reviews
- We are fully insured
- Homes, businesses and hotels
- A sealant colour to suit the surroundings
Take a look at what affects the cost and customer reviews.
When it is not the sealant
A few problems are outside what sealant work can do:
- Cutting new joints into brickwork, which is building work rather than sealant work
- Structural movement, which needs a surveyor or engineer
- Loose or hollow render, which needs re-rendering
If in doubt, phone 0345 464 0079 or email us and we’ll say what we think.
Where we work in South Mimms
- Brickwork movement joints
- Façade panels
- Copings & trims
- Joints between brick and frames
- Render & cladding joints
- Concrete & block
What external mastic looks like in South Mimms
Historic houses like Wyllyotts Manor (about 1.6 miles east) are a reminder that the area around South Mimms has older buildings as well as new. Where a home is older, older brick and stone need a sealant that suits them, at the right joint depth. 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.
Rented homes near Potters Bar station change hands often, and split movement joints are easy to miss on a rental until damp shows inside. For an older house near a landmark such as Church of St Giles, older walls, gutters and the joints where extensions meet them need a flexible sealant. Schools such as St Giles' CofE Primary School are buildings too, and movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
South Mimms is about 2 miles west of Potters Bar, in Hertfordshire. Anywhere in EN6, we can carry out external mastic at your property. Across Hertfordshire, we cover 381 places, and South Mimms is one of them. London is on our list too, about 15 miles from South Mimms.
Jobs for external mastic in EN6 is quoted and booked the same way as anywhere else. You will find streets such as St Giles' Avenue, Blanche Lane and Greyhound Lane, and we cover them all. We also cover the places around South Mimms: Ridge (1 mile south-west), Dancers Hill (1 mile south-east), Kitts End (2 miles south-east), Well End (2 miles south-west) and Green Street (2 miles south-west). Further out, we also cover Watford (8 miles west), Hemel Hempstead (11 miles west), Stevenage (15 miles north), St Albans (6 miles north-west), Welwyn Garden City (7 miles north) and Harpenden (10 miles north-west).
What’s near South Mimms
Locally, jobs take us to homes and businesses close to The White Hart Public House, North Mimms Park and Dame Alice Owen's School. The nearest railway station is Potters Bar station, roughly 1.6 miles east of the centre. Well-known places in the area include Spires Shopping Centre (2.9 miles south-east) and Shenley Hospital (2.7 miles west). The countryside around South Mimms includes Darland's Lake and Furzefield Wood and Lower Halfpenny.
Landlords, agents and businesses in South Mimms
For anyone letting property in or around South Mimms, several properties can be quoted together. Just tell us the addresses and what each one needs, and pictures by email help.
Letting agents often deal with us directly. Send the address, what’s needed and the access arrangements and we’ll give you a quote.
The process
Once we’re on site, we compare the joints with what we discussed. If anything is different, we explain it before carrying on. After that, the work takes anything from a few hours to several days, depending on the building. For a village or hamlet like South Mimms, the journey is planned in advance: tell us about narrow lanes, gates, long drives and where we can park. Everything for the job comes with us, so a second trip is avoided where possible.
- First we look over the joints with you, agree which to renew and talk through access.
- We cut out the failed sealant and rake out any dirt or growth.
- Both sides are cleaned back to sound material and primed if needed.
- Backing rod goes in next, setting the depth and keeping the sealant off the back of the joint.
- A flexible exterior sealant is applied and tooled in a colour to suit the wall.
How to prepare
- Tell us about access, such as stairs, a lift or high-level joints
- Try not to wet indoor joints just before the visit
- Tell us about any water getting in
Get a quote
We quote each job on its own, so the first step is telling us about yours. Simply ring 0345 464 0079 or send us an email and describe the job.
Read more
DIY versus a professional finish
Overfilling a joint is a classic DIY mistake. A thick, smeared bead looks untidy and doesn’t move well, and the joint depth matters as much as the finish.
A careful DIYer can reseal a simple joint, like a short, easy-to-reach joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
Keeping the joints in good condition
How long the joints last depends on use and care. Here’s what we suggest:
- Ask before painting over external sealant
- Show decorators and builders where the movement joints are
- Walk round the building once a year and look at the joints
- Never let anyone fill a movement joint with mortar
Look over the joints once a year, ideally after winter. Splits, gaps at the edges or plants in the joint are early warning signs.
A joint that has stopped moving pushes the movement elsewhere, often as cracks near the joint. Catch it early and you reduce the risk.
FAQs for South Mimms
Will you come out to South Mimms?
Yes, smaller places are covered as well as towns. Our work covers London and the South East. Let us know about access, parking and anything unusual about getting there when you book.
Can you help a landlord with a rental near Potters Bar station?
Yes. We work for landlords and letting agents as well as homeowners, and several properties can be quoted together. Just ring 0345 464 0079 or email us with the address and what needs doing, and we will give you a clear quote.
Where do you work from?
Our base is Crawley. Our area covers South East England, London and Scotland.
Can I add another job to the visit?
Of course. Combining jobs makes good use of the visit.
Do the sealants smell?
That depends on the sealant. Some products have a noticeable smell, others very little.
What do you put in the joint?
We choose the sealant for the joint, not the other way round. Where it moves, gets wet or faces the weather makes a difference, and we’ll explain our choice.
How long does external mastic take?
As a guide, most jobs take anything from a few hours to several days, depending on the building. Larger jobs naturally take longer.
Do you do commercial work?
Yes. We’ve worked for hotels, offices and other businesses and we’re fully insured.