Hertfordshire · England
External Mastic in Redbourn
External mastic in Redbourn from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Gaps where render, brick and frames meet
- Panel joints letting water in
- Damp patches traced to an open external joint
When something else is needed
We’d rather tell you now than do work that will not last, so these are the limits:
- Failed render or damaged cladding panels
- Cutting new joints into brickwork, which is building work rather than sealant work
- Subsidence or other structural problems
If in doubt, ring 0345 464 0079 or drop us an email and we will say what we think before you book.
What we seal
- Façade panels
- Copings & trims
- Brickwork movement joints
- Joints between brick and frames
- Concrete & block
- Render & cladding joints
External mastic in Redbourn
Many failed façade joints only get noticed once there’s a stain or a damp patch inside. We look over the joints, agree the ones to renew and reseal with a flexible, weatherproof product in a matching colour. We’re often asked to deal with movement joints with cracked, split or missing sealant and joints where the bead has come unstuck, across render & cladding joints, concrete & block and joints between brick and frames.
Outbuildings, garages and conservatories around homes in places like Redbourn add more joints to look after. Gutter ends, garage door frames and the joints where an extension meets the house are typical spots for leaks.
Every job is covered by a one-year guarantee.
- Where
- Redbourn (AL3)
- Wider area
- Hertfordshire
- Cover
- A year, on every job
- Quote
- A clear quote up front
- Call
- 0345 464 0079
- Updated
- 26 October 2026
How the visit works
There isn’t much for you to do on the day. Point us to the joints and we will get on with it. The job generally takes anything from a few hours to several days, depending on the building. A visit to Redbourn is planned like any other: the time, the access and where to park are agreed in advance. Outdoor jobs depend on a dry day, since sealant needs a dry surface.
- We look at every joint and agree a colour to suit the wall.
- We take out the old sealant until the faces are sound.
- Backing rod goes in so the sealant can stretch between the two faces.
- We prime the faces where required.
- A low-modulus exterior sealant is gunned in and tooled to a neat finish.
Before we arrive
- Mention if the joints have been sealed before
- Mention any leaks or damp you’ve noticed
- Clear the area around the work
Ask for a quote
To get a quote, ring 0345 464 0079 or email us and tell us where the job is and what the problem looks like. We’ll give you a clear price before any work starts.
Related advice
What else we do in Redbourn
Landlord and commercial work in Redbourn
We also work for businesses, from offices to washrooms and kitchens. For commercial premises, we can talk through working times when we quote.
Letting agents and landlords in Redbourn can book us as well as householders. Sealant work between tenants is a simple way to keep a property in good order.
What we are called out for in Redbourn
A lot of failed joints come down to preparation: joint faces that were dusty or damp, unprimed where they needed it, or still carrying old sealant. The sealant never bonds properly.
The most common problems we see are:
- Joints pointed up with cement by mistake
- Failed seals between different materials
- Sealant that has lost its bond to the brick or render
- Weathered mastic that no longer stretches
For site and facilities teams at buildings such as Redbourn Primary School, larger buildings have long runs of movement joint that eventually need resealing.
What your quote should include
- What happens if they find a problem under the old sealant
- What guarantee comes with the work
- Whether the sealant suits the joint
- Whether they’re fully insured
Looking after it afterwards
Once the sealant has cured, a few habits help it last:
- Wash walls gently around the sealant
- Walk round the building once a year and look at the joints
- Point out the joints to other trades
- Do not let climbing plants root in the sealant
Look over the joints once a year, ideally after winter. Watch for splits, edges coming away or growth in the joint.
Once a joint cannot move, the wall finds another way, generally as cracking in the brickwork or render nearby. Resealing it early helps prevent that.
DIY sealant or a professional job?
What a professional job adds is preparation and the right product. We take joints back to clean, dry surfaces, and the sealant is matched to the joint and its conditions.
A DIY attempt doesn’t rule out a professional job. We cut it out and start again, so tell us about it when you ask for a quote.
Your questions about external mastic in Redbourn
Can you help a landlord with a rental near Harpenden station?
Yes, rental work is part of what we do. Just call 0345 464 0079 or send us an email and tell us about the property, and we will send you a clear quote.
Is Redbourn in your area for external mastic?
Yes. We work across London and the South East, and Redbourn is part of that. Just call 0345 464 0079 or send us an email with a few details of the job, and we will give you a clear quote.
Do I have to be there?
That depends on where the joints are. For work indoors, someone needs to let us in, while outside work can sometimes be arranged differently.
How long will you be here?
That depends on the amount of work, but as a guide it takes a few hours for a handful of joints, longer for a whole elevation. We’ll give you a better idea when we quote.
How often do external joints need resealing?
It depends on the exposure, the movement and the product. Sealant is a maintenance item, so check the joints once a year and renew it when it starts to fail.
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. We use products from Arbo and Everbuild.
Can you reach joints on upper floors?
It depends on the building. We work on joints that can be reached safely. Give us some details and we will confirm the access.
Will it make a mess?
Tidy work is part of the job. We protect what’s around the joints, and we clear up when we are done.
Surface by surface
Render joints
The face of render can be soft, so a low-modulus sealant is kinder to the joint edges. We prime where the product needs it.
Brickwork movement joints
Brick movement joints are often mistaken for a missing mortar line. If that is happened, we rake it out and reseal it properly where it can be done safely.
Redbourn buildings and the weather
With historic houses such as Childwickbury Manor (about 2.6 miles south-east) nearby, there’s older building stock in the area around Redbourn as well as newer homes. In older buildings, older brick and stone need a sealant that suits them, at the right joint depth. The South East is one of the drier parts of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day.
For an older house near a landmark such as Mount Zion Evangelical Church, older walls, gutters and the joints where extensions meet them need a flexible sealant. If you let a flat or house near Harpenden station, outside joints that have cracked can let damp into a rental, so check them between lets.
Redbourn is about 2 miles south-west of Harpenden, in Hertfordshire. Jobs in Redbourn get the same care as everywhere else we work: the old material taken out, joints prepared properly and a 12-month guarantee. 381 places in Hertfordshire are on our list, from the larger towns to small villages. Our London page covers work nearby.
Every address in AL3 is covered for external mastic. Whether your property is on High Street, The Square and Lords Meadow or anywhere close by, we can help. Nearby, we also carry out external mastic in Holtsmere End (2 miles south-west), Highfield (3 miles south-west), Westwick Row (4 miles south), Leverstock Green (4 miles south) and Adeyfield (4 miles south-west). Further out, we also cover Watford (9 miles south), Hemel Hempstead (4 miles south-west), Stevenage (12 miles north-east), St Albans (4 miles south-east), Welwyn Garden City (9 miles east) and Hitchin (12 miles north-east).
Near you in Redbourn
Locally, jobs take us to homes and businesses close to The Bell And Shears Public House, Roundwood Park School and Rothamsted Park and the streets around them. For rail, the closest station is Harpenden station, about 2.3 miles north-east. Other landmarks nearby include Redbourn Museum (under half a mile south-east) and St Albans City Hospital (3.6 miles south-east). Not far away are Grebe House Wildlife Garden and Verulamium Lake.