Hertfordshire · England
External Mastic in Clothall
Problem with your movement joints in Clothall? We cut out the old, prepare the joints and apply the right sealant, and the work is guaranteed for a year.
- Hard, crazed mastic that has stopped moving
- Joints pointed up with cement by mistake
- Joints with sealant missing in places
About our external mastic in Clothall
Where two different materials meet, such as brick and render or blockwork and metal, they move at different rates. A flexible sealant bridges the two where a rigid filler would soon crack. If you have joints where the bead has come unstuck and hard, crazed mastic that has stopped moving, we can help, whatever the surface.
Outside joints can only be sealed when they’re dry, so work in Clothall is booked around the forecast. Tell us about access to all sides of the building, including outbuildings and garages.
All our work comes with a one-year guarantee.
- Where
- Clothall (SG7)
- Wider area
- Hertfordshire
- Cover
- A year, on every job
- Price
- A clear quote up front
- Phone
- 0345 464 0079
- Updated
- 26 October 2026
Why it’s worth doing now in Clothall
Sealing over the top of old mastic does not hold for long. The new layer cannot bond properly to old, weathered material, so we always take the old sealant out. In a small place like Clothall, homes can be exposed to wind and rain, which finds any gap, and older walls, once damp, take a long time to dry.
Combining jobs into one visit generally makes better use of the time than several visits, so it’s worth mentioning everything you’d like done. You will get one clear quote for the whole job.
Why book with us
- Full insurance on every job
- 180+ five-star Google reviews
- Any old sealant cut out fully, not covered over
- Every job guaranteed for a year
Read what affects the cost or customer reviews.
Walls and rooflines in Clothall
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 Baldock station change hands often, and split movement joints are easy to miss on a rental until damp shows inside. Schools such as Weston Primary School are buildings too, and movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
Clothall is about 3 miles east of Letchworth, in Hertfordshire. Clothall gets the same service as everywhere we cover: the old material taken out, joints prepared properly and a 12-month guarantee. We cover 381 towns and villages across Hertfordshire. For nearby work, see our Chelmsford page.
All of SG7 is covered for external mastic. We also cover the places around Clothall: Weston (1 mile south-west), Wallington (2 miles north-east), Baldock (2 miles north-west), St Nicholas (3 miles south) and Rooks Nest (4 miles south-west). Within a short drive, we also cover Stevenage (4 miles south), Bishop's Stortford (15 miles south-east), Welwyn Garden City (12 miles south), Harpenden (14 miles south-west), Hitchin (5 miles west) and Hatfield (15 miles south).
Near you in Clothall
We work in homes and buildings around The Knights Templar School. The closest station to Clothall is Baldock station, about 2.2 miles north-west. Other landmarks nearby include First Garden City Heritage Museum (3.1 miles west) and Clothall Castle (under half a mile south-east). Green spaces nearby include Pryor's Wood.
For landlords and businesses
Landlords and letting agents in Clothall can book us as well as homeowners. Sealant work between tenants is a simple way to keep a property in good order before the next move-in.
We also work for businesses, from offices to washrooms and kitchens. For commercial premises, we can talk through working times when we quote.
DIY versus a professional finish
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is chosen for how the joint moves and where it is.
Some sealant jobs are within reach of a careful DIYer, 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.
When to call us in Clothall
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 new sealant then lets go long before it should.
People normally contact us when they notice something like this:
- Joints with sealant missing in places
- Rain getting behind render or cladding at a joint
- Failed seals between different materials
- Failed sealant between panels on a façade
In the older streets around Church of St Mary, an extension built onto an older house moves differently, and the joint between them takes the strain.
Comparing quotes
- What insurance they hold
- Which colour the sealant will be
- Is the old sealant removed completely?
- What preparation is included
What sealant work can’t fix
To be straight with you, there are a few things sealant won’t fix:
- Movement that is more than a sealant joint can take
- Cracked brickwork or render that needs a builder or plasterer
- Cutting new joints into brickwork, which is building work rather than sealant work
Not sure which it is? You can phone 0345 464 0079 or email us and we will tell you honestly.
What we seal
- Façade panels
- Joints between brick and frames
- Render & cladding joints
- Copings & trims
- Brickwork movement joints
- Concrete & block
Different surfaces, different methods
Render joints
Cracks along render joints let water in behind the coat. Resealing the joints early keeps water out.
Cladding and façade panels
Panel systems often rely on sealant between and around the panels. Each joint gets a sealant that suits the panel and its movement.
The process
Before we leave, we go over the finished joints with you and explain the cure time. The visit itself normally takes a few hours for a handful of joints, longer for a whole elevation, depending on the size of the job. Somewhere as small as Clothall, access is often the only tricky part. For outside work, also let us know about exposed walls and any outbuildings involved.
- Each joint is checked and the colour of the new sealant agreed.
- Failed sealant is removed back to clean, sound faces.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
How to prepare
- Mention any leaks or damp you’ve noticed
- Mention any tricky access
- Tell us if parking is tricky
How to get a quote
The more we know about the job, the more useful the quote. Tell us where the job is, what’s wrong and how much there is.
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Common questions in Clothall
I let a flat near Baldock station. Can you help?
Yes, we work for landlords and agents. Just phone 0345 464 0079 or drop us an email and tell us about the property, and we will give you a clear quote.
Is Clothall within the area you cover?
Yes, we do. We work across London and the South East, and smaller places are part of that. The journey is planned ahead, so it helps to know about access.
What is backing rod for?
We fit closed-cell backing rod wherever the joint depth needs controlling. It sets the sealant depth and prevents three-sided bonding, so the joint can move.
Will there be a smell?
Sometimes, a little. It fades as the sealant cures.
Is it OK to fill a movement joint with cement?
No. A mortar-filled joint can’t move, so the wall cracks somewhere else instead. Use a flexible sealant with backing rod.
Where is Mr Mastic based?
We’re a Crawley-based firm, with over 20 years’ experience. We work across South East England, London and Scotland.
What do you need from me for a quote?
A short description and the location. We will ask anything else we need to know.
How long before the joint can be used?
Many sealants skin over quickly but take longer to cure fully. We’ll tell you how long to leave the joint before we leave.