Hertfordshire · England
Astwick External Mastic
External mastic in Astwick from a team with over 20 years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Leaking joints around cladding and façade panels
- Weeds or debris growing in open joints
- Gaps where render, brick and frames meet
External mastic in Astwick, done properly
Joints between dissimilar materials, like brick against render or concrete against a steel frame, see movement from both sides. A flexible sealant bridges the two. If you have leaking joints around cladding and façade panels and rain getting behind render or cladding at a joint, we can put it right, on joints between brick and frames, façade panels and render & cladding joints alike.
In a village or hamlet like Astwick, older cottages and farm buildings often stand in the open, so walls and rooflines take the full force of wind and rain. Gutter joints and wall joints there need a sealant that can flex and stay put.
We guarantee the work for a year. If there’s a problem with our work within the year, let us know and we will sort it.
- Place
- Astwick (SG5)
- Region
- Hertfordshire
- Guarantee
- A year, on every job
- Quotes
- Quoted before any work starts
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Work for landlords, hotels and businesses
Water getting past a failed joint can damage the building, which matters even more when someone else lives there. Keeping joints in good order is simple maintenance that we can handle for you.
Failed sealant is one of the commonest items on a check-out report. We can quote for more than one property at once.
Towns and villages near Astwick
More services for Astwick
How it works
Good joint work is mostly preparation, so that’s where we spend the time. Every joint is cleaned and dried before new material goes in. All told, the work takes a few hours for a handful of joints, longer for a whole elevation. For a village or hamlet like Astwick, the journey is planned in advance: tell us about narrow lanes, gates, long drives and where we can park. We bring what the job needs, so it can be finished in one trip where possible.
- 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 sign-in or site rules at work premises
- Tell us if parking is tricky
- Keep children and pets away from the work area
How to get a quote
There’s no standard price list. Instead, we give you a clear quote for your job. To arrange one, phone 0345 464 0079 or email us.
Related advice
What sealant work cannot fix
In fairness, some problems need a different trade:
- Cutting new joints into brickwork, which is building work rather than sealant work
- Damp that is not coming from the joint
- Render that’s blown, hollow or coming away
Not sure which it is? You can call 0345 464 0079 or send us an email and we will tell you honestly before booking.
What we seal
- Render & cladding joints
- Concrete & block
- Copings & trims
- Brickwork movement joints
- Joints between brick and frames
- Façade panels
Astwick questions
Is Astwick in your area for external mastic?
Yes. We work across London and the South East, and Astwick is part of that. You can call 0345 464 0079 or drop us an email and tell us what needs doing.
Is Astwick within the area you cover?
Yes, we do. We work across London and the South East, and smaller places are part of that. Longer journeys are simply planned in advance.
Do I have to be there?
We need access to the joints, so we will agree that with you when we book. Indoors, that usually means someone at home.
Are you insured?
Yes. We are fully insured for every job we do.
Is the work guaranteed?
Yes. All our work carries our 12-month guarantee.
Where are you based?
Mr Mastic is based in Crawley. Our applicators cover Astwick.
How much does external mastic cost in Astwick?
The cost depends on the size of the job, access and how much old sealant has to come out. Call for a quick quote.
What’s an expansion joint in brickwork?
Brickwork, render and cladding all move a little, so long walls have planned gaps to take that movement. It’s closed with backing rod and a flexible sealant.
What we are called out for in Astwick
UV, rain and frost all age exterior sealant. Over the years it hardens, cracks on the surface and loses its give, so the next time the wall moves, it splits or pulls away.
Any of these means the joints need attention:
- Joints where the bead has come unstuck
- Gaps where render, brick and frames meet
- Moss and dirt in joints with no sealant left
- Old sealant gone brittle and cracked
Letting a property close to Arlesey station? Then split movement joints are easy to miss on a rental until damp shows inside.
Questions to ask before booking
- The length of the guarantee
- Whether they seal over old material or remove it
- How hidden problems are handled
- What product goes in the joint
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 chosen for how the joint moves and where it is, then guaranteed for a year.
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and the joint depth matters as much as the finish.
Outside joints around Astwick
The South East is one of the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind. With historic houses such as Hinxworth Place (about 1.7 miles east) nearby, there’s older building stock in the area around Astwick as well as newer homes. In older buildings, older brick and stone need a sealant that suits them, at the right joint depth.
For an older house near a landmark such as Church of Saint Guthlac, older walls, gutters and the joints where extensions meet them need a flexible sealant. If you look after a building such as St Mary's CofE Academy Stotfold, movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
Astwick is about 1 mile north of Stotfold, in Hertfordshire. If you need external mastic in Astwick, it’s easy to get a quote: please phone 0345 464 0079 or email us. We cover Hertfordshire from our Crawley base. Astwick is one of 381 places in Hertfordshire we cover for external mastic. For nearby work, see our London page, about 37 miles away.
Work in SG5 is quoted and booked the same way as anywhere else. External mastic is available to properties on Astwick Road and Sycamore Avenue. Close by, we work in Stotfold Common (1 mile south), Stotfold (1 mile south) and Radwell (2 miles south-east). Within a short drive, we also cover Stevenage (9 miles south), Hitchin (6 miles south), Letchworth (4 miles south), Letchworth Garden City (4 miles south), Baldock (4 miles south-east) and Benslow (6 miles south).
Around Astwick
The nearest railway station is Arlesey station, roughly 1.5 miles west of the centre. Other landmarks nearby include Fairfield Hospital (2.2 miles south) and Bygrave House (3.6 miles south-east). Open spaces near Astwick include Arlesey Old Moat and Glebe Meadows.
How the job changes by surface
Render joints
Water behind render can lead to blown patches. Resealing the joints early keeps water out and helps it last.
Joints between dissimilar materials
Joints where frames, sills or panels meet the wall are common leak points. The old joint is removed and a sealant that bonds to both sides goes in.
Looking after it afterwards
Once the sealant has cured, a few habits help it last:
- Have failed joints looked at early
- Do not let climbing plants root in the sealant
- Look over the joints every year, ideally after winter
- Fix overflowing gutters above sealed joints
Don’t let soil, plants or ivy build up against the new joints. Damp material against the sealant shortens its life.
If you can see gaps, plants or bare sections in a joint, have it checked. Earlier resealing means a smaller job and a better result.