Hertfordshire · England
Walsworth External Mastic
Specialist external mastic for Walsworth: the right sealant, proper preparation and a neat finish. Call for a quick quote.
- Moss and dirt in joints with no sealant left
- Movement joints with cracked, split or missing sealant
- Joints where the bead has come unstuck
Honest limits
New sealant can’t fix everything, and we’d rather say so up front. Sealant won’t put right:
- Cracks in the bricks or render themselves, away from the joints
- Cutting new joints into brickwork, which is building work rather than sealant work
- Loose or hollow render, which needs re-rendering
If in doubt, phone 0345 464 0079 or drop us an email and we’ll say what we think before booking.
Joints and surfaces we work on
- Render & cladding joints
- Joints between brick and frames
- Brickwork movement joints
- Façade panels
- Concrete & block
- Copings & trims
External mastic in Walsworth
We are ARBOMaster approved applicators, and each external joint gets a sealant suited to it. Some surfaces need a primer before sealing. Typical jobs include damp patches traced to an open external joint and brick movement joints where the sealant has split, on concrete & block, render & cladding joints and brickwork movement joints.
Homes around Walsworth range from older cottages to newer houses, with walls and rooflines of every type. Older homes need their gutter and trim joints kept tight, newer ones their movement joints.
We guarantee the work for a year. If there’s a problem with our work within the year, let us know and we’ll sort it.
- Location
- Walsworth (SG4, SG5)
- Region
- Hertfordshire
- Guarantee
- 12 months on all our work
- Quotes
- Quoted before any work starts
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
Your questions about external mastic in Walsworth
Do you work for landlords with property near Hitchin station?
Yes, landlords and agents are among the people we work for. You can phone 0345 464 0079 or drop us an email with the details for a clear quote.
Is Walsworth in your area for external mastic?
Yes, Walsworth is within the area we cover. We work across London and the South East. You can call 0345 464 0079 or drop us an email and let us know what needs doing.
Can you seal joints between two different materials?
Yes. Different materials move at different rates, so a flexible sealant is needed where they meet. The sealant is matched to both sides.
Is there a guarantee?
Yes. There’s a 12-month guarantee on every job.
Is it worth trying it myself?
For a simple, easy-to-reach joint, a careful DIYer can do a reasonable job. Most DIY failures come from sealing over old material, wet joints or too much sealant.
Will the new joint stand out?
We aim for a joint that suits the wall rather than one that jumps out. Colour is agreed with you before we begin, matched as closely as the range allows.
Are you insured?
Yes, we are fully insured for every job we do.
How do I get a quote for external mastic in Walsworth?
There’s no set price, as it depends on the job: how much there is, what’s there now, how we reach it and what it needs. We agree the price before any work begins.
DIY versus a professional finish
A DIY attempt does not rule out a professional job. We cut it out and start again.
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.
How the visit works
There isn’t much for you to do on the day. Show us the job and we will take it from there. The job generally takes anything from a few hours to several days, depending on the building, including the tidy-up. For a job in Walsworth, we agree the time, the access and parking before the day. If the work is outside, the weather plays a part, as 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.
- We gun in low-modulus sealant and tool it neatly.
Before we arrive
- Let us know about earlier repairs to the joints
- Mention any parking rules near the property
- Move anything stored near the joints
Get a quote
For a quote, call 0345 464 0079 or email us and tell us where the job is and what the problem looks like. You will have a clear quote before we start.
Related advice
Surface by surface
Concrete and blockwork
Concrete and block walls shrink as they dry and move with temperature. Their movement joints are sealed over backing rod with a flexible sealant.
Brickwork movement joints
Brick moves with heat and moisture, and grows a little over time. That movement goes into the joint, so the sealant in it must stay soft and stretchy.
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. The correct repair is a flexible sealant with the right backing. In an older home around Walsworth, damp from a failed joint can get into timber and plaster, which is far harder to put right than the sealant itself.
A few things move the cost up or down: how much old sealant there is and how stubborn it is, whether mould needs treating, and whether we need extra access for height. We take all of that into account in your quote.
Why Walsworth clients choose us
- Sealant colour chosen to suit
- 4.9 on Google from 180+ five-star reviews
- Colour agreed with you before work begins
- Over 20 years’ experience
Read how sealant jobs are priced and our reviews.
Quotes for external mastic in Walsworth
The price is agreed before any work begins. It takes into account:
- Any working-time requirements on site
- The size of the job
- Mould in or behind the old joints
- How much old sealant there is and how hard it is to remove
Leaving a failed joint generally makes the job bigger, not smaller. If you’re not sure whether it needs doing, ring 0345 464 0079 or send us an email for an honest opinion and a quote.
What we need to know
When you call or email, it’s useful to know:
- The address or postcode of the job
- If it’s domestic, commercial or a hotel
- Any previous sealing or DIY work
- A few photos by email, if you can
Need a quote? Please phone 0345 464 0079 or email us with a few details. You’ll know what we plan to do, and what it will cost, before any work begins.
Outside joints around Walsworth
Compared with the north and west, the South East gets less rain, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
If you let a flat or house near Hitchin station, failed wall and movement joints let damp in, so they’re worth checking between tenancies. Homes close to St Faith's Church include some older properties, and an extension built onto an older house moves differently, and the joint between them takes the strain.
Walsworth is about 1 mile north-east of Hitchin, in Hertfordshire. Our applicators cover external mastic for householders, landlords and businesses in Walsworth and nearby. Across Hertfordshire, we cover 381 places, and Walsworth is one of them. You can also see our page for London, roughly 32 miles from Walsworth.
Our applicators cover all of the SG4 and SG5 postcode area for external mastic and the streets around it. If you need external mastic at a property on Green Lane, Orchard Road and Purwell Lane or anywhere close by, our applicators can take on the job. We also cover Poets Estate (1 mile south), Benslow (1 mile south-west), Hitchin (1 mile south-west), Bearton (1 mile west) and Great Wymondley (1 mile south-east). Further out, we also cover Stevenage (5 miles south-east), St Albans (14 miles south), Welwyn Garden City (11 miles south), Harpenden (10 miles south), Hatfield (13 miles south) and Hertford (13 miles south-east).
What’s near Walsworth
Typical jobs here are in homes near The Millstream pub, Kingshott School and St Mary's Church. Nearby too are Hitchin Girls' School (0.8 miles south-west) and Butts Close (1.2 miles west). Walsworth has its own railway station: Hitchin station. Nearby you’ll also find Wymondley Castle (1.4 miles south-east) and Lister Hospital (2.9 miles south-east). Open spaces near Walsworth include Markham's Hill and Purwell Ninesprings.
When to call us in Walsworth
Joints sealed without backing rod, or far too deep, rarely last. Sealant bonded to three sides has nowhere to go and tears as soon as the joint widens.
It’s worth asking for a quote if you see:
- Failed sealant between panels on a façade
- Gaps where render, brick and frames meet
- Brick movement joints where the sealant has split
- Joints where the bead has come unstuck
Managing a site like Highover Junior Mixed and Infant School? Then movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
What your quote should include
- Whether the sealant suits the joint
- Whether VAT is included
- Whether they’re fully insured
- What guarantee comes with the work