Hertfordshire · England
External & façade joints in Radlett, Hertfordshire
Problem with your movement joints in Radlett? We cut out the old, prepare the joints and apply the right sealant, and the work is guaranteed for a year.
- Failed seals between different materials
- Water getting into walls through failed joints
- Sealant pulling away from one side of the joint
How we handle external mastic in Radlett
Ground-floor and low-level joints are straightforward to reach. For joints higher up, give us some details of the building and we’ll confirm what’s needed to reach them safely. Common call-outs are for movement joints filled with mortar instead of sealant and failed seals between different materials, across copings & trims, brickwork movement joints and render & cladding joints.
Around Radlett, garages, outbuildings and extensions all add to the joints on the outside of a home. Leaks normally start at a gutter end, a garage door frame or where an extension meets the house.
All our work is covered by a 12-month guarantee, wherever you are in Hertfordshire.
- Where
- Radlett (WD7)
- Region
- Hertfordshire
- Guarantee
- One year on every job
- Quotes
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
How we quote for external mastic
You’ll get a clear quote before we start. It’s based on:
- Whether there’s mould to deal with
- Working hours on commercial sites
- Whether old sealant or filler has to be cut out
- Access and height
The cost reflects the work involved, not guesswork. That’s why we ask a few questions first and agree the price before starting.
Helping us quote
You do not need to know the technical terms. Just tell us:
- How many joints, rooms or windows are involved
- Pictures of the joints, sent by email
- How we’d reach the joints
- What’s wrong with the joints now
For a quote, call 0345 464 0079 or email us and tell us where the job is and what the problem looks like. You’ll have a clear quote before we start.
Work for landlords, hotels and businesses
Mouldy or split sealant often shows up at the end of a tenancy, and it’s quick to put right between tenancies. We can quote for more than one property at once.
Businesses can book us for washrooms, kitchens, offices and more. For commercial premises, we can talk through working times when we quote.
Surface by surface
Brickwork movement joints
Brick walls have vertical movement joints to absorb expansion. They’re resealed over backing rod with a low-modulus sealant.
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.
Why deal with it now?
It often makes sense to reseal all the failing joints on an elevation together. Joints of the same age tend to fail together and it means sorting access once. Homes in smaller places like Radlett can face more weather, and failed outside joints let damp into walls. Inside, a split seal lets water into floors and panels just as it would anywhere.
Commercial jobs are quoted on the same basis as homes: the amount of work, the access and the products needed, plus any working-time requirements on site. Call for a quick quote and we will go through it with you.
What you get with us
- An ARBOMaster approved applicator
- Rated 4.9 stars on Google
- Any old sealant cut out fully, not covered over
- Over 20 years’ experience
Take a look at our cost guide and what customers say.
Nearby places to Radlett
Other services in Radlett
FAQs for Radlett
Is Radlett within the area you cover?
Yes, smaller places are covered as well as towns. We work across London and the South East. Let us know about access, parking and anything unusual about getting there when you book.
Do you cover Radlett for external mastic?
Yes. Our work covers London and the South East, and Radlett is part of that. Just phone 0345 464 0079 or email us with a few details of the job, and we will give you a clear quote.
Can you seal over the old sealant?
No. Fresh sealant doesn’t stick to old sealant, and anything trapped underneath, including mould and water, stays there. We remove it all first.
How long does external mastic take?
Most jobs take a few hours for a handful of joints, longer for a whole elevation, including the preparation. Your quote will say how long we expect yours to take.
Should I point up the gap in my brickwork?
No. Mortar locks the joint solid, so the movement cracks the wall elsewhere. It needs a flexible sealant over backing rod.
How long before the joint can be used?
That depends on the sealant used, so please follow the time we give you when we finish.
Will the new joint stand out?
The aim is a neat, even joint in a colour that suits the wall. Colour is agreed with you before we begin, matched as closely as the range allows.
Do you use backing rod?
We fit closed-cell backing rod wherever the joint depth needs controlling. It sets the sealant depth and prevents three-sided bonding so the bead can stretch.
Walls and rooflines in Radlett
With historic houses such as High Elms Manor (about 3.3 miles west) nearby, there’s older building stock in the area around Radlett as well as newer homes. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material. 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.
For site and facilities teams at buildings such as St John's Church of England Infant and Nursery School, its movement joints, gutters and trims need looking after like any other building’s. For landlords with property near Radlett station, outside joints that have cracked can let damp into a rental, so check them between lets.
Radlett is about 3 miles north-west of Borehamwood, in Hertfordshire. From the centre of Radlett to the outskirts, we cover external mastic for every kind of property, from flats and houses to offices and hotels. 381 places in Hertfordshire are on our list, large and small. For nearby work, see our London page.
Here we cover the WD7 postcode area for external mastic. We cover properties on Upper Station Road, Station Road and Barn Close. Radlett is on the B462 and A5183, which makes it straightforward to reach with everything needed for external mastic. Nearby, we also carry out external mastic in Kemprow (1 mile west), Round Bush (1 mile south-west), Letchmore Heath (1 mile south-west), Aldenham (2 miles south-west) and Patchetts Green (2 miles south-west). Larger places within reach include Watford (4 miles south-west), Hemel Hempstead (8 miles north-west), St Albans (5 miles north), Welwyn Garden City (10 miles north-east), Harpenden (9 miles north) and Hoddesdon (14 miles east).
Near you in Radlett
We work in homes and buildings around The Cat And Fiddle Public House, among other places. Radlett has its own railway station: Radlett station. Well-known places in the area include Radlett and District Museum (less than half a mile south-east) and Harlequin Centre (3.7 miles south-west). Not far away are Verulamium Lake and Broad Colney Lakes.
When it is not the sealant
Some problems need a builder, plumber or other trade rather than us:
- Loose or hollow render, which needs re-rendering
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
- Adding movement joints to masonry that has none
If you’re not sure, just call 0345 464 0079 or email us and we will give you a straight answer.
What we seal
- Joints between brick and frames
- Render & cladding joints
- Concrete & block
- Copings & trims
- Brickwork movement joints
- Façade panels
Signs you need external mastic in Radlett
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 sealant never bonds properly.
The problems people generally mention when they call are:
- Panel joints letting water in
- Rain getting behind render or cladding at a joint
- Weeds or debris growing in open joints
- Weathered mastic that no longer stretches
In the older streets around St John, older walls, gutters and the joints where extensions meet them need a flexible sealant.
Questions to ask before you book
- Whether all the old sealant comes out first
- What product goes in the joint
- What insurance they hold
- What preparation is included
What happens on the day
We keep the work tidy and contained to the area we are working on, so you can get on with your day. Expect the work to take a few hours for a handful of joints, longer for a whole elevation, and we explain the cure time before we leave. For a job in Radlett, 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.
- A low-modulus exterior sealant is gunned in and tooled to a neat finish.
How to prepare
- Let us know about earlier repairs to the joints
- Try not to wet indoor joints just before the visit
- Mention any leaks or damp you’ve noticed
Get a quote
There’s no standard price list, because every job is different. Instead, your job gets its own clear quote. To arrange one, call 0345 464 0079 or email us.