Hertfordshire · England
Shenleybury External Mastic
Our applicators work in Shenleybury on sealing brickwork movement joints, render, cladding and façade joints. Old material cut out, joints cleaned and sealed neatly.
- Movement joints with cracked, split or missing sealant
- Joints where the bead has come unstuck
- Moss and dirt in joints with no sealant left
How we handle external mastic in Shenleybury
As ARBOMaster approved applicators, we choose exterior sealants to suit the joint and the surfaces. Some surfaces need a primer before sealing, and we do not skip that step. We work on brickwork movement joints, concrete & block and joints between brick and frames, and people most often call us about rain getting behind render or cladding at a joint and sealant pulling away from one side of the joint.
Outside joints can only be sealed when they’re dry, so work in Shenleybury is booked around the forecast. Let us know about access to every wall, plus any garages or outbuildings.
We guarantee the work for a year. If something is not right with it in that time, tell us and we’ll put it right.
- Location
- Shenleybury (WD7)
- Wider area
- Hertfordshire
- Cover
- A year, on every job
- Price
- A clear price before we start
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
Work for landlords, hotels and businesses
If you manage several properties in or around Shenleybury, several properties can go on one quote. Send us the addresses and the work at each.
Landlords and letting agents in Shenleybury can book us as well as homeowners. Resealing between tenancies is a simple way to keep a property in good order before the next move-in.
Places near Shenleybury
What else we do in Shenleybury
Why act early in Shenleybury
An open joint keeps letting water into the wall with every downpour. In cold weather, frost can damage wet brick and render around the joint, so the problem grows beyond the joint itself. In a small place like Shenleybury, homes can be exposed to wind and rain, which finds any gap, and damp in older walls is slow to dry out.
A few things move the cost up or down: the old material and how easily it comes out, any mould to treat, and whether the work is at height. Your quote takes all of that into account.
Why us?
- You choose the colour before work begins
- Domestic, commercial and hotel work
- Quality sealants from Arbo and Everbuild
- Rated 4.9 stars on Google
See our cost guide and our reviews.
How to look after the new joints
Once the sealant has cured, a few habits help it last:
- Make sure movement joints aren’t pointed over
- Get split or bare joints resealed while the damage is small
- Wash walls gently around the sealant
- Don’t let climbing plants root in the sealant
Avoid pressure-washing straight into the joints. A strong jet can damage the edges of the bead.
Small splits are the time to act. Then it’s a straightforward cut-out and reseal with no damage behind it to deal with.
How it works
The work is kept neat and contained to the joints we are treating, so you can carry on as normal. The job normally takes anything from a few hours to several days, depending on the building. Somewhere as small as Shenleybury, access is often the only tricky part. For outside work, also let us know about exposed walls and any outbuildings involved.
- We start by walking round the building and agreeing the joints and the access.
- Every bit of old sealant and any mortar or debris is cut out.
- The faces are brushed clean and primed where the product requires it.
- We fit closed-cell backing rod to control the depth.
- The exterior sealant is applied, tooled and checked along its length.
Preparing for the visit
- Let us know about parking restrictions
- Where the joints are inside, avoid wetting them before we arrive
- Mention if the joints have been sealed before
Ask for a quote
There’s no standard price list, as no two jobs are quite the same. Instead, we send you a clear quote for your job. To get started, phone 0345 464 0079 or email us.
Related advice
Outside joints around Shenleybury
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. With historic houses such as Wyllyotts Manor (about 4.1 miles east) nearby, there’s older building stock in the area around Shenleybury as well as newer homes. In older buildings, older walls and rooflines need a sealant that moves with them and suits the material.
Rented homes near Radlett station change hands often, and outside joints that have cracked can let damp into a rental, so check them between lets. Homes close to St Botolphs include some older properties, and the joints between older walls, newer extensions and the roofline need a sealant that can move. Managing a site like Clore Shalom School? Then movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
Shenleybury is about 3 miles north of Borehamwood, in Hertfordshire. For external mastic in and around Shenleybury, it’s easy to get a quote: please call 0345 464 0079 or drop us an email. We cover Hertfordshire from our Crawley base, Shenleybury included. Shenleybury is one of 381 places in Hertfordshire we cover for external mastic. You can also see our page for London, roughly 16 miles from Shenleybury.
All of WD7 is within our area for external mastic, from the main roads to the quietest streets. We cover properties on Hugo Gryn Way, Farm Close and Shenleybury. If you’re just outside Shenleybury, we cover Broad Colney (1 mile north-west), London Colney (1 mile north), Tyttenhanger (2 miles north), Colney Heath (3 miles north-east) and North Mymms (3 miles east). We also work in nearby towns such as Watford (5 miles south-west), Hemel Hempstead (8 miles north-west), Stevenage (15 miles north), St Albans (4 miles north-west), Welwyn Garden City (8 miles north-east) and Harpenden (8 miles north).
Near you in Shenleybury
Locally, jobs take us to homes and businesses close to The Black Lion pub, Manor Lodge School and North Mimms Park and the streets around them. Shenleybury’s nearest station is Radlett station, roughly 1.8 miles south-west. Other landmarks nearby include Hilfield Castle (4 miles south-west) and The Maltings (3.8 miles north-west). Open spaces near Shenleybury include Verulamium Lake and Broad Colney Lakes.
When it isn’t the sealant
Sealant isn’t the answer to every problem, and we’ll tell you before work begins. Sealant will not put right:
- Cracks in the bricks or render themselves, away from the joints
- Damp that isn’t coming from the joint
- Structural movement, which needs a surveyor or engineer
If in doubt, ring 0345 464 0079 or email us and we’ll say what we think before you book.
What we seal
- Façade panels
- Copings & trims
- Joints between brick and frames
- Concrete & block
- Render & cladding joints
- Brickwork movement joints
DIY sealant or a professional job?
Some jobs are best left to a professional: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.
The biggest DIY mistake is sealing over old sealant. New silicone won’t bond to old, so it peels away and traps moisture behind it. All the old material has to come out first.
What the job involves on each surface
Cladding and façade panels
Where a cladding system has its own specified sealant, we follow it or an approved alternative. Tell us what the building has when you get in touch.
Brickwork movement joints
Clay brickwork grows slightly over its life and moves with the weather. That movement goes into the joint, so the sealant in it must stay soft and stretchy.
FAQs for Shenleybury
Is Shenleybury in your area for external mastic?
Yes. Our work covers London and the South East, and Shenleybury is part of that. You can phone 0345 464 0079 or send us an email and let us know what needs doing.
Do you cover smaller places like Shenleybury?
Yes. Shenleybury is within the area we cover, which takes in towns, villages and rural addresses. Our work covers London and the South East. Just mention lanes, gates or anything else about the route when you book.
Can you seal joints between two different materials?
Yes. Joints between dissimilar materials are a big part of external work. We use a flexible sealant suited to both surfaces, primed where needed.
When will the joints need doing again?
That varies with the weather the wall faces, how much it moves and the sealant used. Treat it as a maintenance item and look at it yearly.
How long does external mastic take?
It depends on the size of the job, but most jobs take a few hours to a few days, depending on the length of joint and the access. We’ll give you a better idea when we quote.
Do you remove the old sealant?
Yes. We cut out all the old sealant and clean the joint before resealing.
How do I get a quote for external mastic in Shenleybury?
It depends on the job, so we quote each one individually. For a quick quote, ring 0345 464 0079 or drop us an email and let us know what needs doing and where.
I rent my home. Can I book you?
Of course. Check with your landlord; we can send the quote to them too.