Hertfordshire · England
External Mastic in Elstree
Sealing brickwork movement joints, render, cladding and façade joints for householders, landlords and businesses in Elstree. ARBOMaster approved applicators, fully insured, with a 12-month guarantee.
- Cracked joints where brick meets render or frames
- Water getting into walls through failed joints
- Hard, crazed mastic that has stopped moving
Surface by surface
Joints between dissimilar materials
Wherever two materials meet, they move differently. We seal the joint with a flexible exterior sealant.
Copings and trims
Copings expand and contract through the day, so a flexible sealant suits them best in all weathers.
External mastic for homes and businesses in Elstree
A movement joint is only as good as its depth. Backing rod controls how deep the sealant goes and keeps it off the back of the joint, leaving it bonded to two faces so it can move with the wall. If you have moss and dirt in joints with no sealant left and gaps where render, brick and frames meet, we can help.
External sealant needs dry, clean surfaces, so work around Elstree is planned for dry weather. Tell us about access to all sides of the building, including outbuildings and garages.
Whatever the size of the job, you get the same 12-month guarantee in Elstree and across Hertfordshire.
- Where
- Elstree (WD6)
- Region
- Hertfordshire
- Guarantee
- 12 months on all our work
- Price
- A clear price before we start
- Call
- 0345 464 0079
- Updated
- 26 October 2026
Other services in Elstree
What we do, step by step
The work is kept neat and contained to the joints we’re treating. The job normally takes anything from a few hours to several days, depending on the building. In a small place like Elstree, access is normally the main thing to plan. For outside work, also let us know about exposed walls and any outbuildings involved.
- First we look over the joints with you, agree which to renew and talk through access.
- We cut out the failed sealant and rake out any dirt or growth.
- The joint faces are cleaned and primed where the sealant needs it.
- Closed-cell backing rod is fitted to set the depth and stop three-sided bonding.
- The new sealant, chosen to suit the brick or render, is applied and tooled to a neat finish.
Before we arrive
- Mention any leaks or damp you’ve noticed
- Plan for the work area to be out of bounds to pets and children
- Tell us if parking is tricky
Getting a quote
We do not publish a price list. Instead, your job gets its own clear quote. To arrange one, call 0345 464 0079 or send us an email.
Advice
DIY versus a professional finish
If you do try it yourself, take your time over the preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it fails, we can still redo it.
Too much sealant is as bad as too little. A thick, smeared bead looks untidy and doesn’t move well, and the joint depth matters as much as the finish.
Walls and rooflines in Elstree
Rainfall in the South East is lower than in much 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 Headstone Manor (about 4.1 miles south-west) nearby, there’s older building stock in the area around Elstree 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.
Managing a site like St Nicholas Elstree Church of England VA Primary School? Then its movement joints, gutters and trims need looking after like any other building’s. If you live in an older home near Church of St Nicholas, the joints between older walls, newer extensions and the roofline need a sealant that can move.
Elstree is about 2 miles south-west of Borehamwood, in Hertfordshire. Across the WD6 area, we can carry out external mastic at your property. We cover 381 towns and villages across Hertfordshire, large and small. You can also see our page for London, about 13 miles away.
Every address in WD6 is covered for external mastic, from the main roads to the quietest streets. We cover properties on High Street, West View Gardens and Summer Grove. If you are just outside Elstree, we cover Deacon's Hill (1 mile east), Edgware Bury (1 mile south-east), Broadfields Estate (2 miles south-east), Borehamwood (2 miles north-east) and Edgware (2 miles south-east). Further out, we also cover Watford (5 miles west), Hemel Hempstead (10 miles north-west), St Albans (8 miles north), Welwyn Garden City (12 miles north-east), Harpenden (12 miles north) and Hoddesdon (14 miles north-east).
Near you in Elstree
Locally, jobs take us to homes and businesses close to The Holly Bush pub, London Academy and Aldenham Country Park and the streets around them. Elstree’s nearest station is Elstree & Borehamwood station, roughly 1.1 miles north-east. Nearby you will also find Elstree and Borehamwood Museum (1.4 miles north-east) and Royal National Orthopaedic Hospital (0.8 miles south). Green spaces nearby include Darland's Lake and Edgware Way Grassland.
What happens if it’s left?
Sealing over the top of old mastic does not hold for long. The new layer can’t bond properly to old, weathered material, so we always take the old sealant out. Around Elstree, older homes often have timber in their floors and frames, where water from a failed joint can cause rot if it’s left.
What it costs depends on the size of the job, how much old material has to come out and how easy the joints are to reach. You’ll have a clear quote before any work starts, so you know where you stand.
Why Elstree customers choose us
- More than 20 years in sealant work
- Sealant colour chosen to suit
- Anti-fungal sanitary silicone in wet areas
- We are fully insured
When to call us in Elstree
Weeds, moss and debris in a joint are a sign the sealant has gone. Roots and dirt hold water against the wall.
People usually contact us when they notice one of these:
- Brick movement joints where the sealant has split
- Moss and dirt in joints with no sealant left
- Leaking joints around cladding and façade panels
- Hard, crazed mastic that has stopped moving
If you let a flat or house near Elstree & Borehamwood station, outside joints that have cracked can let damp into a rental, so check them between lets.
Before you book anyone
- How long to leave it before use
- Whether they’re fully insured
- Which sealant they’ll use, and why
- What happens if the job turns out different
Honest limits
We will not take on work that will not last, so here’s what sealant can’t put right:
- Rising or penetrating damp from elsewhere in the wall
- Adding movement joints to masonry that has none
- Cracking across the wall rather than at a joint
If in doubt, phone 0345 464 0079 or email us and we will say what we think before you book.
What we seal
- Concrete & block
- Render & cladding joints
- Brickwork movement joints
- Façade panels
- Joints between brick and frames
- Copings & trims
How we quote for external mastic
We quote each job individually. This is what makes a difference:
- How much old sealant there is and how hard it is to remove
- The number of rooms or windows
- Whether there’s mould to deal with
- Any working-time requirements on site
The cost reflects the work involved, not guesswork. That’s why we ask about the job first and send you a clear quote before we start.
Helping us quote
To help us quote quickly, please include:
- Where the job is, and your postcode
- A few photos by email, if you can
- Roughly how big the job is
- If someone has resealed it before
For external mastic in Elstree, ring 0345 464 0079 or drop us an email. Tell us what the problem is and where, and we will agree the price before any work begins.
Your questions about external mastic in Elstree
Do you work for landlords with property near Elstree & Borehamwood station?
Yes, rental work is part of what we do. You can call 0345 464 0079 or send us an email with the address and a few details, and we’ll give you a fixed price before work begins.
Is Elstree in your area for external mastic?
Yes. We work across London and the South East, and Elstree is part of that. Just ring 0345 464 0079 or send us an email with a few details of the job.
When is the sealant fully cured?
It depends on the product and the temperature. We tell you how long to leave it before we go.
Are you ARBOMaster approved?
Yes. ARBOMaster is the approved applicator scheme for Arbo sealants, and we’re part of it.
Is it OK to seal over old sealant?
No, because it fails. We remove every bit of old sealant first.
Is it worth trying it myself?
That depends on the joint. High-level, external movement and fire-rated joints are professional jobs, while a short indoor joint may be within reach.
Do you take out the old sealant first?
Yes. All of the old material is cut out and the joint cleaned before applying anything new.
Do you guarantee your work?
Yes. Every job comes with a 12-month guarantee.