Hertfordshire · England
External Mastic in Hemel Hempstead
We cover Hemel Hempstead for sealing brickwork movement joints, render, cladding and façade joints. Old sealant removed completely, joints prepared properly and every job guaranteed for a year.
- Moss and dirt in joints with no sealant left
- Sealant pulling away from one side of the joint
- Joints with sealant missing in places
Landlord and commercial work in Hemel Hempstead
From a single let to a portfolio, the work is the same standard: old sealant fully removed, joints prepared properly and a one-year guarantee.
We also work for property managers and facilities teams. Several sites can go on one quote.
External mastic for homes and businesses in Hemel Hempstead
Short cuts in external joints show up within a season or two. New sealant over old, joints packed with mortar and beads with no backing rarely last long. We strip the joint back and start again. We work on concrete & block, brickwork movement joints and render & cladding joints, and common reasons people get in touch are water getting into walls through failed joints and cracked joints where brick meets render or frames.
Larger buildings in Hemel Hempstead have plenty of movement joints, cladding joints and roofline trims. When those fail, water gets behind the face of the building, often unseen until it shows inside.
All of our work is guaranteed for twelve months, and the guarantee is the same wherever you are.
- Place
- Hemel Hempstead (HP2, HP3, HP1)
- Wider area
- Hertfordshire
- Guarantee
- A year, on every job
- Quotes
- Quoted before any work starts
- Phone
- 0345 464 0079
- Last updated
- 26 October 2026
DIY versus a professional finish
The biggest DIY mistake is sealing over old sealant. Silicone doesn’t stick to old silicone, so it lifts and traps water and mould underneath. Everything old must be removed first.
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and getting the depth right matters as much as the look.
The process
We work through the job in order: protection first, then preparation, sealing and a tidy-up. For most jobs that takes anything from a few hours to several days, depending on the building. In Hemel Hempstead, we work in everything from flats and family homes to offices and hotels. Whichever it is, tell us how to get in, where to park and where the work is.
- First, the joints are inspected and the access agreed.
- 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.
Getting ready for the visit
- Mention any leaks or damp you’ve noticed
- Tell us about access, such as stairs, a lift or high-level joints
- Keep pets and children clear of the area while we work
Getting a quote
Call for a quick quote, or send an email if you’d rather. Tell us about the joints that need doing and we’ll explain what’s involved.
Related advice
Keeping the joints in good condition
Looking after new joints is easy:
- Wash walls gently around the sealant
- Keep water from gutters off the wall
- Keep soil, plants and ivy away from the joints
- Look over the joints every year, ideally after winter
Make sure anyone working on the wall later knows where the movement joints are. They should be kept open and resealed, not filled.
An open movement joint lets rain into the wall every time it pours. That can lead to damp patches, staining and frost damage which cost more to put right than the joint.
What external mastic looks like in Hemel Hempstead
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. Historic houses like High Elms Manor (about 4.6 miles south-east) are a reminder that the area around Hemel Hempstead has older buildings as well as new. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material.
Managing a site like Broadfield Academy? Then its movement joints, gutters and trims need looking after like any other building’s. If you let a flat or house near Apsley station, outside joints that have cracked can let damp into a rental, so check them between lets. If you live in an older home near St Barnabas, the joints between older walls, newer extensions and the roofline need a sealant that can move.
Hemel Hempstead is about 24 miles north-west of London, in Hertfordshire. If you need external mastic in Hemel Hempstead, please call 0345 464 0079 or drop us an email for a quick quote. We cover Hertfordshire from our Crawley base, Hemel Hempstead included. Hemel Hempstead is one of 381 places in Hertfordshire where we work for external mastic. We also work in London, about 24 miles from Hemel Hempstead.
Our applicators cover all of HP2, HP3 and HP1 for external mastic and the streets around it. Streets in the area include The Queen's Square, High Street and Sun Square, all of which we cover. Being close to the A41 and A414, Hemel Hempstead is simple for us to get to. If you’re just outside Hemel Hempstead, we cover Grovehill (1 mile west), Woodhall Farm (1 mile west), Adeyfield (1 mile north-east), Highfield (1 mile north) and Bennetts End (1 mile south-east). Larger places within reach include Watford (7 miles south-east), St Albans (6 miles east), Welwyn Garden City (12 miles east), Harpenden (6 miles north-east), Hatfield (10 miles east) and Borehamwood (10 miles south-east). Hemel Hempstead is among the bigger towns we cover in Hertfordshire.
Near you in Hemel Hempstead
Around Hemel Hempstead, our work takes us to homes and buildings near Gadebridge Park, The Full House and Adeyfield School. For rail, the closest station is Apsley station, about 1.4 miles south of the centre. Well-known places in the area include Redbourn Museum (4 miles north-east) and Hemel Hempstead Hospital (0.5 miles west). For a walk, there’s Verulamium Lake and Long Deans.
When it is not the sealant
We will always be straight with you, so here’s what new sealant will not do:
- Cracking across the wall rather than at a joint
- Rising or penetrating damp from elsewhere in the wall
- Movement that’s more than a sealant joint can take
If you’re not sure, just phone 0345 464 0079 or drop us an email and we’ll give you a straight answer.
Joints and surfaces we work on
- Brickwork movement joints
- Façade panels
- Joints between brick and frames
- Render & cladding joints
- Concrete & block
- Copings & trims
Nearby places to Hemel Hempstead
More services for Hemel Hempstead
What affects the quote in Hemel Hempstead
The quote reflects the job in front of us. We take into account:
- Whether old sealant or filler has to be cut out
- The number of rooms or windows
- Any working-time requirements on site
- Whether there’s mould to deal with
Rather than a set price list, we look at what your job involves: the amount of work, the old material and the access. The price is agreed before we begin.
What we need to know
A few details help us give you an accurate quote. When you ask for a quote, tell us:
- If it’s domestic, commercial or a hotel
- Roughly how big the job is
- What the problem is, such as mould, gaps, leaks or cracking
- Whether it has been sealed before
We quote each job on its own. Just phone 0345 464 0079 or email us with the details and send pictures if you have them.
Questions from Hemel Hempstead
Is it worth replacing old sealant in an older home in Hemel Hempstead?
If it hasn’t been replaced for some years, it’s generally worth it. Sealant is a maintenance item: how long it lasts depends on use, cleaning and exposure.
Can you do external mastic in Hemel Hempstead?
Yes. We work across London and the South East, and Hemel Hempstead is part of that. Just ring 0345 464 0079 or send us an email with a few details of the job, and we will send you a clear quote.
Is there a guarantee?
Yes, always. There’s a 12-month guarantee on every job.
How long should I leave it?
Many sealants skin over quickly but take longer to cure fully. We’ll tell you how long to leave the joint before we leave.
How do I get a quote for external mastic in Hemel Hempstead?
There’s no set price, as it depends on the job: its size, the old material, access and the product needed. You will get a clear quote before any work starts.
Do you seal joints where cladding meets other materials?
Yes. The old joint is removed, both surfaces cleaned and primed where needed, and a flexible sealant applied. We pick a colour that works with both materials.
How do you reach high-level joints?
It depends on the height and the site. Low-level joints are straightforward; for higher work, tell us about the building and we will confirm what’s needed.
Can tenants book the work?
Yes. Ask your landlord first, and we can send them the quote if that helps.
Different surfaces, different methods
Copings and trims
Coping and trim joints face rain and sun head on. Each is resealed with a weatherproof, flexible sealant.
Concrete and blockwork
The face of concrete or block is often dusty, so preparation is key. A primer goes on where the product requires one before sealing.