Hertfordshire · England
Nash Mills External Mastic
Our applicators work in Nash Mills on sealing brickwork movement joints, render, cladding and façade joints. Old material cut out, joints cleaned and sealed neatly.
- Sealant that has lost its bond to the brick or render
- Plants rooting in failed movement joints
- Rigid filler in a joint that should flex
How it works
Once we are on site, we compare the joints with what we discussed. If we find something unexpected, we talk it through with you first. After that, the work takes a few hours for a handful of joints, longer for a whole elevation. Parking around Nash Mills is generally easier than in a town centre, but mention any lanes, gates or long drives. For outside work, side access and the height of the joints help us plan.
- First, the joints are inspected and the access agreed.
- We cut out the old mastic and rake out anything in the joint.
- The faces are brushed clean and primed where the product requires it.
- Backing rod sized to the joint goes in to set the depth.
- The exterior sealant is applied, tooled and checked along its length.
Getting ready for the visit
- Mention any parking rules near the property
- For indoor joints, keep the area dry beforehand if you can
- Clear the area around the work
Ask for a quote
Need a quote? Please phone 0345 464 0079 or drop us an email with a few details. We will explain what we’d do and send you a clear quote before we start.
Related advice
External mastic for homes and businesses in Nash Mills
Failed sealant is cut out, the depth set with closed-cell backing rod, and the joint resealed with a low-modulus sealant made for outside. We pick a colour that sits well with the wall so the joint doesn’t stand out. If you have movement joints filled with mortar instead of sealant and plants rooting in failed movement joints, we can help, on joints between brick and frames, façade panels and brickwork movement joints alike.
Around Nash Mills, garages, outbuildings and extensions all add to the joints on the outside of a home. Leaks generally start at a gutter end, a garage door frame or where an extension meets the house.
There’s a 12-month guarantee on every job.
- Location
- Nash Mills (HP3, WD4)
- Wider area
- Hertfordshire
- Cover
- A year, on every job
- Quote
- A clear price before work begins
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
Work for landlords, hotels and businesses
We also work for businesses, from offices to washrooms and kitchens. On commercial sites, working times can be discussed when we quote.
If you manage several properties in or around Nash Mills, jobs at different addresses can go on one quote. Send us the addresses and the work at each.
Also near Nash Mills
What else we do in Nash Mills
How to look after the new joints
After the cure time, these simple habits help:
- Tell anyone working on the walls about the movement joints
- Deal with leaking gutters that soak the joints below
- Wash walls gently around the sealant
- Leave the joints unpainted unless we have said otherwise
Avoid pressure-washing straight into the joints. A strong jet can damage the edges of the bead.
Gaps, plants or missing sealant in a joint are worth getting looked at. Early work is quicker and leaves a better finish.
What affects the cost of external mastic
For a quick quote, just ask. The main things that affect it are:
- Which sealant suits the joint
- The number of rooms or windows
- How much old sealant there is and how hard it is to remove
- Any mould that needs treating
We don’t show prices on the website, because each job is priced on what it involves. For a quick quote, please call 0345 464 0079 or send us an email and we will talk you through it.
Asking for a quote
Photos by email are helpful but not essential. Try to tell us:
- A few pictures by email, if you can
- The address or postcode of the job
- What the problem is, such as mould, gaps, leaks or cracking
- How many joints, rooms or windows are involved
We quote each job on its own, so the first step is telling us about yours. Simply call 0345 464 0079 or drop us an email and describe the job, and pictures are welcome.
Surface by surface
Concrete and blockwork
Concrete faces can be dusty and porous, so cleaning and priming matter. A primer goes on where the product requires one before the bead.
Cladding and façade panels
If the façade has a specified sealant, that’s what we use or an approved alternative. Send us any details you have about the façade.
Can I do it myself?
A DIY attempt does not rule out a professional job. We cut it out and start again.
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is matched to the joint and its conditions, then guaranteed for a year.
Questions from Nash Mills
Is Nash Mills within the area you cover?
Yes, we do. We work across London and the South East, and smaller places are part of that. The journey is planned ahead, so it helps to know about access.
Should the sealant in an older Nash Mills home be renewed?
If it hasn’t been replaced for some years, it’s normally worth it. Sealant is a maintenance item: how long it lasts depends on use, cleaning and exposure, and many homes in Nash Mills may already be on their second or third set.
Can you seal over the old sealant?
No. Fresh sealant does not stick to old sealant, and anything trapped underneath, including mould and water, stays there. We remove it all first.
What does external mastic cost?
Size, access and the old material all affect the cost. Call for a quick quote and we will talk you through it.
Where are you based?
Our base is Crawley, with over 20 years’ experience. Our area covers South East England, London and Scotland.
Do you work for hotels and businesses?
Yes. We’ve worked for hotels, offices and other businesses and we’re fully insured.
How long does external mastic last?
That depends on the wall, the weather and the movement. Signs to watch for are cracking, hardening and gaps at the edges, and reseal at that point.
Is it messy?
No. We protect the surfaces around the joints, and we tidy up before we go.
Nash Mills buildings and the weather
Historic houses like High Elms Manor (about 3.1 miles south-east) are a reminder that the area around Nash Mills has older buildings as well as new. Where a home is older, older brick and stone need a sealant that suits them, at the right joint depth. Hemel Hempstead, which Nash Mills is part of, is one of England’s post-war new towns. Homes here were built in phases, many of them in the post-war decades, so neighbouring houses often have rooflines and wall joints of the same age, wearing out at the same time.
For landlords with property near Apsley station, split movement joints are easy to miss on a rental until damp shows inside. In the older streets around Church of St Mary, older walls, gutters and the joints where extensions meet them need a flexible sealant. For site and facilities teams at buildings such as Nash Mills Church of England Primary School, its movement joints, gutters and trims need looking after like any other building’s.
Nash Mills is about 2 miles south of Hemel Hempstead, in Hertfordshire. We carry out external mastic for homes and businesses in Nash Mills and the surrounding area. Nash Mills is one of 381 places in Hertfordshire we cover. London is on our list too, around 22 miles away.
All of HP3 and WD4 is within our area for external mastic. You’ll find streets such as Pond Road, Rose Lane and Lower Road. Neighbouring places we cover for external mastic include Felden (1 mile west), Rucklers Lane (1 mile south-west), Bennetts End (1 mile north), Apsley (1 mile north-west) and Kings Langley (1 mile south). We also work in nearby towns such as Watford (5 miles south-east), St Albans (5 miles east), Welwyn Garden City (12 miles north-east), Harpenden (7 miles north-east), Hatfield (10 miles east) and Borehamwood (9 miles south-east).
Near you in Nash Mills
Around Nash Mills, our work takes us to homes and buildings near Longdean School and Red Lion Public House, among other places. The nearest railway station is Apsley station, roughly 0.5 miles west of the centre. Well-known places in the area include Hemel Hempstead Hospital (1.7 miles north-west). Open spaces near Nash Mills include Long Deans and Verulamium Lake.
Why deal with it now?
A failed movement joint lets water into the wall and can run behind render or cladding. Dealing with it early keeps the repair to the joint, rather than the wall around it. In an older home around Nash Mills, damp from a failed joint can get into timber and plaster, which is far harder to put right than the sealant itself.
Commercial jobs are quoted on the same basis as homes: how much there is to do, how we reach it and what it needs, along with when we can work on site. Ask us for a quote and we’ll explain what it covers.
Why Nash Mills customers choose us
- ARBOMaster approved applicator
- More than 20 years in sealant work
- Arbo and Everbuild products
- Every job guaranteed for a year