Hertfordshire · England
External & façade joints in Northaw Valley, Hertfordshire
Our applicators work in Northaw Valley on sealing brickwork movement joints, render, cladding and façade joints. Old sealant removed completely, joints prepared properly.
- Leaking joints around cladding and façade panels
- Failed seals between different materials
- Plants rooting in failed movement joints
About our external mastic in Northaw Valley
We are ARBOMaster approved applicators, and each external joint gets a sealant suited to it. Porous or awkward surfaces are primed where the sealant needs it. Common call-outs are for failed seals between different materials and water getting into walls through failed joints, on render & cladding joints, joints between brick and frames and brickwork movement joints.
Older homes in small places like Northaw Valley may be stone, brick or timber-framed, often with later extensions. The joints where those materials meet are the weak points, and they need the right sealant at the right depth.
Big or small, you get the same one-year guarantee in Northaw Valley and across Hertfordshire.
- Place
- Northaw Valley (EN6)
- Region
- Hertfordshire
- Cover
- A year, on every job
- Price
- A clear price before we start
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Outside joints around Northaw Valley
London and the South East are among the drier parts of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind. Historic houses like Wyllyotts Manor (about 2.4 miles west) are a reminder that the area around Northaw Valley has older buildings as well as new. In older buildings, older brick and stone need a sealant that suits them, at the right joint depth.
For site and facilities teams at buildings such as St. John's Senior School, larger buildings have long runs of movement joint that eventually need resealing. Rented homes near Crews Hill station change hands often, and failed wall and movement joints let damp in, so they’re worth checking between tenancies.
Northaw Valley is about 2 miles east of Potters Bar, in Hertfordshire. Wherever you are in the EN6 postcode area, our applicators can take on external mastic. We cover 381 towns and villages across Hertfordshire, from the larger towns to small villages. There’s also a page for London, roughly 14 miles from Northaw Valley.
Jobs for external mastic in EN6 is quoted and booked the same way as anywhere else. Other places close to Northaw Valley include Botany Bay (1 mile south-east), Potters Bar (2 miles west), Hadley Wood (3 miles south-west), Bentley Heath (3 miles west) and Cockfosters (3 miles south). Larger places within reach include Watford (11 miles west), Hemel Hempstead (14 miles west), Stevenage (15 miles north), St Albans (9 miles north-west), Welwyn Garden City (8 miles north) and Harpenden (12 miles north-west).
What’s near Northaw Valley
Locally, jobs take us to homes and businesses close to Two Brewers Public House, Northaw Church of England Primary School and Mount Grace School and the streets around them. The nearest railway station is Crews Hill station, about 1.4 miles south-east. Other landmarks nearby include Spires Shopping Centre (3.8 miles south-west) and Chase Farm Hospital (2.3 miles south-east). Not far away are Bowyer's Water and Fir and Pond Woods.
When something else is needed
Before booking, it’s worth knowing the limits:
- Render that’s blown, hollow or coming away
- Movement that’s more than a sealant joint can take
- Cracked brickwork or render that needs a builder or plasterer
If in doubt, call 0345 464 0079 or drop us an email and we will say what we think.
Where we work in Northaw Valley
- Concrete & block
- Joints between brick and frames
- Façade panels
- Copings & trims
- Render & cladding joints
- Brickwork movement joints
Common questions in Northaw Valley
Is Northaw Valley in your area for external mastic?
Yes. Our work covers London and the South East, and Northaw Valley is part of that. Just phone 0345 464 0079 or send us an email with a few details of the job, and we will give you a clear quote.
Can you help a landlord with a rental near Crews Hill station?
Yes, landlords and agents are among the people we work for, and several properties can go on one quote. Just call 0345 464 0079 or email us with the address and what needs doing, and we will give you a clear quote.
Are you insured?
Yes. Mr Mastic is fully insured, with over 20 years’ experience in sealant work.
How long does external mastic take?
As a guide, most jobs take anything from a few hours to several days, depending on the building. Bigger jobs take longer, and we’ll tell you how long to expect.
Is it OK to seal over old sealant?
No, because it fails. We remove every bit of old sealant first, so the new joint bonds to clean surfaces.
Do you guarantee your work?
Yes, for a year. If there’s a problem with our work in that time, tell us and we will put it right.
Can I do it myself?
Sometimes. Preparation is everything: all the old sealant out, and a clean, dry joint. If it doesn’t work out, we can redo it.
Will the old sealant be removed?
Always. Sealing over old sealant is the main reason resealing fails early, so we never do it.
Landlords, agents and businesses in Northaw Valley
We also work for property managers and facilities teams in Northaw Valley and across Hertfordshire. We can quote a run of properties together, and we are fully insured.
In hotels, rooms out of use cost money, so the work can be planned room by room. Hotel work is part of what we do, alongside homes and businesses.
Why it’s worth doing now in Northaw Valley
Pointing a movement joint with mortar might seem a neat fix, but it locks the joint solid. The wall then cracks somewhere else. The correct repair is a flexible sealant with the right backing. Where a wall is exposed, as many are in small places like Northaw Valley, wind-driven rain gets into any failed joint, and older walls, once damp, take a long time to dry.
Every job is a little different, so we quote each one individually. Size, access and the product the joint needs all play a part.
Why choose Mr Mastic in Northaw Valley
- 12-month guarantee on every job
- A choice of colours where the product allows
- Experience in homes, commercial sites and hotels
- More than 20 years in sealant work
See our cost guide or our reviews.
Places near Northaw Valley
Other services in Northaw Valley
How the visit works
Most of a good job is in the preparation, and we don’t rush it. Joints are cleaned back and dried before anything new goes in. All told, the work takes anything from a few hours to several days, depending on the building. Somewhere as small as Northaw Valley, access is often the only tricky part. If the job is outside, mention outbuildings, exposed walls and how to reach them.
- First, the joints are inspected and the access agreed.
- We cut out the old mastic and rake out anything in the joint.
- Joint faces are cleaned back and primed if the sealant needs it.
- We fit closed-cell backing rod to control the depth.
- The exterior sealant is applied, tooled and checked along its length.
How to prepare
- Clear items away from the joints we’re working on
- Mention any parking rules near the property
- Let us know if you’ve seen damp or leaks
Get a quote
There’s no standard price list. Instead, we send you a clear quote for your job. To get started, phone 0345 464 0079 or email us.
Related advice
What the job involves on each surface
Copings and trims
Coping joints that leak let water straight down into the wall. Sealing them early saves the wall below.
Joints between dissimilar materials
Different materials may need different primers. We prepare both faces so the sealant bonds properly.
Common problems we fix in Northaw Valley
Using the wrong sealant is another common reason. A high-modulus or general-purpose sealant can be too rigid for a busy joint, so it pulls away from the edges.
The problems people generally mention when they call include:
- Water getting into walls through failed joints
- Rigid filler in a joint that should flex
- Moss and dirt in joints with no sealant left
- Leaking joints around cladding and façade panels
If you live in an older home near Parish Church of St Thomas A Becket, old and new materials meet at the roofline and walls, which is where sealant earns its keep.
What your quote should include
- Whether VAT is included
- What happens if they find a problem under the old sealant
- How long to leave it before use
- Whether they seal over old material or remove it
Keeping the joints in good condition
So the new joints stay in good condition:
- Keep high-pressure jets off the joints
- Keep water from gutters off the wall
- Keep movement joints as flexible joints, not mortar
- 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.