Hertfordshire · England
External Mastic in Northaw
Movement joints in Northaw need attention? We cut out the old, prepare the joints and apply the right sealant, and the work is guaranteed for a year.
- Joints where the bead has come unstuck
- Water getting into walls through failed joints
- Leaking joints around cladding and façade panels
External mastic for homes and businesses in Northaw
For buildings in Northaw, we reseal external joints of all kinds, from brick movement joints to cladding panels. Every joint gets the same careful preparation: clean joint faces and the right depth. Typical jobs include panel joints letting water in and joints where the bead has come unstuck, on joints between brick and frames, copings & trims and render & cladding joints.
Older homes in small places like Northaw may be stone, brick or timber-framed, often with later extensions. The joints where those materials meet are the weak points.
We guarantee the work for a year. If something isn’t right with it in that time, tell us and we will put it right.
- Location
- Northaw (EN6)
- Region
- Hertfordshire
- Guarantee
- 12 months on all our work
- Quote
- A clear price before work begins
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
DIY sealant or a professional job?
Sealing over old silicone is the commonest DIY error. Silicone does not stick to old silicone, so it peels away and traps moisture behind it. Everything old must be removed first.
If you’ve already had a go yourself, that is fine. We cut it out and start again, so tell us about it when you ask for a quote.
What affects the quote in Northaw
We do not publish a price list. What we look at:
- The number and length of the joints
- Whether there’s mould to deal with
- The number of rooms or windows
- When we can work, for business premises
Combining jobs into one visit normally makes better use of the time than several visits, so tell us about everything that needs sealing. You’ll get one clear quote for the whole job.
Asking for a quote
When you contact us, it’s useful to know:
- Whether it has been sealed before
- The address or postcode of the job
- Any access issues, like height or stairs
- What’s wrong with the joints now
It all starts with a short chat. Describe the problem, the location and the size of the job, and we will talk you through what we’d do. Whenever you are ready, phone 0345 464 0079 or drop us an email.
Towns and villages near Northaw
More services for Northaw
What sealant work can’t fix
A few problems are outside what sealant work can do:
- Walls that need new movement joints cut into them
- Rising or penetrating damp from elsewhere in the wall
- 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 before you book.
Joints and surfaces we work on
- Render & cladding joints
- Brickwork movement joints
- Joints between brick and frames
- Copings & trims
- Façade panels
- Concrete & block
Walls and rooflines in Northaw
With historic houses such as Wyllyotts Manor (about 2.1 miles west) nearby, there’s older building stock in the area around Northaw as well as newer homes. In older buildings, older walls and rooflines need a sealant that moves with them and suits the material. The South East is one of the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
Letting a property close to Cuffley station? Then split movement joints are easy to miss on a rental until damp shows inside. For an older house near a landmark such as Parish Church of St Thomas A Becket, older walls, gutters and the joints where extensions meet them need a flexible sealant. Schools such as Northaw Church of England Primary School are buildings too, and movement joints, cladding joints and gutters on larger buildings need the same care as a house’s.
Northaw is about 2 miles north-east of Potters Bar, in Hertfordshire. We provide external mastic to homes and businesses in Northaw and nearby. Our Hertfordshire coverage runs to 381 places, and Northaw is one of them. For nearby work, see our London page.
Our applicators cover all of EN6 for external mastic. You’ll find streets such as Vineyards Road, Church Lane and Northaw Road West. Other places close to Northaw include Cuffley (1 mile east), Brookmans Park (2 miles north-west), Newgate Street (2 miles north-east), Bell Bar (2 miles north-west) and Little Berkhamsted (3 miles north). Within a short drive, we also cover Watford (11 miles west), Hemel Hempstead (14 miles west), Stevenage (14 miles north), St Albans (8 miles west), Welwyn Garden City (7 miles north) and Harpenden (12 miles north-west).
Local landmarks in Northaw
Around Northaw, our work takes us to homes and buildings near Two Brewers Public House and Mount Grace School. For rail, the closest station is Cuffley station, roughly 1.6 miles east. Well-known places in the area include Potters Bar Museum (2.1 miles west) and Chase Farm Hospital (3.3 miles south-east). Open spaces near Northaw include Fir and Pond Woods.
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 a few hours to a few days, depending on the length of joint and the access. Somewhere like Northaw needs a little journey planning: let us know about lanes, gates and parking. We bring what the job needs, so it can be finished in one trip where possible.
- 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.
- Backing rod sized to the joint goes in to set the depth.
- The exterior sealant is applied, tooled and checked along its length.
How to prepare
- Mention any leaks or damp you’ve noticed
- Plan for the work area to be out of bounds to pets and children
- For indoor joints, keep the area dry beforehand if you can
Get a quote
Call for a quick quote, or send an email if you’d rather. Describe what needs sealing and we’ll talk you through the work.
Read more
FAQs for Northaw
Is Northaw within the area you cover?
Yes, we do. We work across London and the South East, and smaller places are part of that. Longer journeys are simply planned in advance.
Can you do external mastic in Northaw?
Yes, Northaw is within the area we cover. We work across London and the South East. Just call 0345 464 0079 or email us with a few details of the job, and we will give you a clear quote.
Can new sealant go over the old?
No. New silicone won’t bond to old silicone, and it traps any mould or water underneath. It all has to come out first.
Do you work for letting agents?
Yes, regularly. Several properties can go on one quote.
Is there any odour?
Some sealants have a smell while they cure, but it fades. Opening a window helps.
What is backing rod for?
The foam is closed-cell backing rod. It stops the sealant going in too deep and bonding to three sides so it can flex with the joint.
What do you need from me for a quote?
A short description and the location. We’ll ask anything else we need to know.
What does external mastic cost?
Every job is different, so each one gets its own quote. To get one, call 0345 464 0079 or send us an email and let us know what needs doing and where.
Why deal with it now?
A failed movement joint lets water into the wall. Resealing early keeps the job to the joint itself, rather than the wall around it. Around Northaw, older homes often have timber in their floors and frames, and water through a failed joint can rot timber if it’s left.
Instead of a standard rate, we price the job in front of us: how many joints, what’s in them now and how we reach them. You will know the price before we begin.
Why book with us
- Neat joints and a tidy finish
- More than 20 years in sealant work
- A choice of colours where the product allows
- Sanitary silicone with an anti-fungal additive in wet areas
Read what affects the cost or our reviews.
Work for landlords, hotels and businesses
Housing providers, facilities teams and property managers book us too in Northaw and across Hertfordshire. Several sites can be quoted together, and we are fully insured for the work.
Failed sealant is one of the commonest items on a check-out report. Several properties can go on one quote.
Surface by surface
Cladding and façade panels
Cladding and façade panels are usually separated by sealed joints. Each joint gets a sealant that suits the panel and its movement.
Concrete and blockwork
Concrete faces can be dusty and porous, so preparation is key. A primer goes on where the product requires one.