Greater London · England
External & façade joints in Northwood, Greater London
Sealing brickwork movement joints, render, cladding and façade joints for homes and businesses in Northwood and across Greater London. Fully insured, ARBOMaster approved and guaranteed for a year.
- Water getting into walls through failed joints
- Joints where the bead has come unstuck
- Movement joints with cracked, split or missing sealant
What sealant work can’t fix
A few problems are outside what sealant work can do:
- Damp that is not coming from the joint
- Walls that need new movement joints cut into them
- Cracking across the wall rather than at a joint
Not sure which it is? You can ring 0345 464 0079 or drop us an email and we’ll tell you honestly.
What we seal
- Façade panels
- Copings & trims
- Concrete & block
- Joints between brick and frames
- Brickwork movement joints
- Render & cladding joints
About our external mastic in Northwood
Many failed façade joints only get noticed once there’s a stain or a damp patch inside. We inspect them, agree which need doing and reseal with a weatherproof, flexible sealant. Typical jobs include weathered mastic that no longer stretches and gaps where render, brick and frames meet, across render & cladding joints, concrete & block and façade panels.
In London terraces and converted houses, gutters and walls are often shared with the house next door, so a leaking gutter joint or failed wall joint can affect more than one home. In a converted house in Northwood, it’s worth checking who is responsible for the outside before booking.
You are covered for a year from the day we finish. If there’s a problem with it, please call 0345 464 0079 or send us an email.
- Where
- Northwood (HA6)
- Region
- Greater London
- Guarantee
- One year on every job
- Quote
- A clear quote up front
- Call
- 0345 464 0079
- Updated
- 26 October 2026
The process
You do not need to clear the whole room or building before we come, only the area right around the joints. We protect the rest, and the job takes a few hours to a few days, depending on the length of joint and the access for a typical job. In Northwood, flats, stairs and shared entrances are part of the routine. If the building has a concierge, managing agent or access rules, tell us when you book.
- We look at every joint and agree a colour to suit the wall.
- Failed sealant is removed back to clean, sound faces.
- Backing rod goes in so the sealant can stretch between the two faces.
- Primer is applied wherever the sealant needs it.
- We gun in low-modulus sealant and tool it neatly.
Preparing for the visit
- Let us know about earlier repairs to the joints
- Clear items away from the joints we’re working on
- Mention any sign-in or site rules at work premises
How to get a quote
If you’re in Northwood and need external mastic, ring 0345 464 0079 or email us. Tell us what the problem is and where, and we’ll agree the price before any work begins.
Read more
Keeping the joints in good condition
Joint life depends on how it’s used and looked after. We suggest:
- Clear growth from the base of walls and joints
- Have failed joints looked at early
- Keep movement joints as flexible joints, not mortar
- Keep water from gutters off the wall
Avoid pressure-washing straight into the joints. A strong jet can damage the edges of the bead over time.
Water getting behind cladding or render can go unnoticed for a long time. When it finally shows inside, the joint may have been open for years.
External mastic in Northwood: local notes
Historic houses like Headstone Manor (about 3.3 miles south-east) are a reminder that the area around Northwood 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. London terraces and converted houses often share gutters, downpipes and walls, so check who is responsible for the outside before booking.
For site and facilities teams at buildings such as Frithwood Primary School, its movement joints, gutters and trims need looking after like any other building’s. If you let a flat or house near Carpenders Park station, split movement joints are easy to miss on a rental until damp shows inside.
Northwood is about 3 miles south-east of Rickmansworth, in Greater London. For external mastic in and around Northwood, please ring 0345 464 0079 or email us for a quick quote. We’re based in Crawley and cover Greater London, Northwood included. Our Greater London coverage runs to 764 places, Northwood among them. We also work in London, around 16 miles away.
Postcode districts we cover here for external mastic: HA6. That includes homes and businesses on Little Stream Close and Sandy Lodge Way and the roads around them. Close by, we work in Eastbury (1 mile north-east), Moor Park (1 mile north-west), Batchworth Heath (1 mile west), Batchworth (2 miles north-west) and Holywell (2 miles north). Within a short drive, we also cover City of Westminster (14 miles south-east), Marylebone (14 miles south-east), Kensington (12 miles south-east), St Pancras (14 miles south-east), Hampstead (11 miles south-east) and Ruislip (3 miles south).
Landmarks near Northwood
Typical jobs here are in homes near King George V Playing Fields, The Gate Public House and London School of Theology and the streets around them. Northwood’s nearest station is Carpenders Park station, roughly 1.7 miles north-east of the centre. Nearby you’ll also find Harlequin Centre (2.9 miles north-east) and Heath Robinson Museum (2.2 miles south-east). Open spaces near Northwood include Dews Farm Sand Pits and Tumbling Bay.
Different surfaces, different methods
Render joints
Render is weaker at the surface than brick, so a sealant that stretches easily protects the edges. Priming is done where the sealant calls for it.
Concrete and blockwork
Wide joints in concrete need the depth controlling carefully. We size the backing rod to the gap.
Towns and villages near Northwood
Also in Northwood
Common questions in Northwood
Is Northwood in your area for external mastic?
Yes, Northwood is within the area we cover. Our work covers London and the South East. You can ring 0345 464 0079 or drop us an email and let us know what needs doing, and we’ll send you a clear quote.
Is parking an issue for external mastic in Northwood?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. That way the visit can be planned around it.
Can you seal over the old sealant?
No, and we never do. It can look neat for a few weeks, but the new bead soon lifts. Removing the old sealant completely is the only lasting way.
Do you work for letting agents?
Yes. We work in homes, commercial premises and hotels, and we are fully insured.
Can you seal joints between two different materials?
Yes. Different materials move at different rates, so a flexible sealant is needed where they meet. We choose one that suits both surfaces.
How long before the joint can be used?
Cure times vary by product and the conditions. Before we leave, we’ll tell you the cure time.
Can you match the colour of my brickwork?
There’s a good range of exterior colours, including greys, browns, whites and stone tones. We choose the closest to your brick or render so it does not stand out.
Is there a guarantee?
Yes, always. Each job is guaranteed for twelve months.
Landlords, agents and businesses in Northwood
From a single let to a portfolio, you get the same standard of work: old sealant fully removed, joints prepared properly and a 12-month guarantee.
Hotels need rooms back in use, so the work can be planned room by room around your bookings where we can. Hotel work is part of what we do, alongside homes and businesses.
Common problems we fix in Northwood
Poor preparation causes many early failures: dusty or wet faces, no primer where one was needed, or old sealant left in. The new sealant then lets go long before it should.
Look out for any of the following:
- Sealant pulling away from one side of the joint
- Movement joints with cracked, split or missing sealant
- Hard, crazed mastic that has stopped moving
- Damp patches traced to an open external joint
If you live in an older home near Emmanuel Church, older walls, gutters and the joints where extensions meet them need a flexible sealant.
Comparing quotes
- Whether they’re fully insured
- How long to leave it before use
- What preparation is included
- What the quote includes, VAT included or not
DIY sealant or a professional job?
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is chosen for how the joint moves and where it is, then guaranteed for a year.
Not every job suits DIY: work at height, external movement joints, fire-rated sealant and large areas call for the right materials, safe access and experience.