Hampshire · England
External Mastic in Northbrook
External mastic for Northbrook, by sealant specialists with 20+ years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Damp patches traced to an open external joint
- Panel joints letting water in
- Rigid filler in a joint that should flex
External mastic for homes and businesses in Northbrook
A movement joint is only as good as its depth. Closed-cell backing rod sets the depth and stops the sealant sticking to the back, so it bonds to the two sides only and can stretch. Typical jobs include water getting into walls through failed joints and rigid filler in a joint that should flex, on façade panels, brickwork movement joints and joints between brick and frames.
External sealant needs dry, clean surfaces, so work around Northbrook is planned for dry weather. Let us know about access to every wall, plus any garages or outbuildings.
All of our work is guaranteed for twelve months, and the guarantee is the same wherever you are.
- Place
- Northbrook (SO21)
- Region
- Hampshire
- Cover
- A year, on every job
- Price
- Quoted before any work starts
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
Different surfaces, different methods
Concrete and blockwork
Blockwork and concrete shrink over time and move with the seasons. We reseal their joints with backing rod and a flexible product.
Joints between dissimilar materials
Different materials may need different primers. Both surfaces are cleaned and primed as the product requires.
For landlords and businesses
Housing providers, facilities teams and property managers book us too. Several sites can go on one quote, and we’re fully insured for the work.
Landlords and agents in Northbrook can book us as well as homeowners. Resealing between tenancies keeps a property looking cared for before the next move-in.
How we quote for external mastic
The price is agreed before any work begins. It’s based on:
- Whether there’s mould to deal with
- Any working-time requirements on site
- Access and height
- Whether old sealant or filler has to be cut out
Doing several joints on one visit usually makes better use of the time than several visits. You’ll get one clear quote for the whole job.
What we need to know
Photos by email are helpful but not essential. Try to tell us:
- The type of property
- What the problem is, such as mould, gaps, leaks or cracking
- How we’d reach the joints
- Whether it has been sealed before
If you’re in Northbrook and need external mastic, phone 0345 464 0079 or email us. Tell us what the problem is and where, and you will get a clear quote before any work starts.
DIY versus a professional finish
Some jobs are best left to a professional: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.
Sealing over old silicone is the commonest DIY error. New silicone will not bond to old, so it peels away and traps moisture behind it. All the old material has to come out first.
Looking after it afterwards
Good habits help new joints last longer. Our tips:
- Check external joints each spring
- Keep soil, plants and ivy away from the joints
- Tell anyone working on the walls about the movement joints
- Get split or bare joints resealed while the damage is small
Have a quick look at the joints each spring. Watch for splits, edges coming away or growth in the joint.
Gaps, plants or missing sealant in a joint are worth getting looked at. Earlier resealing means a smaller job and a better result.
When something else is needed
We will always be straight with you, so here’s what new sealant won’t do:
- Damp that is not coming from the joint
- Render that’s blown, hollow or coming away
- Walls that need new movement joints cut into them
Not sure which it is? You can phone 0345 464 0079 or send us an email and we’ll tell you honestly.
Where we work in Northbrook
- Joints between brick and frames
- Brickwork movement joints
- Copings & trims
- Render & cladding joints
- Concrete & block
- Façade panels
Northbrook: your questions answered
Is Northbrook within the area you cover?
Yes, smaller places are covered as well as towns. We work across London and the South East. Let us know about access, parking and anything unusual about getting there when you book.
Is Northbrook in your area for external mastic?
Yes, Northbrook is within the area we cover. We work across London and the South East. You can call 0345 464 0079 or send us an email and let us know what needs doing, and we will send you a clear quote.
How long will you be here?
As a guide, most jobs take a few hours to a few days, depending on the length of joint and the access. Bigger jobs take longer, and we’ll say how long yours will take.
Why do you put foam in the joint first?
The foam is closed-cell backing rod. It keeps the sealant at the right depth and bonded to the sides only.
Do you work for letting agents?
Yes. We work in homes, commercial premises and hotels, and we are fully insured.
Is it OK to seal over old sealant?
No, it will not last. It may look fine at first, but the new layer lifts away from the old one. The old sealant has to come out completely.
Which products do you use?
Each joint gets the product that suits it. Where it moves, gets wet or faces the weather makes a difference.
Do you guarantee your work?
Yes, always. There’s a 12-month guarantee on every job.
Northbrook buildings and the weather
London and the South East are among the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
Homes close to Church of St Mary include some older properties, and the joints between older walls, newer extensions and the roofline need a sealant that can move. Letting a property close to Micheldever station? Then outside joints that have cracked can let damp into a rental, so check them between lets. For site and facilities teams at buildings such as Micheldever CofE Primary School, its movement joints, gutters and trims need looking after like any other building’s.
Northbrook is about 7 miles north of Winchester, in Hampshire. Every kind of property in Northbrook can book us for external mastic. Every job comes with our 12-month guarantee. Northbrook is one of 683 towns and villages in Hampshire where we work for external mastic. Southampton is on our list too, around 17 miles away.
Work in SO21 works the same way as everywhere else we cover. We also cover Micheldever (1 mile south-east), Stoke Charity (1 mile west), Hunton (2 miles west), Micheldever Station (2 miles north) and East Stratton (2 miles east). Larger places within reach include Basingstoke (11 miles north-east), Winchester (7 miles south), Eastleigh (13 miles south), Andover (10 miles north-west), Chandler's Ford (13 miles south-west) and Alton (13 miles east).
Local landmarks in Northbrook
Around Northbrook, our work takes us to homes and buildings near Half Moon and Spread Eagle pub, among other places. The closest station to Northbrook is Micheldever station, roughly 2.1 miles north of the centre.
How it works
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, and the area is left clean. Somewhere like Northbrook needs a little journey planning: let us know about lanes, gates and parking. Everything for the job comes with us, so a second trip is avoided where possible.
- First, the joints are inspected and the access agreed.
- Every bit of old sealant and any mortar or debris is cut out.
- 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.
Getting ready for the visit
- Keep children and pets away from the work area
- Let us know about stairs, lifts or work at height
- Tell us about any previous sealing or DIY attempts
Ask for a quote
There’s no standard price list, as no two jobs are quite the same. Instead, your job gets its own clear quote. To get started, phone 0345 464 0079 or send us an email.