Hampshire · England
Knowle External Mastic
External mastic across Knowle and nearby, with every bit of old sealant taken out first.
- Gaps where render, brick and frames meet
- Hard, crazed mastic that has stopped moving
- Water getting into walls through failed joints
When something else is needed
Before booking, it’s worth knowing the limits:
- Rising or penetrating damp from elsewhere in the wall
- Subsidence or other structural problems
- Loose or hollow render, which needs re-rendering
If in doubt, ring 0345 464 0079 or drop us an email and we will say what we think.
Where we work in Knowle
- Brickwork movement joints
- Joints between brick and frames
- Façade panels
- Copings & trims
- Render & cladding joints
- Concrete & block
About our external mastic in Knowle
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. We work on concrete & block, brickwork movement joints and copings & trims, and common reasons people get in touch are weeds or debris growing in open joints and leaking joints around cladding and façade panels.
Around Knowle, older buildings can be stone, brick or timber-framed, many with extensions added later. Where one material meets another is where water generally gets in, and they need the right sealant at the right depth.
All our work is covered by our 12-month guarantee, wherever you are in Hampshire.
- Location
- Knowle (PO17)
- Wider area
- Hampshire
- Cover
- 12 months on all our work
- Quotes
- A clear quote up front
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
Do you need external mastic in Knowle?
Poor preparation causes many early failures: dusty or wet faces, no primer where one was needed, or old sealant left in. The sealant never bonds properly.
These are the problems we’re asked about most:
- Joints pointed up with cement by mistake
- Brick movement joints where the sealant has split
- Old sealant gone brittle and cracked
- Weeds or debris growing in open joints
Managing a site like Orchard Lea Infant School? Then its movement joints, gutters and trims need looking after like any other building’s.
Before booking anyone
- What the quote includes, VAT included or not
- How much experience the applicator has
- When the joint can take water or movement
- What happens if they find a problem under the old sealant
What external mastic looks like in Knowle
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.
For landlords with property near Fareham station, failed wall and movement joints let damp in, so they’re worth checking between tenancies. For an older house near a landmark such as Church of St Francis, an extension built onto an older house moves differently, and the joint between them takes the strain.
Knowle is about 2 miles north of Fareham, in Hampshire. Homes, rented property, offices and hotels in Knowle can book us for external mastic. Every job comes with our 12-month guarantee. Our Hampshire coverage runs to 683 places, and Knowle is one of them. For nearby work, see our Portsmouth page.
Here we cover the PO17 postcode area for external mastic. Whether your property is on Serotine Close, Boundary Walk and Park Approach or a nearby road, our applicators can take on the job. We also cover the places around Knowle: Funtley (1 mile south), Tapnage (1 mile north-west), Heathfield (2 miles south), Segensworth (2 miles west) and Titchfield Park (2 miles south-west). We also work in nearby towns such as Winchester (13 miles north), Gosport (6 miles south-east), Havant (10 miles east), Eastleigh (9 miles north-west), Horndean (9 miles east) and Totton (13 miles west).
What’s near Knowle
Locally, jobs take us to homes and businesses close to The Miners Arms and The Henry Cort Community College. For rail, the closest station is Fareham station, roughly 2 miles south. Other landmarks nearby include Portchester Castle (4.9 miles south-east) and Knowle Hospital (within half a mile north-east). Green spaces nearby include Portsdown Hill and Swanwick Lakes.
Questions from Knowle
Do you cover Knowle for external mastic?
Yes. Our work covers London and the South East, and Knowle is part of that. You can phone 0345 464 0079 or drop us an email and tell us what needs doing, and we will send you a clear quote.
Can you help a landlord with a rental near Fareham station?
Yes, landlords and agents are among the people we work for. Just call 0345 464 0079 or send us an email with the address and what needs doing, and we will give you a clear quote.
How long does the job take?
That depends on the amount of work, but most jobs take anything from a few hours to several days, depending on the building. We will tell you when we quote.
Do the sealants smell?
It depends on the product. Some smell for a while, some hardly at all.
Should I try DIY first?
Sometimes. The key is preparation: remove all the old material and work on a clean, dry joint. If it doesn’t work out, we can redo it.
Do you take out the old sealant first?
Yes, always, and completely. New sealant won’t bond properly to old, so any old material comes out before anything new goes in.
Are you ARBOMaster approved?
Yes. We’re ARBOMaster approved, the scheme for applicators of Arbo sealants.
Is the work guaranteed?
Yes. There’s a 12-month guarantee on every job.
What affects the quote in Knowle
We do not publish a price list, because no two jobs are the same. What we look at:
- Access and height
- Whether old sealant or filler has to be cut out
- Whether there’s mould to deal with
- Which sealant suits the joint
A failed joint rarely gets cheaper to fix by waiting. If you are unsure, call 0345 464 0079 or drop us an email and we’ll give you an honest view and a quote.
Asking for a quote
Photos by email are helpful but not essential. Try to tell us:
- Where the job is, and your postcode
- If it’s domestic, commercial or a hotel
- How many joints, rooms or windows are involved
- The problem you’ve noticed
The more we know about the job, the more useful the quote. Let us know the location, the problem and roughly how many joints, and email pictures if that’s easy.
What happens on the day
There’s no need to move everything out before we come, just the space around the work. Everything nearby is protected, and the job takes a few hours to a few days, depending on the length of joint and the access for a typical job. Somewhere as small as Knowle, access is often the only tricky part. For outside work, also let us know about exposed walls and any outbuildings involved.
- We start by walking round the building and agreeing the joints and the access.
- 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.
- We fit closed-cell backing rod to control the depth.
- The exterior sealant is applied, tooled and checked along its length.
How to prepare
- Plan for the work area to be out of bounds to pets and children
- Try not to wet indoor joints just before the visit
- Tell us about any previous sealing or DIY attempts
Getting a quote
There’s no standard price list, because every job is different. Instead, your job gets its own clear quote. To get started, ring 0345 464 0079 or drop us an email.
Related advice
Also in Knowle
DIY versus a professional finish
The biggest DIY mistake is sealing over old sealant. New silicone won’t bond to old, so it peels away and traps moisture behind it. All the old material has to come out first.
Some jobs are best left to a professional: work at height, external movement joints, fire-rated sealant and large areas need the right product, the right access and the right method.
Why act early in Knowle
A low-modulus sealant is chosen because it moves without pulling hard at the edges. That protects surfaces like brick, render and concrete. A stiffer product can damage the joint edge as it fails. In a small place like Knowle, homes can be exposed to wind and rain, which finds any gap, and damp in older walls is slow to dry out.
Commercial jobs are quoted on the same basis as homes: how much there is to do, how we reach it and what it needs. Call for a quick quote and we’ll go through it with you.
What you get with us
- Experience in homes, commercial sites and hotels
- Over 20 years’ experience
- We agree the colour with you first
- Every job guaranteed for a year
Read our cost guide or customer reviews.
Looking after it afterwards
Aftercare is simple:
- Make sure movement joints aren’t pointed over
- Point out the joints to other trades
- Clear growth from the base of walls and joints
- Get split or bare joints resealed while the damage is small
Follow the cure time we give you before the joint is knocked or disturbed. The surface skins over quickly, but full cure takes longer.
An open movement joint lets rain into the wall every time it pours. That can lead to damp patches, staining and frost damage.