Portsmouth · England
External Mastic in Portsea
Sealing brickwork movement joints, render, cladding and façade joints for householders, landlords and businesses in Portsea. ARBOMaster approved applicators, fully insured, with a 12-month guarantee.
- Rain getting behind render or cladding at a joint
- Failed seals between different materials
- Plants rooting in failed movement joints
Your questions about external mastic in Portsea
Do you work for landlords with property near Portsmouth Harbour station?
Yes, we work for landlords and letting agents. Just ring 0345 464 0079 or drop us an email and tell us about the property, and we’ll give you a clear price.
Do you cover smaller places like Portsea?
Yes, smaller places are covered as well as towns. Our work covers London and the South East. Just mention lanes, gates or anything else about the route when you book.
Can I do it myself?
For a simple, easy-to-reach joint, a careful DIYer can do a reasonable job. Most DIY failures come from sealing over old material, wet joints or too much sealant.
How long does external mastic take?
That depends on the amount of work, but as a guide it takes a few hours to a few days, depending on the length of joint and the access. We’ll give you a better idea when we quote.
How much does external mastic cost in Portsea?
It depends on the job, so we quote each one individually. To get one, call 0345 464 0079 or email us with a short description of the job.
Does someone need to be in?
It depends on the job. Inside work needs someone to give us access.
Do you hold any approvals?
Yes. We hold ARBOMaster approved applicator status and we’re fully insured too.
When will the joints need doing again?
It depends on the exposure, the movement and the product. Sealant is a maintenance item, so check the joints once a year and renew it when it starts to fail.
How we handle external mastic in Portsea
Getting the depth right is half the job. 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. If you are dealing with sealant pulling away from one side of the joint and cracked joints where brick meets render or frames, we can put it right, on concrete & block, copings & trims and façade panels alike.
Homes around Portsea range from older cottages to newer houses, with walls and rooflines of every type. Older homes need their gutter and trim joints kept tight, newer ones their movement joints.
You get a 12-month guarantee, the same in Portsea as everywhere else we work.
- Place
- Portsea (PO1, PO12, PO5)
- Wider area
- Portsmouth
- Guarantee
- One year on every job
- Quotes
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
When to call us in Portsea
The wrong product in a moving joint is a classic cause. A stiff, general-purpose sealant can’t cope with a joint that moves a lot, and it tears off the sides.
Any of these means the joints need attention:
- Leaking joints around cladding and façade panels
- Weathered mastic that no longer stretches
- Water getting into walls through failed joints
- Cracked joints where brick meets render or frames
In the older streets around St Ann's Church, the joints between older walls, newer extensions and the roofline need a sealant that can move.
Questions to ask before booking
- The length of the guarantee
- Whether the sealant suits the joint
- How long to leave it before use
- Whether they’re fully insured
Portsea buildings and the weather
Portsea is within about 1 mile of the coast, where wind-driven rain is a fact of life and, nearer the shore, so is salt air. Both are hard on movement joints and outside wall joints, which can dry out and crack sooner where a building faces the weather. Compared with the north and west, the South East gets less rain, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day.
Schools such as Portsmouth Grammar School are buildings too, and its movement joints, gutters and trims need looking after like any other building’s. Letting a property close to Portsmouth Harbour station? Then split movement joints are easy to miss on a rental until damp shows inside.
Portsea is about 1 mile south-west of Portsmouth, in Portsmouth. Wherever you are in the PO1 postcode area, we can carry out external mastic at your property. Our area takes in 19 places across Portsmouth, from the larger towns to small villages.
Our applicators cover all of PO1, PO12 and PO5 for external mastic. You will find streets such as Main Road, Park Road and Scott Road, and we cover them all. We also cover the places around Portsea: Portsmouth Point (1 mile south), Clayhall (2 miles south-west), Haslar (2 miles south-west), Alverstoke (2 miles south-west) and Privett (2 miles west). We also work in nearby towns such as Hilsea (3 miles north-east), Wymering (4 miles north-east), Paulsgrove (4 miles north), Cosham (3 miles north-east), Drayton (4 miles north-east) and Farlington (5 miles north-east).
Landmarks near Portsea
Locally, jobs take us to homes and businesses close to The Ship & Castle pub, St Jude's CofE Primary School and Charter Academy. There’s a railway station in Portsea itself: Portsmouth Harbour station. Nearby you’ll also find Royal Portsmouth Hospital (0.8 miles east) and Genesis Expo Creationist Museum (less than half a mile south). Not far away are Milton Locks and Portsdown Hill.
DIY sealant or a professional job?
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and getting the depth right matters as much as the look.
Some sealant jobs are within reach of a careful DIYer, like a short, easy-to-reach joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
Why it’s worth doing now in Portsea
Pointing a movement joint with mortar might seem a neat fix, but it stops the joint moving. The movement then cracks the brickwork or render nearby. The correct repair is a flexible sealant with the right backing. In a smaller place like Portsea, wherever a wall is exposed, a failed outside joint is a real source of damp. Indoors, a failed seal lets water into floors and panels as it would anywhere.
What you pay reflects the work, not guesswork. That’s why we ask a few questions first.
Why choose Mr Mastic in Portsea
- Anti-fungal silicone where joints get wet
- 180+ five-star Google reviews
- White, clear, grey or coloured to suit, where the product allows
- Full insurance on every job
Take a look at our cost guide and our reviews.
What happens on the day
A visit follows a simple pattern: we check the joints, mask and protect the surrounding surfaces, carry out the job and tidy away. Most jobs take a few hours for a handful of joints, longer for a whole elevation. In a smaller place like Portsea, parking is seldom the issue; lanes, gates and long drives are worth mentioning. If the job is outside, tell us about side access and how high the joints are.
- First, the joints are inspected and the access agreed.
- Every bit of old sealant and any mortar or debris is cut out.
- The faces are brushed clean and primed where the product requires it.
- Backing rod sized to the joint goes in to set the depth.
- The exterior sealant is applied, tooled and checked along its length.
Preparing for the visit
- Plan for the work area to be out of bounds to pets and children
- Clear items away from the joints we’re working on
- For indoor joints, keep the area dry beforehand if you can
How to get a quote
For a quote, call 0345 464 0079 or send us an email and tell us where the job is and what the problem looks like. You’ll have a clear quote before any work starts.
Related advice
How to look after the new joints
Joint life depends on how it’s used and looked after. Here’s what we suggest:
- Never let anyone fill a movement joint with mortar
- Avoid pressure-washing directly into sealant joints
- Get split or bare joints resealed while the damage is small
- Do not let climbing plants root in the sealant
Look over the joints once a year, ideally after winter. Watch for splits, edges coming away or growth in the joint.
Small splits are the time to act. Then it’s a straightforward cut-out and reseal.
Work for landlords, hotels and businesses
Businesses can book us for washrooms, kitchens, offices and more. On commercial sites, working times can be discussed when we quote.
Whether it’s one flat or a portfolio, the work is the same standard: old sealant fully removed, joints prepared properly and a 12-month guarantee.
Honest limits
New sealant cannot fix everything, and we’ll tell you before we start. It won’t solve:
- Failed render or damaged cladding panels
- Rising or penetrating damp from elsewhere in the wall
- Walls that need new movement joints cut into them
If in doubt, phone 0345 464 0079 or email us and we’ll say what we think.
Joints and surfaces we work on
- Concrete & block
- Copings & trims
- Façade panels
- Brickwork movement joints
- Render & cladding joints
- Joints between brick and frames