Southampton · England
External & façade joints in Portswood, Southampton
External mastic in Portswood from a team with over 20 years’ experience. Rated 4.9 on Google from 180+ five-star reviews.
- Leaking joints around cladding and façade panels
- Failed seals between different materials
- Water getting into walls through failed joints
Portswood buildings and the weather
Portswood is close to 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. With historic houses such as South Stoneham House (about 1 mile north-east) nearby, there’s older building stock in the area around Portswood as well as newer homes. In older buildings, older walls and rooflines need a sealant that moves with them and suits the material.
Rented homes near St Denys station change hands often, and outside joints that have cracked can let damp into a rental, so check them between lets. Schools such as St Denys Primary School are buildings too, and larger buildings have long runs of movement joint that eventually need resealing. In the older streets around Highfield Church, old and new materials meet at the roofline and walls, which is where sealant earns its keep.
Portswood is about 1 mile north of Southampton, in Southampton. Across the SO17 area, we cover external mastic for homes and businesses. Across Southampton, we cover 40 places, and Portswood is one of them.
Every address in SO17, SO14 and SO18 is covered for external mastic, from the main roads to the quietest streets. If you need external mastic at a property on Ivy Road, Alma Road and Lawn Road or anywhere close by, our applicators can take on the job. Being close to the A335 and A3035, Portswood is simple for us to get to. Neighbouring places we cover for external mastic include St Denys (1 mile south-east), Southampton (1 mile south), Inner Avenue (1 mile south-west), Bitterne Manor (1 mile south-east) and Bitterne Park (1 mile east). Within a short drive, we also cover Thornhill (3 miles south-east), Maybush (3 miles west), Eling (4 miles west), Rownhams (3 miles north-west), Millbrook (3 miles west) and Weston (3 miles south).
What’s near Portswood
Typical jobs here are in homes near St Anne's Catholic School, St Mary's Independent School and South Western Arms, among other places. Portswood has its own railway station: St Denys station. Well-known places in the area include Marlands Shopping Centre (1.5 miles south) and Royal South Hants Hospital (0.9 miles south). Not far away are Netley Common.
How we handle external mastic in Portswood
Movement joints let brickwork, render and cladding expand and shrink without cracking. The sealant in it has to stretch and squeeze for years, so once it splits or hardens, the joint stops working and water gets in. If you have joints where the bead has come unstuck and joints pointed up with cement by mistake, we can put it right, on concrete & block, render & cladding joints and brickwork movement joints alike.
Outbuildings, garages and conservatories around homes in places like Portswood add more joints to look after. Leaks normally start at a gutter end, a garage door frame or where an extension meets the house.
A one-year guarantee comes with the work, just as it does everywhere we cover.
- Where
- Portswood (SO17, SO14, SO18)
- Wider area
- Southampton
- Cover
- 12 months on all our work
- Quote
- A clear price before we start
- Call
- 0345 464 0079
- Page updated
- 26 October 2026
Towns and villages near Portswood
Also in Portswood
How the visit works
We work through the job in order: protect, prepare, seal, tidy. Typically it takes a few hours for a handful of joints, longer for a whole elevation, and the area is left clean. Parking around Portswood is normally easier than in a town centre, but mention any lanes, gates or long drives. For outside work, side access and the height of the joints help us plan.
- Each joint is checked and the colour of the new sealant agreed.
- We take out the old sealant until the faces are sound.
- Closed-cell backing rod is pushed in so the sealant bonds to two sides only.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
Getting ready for the visit
- Where the joints are inside, avoid wetting them before we arrive
- Tell us about access, such as stairs, a lift or high-level joints
- Mention any parking rules near the property
How to get a quote
A good description makes for an accurate quote. Let us know the location, the problem and roughly how many joints, and email pictures if that is easy.
Related advice
Aftercare tips
Simple care keeps the joints in good condition. Our advice:
- Wash walls gently around the sealant
- Show decorators and builders where the movement joints are
- Keep movement joints as flexible joints, not mortar
- Check the sealant is paintable before painting near it
Give the sealant the cure time we tell you before anything rubs against it. Most exterior sealants skin fast but take longer to cure right through.
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 so early resealing is worth it.
Why act early in Portswood
Sealing over the top of old mastic doesn’t hold for long. The new layer can’t bond properly to old, weathered material, so we always take the old sealant out. In a smaller place like Portswood, 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 is why we ask a few questions first.
What you get with us
- Trusted Arbo and Everbuild sealants
- A 12-month guarantee on all work
- Fully insured
- Old sealant always removed completely
DIY sealant or a professional job?
A DIY attempt doesn’t rule out a professional job. We cut it out and start again.
If you are set on DIY, put the effort into preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it fails, we can still redo it.
FAQs for Portswood
Does the coastal weather in Portswood affect outside sealant?
Coastal weather is harder on outside sealant: there’s more wind-driven rain and, closer to the shore, salt in the air. Choosing the right sealant for the frame and wall, laid at the right depth, helps it last.
Is Portswood within the area you cover?
Yes. Portswood is within the area we cover, which takes in towns, villages and rural addresses. Our work covers London and the South East. Just mention lanes, gates or anything else about the route when you book.
Can a movement joint be filled with mortar?
No. A mortar-filled joint cannot move, so the wall cracks somewhere else instead. It needs a flexible sealant over backing rod.
What is a movement joint?
Walls move with heat, cold and moisture, so long walls have planned gaps to take that movement. The gap is sealed with a flexible sealant over backing rod.
Where is Mr Mastic based?
Our base is in Crawley, and we cover South East England, London and all of Scotland.
When is the sealant fully cured?
That depends on the sealant used, so follow the cure time we give you.
How long does external mastic last?
That depends on the wall, the weather and the movement. Look for splits, hardening or edges coming away, and reseal at that point.
Is there a guarantee?
Yes. Each job is guaranteed for twelve months, large or small.
Landlords, agents and businesses in Portswood
Letting agents often deal with us directly. Send the address, what’s needed and the access arrangements and we’ll give you a quote.
We also work for businesses, from offices to washrooms and kitchens. On commercial sites, working times can be discussed when we quote.
When something else is needed
We will always be straight with you, so here’s what sealant can’t fix:
- Cracked brickwork or render that needs a builder or plasterer
- Render that is blown, hollow or coming away
- Adding movement joints to masonry that has none
If you’re not sure, just phone 0345 464 0079 or email us and we’ll give you a straight answer.
Where we work in Portswood
- Façade panels
- Copings & trims
- Brickwork movement joints
- Render & cladding joints
- Joints between brick and frames
- Concrete & block
What affects the cost of external mastic
The quote reflects the job in front of us. We look at:
- The product the joint needs
- The old material and how stubborn it is
- Mould in or behind the old joints
- Whether the work is at height
Homes and businesses are quoted the same way: the amount of work, the access and the products needed, along with when we can work on site. Ask us for a quote and we’ll explain what it covers.
What we need to know
A few details help us give you an accurate quote. When you get in contact, it helps to mention:
- The rough size of the job
- How we’d reach the joints
- If someone has resealed it before
- Whether it’s a home or a business
For a quote, phone 0345 464 0079 or email us with the location and a short description of the problem. We’ll give you a clear quote before any work starts.