Hampshire · England
External Mastic in Portchester
Movement joints in Portchester need attention? We cut out the old, prepare the joints and apply the right sealant.
- Plants rooting in failed movement joints
- Brick movement joints where the sealant has split
- Gaps where render, brick and frames meet
Surface by surface
Cladding and façade panels
Where a cladding system has its own specified sealant, we follow it or an approved alternative. Tell us what the building has when you get in touch.
Concrete and blockwork
The face of concrete or block is often dusty, so cleaning and priming matter. We prime where the sealant needs it before sealing.
About our external mastic in Portchester
A movement joint is a deliberate break that lets a wall expand and contract. The sealant in it has to stretch and squeeze for years, and when it fails, the wall takes the strain and water finds a way in. If you’re dealing with movement joints with cracked, split or missing sealant and failed seals between different materials, we can help, whatever the surface.
In and around Portchester, older properties sit alongside newer ones, each with its own outside joints. Older gutters and trims need their joints resealed; newer brick and render need their movement joints kept sound.
Big or small, you get the same one-year guarantee in Portchester and across Hampshire.
- Place
- Portchester (PO16, PO6, PO17)
- Wider area
- Hampshire
- Guarantee
- One year on every job
- Price
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
Nearby places to Portchester
More services for Portchester
Common questions in Portchester
Does living near the coast affect external mastic in Portchester?
Coastal homes put outside sealant through more weather than inland ones, so the choice of sealant and the preparation matter even more. Walls facing the sea are usually the first to need attention.
Can you help a landlord with a rental near Portchester station?
Yes, landlords and agents are among the people we work for, and several properties can be quoted together. Just ring 0345 464 0079 or drop us an email with the address and what needs doing, and we will give you a clear price.
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, and we will explain our choice.
Is it OK to fill a movement joint with cement?
No. Mortar locks the joint solid, so the wall cracks somewhere else instead. Use a flexible sealant with backing rod.
Where is Mr Mastic based?
Our base is in Crawley, and we work across South East England, London and Scotland.
Will the old sealant be removed?
Always. Sealing over the old bead is the commonest cause of early failure, so we never do it.
What should I tell you?
A short description and the location, with pictures by email if possible. We will ask anything else we need to know.
Can you seal over the old sealant?
No. New silicone will not bond to old silicone, and it traps any mould or water underneath. We remove it all first.
Signs you need external mastic in Portchester
The wrong product in a moving joint is a classic cause. A high-modulus or general-purpose sealant can be too rigid for a busy joint, and it tears off the sides.
People generally contact us when they notice something like this:
- Weathered mastic that no longer stretches
- Cracked joints where brick meets render or frames
- Brick movement joints where the sealant has split
- Rigid filler in a joint that should flex
If you look after a building such as Castle Primary School, its movement joints, gutters and trims need looking after like any other building’s.
What to look for in a quote
- Is VAT in the price?
- What insurance they hold
- How hidden problems are handled
- How the colour is chosen
What affects the cost of external mastic
Your quote is based on your job. We take into account:
- Whether there’s mould to deal with
- When we can work, for business premises
- The type of sealant required
- The amount of work
No two jobs are quite the same, so we quote each one individually. Size, access and the product the joint needs all make a difference.
Helping us quote
You don’t need to know the technical terms. Just tell us:
- How we’d reach the joints
- Where the property is
- Whether it has been sealed before
- Photos by email, if that’s easy
For a quote, phone 0345 464 0079 or send us an email and tell us where the job is and what the problem looks like. You will have a clear quote before any work starts.
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.
Mouldy or split sealant often shows up at the end of a tenancy, and it’s quick to put right between tenancies. We can quote for more than one property at once.
How to look after the new joints
A little care helps the new joints last. We recommend:
- Check the sealant is paintable before painting near it
- Don’t let climbing plants root in the sealant
- Show decorators and builders where the movement joints are
- Never let anyone fill a movement joint with mortar
Keep the joints clear of soil, plants and climbing growth. Anything that holds water against the joint wears it out sooner.
Leaks behind façade panels and render often go unseen. By the time there’s a damp patch, the damage can be well established so early resealing is worth it.
What happens on the day
Every visit runs the same way: we look at the joints together, protect the area around them, do the work and tidy away. It generally takes anything from a few hours to several days, depending on the building. A visit to Portchester is planned like any other: the time, the access and where to park are agreed in advance. If the work is outside, the weather plays a part, as sealant needs a dry surface.
- Each joint is checked and the colour of the new sealant agreed.
- We take out the old sealant until the faces are sound.
- Backing rod goes in so the sealant can stretch between the two faces.
- We prime the faces where required.
- We gun in low-modulus sealant and tool it neatly.
Before we arrive
- On commercial sites, let us know about site rules
- Let us know about stairs, lifts or work at height
- Mention any parking rules near the property
Getting a quote
We quote each job on its own. Just ring 0345 464 0079 or send us an email with the details.
Advice
Outside joints around Portchester
Portchester 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. 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.
Rented homes near Portchester station change hands often, and outside joints that have cracked can let damp into a rental, so check them between lets. Homes close to Church of St Mary include some older properties, and older walls, gutters and the joints where extensions meet them need a flexible sealant.
Portchester is about 3 miles north-east of Gosport, in Hampshire. Anywhere in PO16, our applicators can take on external mastic. Our area takes in 683 places across Hampshire.
We work across the PO16, PO6 and PO17 postcode area for external mastic and the streets around it. That includes homes and businesses on Cow Lane, Hill Road and Ralph Road and the roads around them. Neighbouring places we cover for external mastic include Boarhunt (2 miles north-west), Southwick (2 miles north), Elson (2 miles south-west), Wallington (2 miles west) and Priddy's Hard (2 miles south). Larger places within reach include Gosport (3 miles south-west), Havant (6 miles east), Eastleigh (13 miles north-west), Fareham (3 miles west), Horndean (7 miles north-east) and Chandler's Ford (15 miles north-west).
Around Portchester
We work in homes and buildings around Portchester Community School and The Cormorant pub. The nearest railway station is Portchester station, about 0.5 miles north-west of the centre. Well-known places in the area include Portchester Castle (under half a mile south-east) and Queen Alexandra Hospital (2.3 miles east). For a walk, there’s West of the River Alver and Portsdown Hill.
Should I try it myself first?
If you do try it yourself, take your time over the preparation: take out all the old sealant, make sure the joint is clean and dry, and give it the full cure time. If it fails, we can still redo it.
Overfilling a joint is a classic DIY mistake. A thick, smeared bead looks untidy and does not move well, and getting the depth right matters as much as the look.