Hampshire · England
Haslar External Mastic
Professional external mastic in and around Haslar, with old sealant always removed completely.
- Panel joints letting water in
- Water getting into walls through failed joints
- Old sealant gone brittle and cracked
FAQs for Haslar
Is Haslar within the area you cover?
Yes, Haslar is covered. We work across London and the South East, from towns to the smallest places. The journey is planned ahead, so it helps to know about access.
Do you work for landlords with property near Portsmouth Harbour station?
Yes, landlords and agents are among the people we work for, and several properties can be quoted together. You can ring 0345 464 0079 or drop us an email with the details for a clear quote.
What sealant do you use?
It depends on the joint: sanitary silicone where it gets wet, and sealants suited to movement or weather elsewhere. Brands we use include Arbo and Everbuild.
Can you seal joints between two different materials?
Yes. The old joint is removed, both surfaces cleaned and primed where needed, and a flexible sealant applied. The colour is chosen to suit.
Are you ARBOMaster approved?
Yes. We are ARBOMaster approved, the scheme for applicators of Arbo sealants.
Will you leave a mess?
No. The area is protected while we work and cleaned up afterwards.
How long should I leave it?
Cure times vary by product and the conditions. Before we leave, we’ll tell you the cure time.
What should I tell you?
A short description and the location. If we need more, we will ask.
External mastic in Haslar
Where two different materials meet, such as brick and render or blockwork and metal, they move at different rates. A flexible sealant bridges the two where mortar or filler would crack. If you are dealing with old sealant gone brittle and cracked and movement joints with cracked, split or missing sealant, we can help, on render & cladding joints, brickwork movement joints and joints between brick and frames alike.
Around Haslar, older buildings can be stone, brick or timber-framed, many with extensions added later. The joints where those materials meet are the weak points.
All of our work is guaranteed for twelve months, and the guarantee is the same wherever you are.
- Location
- Haslar (PO12)
- Wider area
- Hampshire
- Cover
- A year, on every job
- Quotes
- A clear quote up front
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Honest limits
We won’t take on work that will not last, so these are the limits:
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
- Structural movement, which needs a surveyor or engineer
- Render that’s blown, hollow or coming away
If in doubt, ring 0345 464 0079 or send us an email and we’ll say what we think.
Surfaces we seal
- Concrete & block
- Joints between brick and frames
- Render & cladding joints
- Brickwork movement joints
- Copings & trims
- Façade panels
Nearby places to Haslar
What else we do in Haslar
For landlords and businesses
For anyone letting property in or around Haslar, several properties can be quoted together. Send us the addresses and the work at each.
Mouldy or split sealant often shows up at the end of a tenancy, and it’s easy to sort out between tenants. Several properties can go on one quote.
Different surfaces, different methods
Joints between dissimilar materials
Brick against render, concrete against metal, stone against timber: every change of material is a joint. We seal the joint with a flexible exterior sealant so the movement is taken up.
Cladding and façade panels
Cladding and façade panels are usually separated by sealed joints. Each joint gets a sealant that suits the panel and its movement.
What happens if it’s left?
Mortar or ordinary filler might look like a quick way to close an open joint, but it locks the joint solid. The movement then cracks the brickwork or render nearby. A flexible sealant over backing rod is what the joint needs. Around Haslar, older homes often have timber in their floors and frames, and water through a failed joint can rot timber if it’s left.
Commercial jobs are quoted on the same basis as homes: the amount of work, how we reach it and what it needs. Call for a quick quote and we will go through it with you.
Why choose Mr Mastic in Haslar
- One-year guarantee on every job
- Sanitary silicone with an anti-fungal additive in wet areas
- We never seal over old sealant
- Rated 4.9 stars on Google
Read what affects the cost or customer reviews.
Common problems we fix in Haslar
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 normally contact us when they notice something like this:
- Plants rooting in failed movement joints
- Failed seals between different materials
- Joints with sealant missing in places
- Joints pointed up with cement by mistake
If you look after a building such as Haselworth Primary School, its movement joints, gutters and trims need looking after like any other building’s.
Questions to ask before you book
- What happens if they find a problem under the old sealant
- How much experience the applicator has
- Whether all the old sealant comes out first
- Whether the sealant suits the joint
Haslar buildings and the weather
Haslar is close to the coast, and homes near the sea take more wind-driven rain, with salt in the air closer to the shore. Both are hard on movement joints and outside wall joints, which can dry out and crack sooner where a building faces the weather. The South East is one of the drier parts of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day.
Letting a property close to Portsmouth Harbour station? Then failed wall and movement joints let damp in, so they’re worth checking between tenancies. For an older house near a landmark such as St Francis, an extension built onto an older house moves differently, and the joint between them takes the strain.
Haslar is about 2 miles south-east of Gosport, in Hampshire. Every kind of property in Haslar can book us for external mastic. The work is guaranteed for a year. Our Hampshire coverage runs to 683 places, Haslar among them.
We work across PO12 for external mastic and the streets around it. Whether your property is on Froude Road, Military Road and Monckton Road or a nearby road, our applicators can take on the job. Nearby, we also carry out external mastic in Clayhall (1 mile north-west), Alverstoke (1 mile west), Portsmouth Point (1 mile north-east), Privett (2 miles north-west) and Portsea (2 miles north-east). Larger places within reach include Havant (8 miles north-east), Fareham (6 miles north-west), Horndean (10 miles north-east), Hedge End (12 miles north-west), Waterlooville (8 miles north-east) and Purbrook (7 miles north-east).
Landmarks near Haslar
Typical jobs here are in homes near The Fighting Cocks pub, Bay House School and St Vincent College and the streets around them. For rail, the closest station is Portsmouth Harbour station, about 1.5 miles north-east of the centre. Nearby you will also find Tricorn Centre (2.3 miles north-east) and Southsea Castle (1.8 miles east). Green spaces nearby include West of the River Alver.
How it works
On the day, we look over the joints with you first. We protect the surfaces around the joints before any work starts. The work usually takes a few hours to a few days, depending on the length of joint and the access. For a village or hamlet like Haslar, the journey is planned in advance: tell us about narrow lanes, gates, long drives and where we can park. Everything for the job comes with us, so a second trip is avoided where possible.
- 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.
- Primer is applied wherever the sealant needs it.
- A low-modulus exterior sealant is gunned in and tooled to a neat finish.
How to prepare
- Tell us about any previous sealing or DIY attempts
- Keep pets and children clear of the area while we work
- Mention any tricky access
Getting a quote
Want a quote for external mastic? Please ring 0345 464 0079 or email us with a few details. We’ll explain what we’d do and send you a clear quote before we start.
Read more
How to look after the new joints
Good habits help new joints last longer. A few tips:
- Leave the joints unpainted unless we have said otherwise
- Keep soil, plants and ivy away from the joints
- Walk round the building once a year and look at the joints
- Keep high-pressure jets off the joints
Look over the joints once a year, ideally after winter. Watch for splits, edges coming away or growth in the joint.
Act while the splits are small. Then it’s a straightforward cut-out and reseal.