Hampshire · England
External Mastic in Horndean
External mastic for Horndean, by sealant specialists with 20+ years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Failed sealant between panels on a façade
- Weeds or debris growing in open joints
- Sealant pulling away from one side of the joint
External mastic for homes and businesses in Horndean
External mastic is a job where short cuts show quickly. Overfilled joints, missing backing rod and sealant laid over old sealant all tend to fail early. We strip the joint back and start again. Common call-outs are for movement joints with cracked, split or missing sealant and leaking joints around cladding and façade panels, across joints between brick and frames, copings & trims and brickwork movement joints.
Horndean mixes older houses and their gutters with newer estates of brick, render and uPVC trims. All of those joints move, so they need a flexible sealant rather than a rigid filler.
Each job carries a 12-month guarantee.
- Where
- Horndean (PO8, PO7)
- Wider area
- Hampshire
- Cover
- 12 months on all our work
- Quote
- Quoted before any work starts
- Phone
- 0345 464 0079
- Last updated
- 26 October 2026
DIY versus a professional finish
The biggest DIY mistake is sealing over old sealant. Silicone doesn’t stick to old silicone, so it lifts and traps water and mould underneath. Everything old must be removed first.
A DIY attempt doesn’t rule out a professional job. We remove it and do the joint properly.
Keeping the joints in good condition
No joint lasts for ever, but care makes a real difference. A few tips:
- Clear growth from the base of walls and joints
- Get split or bare joints resealed while the damage is small
- Point out the joints to other trades
- Keep movement joints as flexible joints, not mortar
Keep pressure washers away from the sealant. A strong jet can damage the edges of the bead and let water in behind.
If you can see gaps, plants or bare sections in a joint, have it checked. Earlier resealing means a smaller job and a better result.
Different surfaces, different methods
Concrete and blockwork
Wide joints in concrete need the depth controlling carefully. Backing rod sized to the joint sets it.
Brickwork movement joints
Brick walls have vertical movement joints to absorb expansion. They’re resealed over backing rod with a low-modulus sealant.
What affects the quote in Horndean
Jobs vary more than people expect. The main factors:
- Whether there’s mould to deal with
- The number of rooms or windows
- When we can work, for business premises
- Which sealant suits the joint
A few things move the cost up or down: how much old sealant there is and how stubborn it is, whether mould needs treating, and whether the work is at height. We take all of that into account in your quote.
What we need to know
A few details help us give you an accurate quote. When you get in contact, it helps to mention:
- If it’s domestic, commercial or a hotel
- Roughly how big the job is
- Whether it has been sealed before
- The problem you’ve noticed
It all starts with a short chat. Describe the problem, the location and the size of the job. When it suits you, ring 0345 464 0079 or send us an email.
How it works
When we get to you, we compare the joints with what we discussed. If we find something unexpected, we talk it through with you first. Most jobs then take a few hours for a handful of joints, longer for a whole elevation. Parking in a town like Horndean is normally straightforward, but tell us if there’s a driveway or any restrictions, and let us know if the work is upstairs, in a flat or up high outside.
- 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.
- We apply the sealant, tool it and check the whole run.
How to prepare
- Let us know about earlier repairs to the joints
- Let us know about stairs, lifts or work at height
- Tell us about any water getting in
Getting a quote
Want a quote for external mastic? Please phone 0345 464 0079 or email us and tell us about the job. You will know what we plan to do, and what it will cost, before any work begins.
Related advice
Places near Horndean
What else we do in Horndean
FAQs for Horndean
Is Horndean in your area for external mastic?
Yes, Horndean is within the area we cover. We work across London and the South East. Just phone 0345 464 0079 or drop us an email with a few details of the job.
What guarantee comes with external mastic in Horndean?
All our work, in Horndean and everywhere else, comes with a 12-month guarantee. We are also fully insured and ARBOMaster approved.
Does someone need to be in?
For indoor joints, yes, someone needs to let us in. After that, you can carry on with your day.
Where is Mr Mastic based?
Mr Mastic is based in Crawley. We cover Horndean and the rest of Hampshire.
Can a movement joint be filled with mortar?
No. Cement or mortar can’t stretch, so the joint stops doing its job. If it has already been filled, we can normally cut it out and reseal it.
What should I tell you?
Only a few details: the address or postcode, what’s wrong and any access issues. Then ring 0345 464 0079 or email us.
Is there any odour?
Possibly a little. It fades as the sealant cures, and ventilation helps.
Do you have insurance?
Yes. We are fully insured, and we can confirm the details when we quote.
What we can’t put right
Before booking, it’s worth knowing the limits too:
- Failed render or damaged cladding panels
- Rising or penetrating damp from elsewhere in the wall
- Walls that need new movement joints cut into them
Not sure which it is? You can call 0345 464 0079 or email us and we’ll tell you honestly before you book.
Joints and surfaces we work on
- Concrete & block
- Brickwork movement joints
- Copings & trims
- Façade panels
- Render & cladding joints
- Joints between brick and frames
Why it’s worth doing now in Horndean
It often makes sense to reseal all the failing joints on an elevation together. They’ve weathered the same way, and access only has to be arranged once. Gaps in sealant and mould in the bead never get better on their own, and in a busy household in Horndean they spread with every shower and every downpour. Now is the easy time to put it right.
Doing several joints on one visit is usually more efficient than separate visits, so it’s worth mentioning everything you’d like done. We will give you a clear quote for the lot.
Why book with us
- Colour picked to suit the job
- White, clear, grey or coloured to suit, where the product allows
- We never seal over old sealant
- Every job guaranteed for a year
See our cost guide or our reviews.
Walls and rooflines in Horndean
Rainfall in the South East is lower than in much of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. Historic houses like Warblington Castle (about 4.8 miles south-east) are a reminder that the area around Horndean has older buildings as well as new. Where a home is older, older walls and rooflines need a sealant that moves with them and suits the material.
Schools such as Horndean Technology College are buildings too, and larger buildings have long runs of movement joint that eventually need resealing. Letting a property close to Rowlands Castle station? Then split movement joints are easy to miss on a rental until damp shows inside. In the older streets around Saint Wilfrid's, an extension built onto an older house moves differently, and the joint between them takes the strain.
Horndean is about 7 miles north-east of Portsmouth, in Hampshire. For external mastic in and around Horndean, please phone 0345 464 0079 or email us for a quick quote. We cover Hampshire from our Crawley base, Horndean included. Our Hampshire coverage runs to 683 places, and Horndean is one of them. Our Portsmouth page covers work nearby, about 7 miles away.
Every address in PO8 and PO7 is within our area for external mastic, from the main roads to the quietest streets. External mastic is available to properties on London Road, Kings Mede and Causeway Farm. You’ll find Horndean on the A3 and A3(M), which makes it straightforward to reach. If you are just outside Horndean, we cover Lovedean (1 mile west), Wecock Farm (1 mile south-west), Catherington (2 miles north), Anmore (2 miles west) and Denmead (2 miles west). We also work in nearby towns such as Gosport (9 miles south-west), Havant (3 miles south), Eastleigh (15 miles west), Fareham (9 miles south-west), Hedge End (13 miles west) and Petersfield (7 miles north-east). Horndean is one of the larger places we cover in Hampshire.
Near you in Horndean
Around Horndean, our work takes us to homes and buildings near Horndean Infant School and Red Lion Inn. The closest station to Horndean is Rowlands Castle station, roughly 2.6 miles south-east. Well-known places in the area include Havant War Memorial Hospital (3.8 miles south) and Clanfield Earthwork (3 miles north-east). Open spaces near Horndean include Windmill Hill and Southmoor Nature Reserve.