Southampton · England
External & façade joints in Thornhill, Southampton
Sealing brickwork movement joints, render, cladding and façade joints for householders, landlords and businesses in Thornhill. Fully insured, ARBOMaster approved and guaranteed for a year.
- Joints pointed up with cement by mistake
- Sealant that has lost its bond to the brick or render
- Leaking joints around cladding and façade panels
External mastic in Thornhill: local notes
Thornhill 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, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
For site and facilities teams at buildings such as Thornhill Primary School, its movement joints, gutters and trims need looking after like any other building’s. Rented homes near Sholing station change hands often, and outside joints that have cracked can let damp into a rental, so check them between lets.
Thornhill is about 2 miles east of Southampton, in Southampton. We carry out external mastic for homes and businesses in Thornhill and the surrounding area. Across Southampton, we cover 40 places, Thornhill among them.
Every address in SO19, SO18 and SO30 is within our area for external mastic. Whether your property is on Drove Road, Barry Road and Luton Road or a nearby road, our applicators can take on the job. Main roads around Thornhill include the A334, which makes travel easy. Nearby, we also carry out external mastic in Harefield (1 mile north), Sholing (1 mile south-west), Bitterne (1 mile west), West End (1 mile north) and Chartwell Green (1 mile north). Further out, we also cover Shirley (4 miles west), Regents Park (4 miles west), Maybush (5 miles west), Portswood (3 miles north-west), Coxford (5 miles west) and Freemantle (4 miles west). As one of the bigger places in Southampton, Thornhill has homes, rented property and businesses of every kind.
Around Thornhill
Locally, jobs take us to homes and businesses close to Westwood Woodland Park, Woodlands Community College and Grove Park Business and Enterprise College. The closest station to Thornhill is Sholing station, roughly 1.4 miles south-west of the centre. Other landmarks nearby include Moorgreen Hospital (1.4 miles north-east) and Bitterne Local History Society Heritage And Research Centre (1.1 miles west). Not far away are Netley Common.
External mastic in Thornhill
We cut out failed sealant, set the joint depth with closed-cell backing rod and reseal with a low-modulus exterior sealant. The colour is chosen to suit the brick or render so the joint does not stand out. We work on façade panels, concrete & block and render & cladding joints, and people most often call us about leaking joints around cladding and façade panels and joints where the bead has come unstuck.
Around Thornhill, garages, outbuildings and extensions all add to the joints on the outside of a home. Gutter ends, garage door frames and the joints where an extension meets the house are typical spots for leaks.
There’s a 12-month guarantee on every job.
- Where
- Thornhill (SO19, SO18, SO30)
- Wider area
- Southampton
- Guarantee
- One year on every job
- Price
- A clear quote up front
- Call
- 0345 464 0079
- Updated
- 26 October 2026
When to call us in Thornhill
Some movement joints have been pointed up with mortar, often by someone who didn’t know what it was for. With the joint locked solid, the movement turns into cracks elsewhere in the wall.
Signs it’s time to call us include:
- Hard, crazed mastic that has stopped moving
- Failed seals between different materials
- Joints with sealant missing in places
- Sealant pulling away from one side of the joint
For an older house near a landmark such as St Christopher, old and new materials meet at the roofline and walls, which is where sealant earns its keep.
What your quote should include
- What preparation is included
- Which sealant they’ll use, and why
- Whether they’re fully insured
- What the cure time is
The process
You do not need to clear the whole room or building before we come, just the space around the work. We protect the rest, and the work takes a few hours for a handful of joints, longer for a whole elevation in most cases. A visit to Thornhill 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.
- First, the joints are inspected and the access agreed.
- We cut out the old mastic and rake out anything in the joint.
- The faces are brushed clean and primed where the product requires it.
- We fit closed-cell backing rod to control the depth.
- We apply the sealant, tool it and check the whole run.
How to prepare
- Tell us about any water getting in
- Mention any sign-in or site rules at work premises
- Tell us about any previous sealing or DIY attempts
Getting a quote
Every job is quoted individually. Just phone 0345 464 0079 or send us an email with the details and send photos if you have them.
Advice
Nearby places to Thornhill
Other services in Thornhill
What happens if it’s left?
Mortar or ordinary filler might look like a quick way to close an open joint, 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 Thornhill, 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 it costs depends on the size of the job, how hard the old material is to remove and how easy the joints are to reach. You’ll have a clear quote before any work starts, so you know where you stand.
Why us?
- Quality sealants from Arbo and Everbuild
- Sealant colour chosen to suit
- A 12-month guarantee on all work
- We are fully insured
See how sealant jobs are priced and our reviews.
Surface by surface
Brickwork movement joints
Clay brickwork grows slightly over its life and moves with the weather. That movement goes into the joint, so its sealant has to stay flexible.
Joints between dissimilar materials
Each side of the joint may need its own preparation. Both surfaces are cleaned and primed as the product requires.
DIY sealant or a professional job?
The biggest DIY mistake is sealing over old sealant. New silicone won’t bond to old, so it peels away and traps moisture behind it. Everything old must be removed 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.
What sealant work cannot fix
To be straight with you, there are a few things sealant will not fix:
- Walls that need new movement joints cut into them
- Damp from another source, such as a leaking gutter or a bridged damp-proof course
- Loose or hollow render, which needs re-rendering
If in doubt, phone 0345 464 0079 or drop us an email and we’ll say what we think.
Joints and surfaces we work on
- Render & cladding joints
- Brickwork movement joints
- Façade panels
- Concrete & block
- Joints between brick and frames
- Copings & trims
For landlords and businesses
For anyone letting property in or around Thornhill, jobs at different addresses can be quoted together. Send us the addresses and the work at each.
A neglected joint can let water reach the structure, which matters even more when someone else lives there. Resealing at the right time is simple maintenance.
Questions from Thornhill
I let a flat near Sholing station. Can you help?
Yes, rental work is part of what we do. You can ring 0345 464 0079 or send us an email with the address and a few details, and we’ll give you a fixed price before work begins.
Is external mastic in a coastal place like Thornhill any different?
Near the coast, wind-driven rain and, nearer the shore, salt air make outside sealant work harder. Choosing the right sealant for the frame and wall, laid at the right depth, helps it last.
Do you cover Thornhill?
We do. Our applicators work in Thornhill, and the service is the same as everywhere else.
Where is Mr Mastic based?
Our base is Crawley, with over 20 years’ experience. Our area covers South East England, London and Scotland.
How long does the job take?
A typical job takes a few hours for a handful of joints, longer for a whole elevation. Your quote will say how long we expect yours to take.
Will the old sealant be removed?
Always. Sealing over the old bead is the commonest cause of early failure, and it’s something we never do.
Do you work for hotels and businesses?
Yes. We’ve worked for hotels, offices and other businesses.
Can you seal joints between two different materials?
Yes. Different materials move at different rates, so a flexible sealant is needed where they meet. The sealant is matched to both sides.