Hampshire · England
External & façade joints in Blackwater, Hampshire
External mastic for Blackwater, by sealant specialists with 20+ years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Rigid filler in a joint that should flex
- Panel joints letting water in
- Gaps where render, brick and frames meet
About our external mastic in Blackwater
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. If you are dealing with water getting into walls through failed joints and joints pointed up with cement by mistake, we can help, whatever the surface.
In a smaller place like Blackwater, some homes face open ground, and walls and rooflines facing the weather take the worst of it. That’s where gutter joints and wall joints tend to fail first.
Big or small, you get the same 12-month guarantee in Blackwater and across Hampshire.
- Place
- Blackwater (GU17)
- Wider area
- Hampshire
- Cover
- One year on every job
- Quote
- A clear price before we start
- Telephone
- 0345 464 0079
- Updated
- 26 October 2026
What we do, step by step
We bring everything the job needs with us. After a quick look at the joints together, the area is protected and the work begins. Most jobs take a few hours to a few days, depending on the length of joint and the access. Parking around Blackwater is usually 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.
How to prepare
- Let us know about stairs, lifts or work at height
- Tell us if parking is tricky
- Try not to wet indoor joints just before the visit
Getting a quote
Need a quote? Please ring 0345 464 0079 or drop us an email with a few details. You’ll know what we plan to do, and what it will cost, before any work begins.
Read more
What else we do in Blackwater
What the job involves on each surface
Brickwork movement joints
People sometimes point up a brick movement joint by mistake. Where one has been mortared, we cut it out and reseal it with sealant if the joint can be cleared.
Render joints
Render is weaker at the surface than brick, so a low-modulus sealant is kinder to the joint edges. We prime where the product needs it.
Why it’s worth doing now in Blackwater
Sealing over the top of old mastic does not hold for long. New sealant doesn’t bond well to old, weathered sealant, so the old joint is cut out fully first. In an older home around Blackwater, damp from a failed joint can get into timber and plaster, and that is a much bigger job than renewing the sealant.
We do not show prices on the website, because the cost depends so much on the job itself. For a quick quote, please call 0345 464 0079 or drop us an email.
Why choose Mr Mastic in Blackwater
- We’re fully insured
- White, clear, grey or another colour, product permitting
- Colour picked to suit the job
- Anti-fungal silicone where joints get wet
Read what affects the cost and our reviews.
Common questions in Blackwater
Do you work for landlords with property near Blackwater station?
Yes, rental work is part of what we do. You can call 0345 464 0079 or send us an email with the address and a few details, and we’ll give you a fixed price before any work starts.
Is Blackwater in your area for external mastic?
Yes. We work across London and the South East, and Blackwater is part of that. Just phone 0345 464 0079 or email us with a few details of the job, and we will give you a clear price.
Do you guarantee your work?
Yes. All our work carries a 12-month guarantee.
Is it worth trying it myself?
That depends on the joint. High-level, external movement and fire-rated joints are professional jobs.
Is it OK to fill a movement joint with cement?
No. Mortar locks the joint solid, so the movement cracks the wall elsewhere. It needs a flexible sealant over backing rod.
Is it messy?
Very little: the area around the joints is protected first, and we tidy up before we go.
Are you insured?
Yes. We are fully insured.
How long will you be here?
That depends on the amount of work, but as a guide it takes anything from a few hours to several days, depending on the building. We’ll give you a better idea when we quote.
Can I do it myself?
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is matched to the joint and its conditions.
Some sealant jobs are within reach of a careful DIYer, like a short, easy-to-reach joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
How to look after the new joints
So the new joints stay in good condition:
- Check the sealant is paintable before painting near it
- Never let anyone fill a movement joint with mortar
- Keep water from gutters off the wall
- Show decorators and builders where the movement joints are
Look over the joints once a year, ideally after winter. Watch for splits, edges coming away or growth in the joint.
A joint that has stopped moving pushes the movement elsewhere, generally as cracking in the brickwork or render nearby. Catch it early and you reduce the risk.
What affects the quote in Blackwater
There’s no set price list, because no two jobs are the same. What we look at:
- How many rooms, windows or areas are involved
- Whether the work is at height
- Working hours on commercial sites
- Whether there’s mould to deal with
Instead of a standard rate, we look at what your job involves: how many joints, what’s in them now and how we reach them. You will know the price before we begin.
What to tell us for a quote
Before you ask for a quote, have a think about:
- Any access issues, like height or stairs
- If it’s domestic, commercial or a hotel
- Pictures of the joints, sent by email
- If someone has resealed it before
Asking for a quote is easy: let us know the job and the location and its rough size. Photos by email help us understand the job, and we’ll come back to you with a quote.
What external mastic looks like in Blackwater
Compared with the north and west, the South East gets less rain, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
If you let a flat or house near Blackwater station, outside joints that have cracked can let damp into a rental, so check them between lets. Managing a site like Frogmore Infant School? Then larger buildings have long runs of movement joint that eventually need resealing. Homes close to St Barnabas Church include some older properties, and old and new materials meet at the roofline and walls, which is where sealant earns its keep.
Blackwater is about 1 mile south of Sandhurst, in Hampshire. From the centre of Blackwater to the outskirts, we cover external mastic for every kind of property. Blackwater is one of 683 towns and villages in Hampshire where we work for external mastic. We also work in Reading, around 11 miles away.
Postcode districts we cover here for external mastic: GU17. Streets in the area include London Road, Bell Lane and Ash Close. We also cover the places around Blackwater: Frogmore (1 mile west), Hawley (1 mile south-east), College Town (1 mile north-east), Sandhurst (1 mile north) and York Town (1 mile east). Larger places within reach include Basingstoke (14 miles west), Farnborough (3 miles south), Fleet (5 miles south-west), Aldershot (6 miles south), Alton (15 miles south-west) and Tadley (15 miles west).
Local landmarks in Blackwater
Around Blackwater, our work takes us to homes and buildings near Mr Bumble pub, Frogmore Community College and Royal Military Academy Library, among other places. For rail, the closest station is Blackwater station, about 0.6 miles east. Well-known places in the area include Frimley Park Hospital (2.4 miles south-east) and Staff College Museum (1.9 miles east). The countryside around Blackwater includes Horseshoe Lake and Ball Hill.
For landlords and businesses
Businesses can book us for washrooms, kitchens, offices and more. On commercial sites, working times can be discussed when we quote.
From a single let to a portfolio, you get the same standard of work: the old material taken out, careful preparation and a 12-month guarantee.