Hampshire · England
Haslar Window Mastic
Window mastic across Haslar and nearby, with old sealant always removed completely.
- Untidy mastic left by window fitters
- Water coming in at the bottom corners of a door
- Mastic that is falling out in pieces
Window mastic for homes and businesses in Haslar
The new joint does not have to be white. White, brown, anthracite grey, black and clear sealants are all available, so the bead blends with the window rather than framing it. We work on aluminium frames, composite doors and patio & French doors, and common reasons people get in touch are untidy mastic left by window fitters and mastic that has split away from the wall.
Somewhere as small as Haslar, older homes often have timber frames set in stone or brickwork. Not every older frame suits a modern silicone bead, and sometimes a traditional sand mastic is the better choice.
All our work is covered by our one-year guarantee, wherever you are in Hampshire.
- Place
- Haslar (PO12)
- Wider area
- Hampshire
- Guarantee
- One year on every job
- Quotes
- A clear price before any work starts
- Phone
- 0345 464 0079
- Updated
- 26 October 2026
Can I do it myself?
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and the joint depth matters as much as the finish.
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 doesn’t work out, we can still put it right.
FAQs for Haslar
Will you come out to Haslar?
Yes. Haslar is within the area we cover, which takes in towns, villages and rural addresses. We work across London and the South East. Just mention lanes, gates or anything else about the route when you book.
Is window mastic in a coastal place like Haslar any different?
Coastal homes put outside sealant through more weather than inland ones, so the choice of sealant and the preparation matter even more. It’s worth checking the walls that face the sea first.
Are you ARBOMaster approved?
Yes. We are ARBOMaster approved, the scheme for applicators of Arbo sealants.
Do I have to be there?
Access is agreed with you when the job is booked. For inside work, that normally means someone being in.
How long before the joint can be used?
Different products cure at different speeds, so follow the cure time we give you when we finish.
Is the new sealant paintable?
Not if it’s silicone. We choose the product with your decorating in mind, so mention it when you book.
Are you insured?
Yes. Mr Mastic is fully insured, with over 20 years’ experience in sealant work.
Can landlords and businesses book you?
Yes, regularly. Several properties can go on one quote, and between tenancies is a good time for the work.
Window mastic in Haslar: local notes
Haslar is within about 1 mile of 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 the mastic around window and door frames, 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, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
If you live in an older home near St Francis, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. If you let a flat or house near Portsmouth Harbour station, renewing tired window mastic between tenants heads off draught and damp complaints. Schools such as Haselworth Primary School are buildings too, and the mastic around its windows and doors needs looking after like any other building’s.
Haslar is about 2 miles south-east of Gosport, in Hampshire. Homes, rented property, offices and hotels in Haslar can book us for window mastic, old or new, large or small. The work is guaranteed for a year. Our Hampshire coverage runs to 683 places, and Haslar is one of them.
Jobs for window mastic in PO12 works the same way as everywhere else we cover. We cover properties on Froude Road, Military Road and Monckton Road. If you are just outside Haslar, we cover 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).
What’s near Haslar
We work in homes and buildings around The Fighting Cocks pub, Bay House School and St Vincent College. For rail, the closest station is Portsmouth Harbour station, roughly 1.5 miles north-east. Other landmarks nearby include Tricorn Centre (2.3 miles north-east) and Southsea Castle (1.8 miles east). The countryside around Haslar includes West of the River Alver.
Why it’s worth doing now in Haslar
Running fresh sealant over the old joint is tempting, but it will not grip old, dirty sealant. It soon lifts and the leak carries on behind it. The old mastic has to come out. 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.
There are no prices on our website, because each job is priced on what it involves. Call for a quick quote and we’ll talk you through it.
Why us?
- Homes, businesses and hotels
- Neat joints and a tidy finish
- Anti-fungal silicone where joints get wet
- Over 20 years’ experience
What affects the quote in Haslar
Some jobs are bigger than they look, and some smaller. The main factors:
- How much old sealant there is and how hard it is to remove
- How many rooms, windows or areas are involved
- How much there is to do
- Whether there’s mould to deal with
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. We give a clear quote before work begins.
Helping us quote
To make quoting easier, please include:
- Pictures of the joints, sent by email
- The rough size of the job
- The address or postcode of the job
- Whether it has been sealed before
To get a quote, ring 0345 464 0079 or drop us an email with the location and a short description of the problem. We will give you a clear price before any work starts.
Work for landlords, hotels and businesses
Letting agents often deal with us directly. Tell us the address, the job and how access works and we’ll quote.
Mouldy or split sealant often shows up at the end of a tenancy, and it’s easy to sort out between tenants. We can quote for more than one property at once.
What happens on the day
We bring everything the job needs with us. Once we’ve agreed what’s being done, we protect the area and start. Most jobs take a few hours for a handful of frames, longer for a whole house. For a village or hamlet like Haslar, the journey is planned in advance: let us know about lanes, gates and parking. We bring what the job needs, so it can be finished in one trip where possible.
- We check each frame and agree which ones need doing.
- Next the failed sealant is cut away and the joint cleaned.
- Where gaps are deep, backing rod goes in first.
- New exterior sealant goes on in a matching colour and is tooled smooth.
- Finally we tidy up and check each joint.
Before we arrive
- Keep children and pets away from the work area
- For business premises, tell us about site rules or sign-in
- Try not to wet indoor joints just before the visit
Getting a quote
Asking for a quote is easy: tell us what needs doing and where and its rough size. Photos by email help us understand the job.
Related advice
Aftercare tips
So the new joints stay in good condition:
- Don’t aim a pressure washer at the joints
- Avoid harsh chemicals near the mastic
- Clear any debris from frame drain holes
- Ventilate rooms so frames don’t stay wet inside
Most silicone sealants won’t take paint, so mention any painting plans before work begins. We can use a paintable sealant where that matters.
On timber windows, water behind the joint can lead to rot. Rotten timber needs a joiner, not a sealant, so early resealing is worth it.
Different surfaces, different methods
Composite doors
An exposed front door gets wind-driven rain. We pay most attention there.
uPVC windows
Fitters’ mastic on plastic frames is sometimes thin and rushed. It comes out, deep gaps get backing rod and the joint is resealed.