Hampshire · England
Window & door mastic in Knapp, Hampshire
Professional window mastic in and around Knapp, with every bit of old sealant taken out first and a one-year guarantee.
- Whistling draughts around closed windows
- Gaps where the sill meets the wall
- White mastic on grey or black frames
DIY versus a professional 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 does not work out, we can still put it right.
A careful DIYer can reseal a simple joint, such as a straightforward joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
Window mastic in Knapp
Colour matters on a frame. We can seal in white, brown, anthracite grey, black or clear, so the line suits the frame instead of standing out. We work on composite doors, uPVC windows and patio & French doors, and people most often call us about mastic that has split away from the wall and rain getting in at the frame or under the sill.
Somewhere as small as Knapp, older homes often have timber frames set in stone or brickwork. Older buildings like these don’t always suit modern silicone, and sometimes a traditional sand mastic is the better choice.
Whatever the size of the job, it’s backed by our 12-month guarantee.
- Where
- Knapp (SO51)
- Wider area
- Hampshire
- Cover
- One year on every job
- Price
- Quoted before any work starts
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
Knapp homes and the weather
Rainfall in the South East is lower than in much of the UK, yet outdoor joints still have to be sealed dry, so jobs are booked with the weather in mind.
Managing a site like Ampfield Church of England Primary School? Then the mastic around its windows and doors needs looking after like any other building’s. Homes close to Church of St Mark include some older properties, and the windows may be timber, sash or later replacements, and each needs the right sealant against the wall.
Knapp is about 2 miles north-west of Chandler's Ford, in Hampshire. Across the SO51 area, we can carry out window mastic at your property. Knapp is one of 683 places in Hampshire where we work. For nearby work, see our Southampton page.
Work in SO51 works the same way as everywhere else we cover. Close by, we work in Ampfield (1 mile south-west), Broadgate (1 mile south-east), Gosport (1 mile south-west), Lower Slackstead (1 mile north-west) and Crampmoor (2 miles south-west). We also work in nearby towns such as Winchester (6 miles north-east), Eastleigh (5 miles south-east), Fareham (15 miles south-east), Andover (14 miles north), Totton (7 miles south-west) and Hedge End (8 miles south-east).
What’s near Knapp
We work in homes and buildings around White Horse Public House. The nearest railway station is Chandlers Ford station, about 2.5 miles south-east. Nearby you will also find Romsey Community Hospital (2.9 miles south-west) and King Johns House (3.7 miles south-west). Not far away are Emer Bog and Baddesley Common.
Aftercare tips
To keep the joints looking good and working properly:
- Walk round the house once a year and look at the joints
- Paint up to the joint, not over it
- Use gentle cleaners on frames and sealant
- Don’t use solvent cleaners on the joint
Try not to touch the new joint while it cures, for as long as we advise. Keep jet washers away from the frames.
Signs to watch for: cracks in the mastic, gaps you can see light through, damp on the reveal or mould around the inside of the frame. If you notice one, it’s time to get the joint looked at.
Leave it or put it right?
Once mastic fails, rain can get between the frame and the wall. Left long enough, it can stain inside walls, spoil plaster and rot wooden frames. A reseal is a much smaller job. Around Knapp, older homes often have timber in their floors and frames, and water through a failed joint can rot timber if it’s left.
What it costs depends on the size of the job, how hard the old material is to remove and access to the work. You’ll have a clear quote before any work starts.
What you get with us
- White, clear, grey or coloured to suit, where the product allows
- Tidy, careful work
- We agree the colour with you first
- Colour picked to suit the job
Take a look at how sealant jobs are priced and our reviews.
How we quote for window mastic
The quote reflects the job in front of us. We take into account:
- Any working-time requirements on site
- How easy the joints are to reach
- How many rooms, windows or areas are involved
- The size of the job
Every job is a little different, so we quote each one individually. Size, access and the product the joint needs all play a part.
Asking for a quote
Photos by email are helpful but not essential. Please mention:
- If someone has resealed it before
- Roughly how big the job is
- What’s wrong with the joints now
- How we’d reach the joints
Getting a quote is simple: let us know what needs doing and where and its rough size. Photos by email help us understand the job.
What happens on the day
There’s no need to move everything out before we come, only the area right around the joints. We protect the rest, and the work takes anything from an hour or two to a full day, depending on how many frames there are for a typical job. Somewhere like Knapp needs a little journey planning: 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.
- Deep gaps are filled with backing rod to set the depth.
- New exterior sealant goes on in a matching colour and is tooled smooth.
- Finally we tidy up and check each joint.
How to prepare
- For business premises, tell us about site rules or sign-in
- Keep pets and children clear of the area while we work
- Let us know about stairs, lifts or work at height
Getting a quote
Every job is quoted individually, so the first step is telling us about yours. Simply ring 0345 464 0079 or drop us an email and describe the job.
Advice
FAQs for Knapp
Do you work for landlords with property near Chandlers Ford station?
Yes, landlords and agents are among the people we work for, and several properties can be quoted together. Just phone 0345 464 0079 or drop us an email with the address and what needs doing, and we’ll give you a clear price.
Is Knapp in your area for window mastic?
Yes, Knapp is within the area we cover. We work across London and the South East. Just ring 0345 464 0079 or drop us an email with a few details of the job, and we’ll give you a clear quote.
Can resealing stop a draught around my window?
Yes, where the draught is at the frame edge. We find where the air is coming from before we reseal.
How long will my window job take?
A handful of frames is a short visit, while a whole house takes longer. You will get a timescale with the quote.
How do I get a quote for window mastic in Knapp?
We don’t publish prices, because the cost depends on the job: how much there is, what’s there now, how we reach it and what it needs. We agree the price before any work begins.
Is it messy?
Very little: the area around the joints is protected first, and we tidy up before we go.
Do you work on first-floor windows?
Yes, where they can be reached safely. Tell us about access when you get in touch and we will plan for it.
Do you work for hotels and businesses?
Yes. Commercial and hotel work is a large part of what we do, as well as homes. Working times can be discussed when we quote.
Nearby places to Knapp
What else we do in Knapp
Do you need window mastic in Knapp?
Water runs down the glass onto the sill, and the ends of the sill, where it meets the wall, are where it gets in. Failed sealant there lets rain into the wall or behind the frame.
Look out for any of the following:
- Old mastic that has gone black or come away
- Untidy mastic left by window fitters
- Damp patches on the reveal after heavy rain
- White mastic on grey or black frames
If you let a flat or house near Chandlers Ford station, cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets.
Questions to ask before booking
- What product goes in the joint
- How the joint is cleaned and prepared
- Are they insured?
- What happens if they find a problem under the old sealant
Different surfaces, different methods
Window sills
Sills catch the water running down the glass, so the sill ends and the joint under the frame are vital. They’re cut out and resealed with exterior sealant.
Aluminium frames
Bi-fold and sliding aluminium doors have long frame joints, and the threshold joint takes a lot of water. We prepare and reseal every joint, backing the deep ones.