Kent · England
Window Mastic in Knockholt
Mastic around window and door frames, sills and patio doors for homes and businesses in Knockholt and across Kent. ARBOMaster approved applicators, fully insured, with a one-year guarantee.
- Draughty joints inside around the window
- Hard, cracked sealant around windows
- Damp patches on the reveal after heavy rain
About our window mastic in Knockholt
Over two decades of sealing frames has taught us which products suit which walls. We’re ARBOMaster approved and fully insured, and we give a one-year guarantee on the work. Typical jobs include leaking joints at the ends of sills and mastic that has split away from the wall, across uPVC windows, window sills and timber windows & doors.
Somewhere as small as Knockholt, older homes often have timber frames set in stone or brickwork. Older buildings like these do not always suit modern silicone, and sometimes a traditional sand mastic is the better choice.
Our work is backed for twelve months, in Knockholt and everywhere else we cover.
- Where
- Knockholt (TN14)
- Wider area
- Kent
- Guarantee
- 12 months on all our work
- Price
- A clear quote up front
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
DIY versus a professional finish
Not every job suits DIY: work at height, external movement joints, fire-rated sealant and large areas call for the right materials, safe access and experience.
A careful DIYer can reseal a simple joint, like a short, easy-to-reach joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
Window mastic in Knockholt: local notes
Rainfall in the South East is lower than in much of the UK, though outdoor sealant still has to go onto a dry joint, so the forecast decides the day. With historic houses such as Down House (about 2.7 miles north-west) nearby, there’s older building stock in the area around Knockholt as well as newer homes. In older buildings, older frames set in brick or stone need a sealant that suits them, and sometimes that is traditional sand mastic.
Homes close to St Katharine's Church include some older properties, and the joint between an old wall and a newer frame is usually the first place rain gets in.
Knockholt is about 4 miles north-west of Sevenoaks, in Kent. Our applicators cover window mastic for homeowners, landlords and businesses in Knockholt and the surrounding area, as part of our work across Kent. Across Kent, we cover 922 places, Knockholt among them. We also work in London, around 16 miles away.
Here we cover the TN14 postcode area for window mastic. If you need window mastic at a property on Main Road and Blueberry Lane or a nearby road, we can help. Other places close to Knockholt include Knockholt Pound (1 mile north-east), Halstead (2 miles north-east), Sepham Heath (2 miles north-east), Pratt's Bottom (2 miles north) and Twitton (3 miles east). We also work in nearby towns such as Dartford (11 miles north-east), Sevenoaks (4 miles south-east), Royal Tunbridge Wells (14 miles south-east), Gravesend (14 miles north-east), Tonbridge (11 miles south-east) and Northfleet (13 miles north-east).
Around Knockholt
We work in homes and buildings around The Three Horseshoes pub and the streets around them. The closest station to Knockholt is Knockholt station, about 2.7 miles north-east. A little further out are Orpington Hospital (3.6 miles north) and Otford Heritage Centre (3.9 miles east). The countryside around Knockholt includes Betsom's Hill and Downe Bank.
How the job changes by surface
Aluminium frames
Coated aluminium needs a compatible sealant, and acetoxy silicones aren’t used, as they can attack some metals. Neutral-cure sealant is the safe choice.
Patio & French doors
Heavy door frames can move more than windows. A flexible sealant copes with that, where a rigid one would crack.
Aftercare tips
Good habits help new joints last longer. Our tips:
- Do not paint over the silicone
- Make sure the drainage slots aren’t blocked
- Walk round the house once a year and look at the joints
- Repaint timber before it’s bare
Have a look at the joints once a year, ideally after winter. Cracks and lifting edges are easy to spot early.
Signs to watch for: split or missing mastic, gaps, damp patches inside or black mould on the reveal. Any of these is worth a call.
Knockholt questions
Do you cover smaller places like Knockholt?
Yes, Knockholt is covered. We work across London and the South East, and smaller places are part of that. The journey is planned ahead, so it helps to know about access.
Do you cover Knockholt for window mastic?
Yes, Knockholt is within the area we cover. Our work covers London and the South East. Just phone 0345 464 0079 or drop us an email with a few details of the job, and we will send you a clear quote.
What do you need from me for a quote?
Where the job is, what the problem is and roughly how big it is. Photos by email help too.
Can you seal over the old sealant?
No. New silicone won’t bond to old silicone, and anything trapped underneath, including mould and water, stays there. It all has to come out first.
Where is Mr Mastic based?
We work from Crawley. Our applicators cover Knockholt, along with the rest of our area.
Can you seal the gap between the frame and the plaster indoors?
Yes. Plenty of draughts come through the inside joint as well as the outside, so it can be worth sealing both.
How do I get a quote for window mastic in Knockholt?
Size, access and the old material all affect the cost. Ask us for a quote and we will talk you through it.
I rent my home. Can I book you?
Yes, but check with your landlord or agent first. Landlords are often happy for the work to be arranged.
Signs you need window mastic in Knockholt
Sun, frost and rain wear sealant out. Sunlight dries the surface out, until it loses its stretch and starts to crack.
The problems people generally mention when they call are:
- Sealant in the wrong colour for the frame
- Cold air getting in at the frame edge
- Leaking joints at the ends of sills
- Mastic that has split away from the wall
Rented homes near Knockholt station change hands often, and cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets.
Comparing quotes
- What preparation is included
- When the joint can take water or movement
- How much experience the applicator has
- Whether VAT is included
What affects the cost of window mastic
The price is agreed before any work begins. It takes into account:
- Whether old sealant or filler has to be cut out
- Mould in or behind the old joints
- The product the joint needs
- How many rooms, windows or areas are involved
Leaving a failed joint normally makes the job bigger, not smaller, as water and mould keep getting in. If you are unsure, ring 0345 464 0079 or send us an email for an honest opinion and a quote.
Helping us quote
Photos help, but a description is a good start. Try to tell us:
- Photos by email, if that’s easy
- The problem you’ve noticed
- Where the job is, and your postcode
- Any access issues, like height or stairs
For a quick quote, get us on the phone, or send an email if you’d rather. Tell us about the joints that need doing and we will explain what’s involved.
Nearby places to Knockholt
What else we do in Knockholt
How the visit works
Our applicators work methodically: protect, prepare, seal, tidy. For most jobs that takes a few hours for a few frames, or a day or more for a whole house, and the area is left clean. Somewhere like Knockholt needs a little journey planning: let us know about lanes, gates and parking. Everything for the job comes with us, so a second trip is avoided where possible.
- First we look at every frame and agree the list.
- We remove the old mastic and clean the frame and the wall.
- Deep gaps are filled with backing rod to set the depth.
- We apply a weatherproof sealant to match the frame and tool it neatly.
- Finally we tidy up and check each joint.
How to prepare
- Tell us about access, such as stairs, a lift or high-level joints
- Mention any leaks or damp you’ve noticed
- Keep pets and children clear of the area while we work
How to get a quote
Every job is quoted individually, so start by telling us what you need. Simply ring 0345 464 0079 or email us and describe the job, and pictures are welcome.
Related advice
Honest limits
Before booking, it’s worth knowing the limits too:
- A frame that has rotted at the joint
- Broken hinges, locks or handles
- Damp coming through the wall itself rather than the frame joint
If in doubt, ring 0345 464 0079 or drop us an email and we will say what we think.
Joints and surfaces we work on
- Patio & French doors
- Window sills
- Aluminium frames
- Timber windows & doors
- Composite doors
- uPVC windows