West Sussex · England
Keymer Window Mastic
Professional window mastic in and around Keymer, with every bit of old sealant taken out first and a 12-month guarantee.
- Gaps between the frame and the inside reveal
- Leaking joints at the ends of sills
- Old mastic that has gone black or come away
How we handle window mastic in Keymer
A cold draught around a closed window often comes from the frame edge. Resealing that joint can make a room feel noticeably less draughty and quietens the whistle on windy days. If the draught is through the window seals instead, we’ll tell you. We work on timber windows & doors, uPVC windows and composite doors, and people most often call us about gaps left after new windows were fitted and rain getting in at the frame or under the sill.
In a smaller place like Keymer, some walls face open ground and catch the full force of the weather. That’s hard on the mastic around frames and sills.
You get a 12-month guarantee, the same in Keymer as everywhere else we work.
- Location
- Keymer (BN6)
- Wider area
- West Sussex
- Guarantee
- A year, on every job
- Price
- Quoted before any work starts
- Telephone
- 0345 464 0079
- Last updated
- 26 October 2026
What window mastic looks like in Keymer
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.
In the older streets around St Cosmas and St Damian Church, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. For site and facilities teams at buildings such as The Windmills Junior School, its window and door frames need their mastic kept sound, just like a home’s.
Keymer is about 2 miles south of Burgess Hill, in West Sussex. Jobs in Keymer get the same care as everywhere else we work: the old material taken out, joints prepared properly and a 12-month guarantee. Across West Sussex, we cover 371 places, Keymer among them. Brighton is on our list too, about 6 miles from Keymer.
Work in BN6 is quoted and booked the same way as anywhere else. Local streets include Flowers Close, The Quadrant and Kymer Gardens, all of which we cover. If you are just outside Keymer, we cover Hassocks (1 mile west), Ditchling (1 mile east), Clayton (1 mile south-west), Hurst Wickham (1 mile north-west) and Westmeston (2 miles south-east). We also work in nearby towns such as Crawley (13 miles north), Horsham (13 miles north-west), Worthing (14 miles south-west), Haywards Heath (5 miles north), East Grinstead (15 miles north) and Shoreham-by-Sea (8 miles south-west).
Local landmarks in Keymer
Around Keymer, our work takes us to homes and buildings near The Greyhound Public House and Downlands Community School. Keymer’s nearest station is Hassocks station, about 0.5 miles west. Other landmarks nearby include The Dene Hospital (3.2 miles north-west) and Clayton Castle (1.2 miles south-west). For a walk, there’s Ditchling Beacon and Bedelands Farm Nature Reserve.
When something else is needed
New sealant cannot fix everything, and we’d rather say so up front. It won’t solve:
- A sash or casement that will not close properly
- Damp coming through the wall itself rather than the frame joint
- Misting between the panes of a double-glazed unit (that needs a new unit)
If in doubt, phone 0345 464 0079 or drop us an email and we will say what we think.
Joints and surfaces we work on
- Aluminium frames
- Timber windows & doors
- Patio & French doors
- uPVC windows
- Composite doors
- Window sills
DIY versus a professional finish
Overfilling a joint is a classic DIY mistake. A thick, smeared bead looks untidy and does not move well, and getting the depth right matters as much as the look.
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.
What happens on the day
Before we leave, we go over the finished joints with you. The visit itself generally takes anything from an hour or two to a full day, depending on how many frames there are, depending on the size of the job. Parking around Keymer is normally 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.
- First, we confirm safe access to each frame.
- Old, cracked mastic is removed completely, along with any loose debris.
- Frame and wall are cleaned and must be dry before sealing, and primed where the sealant calls for it.
- Deep voids are backed, then the sealant is gunned in.
- The joint is shaped to shed water and the area tidied.
How to prepare
- Tell us about access, such as stairs, a lift or high-level joints
- Keep pets and children clear of the area while we work
- Tell us about any previous sealing or DIY attempts
Ask for a quote
To get a quote, call 0345 464 0079 or email us with the location and a short description of the problem. You’ll have a clear quote before we start.
Advice
What the job involves on each surface
Patio & French doors
Not every patio door leak is a mastic problem: blocked drain slots, worn brush seals and threshold details can let water in too. We look for the cause first.
Composite doors
Composite doors are normally hung in an uPVC-type frame, and the joint around it is sealed like a window. The bead is colour-matched to the frame.
Common problems we fix in Keymer
Water runs down the glass onto the sill, so the sill ends and the joint below the frame are common leak points. When that sealant fails, water gets into the wall or under the frame.
Keep an eye out for these signs:
- Draughts coming in around windows and doors
- Damp patches on the reveal after heavy rain
- White mastic on grey or black frames
- Black, perished sealant on frames
For landlords with property near Hassocks station, cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets.
Comparing quotes
- What the cure time is
- Whether the sealant suits the joint
- What insurance they hold
- Whether VAT is included
Landlords, agents and businesses in Keymer
In hotels, rooms out of use cost money, so the work can be planned room by room around your bookings where we can. We’ve worked in hotels as well as homes and businesses.
We also work for businesses, from offices to washrooms and kitchens. For commercial premises, we can talk through working times when we quote.
Towns and villages near Keymer
What else we do in Keymer
Keymer: your questions answered
Do you cover smaller places like Keymer?
Yes, smaller places are covered as well as towns. Our work covers London and the South East. Just mention lanes, gates or anything else about the route when you book.
Can you help a landlord with a rental near Hassocks station?
Yes, rental work is part of what we do. You can phone 0345 464 0079 or drop us an email with the address and a few details, and we’ll give you a fixed price before any work starts.
Should I try DIY first?
It depends on the job. High-level, external movement and fire-rated joints are professional jobs.
Are you ARBOMaster approved?
Yes. We are an ARBOMaster approved applicator, which is run for the Arbo sealant brand.
Do the sealants smell?
There can be a smell while the sealant cures, but it fades. Opening a window helps.
Can you quote for more than one area?
Yes. More than one area can be quoted together.
Can you do upstairs windows?
Yes, where it’s safe. Higher or awkward frames may need extra access, and we’ll confirm what’s needed.
Can I paint over the new sealant?
That depends on the product. Silicone is not paintable, but some hybrid sealants are. Tell us if you are decorating and we’ll choose accordingly.
What happens if it’s left?
Getting a straight, even bead on an outside frame takes practice, especially upstairs. We cut out properly, back deep gaps and tool every joint neatly, in a sealant suited to the wall. Around Keymer, water from a failed joint in an older home can soak into timber and plaster, and that’s a much bigger job than renewing the sealant.
What you pay reflects the work, not a rough estimate. That is why we ask about the job first.
Why us?
- 4.9 on Google from 180+ five-star reviews
- Arbo and Everbuild products
- Domestic, commercial and hotel work
- Every job guaranteed for a year
Take a look at how sealant jobs are priced or our reviews.