West Sussex · England
Sand mastic for sash & case windows in Keynor Estate, West Sussex
We cover Keynor Estate for traditional burnt sand mastic around sash and case windows and doors in stone and brick. Old material cut out, joints cleaned and sealed neatly and every job guaranteed for a year.
- Mastic dropping out of the joint
- A silicone bead on a sash window that spoils the look
- Cement or filler used on old window joints that has cracked
How we handle sand mastic in Keynor Estate
For a listed home or one in a conservation area, ask your local planning authority if consent is needed before window work. Like-for-like sand mastic is often the preferred finish. If you’re dealing with mastic round period door frames that has failed and mastic that needs renewing before redecorating, we can help, on brick reveals, period & listed homes and timber door frames alike.
Around Keynor Estate, many homes face open ground, so their windows and doors take the full weather. That exposure dries out and cracks the mastic around frames and sills faster.
You get a one-year guarantee, the same in Keynor Estate as everywhere else we work.
- Location
- Keynor Estate (PO20)
- Wider area
- West Sussex
- Guarantee
- 12 months on all our work
- Price
- A clear quote up front
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
What we do, step by step
A visit follows a simple pattern: we look at the joints together, mask and protect the surrounding surfaces, do the work and clear up. Most jobs take a few hours per window, depending on the condition of the joints. In a small place like Keynor Estate, access is usually the main thing to plan. For outside work, also let us know about exposed walls and any outbuildings involved.
- We check each window surround and the condition of the joint.
- We rake out the old mastic and clean the joint.
- We fill deep gaps so the new mastic isn’t too thick.
- New sand mastic is applied and shaped by hand.
- We finish the mastic to a tidy line.
Preparing for the visit
- Tell us about any previous sealing or DIY attempts
- Where the joints are inside, avoid wetting them before we arrive
- Clear items away from the joints we’re working on
Getting a quote
It all starts with a short chat. Tell us what’s wrong, where it is and how much there is, and we will talk you through what we’d do. When it suits you, call 0345 464 0079 or drop us an email.
Related advice
Nearby places to Keynor Estate
Also in Keynor Estate
Frames and glazing around Keynor Estate
Keynor Estate is within about 1 mile of the coast, where wind-driven rain is a fact of life and, nearer the shore, so is salt air. Both are hard on the mastic around older windows and doors, which can dry out and crack sooner where a building faces the weather. 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.
For site and facilities teams at buildings such as Sidlesham Primary School, the mastic around its windows and doors needs looking after like any other building’s. If you live in an older home near St Mary Our Lady Sidlesham, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint.
Keynor Estate is about 2 miles north of Selsey, in West Sussex. Whether you’re in the middle of Keynor Estate or further out, we cover sand mastic for every kind of property, from flats and houses to offices and hotels. Keynor Estate is one of 371 towns and villages in West Sussex where we work. Our Portsmouth page covers work nearby.
Every address in PO20 is within our area for sand mastic, from the main roads to the quietest streets. That includes homes and businesses on Chalk Lane and Cow Lane and the roads around them. Nearby, we also carry out sand mastic in Sidlesham (1 mile north-east), Street End (1 mile north), Church Norton (2 miles south-east), Sidlesham Common (2 miles north) and Pagham (2 miles east). Further out, we also cover Bognor Regis (5 miles east), Chichester (5 miles north), Littlehampton (12 miles east), Emsworth (8 miles north-west), Rustington (13 miles east) and Angmering (14 miles east).
Landmarks near Keynor Estate
We work in homes and buildings around The Academy and the streets around them. The nearest railway station is Chichester station, roughly 4.4 miles north of the centre. A little further out are Selsey Lifeboat Museum (2.9 miles south) and St Richard's Hospital (5.2 miles north).
For landlords and businesses
Whether it’s one flat or a portfolio, the work is the same standard: old sealant fully removed, joints prepared properly and a one-year guarantee.
We regularly work with letting and managing agents. Send the address, what’s needed and the access arrangements.
Your questions about sand mastic in Keynor Estate
Is Keynor Estate within the area you cover?
Yes. Keynor Estate is within the area we cover, which takes in towns, villages and rural addresses. Our work covers London and the South East. Just mention lanes, gates or anything else about the route when you book.
Does living near the coast affect sand mastic in Keynor Estate?
Near the coast, wind-driven rain and, nearer the shore, salt air make outside sealant work harder. Choosing the right sealant for the frame and wall, laid at the right depth, helps it last.
Is there any odour?
That depends on the sealant. Some products have a noticeable smell, others very little.
Can I paint the new mastic?
The usual advice is to leave sand mastic unpainted. If you’re redecorating the window, ask us first and we’ll talk you through it.
Where do you work from?
Our base is in Crawley, and we cover South East England, London and all of Scotland.
Can old silicone round a sash window be swapped for sand mastic?
Yes. The silicone is cut out and the joint cleaned, then point it with sand mastic.
Does someone need to be in?
It depends on the job. Inside work needs someone to give us access, and for outside work we’ll agree access with you when we book.
Do you offer different sealant colours?
Most of the time, yes. We will explain which colours are available and agree one before we start.
What we are called out for in Keynor Estate
Timber frames move with the seasons. That movement opens up the mastic joint over time.
Keep an eye out for any of the following:
- Modern sealant on a period surround
- Cracked mastic round a front door frame
- Tired mastic found when preparing windows for paint
- Old sand mastic that has cracked, crumbled or fallen out
Letting a property close to Chichester station? Then any sash windows need sound mastic to keep draughts and rain out.
What your quote should include
- What the quote includes, VAT included or not
- What product goes in the joint
- How the surfaces are prepared before sealing
- How the colour is chosen
Can I do it myself?
Some sealant jobs are within reach of a careful DIYer, 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.
The difference is mostly in the preparation and the product. We take joints back to clean, dry surfaces, and the sealant is chosen for how the joint moves and where it is, and the work is guaranteed for a year.
Surface by surface
Sash and case windows
Most of our sand mastic work is on sash windows. Each joint round the box is raked out and renewed.
Stone surrounds
Sand mastic sits naturally against stone. The finish blends with the masonry.
Keeping the joints in good condition
So the new joints stay in good condition:
- Get any rot dealt with first
- Check the mastic when you check the paintwork
- Avoid patching sand mastic with silicone
- Leave the new mastic unpainted
Check the mastic when you check the paintwork. Small cracks are easier to deal with early.
Good mastic helps keep the frame dry. Failed mastic lets water reach the timber and timber that stays wet can rot.
What happens if it’s left?
Not every draught comes from the sashes themselves. Gaps between the frame and the wall can be just as bad, and renewing the mastic closes them. In a small place like Keynor Estate, homes can be exposed to wind and rain, which finds any gap, and older walls, once damp, take a long time to dry.
Combining jobs into one visit is normally more efficient than separate visits, so tell us about everything that needs sealing. You’ll get one clear quote for the whole job.
Why us?
- Homes, businesses and hotels
- Trusted Arbo and Everbuild sealants
- Sanitary silicone with an anti-fungal additive in wet areas
- Tidy, careful work
See our cost guide and what customers say.