Surrey · England
Sand mastic for sash & case windows in Knaphill, Surrey
We cover Knaphill 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.
- Window mastic to renew ahead of painting
- Gaps round a timber door in stone or brick
- Open joints round the window box
How it works
At the end, we look at the finished work together and tell you how long to leave it. The visit itself generally takes a few hours for a single window, longer for several, depending on how much there is to do. For a job in Knaphill, we agree the time, the access and parking before the day. If the work is outside, the weather plays a part, as sealant needs a dry surface.
- First we agree which joints need doing.
- We remove the old, loose mastic.
- Deep gaps are packed so the mastic sits at the right depth.
- The sand mastic is mixed and pressed into the joint by hand.
- We dress the finish so it sits neatly against the masonry.
Before we arrive
- Tell us about any water getting in
- Mention if the joints have been sealed before
- Try not to wet indoor joints just before the visit
Get a quote
To get a quote, call 0345 464 0079 or send us an email with the location and a short description of the problem. You will have a clear quote before we start.
Read more
Sand mastic for homes and businesses in Knaphill
For a listed home or one in a conservation area, ask your local planning authority whether consent is needed for work to windows. Sand mastic is often favoured as a like-for-like material. We work on sash and case windows, stone surrounds and brick reveals, and people most often call us about patchy fillers round a sash window and gaps where the frame meets the masonry.
In smaller places like Knaphill, homes range from older cottages to newer houses, with windows to match: timber, uPVC and aluminium. Each frame material needs the right sealant against the right wall.
Whatever the size of the job, it’s backed by our one-year guarantee in Knaphill and across Surrey.
- Location
- Knaphill (GU21, GU24)
- Wider area
- Surrey
- Guarantee
- 12 months on all our work
- Quote
- A clear quote up front
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Knaphill: your questions answered
Do you work for landlords with property near Brookwood station?
Yes, we work for landlords and agents. You can phone 0345 464 0079 or send us an email with the address and a few details, and we’ll give you a fixed price before work begins.
Can you do sand mastic in Knaphill?
Yes, Knaphill is within the area we cover. Our work covers London and the South East. You can phone 0345 464 0079 or email us and tell us what needs doing.
Can you quote for more than one area?
Yes. Tell us about everything you’d like done and we will quote it together.
How much does sand mastic cost in Knaphill?
We don’t publish prices, because the cost depends on the job: its size, the old material, access and the product needed. We agree the price before any work begins.
Do you do commercial work?
Yes, regularly. Larger jobs can be planned room by room or area by area to suit the site.
Do you have insurance?
Yes. We’re fully insured for every job we do.
Where is Mr Mastic based?
We are a Crawley-based firm, with over 20 years’ experience. We work across South East England, London and Scotland.
Do you take out the old sealant first?
Yes. We cut out all the old sealant and clean the joint before applying anything new.
How to look after the new joints
To keep the joints looking good and working properly:
- Have rotten timber repaired before new mastic goes in
- Go gently near the mastic when preparing windows
- Avoid patching sand mastic with silicone
- Sort the mastic before the decorators arrive
When preparing windows for paint, take care around the mastic. Hard scraping can loosen it.
Once mastic starts to crumble, rain gets in. That water can reach the timber frame and the wall so early renewal protects both.
Do you need sand mastic in Knaphill?
Decorating can disturb tired mastic. Many people find it crumbling when they prepare the windows, which is a good time to renew it.
Common reasons people contact us are:
- Mastic round period door frames that has failed
- Mastic dropping out of the joint
- Cement or filler used on old window joints that has cracked
- Mastic that needs renewing before redecorating
Letting a property close to Brookwood station? Then older sash windows in a rental need their mastic kept sound to keep the weather out.
What to look for in a quote
- Whether you can choose the colour
- How the joint is cleaned and prepared
- What happens if they find a problem under the old sealant
- Whether VAT is included
Why it’s worth doing now in Knaphill
Before painting the windows, it pays to renew the mastic. Paint over cracked mastic will not stop the gaps and traditional guidance is to leave the new mastic unpainted. In an older home around Knaphill, damp from a failed joint can get into timber and plaster, which is far harder to put right than the sealant itself.
Combining jobs into one visit is usually more efficient than separate visits, so it’s worth mentioning everything you’d like done. We’ll send you a clear quote for the lot.
What you get with us
- More than 20 years in sealant work
- We never seal over old sealant
- ARBOMaster approved applicator
- Fully insured
Take a look at what affects the cost and customer reviews.
Knaphill homes and the weather
London and the South East are among the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
Schools such as Knaphill School are buildings too, and larger buildings have plenty of frames, and the mastic around each one ages. Homes close to St Hugh of Lincoln's Church include some older properties, and the windows may be timber, sash or later replacements, and each needs the right sealant against the wall.
Knaphill is about 2 miles west of Woking, in Surrey. We provide sand mastic to householders, landlords and businesses in Knaphill and the surrounding area, as part of our work across Surrey. Our Surrey coverage runs to 395 places, Knaphill among them. Our Reading page covers work nearby, about 18 miles away.
Every address in GU21 and GU24 is within our area for sand mastic, from the main roads to the quietest streets. If you need sand mastic at a property on Wood Lane, High Street and Barnby Road or anywhere close by, our applicators can take on the job. Other places close to Knaphill include Bisley (1 mile north-west), Sheet's Heath (1 mile south-west), Castle Green (1 mile north), Brookwood (1 mile south-west) and Penny Pot (1 mile north). Within a short drive, we also cover Guildford (5 miles south), Camberley (5 miles west), Epsom (15 miles east), Farnham (11 miles south-west), Egham (8 miles north) and Walton-on-Thames (10 miles north-east).
Near you in Knaphill
Around Knaphill, our work takes us to homes and buildings near Anchor Inn, The Winston Churchill School A Specialist Sports College and Brookwood Lye. The closest station to Knaphill is Brookwood station, roughly 1.4 miles south-west. A little further out are The Peacocks (2.5 miles east) and Brookwood Hospital (less than half a mile south). Open spaces near Knaphill include Brookwood Lye.
Nearby places to Knaphill
More services for Knaphill
How the job changes by surface
Timber door frames
Round a period front door, sand mastic gives the right look.
Brick reveals
Sand mastic is also used where timber frames meet brick. It gives a traditional finish.
When something else is needed
Before you book, it’s worth knowing the limits too:
- Putty and glazing repairs
- Rotten sashes, sills or window boxes (a joiner’s job)
- Sashes that rattle, stick or will not open
If you’re not sure, just ring 0345 464 0079 or email us and we’ll give you a straight answer.
Where we work in Knaphill
- Period & listed homes
- Stone surrounds
- Timber door frames
- Sash and case windows
- Brick reveals
- Tenement windows
DIY versus a professional finish
The biggest DIY mistake is sealing over old sealant. Silicone doesn’t stick to old silicone, so it peels away and traps moisture behind it. All the old material has to come out first.
Not every job suits DIY: high-level joints, fire-rated gaps, external movement joints and big jobs need the right product, the right access and the right method.