Hertfordshire · England
The Folly Sand Mastic
Sand mastic in The Folly from a team with over 20 years’ experience. 180+ five-star Google reviews and a 4.9 rating.
- Draughts and rain around sash boxes
- Crumbling sand mastic round a window
- Failed mastic on an exposed elevation
Sand mastic for homes and businesses in The Folly
If your home is listed or in a conservation area, check with your local planning authority if consent is needed before window work. Like-for-like sand mastic is often the preferred finish. Typical jobs include old cement repairs round a window that have failed and gaps round a timber door in stone or brick, across sash and case windows, brick reveals and tenement windows.
Outdoor sealant needs dry, clean surfaces, so work on frames around The Folly is planned for dry weather. Tell us about access to every side of the house, including upper-floor windows.
All our work comes with our one-year guarantee.
- Place
- The Folly (AL4)
- Wider area
- Hertfordshire
- Cover
- 12 months on all our work
- Quotes
- A clear price before any work starts
- Call
- 0345 464 0079
- Updated
- 26 October 2026
Can I do it myself?
Overfilling a joint is a classic DIY mistake. A heavy bead looks messy and copes badly with movement, and the joint depth matters as much as the finish.
The biggest DIY mistake is sealing over old sealant. New silicone will not bond to old, so it peels away and traps moisture behind it. All the old material has to come out first.
Also near The Folly
Other services in The Folly
Surface by surface
Stone surrounds
The stone is treated with care while raking out the old mastic.
Period and listed homes
Materials matter on listed and conservation-area homes. Sand mastic is often the preferred finish.
The Folly homes and the weather
Historic houses like Shaw's Corner (about 2 miles north-east) are a reminder that the area around The Folly has older buildings as well as new. Where a home is older, older frames set in brick or stone need a sealant that suits them, and sometimes that’s traditional sand mastic. The South East is one of the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
If you live in an older home near St Helen's Church, the joint between an old wall and a newer frame is generally the first place rain gets in. Rented homes near Harpenden station change hands often, and older sash windows in a rental need their mastic kept sound to keep the weather out.
The Folly is about 2 miles east of Harpenden, in Hertfordshire. Homes, rented property, offices and hotels in The Folly can book us for sand mastic. The work is guaranteed for a year. The Folly is one of 381 places in Hertfordshire where we work for sand mastic. Our London page covers work nearby.
Every address in AL4 is covered for sand mastic. That includes homes and businesses on Folly Fields and Lower Luton Road. Neighbouring places we cover for sand mastic include Lea Valley (1 mile west), Amwell (1 mile south), Mackerye End (1 mile north-west), Blackmore End (1 mile north) and Batford (1 mile west). Further out, we also cover Watford (11 miles south), Hemel Hempstead (8 miles south-west), Stevenage (8 miles north-east), St Albans (5 miles south), Welwyn Garden City (5 miles east) and Hitchin (9 miles north).
Local landmarks in The Folly
In The Folly, that means homes and buildings near Sir John Lawes School and The Cherry Trees pub and the streets around them. The nearest railway station is Harpenden station, about 2 miles west of the centre. Other landmarks nearby include St Albans City Hospital (4.2 miles south) and Harpenden Museum (2.2 miles west). For a walk, there’s Wheathampstead Local Nature Reserve.
Do you need sand mastic in The Folly?
Paint, silicone or cement used over old mastic causes problems. They do not suit the joint, and they usually need raking out.
Any of these means the joints need attention:
- Old sand mastic that has cracked, crumbled or fallen out
- Weathered mastic on the most exposed windows
- Cracked mastic round a front door frame
- Draughty sash windows at the surround
Managing a site like St Helen's Church of England Primary School? Then larger buildings have plenty of frames, and the mastic around each one ages.
What to look for in a quote
- What preparation is included
- What the cure time is
- Is the old sealant removed completely?
- What happens if they find a problem under the old sealant
How the visit works
There isn’t much for you to do on the day. Show us the job and we will take it from there. The work itself takes a few hours per window, depending on the condition of the joints. Somewhere as small as The Folly, access is often the only tricky part. For outside work, also let us know about exposed walls and any outbuildings involved.
- We check the window surrounds and agree which joints need renewing.
- Old, loose mastic is raked out and the joint cleaned.
- We pack any deep gaps so the mastic sits at the right depth.
- The mastic is mixed, pressed into the joint by hand and shaped.
- The finish is dressed so it sits neatly against the stone or brick.
Getting ready for the visit
- Mention any leaks or damp you’ve noticed
- Clear the area around the work
- Let us know about parking restrictions
How to get a quote
To get a quote, phone 0345 464 0079 or drop us an email with the location and a short description of the problem. You will have a clear quote before we start.
Related advice
Work for landlords, hotels and businesses
A neglected joint can let water reach the structure, which matters even more when someone else lives there. Resealing at the right time is simple maintenance.
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.
Questions from The Folly
Is The Folly in your area for sand mastic?
Yes, The Folly is within the area we cover. We work across London and the South East. You can ring 0345 464 0079 or drop us an email and tell us what needs doing.
Is The Folly within the area you cover?
Yes, we do. Our work covers London and the South East, and smaller places are part of that. Longer journeys are simply planned in advance.
Do you take out the old sealant first?
Yes, every time. New sealant won’t bond properly to old, so the joint is cleaned back first.
Is consent needed for window work on a listed home?
Yes, it’s worth checking. Your local planning authority can say if consent is needed for work on a listed home or in a conservation area.
Can you replace silicone on a period window with sand mastic?
Usually, yes. Once the silicone is out and the joint prepared, sand mastic is applied by hand.
What do you need from me for a quote?
The location, the problem and the rough size of the job. If you can, email a few photos.
Can you quote for more than one area?
Yes, we can. More than one area can go on one quote.
Are you fully insured?
Yes. We are fully insured, and we can confirm the details when we quote.
Quotes for sand mastic in The Folly
Some jobs are bigger than they look, and some smaller. The main factors:
- Mould in or behind the old joints
- How many rooms, windows or areas are involved
- When we can work, for business premises
- The old material and how stubborn it is
There are no prices on our website, because the cost depends so much on the job itself. Call for a quick quote and we will talk you through it.
Helping us quote
When you contact us, these details help:
- Access, such as stairs, a lift or height
- How many joints, rooms or windows are involved
- What the problem is, such as mould, gaps, leaks or cracking
- The address or postcode of the job
Quotes start with a quick conversation. Describe the problem, the location and the size of the job, and we will explain how we’d tackle it. Whenever you are ready, ring 0345 464 0079 or email us.
Aftercare tips
Good habits help new joints last longer. Our tips:
- Look over the window mastic once a year
- Make sure water runs off the sill
- Sort the mastic before the decorators arrive
- Avoid heavy scraping on the mastic joint
Look at the mastic when you look over the windows. Small cracks are easier to deal with early.
Sound mastic protects the frame. Once it fails, water can sit against the timber, which can lead to rot.