Hertfordshire · England
Sand mastic for sash & case windows in Welwyn, Hertfordshire
We cover Welwyn for traditional burnt sand mastic around sash and case windows and doors in stone and brick. Old sealant removed completely, joints prepared properly and every job guaranteed for a year.
- Gaps round a timber door in stone or brick
- Modern sealant on a period surround
- Open joints round the window box
What sealant work can’t fix
It helps to know what we can’t do:
- Sash cords, weights and draught-proofing of the sashes
- Masonry that needs repairing
- Decayed frames that need repair
If in doubt, ring 0345 464 0079 or email us and we will say what we think.
Surfaces we seal
- Period & listed homes
- Stone surrounds
- Brick reveals
- Timber door frames
- Sash and case windows
- Tenement windows
Sand mastic in Welwyn, done properly
Silicone on a period window often looks wrong and is not always the right material. Sand mastic gives a finish that matches the age of the house and we can swap the silicone for it. We work on brick reveals, stone surrounds and tenement windows, and people most often call us about mastic worn away on windows facing the weather and cracked mastic round a front door frame.
In smaller places like Welwyn, homes range from older cottages to newer houses, with windows to match: timber, uPVC and aluminium. The right sealant depends on the frame and on what it sits in.
Big or small, you get the same one-year guarantee in Welwyn and across Hertfordshire.
- Location
- Welwyn (AL6)
- Wider area
- Hertfordshire
- Guarantee
- 12 months on all our work
- Quotes
- Quoted before any work starts
- Call
- 0345 464 0079
- Last updated
- 26 October 2026
Also in Welwyn
Welwyn: your questions answered
Can you help a landlord with a rental near Welwyn North station?
Yes, rental work is part of what we do. Just phone 0345 464 0079 or drop us an email and tell us about the property, and we will give you a clear quote.
Do you cover Welwyn for sand mastic?
Yes, Welwyn is within the area we cover. We work across London and the South East. You can phone 0345 464 0079 or email us and tell us what needs doing.
What sealant do you use?
Products from Arbo and Everbuild, among others, picked for each joint. We will tell you what we’re using and why.
Can sand mastic be painted?
Sand mastic is normally left unpainted, which is what traditional guidance recommends. Ask us before decorating.
Can you do several jobs on one visit?
Of course. Combining jobs makes good use of the visit, so mention them when you ask for a quote.
Are you insured?
Yes. We are fully insured, and we can confirm the details when we quote.
Can you replace silicone on a period window with sand mastic?
Often, yes. Once the silicone is out and the joint prepared, sand mastic is applied by hand.
Which is right for my windows, sand mastic or modern sealant?
We will talk it through with you. Sand mastic suits many period homes and newer frames suit modern sealant.
What affects the cost of sand mastic
Every job gets its own quote. These are the things that affect it:
- The number and length of the joints
- The type of sealant required
- How easy the joints are to reach
- When we can work, for business premises
Commercial jobs are quoted on the same basis as homes: how much there is to do, how we reach it and what it needs, along with when we can work on site. Call for a quick quote and we’ll explain what it covers.
What we need to know
What to tell us when you ask for a quote:
- The address or postcode of the job
- Whether it has been sealed before
- Whether it’s a home or a business
- What’s wrong with the joints now
Call for a quick quote, or email us if that’s easier. Tell us about the joints that need doing and we will talk you through the work before giving you a price.
Common problems we fix in Welwyn
Water gets into small cracks in the mastic and pushes it out. Exposed elevations generally fail first.
Signs it’s time to call us include:
- Gaps between timber frames and stone or brick
- Mastic worn away on windows facing the weather
- Patchy fillers round a sash window
- Modern sealant on a period surround
If you live in an older home near Parish Church of St Mary, frames set in older brick or stone need a sealant that suits the wall as well as the frame.
Comparing quotes
- Is VAT in the price?
- Whether all the old sealant comes out first
- How the joint is cleaned and prepared
- How the colour is chosen
Should I try it myself first?
If you’ve already had a go yourself, that’s fine. We cut it out and start again, so tell us about it when you ask for a quote.
Some sealant jobs are within reach of a careful DIYer, such as a straightforward joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
How the visit works
There isn’t much for you to do on the day. Point us to the joints and we’ll get on with it. The work itself takes a few hours per window, depending on the condition of the joints from start to finish. A visit to Welwyn is planned like any other: the time, the access and where to park are agreed in advance. If the work is outside, the weather plays a part, as sealant needs a dry surface.
- Each surround is checked first.
- We rake out the old mastic and clean the joint.
- Large voids are packed out.
- We point the joint with sand mastic by hand.
- The finish is dressed neatly.
Before we arrive
- Tell us about any previous sealing or DIY attempts
- Let us know about parking restrictions
- Mention any leaks or damp you’ve noticed
Get a quote
Every job is quoted individually, so the first step is telling us about yours. Simply call 0345 464 0079 or drop us an email and describe the job and send photos if you have them.
Advice
What happens if it’s left?
Cement-based fillers and modern sealants don’t always suit a period surround. Sand mastic is the like-for-like choice and that can be important for listed homes. In an older home around Welwyn, damp from a failed joint can get into timber and plaster, and that is a much bigger job than renewing the sealant.
The cost reflects the work involved, not a rough estimate. That’s why we ask about the job first and agree the price before starting.
Why Welwyn customers choose us
- 12-month guarantee on every job
- Any old sealant cut out fully, not covered over
- Homes, businesses and hotels
- An ARBOMaster approved applicator
Frames and glazing around Welwyn
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. Historic houses like Digswell House (about 0.9 miles south-east) are a reminder that the area around Welwyn has older buildings as well as new. In older buildings, older timber frames in brick or stone need a different approach from a modern uPVC window.
Schools such as Monk's Walk School are buildings too, and the mastic around its windows and doors needs looking after like any other building’s. Rented homes near Welwyn North station change hands often, and cracked sand mastic around sash windows lets in the draughts tenants complain about.
Welwyn is about 2 miles north-west of Welwyn Garden City, in Hertfordshire. Wherever you are in the AL6 postcode area, our applicators can take on sand mastic. Welwyn is one of 381 towns and villages in Hertfordshire we cover. London is on our list too, around 23 miles away.
Every address in AL6 is within our area for sand mastic. That includes homes and businesses on High Street, London Road and Mimram Place and the roads around them. Other places close to Welwyn include Monkswood (1 mile south-east), Ayot St Peter (1 mile south-west), Ayot Green (1 mile south-west), Pottersheath (2 miles north) and Codicote (2 miles north-west). Within a short drive, we also cover Watford (14 miles south-west), Hemel Hempstead (12 miles south-west), Stevenage (6 miles north), St Albans (7 miles south-west), Harpenden (6 miles west) and Hitchin (9 miles north).
Around Welwyn
We work in homes and buildings around Stable Door pub, Danesbury Park and Homerswood Primary and Nursery School and the streets around them. For rail, the closest station is Welwyn North station, about 1.1 miles south-east of the centre. Nearby you’ll also find Queen Elizabeth II Hospital (3.5 miles south) and Datchworth Museum (2.7 miles north-east). For a walk, there’s Mardley Heath.
Work for landlords, hotels and businesses
Failed sealant is one of the commonest items on a check-out report. Several properties can go on one quote.
We also work for businesses, from offices to washrooms and kitchens. For commercial premises, we can talk through working times when we quote.