Hertfordshire · England
Letchworth Window Mastic
Problem with your window and door frames in Letchworth? We cut out the old, prepare the joints and apply the right sealant, and the work is guaranteed for a year.
- Old mastic that has gone black or come away
- Cracked internal joints between frame and plaster
- A bead that does not match the frame
Window mastic in Letchworth, done properly
Behind a thin line of old mastic there’s sometimes a deep void. Packing it solid with sealant gives a joint that can’t flex, so deep gaps get backing rod first. That way the new bead bonds to the frame and the wall only. We work on composite doors, patio & French doors and aluminium frames, and the jobs we see most are rushed sealant from a window installation and draughts coming in around windows and doors.
Letchworth mixes older streets, where windows have often been replaced, with newer estates fitted with uPVC. In every case, the joint between frame and wall is what keeps water out.
All our work comes with a one-year guarantee, wherever you are in Hertfordshire.
- Where
- Letchworth (SG6)
- Region
- Hertfordshire
- Guarantee
- A year, on every job
- Quote
- A clear price before work begins
- Call
- 0345 464 0079
- Updated
- 26 October 2026
Leave it or put it right?
Resealing frames is a short job: the visit takes a morning for a couple of windows and a door. Wait for damp to appear and there may be plaster and decorating to sort out too. In a family home in Letchworth, a failed seal around a bath or a frame lets water into places you cannot see, such as under the floor, behind a panel or into a wall. Whatever the joint, failed sealant only gets worse.
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.
Why book with us
- Trusted Arbo and Everbuild sealants
- Every job guaranteed for a year
- Sealant colour chosen to suit
- 180+ five-star Google reviews
Common problems we fix in Letchworth
Timber windows bring their own problems. Old mastic gets painted over and cracks under the paint, and the wood moves with damp as well as heat.
Any of these means the joints need attention:
- Black, perished sealant on frames
- Water coming in at the bottom corners of a door
- Cracked or shrunken mastic around the frame
- Gaps between the frame and the inside reveal
Schools such as Hillshott Infant School and Nursery are buildings too, and its window and door frames need their mastic kept sound, just like a home’s.
Before booking anyone
- How long to leave it before use
- What preparation is included
- What product goes in the joint
- How much experience the applicator has
Work for landlords, hotels and businesses
We regularly work with letting and managing agents. Tell us the address, the job and how access works and we’ll quote.
Landlords and letting agents in Letchworth can book us as well as homeowners. Resealing between tenancies is a simple way to keep a property in good order before the next move-in.
Looking after it afterwards
How long the joints last depends on use and care. We suggest:
- Clean frames with a soft cloth and soapy water
- Keep paint off silicone joints
- Avoid harsh chemicals near the mastic
- Ventilate rooms so frames do not stay wet inside
On timber frames, keep the paintwork in good order, since wood that gets wet swells and shrinks more. Paint up to the joint, not over the silicone.
Wet, windy weather is when failed mastic shows itself, but sealant goes on best when frames and walls are dry. Dealing with it when you first notice a crack avoids chasing leaks through the wet months.
Honest limits
It helps to know what we cannot do:
- Faulty window hardware
- Soft or decayed wood in the frame
- Penetrating damp from a failed cavity tray or render
If in doubt, call 0345 464 0079 or drop us an email and we will say what we think before booking.
Surfaces we seal
- Timber windows & doors
- Aluminium frames
- Composite doors
- uPVC windows
- Patio & French doors
- Window sills
FAQs for Letchworth
Do older homes in Letchworth need their sealant replacing?
In most cases, yes, if it hasn’t been done for a while. Sealant doesn’t last for ever, and its life depends on use, cleaning and weather.
Can you help a landlord with a rental near Letchworth Garden City station?
Yes, we work for landlords and agents. Just call 0345 464 0079 or drop us an email and tell us about the property, and we will send you a clear quote.
Can you do the inside joint as well?
Yes. The outside joint keeps the weather out, and the inside joint stops draughts and finishes the reveal. We can do either or both.
Can you do upstairs windows?
Yes, where they can be reached safely. Let us know about access when you ask for a quote and we’ll plan for it.
Where do you work from?
Our base is in Crawley, West Sussex, and we cover South East England, London and all of Scotland.
Do you work for hotels and businesses?
Yes. We have worked for hotels, offices and other businesses, and we’re fully insured.
Can you quote for more than one area?
Yes. More than one area can be quoted together.
How do I get a quote for window mastic in Letchworth?
Every job is different, so each one gets its own quote. To get one, phone 0345 464 0079 or send us an email with a short description of the job.
Nearby places to Letchworth
Other services in Letchworth
Letchworth homes and the weather
Historic houses like Hinxworth Place (about 4.5 miles north) are a reminder that the area around Letchworth 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. 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.
Letting a property close to Letchworth Garden City station? Then sound mastic around windows and doors keeps out the draughts and damp that tenants notice first. If you live in an older home near Church of St Paul, the windows may be timber, sash or later replacements, and each needs the right sealant against the wall.
Letchworth is about 5 miles north of Stevenage, in Hertfordshire. From the centre of Letchworth to the outskirts, window mastic is available for homes and businesses alike. Letchworth is one of 381 places in Hertfordshire we cover for window mastic. There’s also a page for London, roughly 34 miles from Letchworth.
We work across the SG6 postcode area for window mastic. Local streets include Station Road, Willian Church Road and Rowland Way, all of which we cover. Letchworth is on the A505 and B656, which makes it straightforward to reach with everything needed for window mastic. Other places close to Letchworth include Letchworth Garden City (1 mile west), Norton (1 mile north-east), Willian (1 mile south), Walsworth (2 miles south-west) and Poets Estate (2 miles south-west). Further out, we also cover Stevenage (5 miles south), Welwyn Garden City (12 miles south), Harpenden (12 miles south-west), Hitchin (3 miles south-west), Hatfield (15 miles south) and Hertford (14 miles south-east).
Around Letchworth
We work in homes and buildings around Norton School, The Highfield School and Three Magnets pub. There’s a railway station in Letchworth itself: Letchworth Garden City station. Nearby you will also find Fairfield Hospital (1.9 miles north-west) and First Garden City Heritage Museum (within half a mile south). For a walk, there’s Purwell Ninesprings.
Surface by surface
uPVC windows
The frame is cleaned with a product that won’t harm the plastic, then the sealant goes in between frame and wall and tooled smooth.
Timber windows & doors
Where timber has rotted at the joint, it needs repairing first. If we find rot, we will tell you before going ahead, as that’s a job for a joiner.
What happens on the day
We keep the work tidy and contained to the joints we are treating. The job usually takes anything from an hour or two to a full day, depending on how many frames there are, and we explain the cure time before we leave. Parking in a town like Letchworth is generally straightforward, but tell us if there’s a driveway or any restrictions, and mention if the work is upstairs, in a flat or high on the outside.
- First, we go round the frames with you and agree the list.
- The old mastic is cut out and scraped back to clean surfaces.
- Where the gap is deep, backing rod goes in first.
- A flexible exterior sealant is applied in a colour to suit the frame.
- Every joint is tooled smooth and checked before we leave.
How to prepare
- Mention any sign-in or site rules at work premises
- Let us know about earlier repairs to the joints
- For indoor joints, keep the area dry beforehand if you can
Ask for a quote
It all starts with a short chat. Tell us what’s wrong, where it is and how much there is. Whenever you’re ready, call 0345 464 0079 or send us an email.