Hertfordshire · England
Window Mastic in Marshalswick
Mastic around window and door frames, sills and patio doors for Marshalswick, backed by a one-year guarantee. Call for a quick quote.
- Hard, cracked sealant around windows
- Cracked internal joints between frame and plaster
- Whistling draughts around closed windows
Window mastic in Marshalswick, done properly
There are two joints on most windows. Outside, the mastic keeps rain out; the internal joint closes the gap to the plaster and stops draughts. Either or both can be done. We work on uPVC windows, window sills and timber windows & doors, and common reasons people get in touch are water coming in at the bottom corners of a door and old mastic that has gone black or come away.
In smaller places like Marshalswick, 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.
Our work is backed for twelve months, in Marshalswick and everywhere else we cover.
- Place
- Marshalswick (AL4, AL1, AL3)
- Region
- Hertfordshire
- Guarantee
- 12 months on all our work
- Quotes
- A clear quote up front
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
DIY sealant or a professional job?
Sealing over old silicone is the commonest DIY error. Silicone doesn’t stick to old silicone, so it lifts and traps water and mould underneath. All the old material has to come out first.
Overfilling a joint is a classic DIY mistake. A thick, smeared bead looks untidy and doesn’t move well, and the joint depth matters as much as the finish.
How the job changes by surface
Window sills
Sills catch the water running down the glass, so the joints at each end and underneath matter. They’re cut out and resealed with exterior sealant.
Patio & French doors
Water at the foot of a door frame is not always the mastic: blocked drain slots, worn brush seals and threshold details can let water in too. We look for the cause first.
Landlord and commercial work in Marshalswick
Whether it’s one flat or a portfolio, you get the same standard of work: the old material taken out, careful preparation and a 12-month guarantee.
Water getting past a failed joint can damage the building, which is a bigger problem in a rented property. Keeping joints in good order is simple maintenance.
Places near Marshalswick
Other services in Marshalswick
Why it’s worth doing now in Marshalswick
Choosing the product is half the job. Decorators’ caulk and bathroom silicone aren’t designed for outside joints that move. A low-modulus exterior sealant keeps its stretch through hot and cold weather. Around Marshalswick, water from a failed joint in an older home can soak into timber and plaster, and that’s a much bigger job than renewing the sealant.
A failed joint rarely gets cheaper to fix by waiting. If you are not sure whether it needs doing, ring 0345 464 0079 or send us an email for an honest opinion and a quote.
What you get with us
- Full insurance on every job
- A 12-month guarantee on all work
- 4.9 on Google from 180+ five-star reviews
- Colour picked to suit the job
Take a look at how sealant jobs are priced or what customers say.
How to look after the new joints
No joint lasts for ever, but care makes a real difference. Our tips:
- Repaint timber before it’s bare
- Clean frames with a soft cloth and soapy water
- Air rooms to keep condensation down around windows
- Check the mastic once a year
On timber frames, keep the paintwork in good order, because bare, wet timber moves more and pulls at the joint. Paint up to the joint, not over the silicone.
Signs to watch for: split or missing mastic, gaps, damp patches inside or black mould on the reveal. If you notice one, it’s time to get the joint looked at.
Marshalswick questions
Is Marshalswick within the area you cover?
Yes, Marshalswick is covered. We work across London and the South East, and smaller places are part of that. Longer journeys are simply planned in advance.
Can you do window mastic in Marshalswick?
Yes, Marshalswick is within the area we cover. We work across London and the South East. Just ring 0345 464 0079 or send us an email with a few details of the job.
How long should I leave it?
Different products cure at different speeds, so please follow the time we give you.
Is it OK to seal over old sealant?
No. New silicone won’t bond to old silicone, and anything trapped underneath, including mould and water, stays there. We remove it all first.
Do you take out the old sealant first?
Always. Sealing over old sealant is the main reason resealing fails early, so we never do it.
Should I try DIY first?
That depends on the joint. High-level, external movement and fire-rated joints are professional jobs, while a short indoor joint may be within reach.
Can you match the sealant to my frames?
Yes. We can use white, brown, anthracite grey, black or clear, so the joint suits the frame.
Where do you work from?
We are a Crawley-based firm. Our area covers South East England, London and Scotland.
What window mastic looks like in Marshalswick
Compared with the north and west, the South East gets less rain, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. Historic houses like Batchwood Hall (about 2 miles west) are a reminder that the area around Marshalswick has older buildings as well as new. Where a home is older, older timber frames in brick or stone need a different approach from a modern uPVC window.
Rented homes near St Albans station change hands often, and renewing tired window mastic between tenants heads off draught and damp complaints. Homes close to Saint Mary's include some older properties, and the joint between an old wall and a newer frame is normally the first place rain gets in.
Marshalswick is about 1 mile north-east of St Albans, in Hertfordshire. Homes, rented property, offices and hotels in Marshalswick is covered for window mastic. Every job comes with our 12-month guarantee. Across Hertfordshire, we cover 381 places, Marshalswick among them. We also work in London, about 21 miles from Marshalswick.
We cover every part of the AL4, AL1 and AL3 postcode area for window mastic and the streets around it. Streets in the area include Milvus Road, Jersey Lane and Sandpit Lane, all of which we cover. We also cover the places around Marshalswick: Sandridge (1 mile north), Bernards Heath (1 mile west), St Albans (1 mile south-west), Childwick Green (2 miles north-west) and Sopwell (2 miles south-west). Within a short drive, we also cover Watford (8 miles south-west), Hemel Hempstead (7 miles west), Stevenage (11 miles north-east), Welwyn Garden City (5 miles north-east), Harpenden (4 miles north-west) and Hitchin (13 miles north).
Near you in Marshalswick
Typical jobs here are in homes near The Baton pub, Sandringham School and Clarence Park and the streets around them. The closest station to Marshalswick is St Albans station, roughly 1.3 miles south-west of the centre. Nearby you’ll also find St Albans Musical Museum (0.8 miles south-west) and The Maltings (1.6 miles south-west). The countryside around Marshalswick includes The Wick Local Nature Reserve and Verulamium Lake.
When to call us in Marshalswick
Joints that are too thin or too deep fail early. A thin smear across a wide gap has nothing to it, while a joint packed solid can’t stretch. That is what backing rod is for.
The most common problems we see are:
- Draughty joints inside around the window
- Draughts coming in around windows and doors
- Old mastic that has gone black or come away
- A bead that does not match the frame
Managing a site like St John Fisher Roman Catholic Primary School? Then larger buildings have plenty of frames, and the mastic around each one ages.
Comparing quotes
- Whether they’re fully insured
- Whether VAT is included
- What guarantee comes with the work
- Which colour the sealant will be
What happens on the day
On the day, we look over the joints with you first, so there are no surprises. Surfaces next to the work are protected before any work begins. The work generally takes most of a day for a typical house, less for a few frames. In a smaller place like Marshalswick, parking is seldom the issue; lanes, gates and long drives are worth mentioning. If the job is outside, tell us about side access and how high the joints are.
- First we look at every frame and agree the list.
- The old mastic is cut out and the surfaces cleaned back.
- Deep gaps are filled with backing rod to set the depth.
- A flexible, weatherproof sealant is applied in a colour to suit the frame.
- We clear up and check every joint is fully closed.
How to prepare
- Try not to wet indoor joints just before the visit
- Tell us about any previous sealing or DIY attempts
- Tell us if parking is tricky
Get a quote
A good description makes for an accurate quote. Let us know the location, the problem and roughly how many joints, and add photos by email if you can.