Hertfordshire · England
Sand Mastic in North Mymms
We cover North Mymms 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 a one-year guarantee.
- Modern sealant on a period surround
- Cement or filler used on old window joints that has cracked
- Open joints round the window box
How we handle sand mastic in North Mymms
Old sand mastic cracks, crumbles and falls out over time, leaving gaps round the window. We rake it out and renew it and tidies the surround. We are often asked to deal with gaps where the frame meets the masonry and mastic that needs renewing before redecorating, across sash and case windows, timber door frames and brick reveals.
Around North Mymms, many homes face open ground, so their windows and doors take the full weather. That exposure dries out and cracks the mastic around frames and sills faster.
Our work is backed for twelve months, and the guarantee is the same wherever you are.
- Where
- North Mymms (AL9)
- Region
- Hertfordshire
- Guarantee
- A year, on every job
- Price
- Quoted before any work starts
- Phone
- 0345 464 0079
- Last updated
- 26 October 2026
What we cannot put right
Sealant is not the answer to every problem, and we’d rather say so up front. Sealant will not put right:
- Broken panes
- Masonry that needs repairing
- Sashes that rattle, stick or won’t open
If in doubt, call 0345 464 0079 or send us an email and we’ll say what we think.
Surfaces we seal
- Tenement windows
- Period & listed homes
- Sash and case windows
- Timber door frames
- Brick reveals
- Stone surrounds
How to look after the new joints
Simple care keeps the joints in good condition. We recommend:
- Plan mastic work ahead of painting
- Avoid patching sand mastic with silicone
- Ask the planning authority about consent for listed or conservation-area homes
- Ask a joiner to look at soft timber first
Make sure water drains away from the window surround. Water sitting against the mastic shortens its life.
Renewing mastic before redecorating saves doing it twice. Paint over cracked mastic only covers it up.
Leave it or put it right?
If you are redecorating, renew the mastic first. Paint over cracked mastic will not stop the gaps, and the new mastic is traditionally left unpainted. Where a wall is exposed, as many are in small places like North Mymms, wind-driven rain gets into any failed joint, and older walls, once damp, take a long time to dry.
Instead of a standard rate, we look at what your job involves: how many joints, what’s in them now and how we reach them. The price is agreed before we begin.
What you get with us
- Trusted Arbo and Everbuild sealants
- Tidy, careful work
- We are fully insured
- Sanitary silicone with an anti-fungal additive in wet areas
See our cost guide or customer reviews.
Places near North Mymms
Other services in North Mymms
The process
Good joint work is mostly preparation, so that is where we spend the time. Joints are cleaned back and dried before anything new goes in. All told, the work takes anything from a few hours to a full day, depending on how many windows. Somewhere like North Mymms needs a little journey planning: tell us about narrow lanes, gates, long drives and where we can park. Everything for the job comes with us, so a second trip is avoided where possible.
- 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.
- We apply the mastic by hand and shape it.
- The surface is finished to suit the stone or brick.
Before we arrive
- Let us know about stairs, lifts or work at height
- For business premises, tell us about site rules or sign-in
- Mention any leaks or damp you’ve noticed
Get a quote
The more we know about the job, the more useful the quote. Tell us where the job is, what’s wrong and how much there is, and email photos if that is easy.
Related advice
North Mymms questions
Will you come out to North Mymms?
Yes, smaller places are covered as well as towns. Our work covers London and the South East. Just mention lanes, gates or anything else about the route when you book.
Do you cover North Mymms for sand mastic?
Yes, North Mymms 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.
I’m a tenant. Can you help?
Yes. Check with your landlord; we can send the quote to them too.
Do I need to be at home?
If the work is inside, we need someone to let us in. After that, you can carry on with your day.
Do you offer different sealant colours?
Most of the time, yes. We will tell you which colours the right product comes in.
Where are you based?
Our base is in Crawley, and we work across South East England, London and Scotland.
How long does sand mastic take to go off?
A skin forms quite soon, but full hardening takes longer. We will tell you what to expect for your job.
Do you work for letting agents?
Yes. We work for homeowners, landlords, letting agents, businesses and hotels.
Do you need sand mastic in North Mymms?
Timber swells and shrinks with the weather. That movement opens up the mastic joint over time.
These are the problems we are asked about most:
- Open joints round the window box
- Mastic worn away on windows facing the weather
- Gaps round a timber door in stone or brick
- Old sand mastic that has cracked, crumbled or fallen out
If you live in an older home near Church of St Mary the Virgin, frames set in older brick or stone need a sealant that suits the wall as well as the frame.
Comparing quotes
- How the surfaces are prepared before sealing
- Is the old sealant removed completely?
- How long the guarantee is
- Is VAT in the price?
For landlords and businesses
We regularly work with letting and managing agents. Send the address, what’s needed and the access arrangements and we will quote.
Failed sealant is one of the commonest items on a check-out report, and it’s easy to sort out between tenants. We can quote for more than one property at once.
What sand mastic looks like in North Mymms
Rainfall in the South East is lower than in much of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast. Historic houses like Wyllyotts Manor (about 2 miles south-east) are a reminder that the area around North Mymms has older buildings as well as new. In older buildings, older frames set in brick or stone need a sealant that suits them, and sometimes that’s traditional sand mastic.
Rented homes near Brookmans Park station change hands often, and cracked sand mastic around sash windows lets in the draughts tenants complain about. If you look after a building such as Brookmans Park Primary School, the mastic around its windows and doors needs looking after like any other building’s.
North Mymms is about 2 miles north-west of Potters Bar, in Hertfordshire. Anywhere in AL9, we can carry out sand mastic at your property. North Mymms is one of 381 places in Hertfordshire where we work. We also work in London, about 16 miles from North Mymms.
We cover every part of AL9 for sand mastic. Sand mastic is available to properties on St Mary's Church Road, Abdale Lane and Warrengate Road and the roads around them. If you’re just outside North Mymms, we cover Welham Green (1 mile north), Colney Heath (2 miles north-west), Sleapshyde (3 miles north-west), Hatfield (3 miles north) and Shenleybury (3 miles west). Larger places within reach include Watford (9 miles south-west), Hemel Hempstead (11 miles west), Stevenage (13 miles north), St Albans (5 miles north-west), Welwyn Garden City (6 miles north) and Harpenden (9 miles north-west).
Near you in North Mymms
In North Mymms, that means homes and buildings near Chancellor's School, North Mimms Park and The Old Maypole Public House. The closest station to North Mymms is Brookmans Park station, roughly 0.7 miles east. Well-known places in the area include Shenley Hospital (3.5 miles south-west) and Potters Bar Museum (2 miles south-east). Green spaces nearby include Furzefield Wood and Lower Halfpenny.
Surface by surface
Brick reveals
Sand mastic is also used where timber frames meet brick. It gives a traditional finish.
Tenement and terrace windows
Windows above ground floor need the right access. Tell us the height and we’ll confirm what’s needed.