Greater London · England
New-build mastic & snagging in High Barnet, Greater London
Problem with your new-build sealant joints in High Barnet? We cut out the old, prepare the joints and apply the right sealant.
- Untidy sealant flagged on a snagging list
- Gaps opening as the house dries out and settles
- Sealant work across a run of new homes
DIY versus a professional finish
If you’re set on DIY, put the effort into preparation: remove every trace of old sealant, clean and dry the joint, and follow the product’s cure time. If it doesn’t work out, we can still put it right.
Too much sealant is as bad as too little. A heavy bead looks messy and copes badly with movement, and getting the depth right matters as much as the look.
About our new build mastic in High Barnet
Failed shower seals, gaps along the skirting and messy beads are common items on a new-home snagging list. While the builder’s snagging or warranty period runs, report it to them first, and if it isn’t put right, get in touch with us. Common call-outs are for skirting joints opening in the first winter and plot mastic for developers ahead of handover, on windows & doors, kitchens and show homes.
Much of London’s new housing is flats in larger developments. In a new development, snags are often reported through the developer or the managing agent, and shower seals that fail early, skirting joints that open up and gaps at thresholds are all common snags.
The work is covered for a year after we finish. If anything is not right with it, ring 0345 464 0079 or email us.
- Where
- High Barnet (EN5)
- Region
- Greater London
- Guarantee
- A year, on every job
- Price
- A clear price before we start
- Phone
- 0345 464 0079
- Updated
- 26 October 2026
What affects the cost of new build mastic
Every job gets its own quote. This is what makes a difference:
- Whether the work is at height
- Mould in or behind the old joints
- How many rooms, windows or areas are involved
- The number and length of the joints
The cost reflects the work involved, not a rough estimate. That is why we ask about the job first and send you a clear quote before work begins.
Asking for a quote
The more you tell us, the more accurate the quote. When you ask for a quote, tell us:
- The rough size of the job
- How we’d reach the joints
- Where the property is
- Whether it’s a home or a business
It all starts with a short chat. Describe the problem, the location and the size of the job, and we will talk you through what we’d do. Whenever you’re ready, ring 0345 464 0079 or drop us an email.
Landlord and commercial work in High Barnet
A neglected joint can let water reach the structure, which is a bigger problem in a rented property. Keeping joints in good order is simple maintenance.
Letting agents often deal with us directly. Tell us the address, the job and how access works and we’ll quote.
Why deal with it now?
Sealant done properly at handover means fewer callbacks. Snagging visits for failed sealant cost time on every plot, and they’re avoidable with good preparation. In a London flat, a failed joint rarely stays your problem alone: water from a shower or window joint can reach the flat below, and gaps in fire-stopping matter to everyone in the building.
What it costs depends on the size of the job, how much old material has to come out and how easy the joints are to reach. We give a clear quote before we start, so you know where you stand.
Why choose Mr Mastic in High Barnet
- Homes, businesses and hotels
- Any old sealant cut out fully, not covered over
- Fully insured
- 20+ years of sealant experience
When to call us in High Barnet
Not every new-build joint gets the right sealant: caulk where water collects, or a rigid product on a moving joint. Neither lasts long.
The most common problems we see are:
- Plot mastic for developers ahead of handover
- New-build shower sealant that has already split
- Gaps opening as the house dries out and settles
- Messy sealant that spoils new finishes
For new homes near Hadley Wood station, it’s worth checking the sealant early, while snags are still fresh.
Comparing quotes
- How long to leave it before use
- What preparation is included
- How much experience the applicator has
- Whether the sealant suits the joint
High Barnet: your questions answered
Is High Barnet in your area for new build mastic?
Yes, High Barnet is within the area we cover. We work across London and the South East. Just call 0345 464 0079 or drop us an email with a few details of the job.
Is parking a problem for a job in High Barnet?
London parking needs a little planning, so let us know about permits, bays or a driveway when you book. The visit is then planned around what’s available.
Is there any odour?
It depends on the product. Some products have a noticeable smell, others very little, and any smell fades as they cure.
What do you need from me for a quote?
Where the job is, what the problem is and roughly how big it is. If you can, email a few photos.
Can you work on commercial sites?
Yes, regularly. We can plan bigger jobs in stages to suit the site.
Can you do several jobs on one visit?
Yes, and it often makes sense. Combining jobs makes good use of the visit.
Can you reseal over the builder’s sealant?
No. New silicone won’t bond to old silicone, so it soon lifts and traps water. We cut the old bead out completely.
Are you fully insured?
Yes. We are fully insured, and we can confirm the details when we quote.
How the visit works
Most of a good job is in the preparation, so that’s where we spend the time. Joints are cleaned back and dried before anything new goes in. In total, it usually takes a few hours in a single home. In a London area like High Barnet, the main things to plan are parking and access: let us know about parking, the floor we will be working on and any lift or shared entrance.
- First, the list of joints is agreed from your snagging sheet or plot schedule.
- Every bit of the old builder’s sealant is cut out.
- Joints are vacuumed and cleaned of building dust.
- We prime where needed and apply a sealant suited to each joint.
- Each bead is tooled and the cure times explained.
Before we arrive
- Clear the area around the work
- Plan for the work area to be out of bounds to pets and children
- On commercial sites, let us know about site rules
Ask for a quote
For a quick quote, get us on the phone, or send an email if you’d rather. Describe what needs sealing and we’ll explain what’s involved and give you a clear quote.
Read more
Keeping the joints in good condition
Aftercare is simple:
- Avoid running a DIY bead over the old one
- Avoid scourers and strong chemicals on sealant
- Do not wait for the house to settle if water is getting through
- Look at the sealant regularly in the first couple of years
Keep the bathroom ventilated, especially in the first year. Run the fan or open a window after bathing.
Report failed sealant to the builder while you are in the snagging period. After that, putting it right may fall to you, so raise it early.
New build mastic in High Barnet: local notes
Much of London’s new housing is flats in larger developments, where snags may need reporting through the developer or the managing agent. London and the South East are among the drier parts of the UK, but outside sealant still needs a dry, clean surface, so outdoor work is planned around the forecast.
As a London address, High Barnet can be tricky for parking: let us know about parking bays, permits or a driveway.
High Barnet is about 1 mile north-west of Barnet, in Greater London. Every kind of property in High Barnet is covered for new build mastic. Every job comes with our one-year guarantee. Our Greater London coverage runs to 764 places, High Barnet among them. Our London page covers work nearby (12 miles or so).
Work in EN5 is quoted and booked the same way as anywhere else. Whether your property is on Byng Road, Park Road and Kings Road or a nearby road, we can help. High Barnet sits on or near the A1081, so getting to you is simple. We also cover Hadley (1 mile east), Arkley (1 mile south-west), Kitts End (1 mile north), Totteridge (1 mile south) and Rowley Green (2 miles west). We also work in nearby towns such as London (12 miles south-east), City of Westminster (10 miles south), Marylebone (10 miles south), Kensington (11 miles south), St Pancras (10 miles south-east) and Shoreditch (11 miles south-east).
Local landmarks in High Barnet
We work in homes and buildings around Susi Earnshaw Theatre School, The White Lion pub and Queen Elizabeth's School and the streets around them. For rail, the closest station is Hadley Wood station, roughly 1.6 miles north-east. Nearby you will also find Spires Shopping Centre (within half a mile east) and Barnet General Hospital (0.5 miles south-west). Not far away are Barnet Countryside Centre and Darland's Lake.