Greater London · England
St Johns Sand Mastic
Traditional burnt sand mastic around sash and case windows and doors in stone and brick in St Johns, with a one-year guarantee on every job. Call for a quick quote.
- Open joints round the window box
- Draughty sash windows at the surround
- Crumbling sand mastic round a window
DIY sealant or a professional job?
Some sealant jobs are within reach of a careful DIYer, such as a straightforward joint indoors. Where it goes wrong is sealing over the old bead, working on a wet joint or overloading the gap.
Sealing over old silicone is the commonest DIY error. Silicone does not stick to old silicone, so it peels away and traps moisture behind it. Everything old must be removed first.
About our sand mastic in St Johns
On many period windows, sand mastic looks right and suits the building. Newer frames usually get a flexible sealant instead and we’ll explain which is best for yours. We work on tenement windows, sash and case windows and stone surrounds, and people most often call us about draughts and rain around sash boxes and failed mastic on an exposed elevation.
From mansion-block windows to modern glazing in new flats, London has every kind of frame. The mastic around them dries out and cracks with age, which is when draughts and damp patches appear in homes in St Johns.
The work is guaranteed for twelve months. If there’s a problem with our work within the year, let us know and we’ll sort it.
- Place
- St Johns (SE13, SE10, SE8)
- Wider area
- Greater London
- Cover
- One year on every job
- Price
- Quoted before any work starts
- Call
- 0345 464 0079
- Updated
- 26 October 2026
What we can’t put right
We will always be straight with you, so here’s what sealant can’t fix:
- Decisions on consent for listed homes
- Putty and glazing repairs
- Timber that has rotted
If you’re not sure, just call 0345 464 0079 or drop us an email and we’ll give you a straight answer.
Surfaces we seal
- Stone surrounds
- Period & listed homes
- Brick reveals
- Sash and case windows
- Timber door frames
- Tenement windows
Keeping the joints in good condition
To keep the joints looking good and working properly:
- Keep sills and gutters clear so water drains away
- Sort the mastic before the decorators arrive
- Don’t run silicone over sand mastic
- Ask the planning authority about consent for listed or conservation-area homes
Don’t touch or press the mastic while it hardens. It forms a skin fairly soon, but takes longer to harden fully.
Small cracks are a sign the mastic is ageing. It’s easier to renew it before it drops out.
What we do, step by step
All our tools and materials come with us in the van. After a quick look at the joints together, the area is protected and the work begins. Most jobs take a few hours for a single window, longer for several. In a London area like St Johns, the main things to plan are parking and access: tell us about permits, visitor bays or off-street space, which floor we’re working on and whether there’s a lift.
- First, we look at the surrounds with you and agree what needs doing.
- The loose and crumbling mastic is raked out and the joint cleaned.
- Deep voids are packed so the mastic is the right thickness.
- Sand mastic is mixed and applied by hand, then shaped to the joint.
- The mastic is finished to sit tidily against the stone or brick.
Before we arrive
- Mention any leaks or damp you’ve noticed
- Keep pets and children clear of the area while we work
- Mention if the joints have been sealed before
Get a quote
For sand mastic in St Johns, phone 0345 464 0079 or drop us an email. Tell us what the problem is and where, and we’ll agree the price before any work begins.
Advice
What affects the cost of sand mastic
Every job gets its own quote. These are the things that affect it:
- Mould in or behind the old joints
- Access and height
- The number and length of the joints
- How many rooms, windows or areas are involved
Instead of a standard rate, we price the job in front of us: how many joints, what’s in them now and how we reach them. The price is agreed before we begin.
Helping us quote
The more you tell us, the more accurate the quote. When you get in contact, it helps to mention:
- Any previous sealing or DIY work
- Access, such as stairs, a lift or height
- A few photos by email, if you can
- If it’s domestic, commercial or a hotel
Call for a quick quote, or send an email if you’d rather. Tell us about the joints that need doing and we’ll explain what’s involved before giving you a price.
Other services in St Johns
Do you need sand mastic in St Johns?
Age is the main cause. Sand mastic is a maintenance item like any pointing, depending on exposure and upkeep.
Any of these means the joints need attention:
- Open joints round the window box
- Mastic round period door frames that has failed
- Mastic worn away on windows facing the weather
- Cement or filler used on old window joints that has cracked
Managing a site like Ashmead Primary School? Then larger buildings have plenty of frames, and the mastic around each one ages.
Before booking anyone
- What insurance they hold
- What preparation is included
- Which colour the sealant will be
- What product goes in the joint
Sand mastic in St Johns: local notes
In London conversions and blocks, the lease decides who is responsible for the frames, so check that before you book. With historic houses such as Queen's House (about 1.1 miles north-east) nearby, there’s older building stock in the area around St Johns as well as newer homes. In older buildings, older frames set in brick or stone need a sealant that suits them, and sometimes that is traditional sand mastic.
If you live in an older home near Church of St John, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. Rented homes near St Johns station change hands often, and older sash windows in a rental need their mastic kept sound to keep the weather out.
St Johns is about 4 miles south-east of London, in Greater London. For sand mastic in and around St Johns, it’s easy to get a quote: please call 0345 464 0079 or drop us an email. We’re based in Crawley and cover Greater London. St Johns is one of 764 places in Greater London we cover for sand mastic.
Jobs for sand mastic in SE13, SE10 and SE8 works the same way as everywhere else we cover. We cover properties on Avon Road, Mill Lane and Clare Road. Main roads around St Johns include the A2210 and A2211. Other places close to St Johns include New Cross (1 mile west), Deptford (1 mile north), Lewisham (1 mile south-east), Telegraph Hill (1 mile west) and Ladywell (1 mile south). We also work in nearby towns such as London (4 miles north-west), City of Westminster (6 miles north-west), Marylebone (6 miles north-west), Kensington (8 miles west), St Pancras (6 miles north-west) and Shoreditch (5 miles north-west).
Local landmarks in St Johns
Typical jobs here are in homes near Wickham Arms, Brookmill Park and Addey and Stanhope School. Nearby too are St. Paul's (0.7 miles north) and Laban Centre (0.8 miles north). St Johns has its own railway station: St Johns station. A little further out are Fan Museum (0.9 miles north-east) and Lewisham Shopping Centre (0.7 miles south-east). Green spaces nearby include Brookmill Road Local Nature Reserve and Tower Hill.
FAQs for St Johns
Can parking be tricky for a visit in St Johns?
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.
Can you do sand mastic in St Johns?
Yes. Our work covers London and the South East, and St Johns is part of that. Just ring 0345 464 0079 or drop us an email with a few details of the job.
I rent my home. Can I book you?
Yes. Check with your landlord; we can send the quote to them too.
Are you ARBOMaster approved?
Yes. ARBOMaster is the approved applicator scheme for Arbo sealants, and we are part of it.
Should I use sand mastic or silicone?
We’ll help you decide. Period homes often look best with sand mastic and newer frames suit modern sealant.
Where do you work from?
We are based in Crawley, West Sussex, and we cover South East England, London and all of Scotland.
Can new sealant go over the old?
No, because it fails. The old sealant always comes out first.
Should I try DIY first?
Some simple jobs can be done by a careful DIYer. Most DIY failures come from sealing over old material, wet joints or too much sealant.
What the job involves on each surface
Sash and case windows
A sash window’s box frame sits in the masonry opening. The gap round it is pointed with sand mastic.
Period and listed homes
Sand mastic is the like-for-like choice for many period homes. If your home is listed, ask your local planning authority about consent.