Greater London · England
Coldblow Sand Mastic
Problem with your window and door surrounds in Coldblow? We remove the old material, prepare the joints and seal them properly, with a 12-month guarantee.
- Cement or filler used on old window joints that has cracked
- Window mastic to renew ahead of painting
- Mastic worn away on windows facing the weather
What sealant work can’t fix
Sealant is not the answer to every problem, and we’d rather say so up front. Sealant won’t put right:
- Broken panes
- Sash cords, weights and draught-proofing of the sashes
- Masonry that needs repairing
If in doubt, call 0345 464 0079 or email us and we’ll say what we think before booking.
Surfaces we seal
- Brick reveals
- Sash and case windows
- Timber door frames
- Tenement windows
- Stone surrounds
- Period & listed homes
About our sand mastic in Coldblow
Old sand mastic cracks, crumbles and falls out over time and gaps open up round the frame. Renewing it closes the gap and tidies the surround. We work on timber door frames, period & listed homes and sash and case windows, and people most often call us about window mastic to renew ahead of painting and mastic round period door frames that has failed.
Much of London’s older housing was built with timber sash windows, some still in place and some long since replaced. Whatever is in the opening now, the joint between frame and wall is what keeps the weather out, in Coldblow as anywhere.
Each job carries a 12-month guarantee.
- Where
- Coldblow (DA5)
- Wider area
- Greater London
- Cover
- A year, on every job
- Price
- A clear quote up front
- Telephone
- 0345 464 0079
- Page updated
- 26 October 2026
For landlords and businesses
Letting agents often deal with us directly. Send the address, what’s needed and the access arrangements.
From a single let to a portfolio, the work is the same standard: old sealant fully removed, joints prepared properly and a 12-month guarantee.
How it works
We work through the job in order: protection first, then preparation, sealing and a tidy-up. Typically it takes anything from a few hours to a full day, depending on how many windows, and the area is left clean. In a London area like Coldblow, the main things to plan are parking and access: let us know about parking, the floor we’ll be working on and any lift or shared entrance.
- We check each window surround and the condition of the joint.
- The joint is raked out and cleaned.
- We fill deep gaps so the new mastic isn’t too thick.
- New sand mastic is applied and shaped by hand.
- We finish the mastic to a tidy line.
Before we arrive
- Let us know about earlier repairs to the joints
- Plan for the work area to be out of bounds to pets and children
- Mention any sign-in or site rules at work premises
Ask for a quote
A good description makes for an accurate quote. Let us know the location, the problem and roughly how many joints.
Advice
Coldblow homes and the weather
Historic houses like Hall Place and Gardens (about 0.7 miles north) are a reminder that the area around Coldblow 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. 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.
Letting a property close to Bexley station? Then any sash windows need sound mastic to keep draughts and rain out. If you live in an older home near Church of St Mary the Virgin, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. For site and facilities teams at buildings such as Maypole Primary School, the mastic around its windows and doors needs looking after like any other building’s.
Coldblow is about 3 miles east of Sidcup, in Greater London. For sand mastic in and around Coldblow, it’s easy to get a quote: please phone 0345 464 0079 or email us. We’re based in Crawley and cover Greater London, Coldblow included. 764 places in Greater London are on our list, large and small. You can also see our page for London, about 12 miles away.
Jobs for sand mastic in DA5 is quoted and booked the same way as anywhere else. Local streets include St Mary's Road, Dartford Road and Wansunt Road. We also cover Joyden's Wood (1 mile south-east), Bowmans (1 mile east), North Cray (1 mile south-west), Crayford (1 mile north-east) and Wilmington (1 mile south-east). Larger places within reach include London (12 miles west), City of Westminster (15 miles west), Marylebone (14 miles north-west), St Pancras (14 miles north-west), Shoreditch (12 miles north-west) and Walthamstow (13 miles north-west).
Around Coldblow
We work in homes and buildings around The Old Wick pub, St Columba's Catholic Boys' School and Braeburn Park. For rail, the closest station is Bexley station, roughly 0.6 miles west of the centre. Well-known places in the area include Stone Castle (5 miles east) and Bexley Museum (0.7 miles north). Green spaces nearby include Wansunt Pit and Summer Hill.
Common questions in Coldblow
I let a flat near Bexley station. Can you help?
Yes, we work for landlords and letting agents. Just call 0345 464 0079 or send us an email and tell us about the property, and we will give you a clear quote.
Is Coldblow in your area for sand mastic?
Yes. Our work covers London and the South East, and Coldblow is part of that. You can phone 0345 464 0079 or drop us an email and let us know what needs doing, and we will give you a clear quote.
Can you quote for more than one area?
Yes. More than one area can go on one quote.
How long does sand mastic take?
Typically it takes a few hours for a single window, longer for several. Larger jobs naturally take longer.
Will it make a mess?
No. The area is protected while we work and cleaned up afterwards.
Do you offer different sealant colours?
Most of the time, yes. We’ll explain which colours are available and agree one before work begins.
Do you take out the old sealant first?
Yes, always, and completely. New sealant will not bond properly to old, so any old material comes out before anything new goes in.
What do you need from me for a quote?
Just the basics: where it is, what you’ve noticed and how we reach it. After that, simply ring 0345 464 0079 or email us.
Towns and villages near Coldblow
Also in Coldblow
Can I do it myself?
Some sealant jobs are within reach of a careful DIYer, such as a straightforward joint indoors. The common mistakes are sealing over old sealant, sealing a damp joint and using far too much.
Sealing over old silicone is the commonest DIY error. New silicone will not bond to old, so it lifts and traps water and mould underneath. Everything old must be removed first.
How we quote for sand mastic
We quote each job individually. This is what makes a difference:
- Whether the work is at height
- The size of the job
- Whether old sealant or filler has to be cut out
- The type of sealant required
A failed joint rarely gets cheaper to fix by waiting, because water and mould keep working on it. If you are not sure whether it needs doing, call 0345 464 0079 or send us an email and we will give you an honest view and a quote.
What we need to know
Photos by email are helpful but not essential. Please mention:
- The rough size of the job
- Access, such as stairs, a lift or height
- Where the job is, and your postcode
- Whether it’s a home or a business
It all starts with a short chat. Tell us what’s wrong, where it is and how much there is. Whenever you’re ready, ring 0345 464 0079 or email us.
Aftercare tips
Joint life depends on how it’s used and looked after. Here’s what we suggest:
- Clear gutters so water doesn’t pour onto the windows
- Check the mastic when you check the paintwork
- Check with your local planning authority if your home is listed
- Sort the mastic before the decorators arrive
Leave the new mastic unpainted, which is the traditional advice. If you are redecorating, ask us first.
An open joint round the box lets weather through. Left, the gap tends to get bigger.
What happens if it’s left?
Not every filler suits an old window surround. Sand mastic matches what was there, which can matter on listed and conservation-area homes. In London conversions, one flat’s bathroom is often above another flat’s ceiling, and a slow leak from a failed seal can end up in the flat below. Putting it right early is much less trouble for homes in Coldblow.
Every job is a little different, so we quote each one individually. Size, access and the product the joint needs all play a part.
Why book with us
- We never seal over old sealant
- An ARBOMaster approved applicator
- Experience in homes, commercial sites and hotels
- Every job guaranteed for a year
Take a look at our cost guide and our reviews.