Greater London · England
Window Mastic in Coldblow
Mastic around window and door frames, sills and patio doors for Coldblow, backed by a 12-month guarantee. Ask us for a quote.
- Water coming in at the bottom corners of a door
- Gaps between the frame and the inside reveal
- Cold air getting in at the frame edge
Window mastic in Coldblow, done properly
A cold draught around a closed window often comes from the frame edge. A new joint stops the air getting through. If the draught is through the window seals instead, we will tell you. We work on patio & French doors, aluminium frames and composite doors, and the jobs we see most are rain getting in at the frame or under the sill and cracked internal joints between frame and plaster.
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.
You are covered for a year from the day we finish. If there’s a problem with it, please call 0345 464 0079 or drop us an email.
- Where
- Coldblow (DA5)
- Wider area
- Greater London
- Guarantee
- 12 months on all our work
- Quotes
- A clear quote up front
- Phone
- 0345 464 0079
- Page updated
- 26 October 2026
What the job involves on each surface
Window sills
The end joints of a sill tend to fail before the rest. We reseal them so rain cannot run into the wall.
Composite doors
Draughts round the door leaf generally come from worn seals or adjustment, not the mastic. We’ll tell you if that’s what we find.
Can I do it myself?
If you’re set on DIY, put the effort into preparation: take out all the old sealant, make sure the joint is clean and dry, and give it the full cure time. If it fails, we can still redo it.
A careful DIYer can reseal a simple joint, 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.
Why deal with it now?
Resealing frames is a short job: the visit takes a few hours for a handful of frames, longer for a whole house. Wait for damp to appear and there may be plaster and decorating to sort out too. In a flat in Coldblow, failed sealant seldom stays inside your own four walls: water can reach the neighbours below, and gaps in fire-rated joints affect the whole building.
What it costs depends on how much there is to do, how hard the old material is to remove and access to the work. We give a clear quote before we start.
Why Coldblow clients choose us
- We agree the colour with you first
- ARBOMaster approved applicator
- We never seal over old sealant
- Sealant colour chosen to suit
Read our cost guide and what customers say.
When to call us in Coldblow
Every frame moves through the day. A plastic or aluminium frame lengthens in sunshine and shortens as it cools, while the masonry beside it stays put. A sealant that can’t keep up eventually tears.
Signs it’s time to call us include:
- Rain getting in at the frame or under the sill
- Mastic that’s falling out in pieces
- Whistling draughts around closed windows
- Draughty joints inside around the window
Coldblow is in London, so parking needs planning: tell us about permits, visitor bays or off-street space when you book.
What your quote should include
- What product goes in the joint
- Which colour the sealant will be
- Is the old sealant removed completely?
- When the joint can take water or movement
How to look after the new joints
How long the joints last depends on use and care. We suggest:
- Check the mastic once a year
- Repaint timber before it’s bare
- Keep jet washers away from the mastic
- Don’t use solvent cleaners on the joint
Check the drainage slots in the frames aren’t blocked, so water can run away instead of sitting against the joint.
A failed joint lets water into the wall a little at a time. Often the first sign is a damp patch inside or flaking paint on the reveal. Early resealing stops it reaching that point.
What window mastic looks like in Coldblow
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 Hall Place and Gardens (about 0.7 miles north) nearby, there’s older building stock in the area around Coldblow as well as newer homes. In older buildings, older timber frames in brick or stone need a different approach from a modern uPVC window.
For an older house near a landmark such as Church of St Mary the Virgin, replacement windows fitted into old openings often leave uneven gaps that need backing and a flexible joint. If you look after a building such as Maypole Primary School, its window and door frames need their mastic kept sound, just like a home’s.
Coldblow is about 3 miles east of Sidcup, in Greater London. Wherever you are in the DA5 postcode area, we cover window mastic for homes and businesses. 764 places in Greater London are on our list, from the larger towns to small villages. For nearby work, see our London page.
We cover every part of DA5 for window mastic. We cover properties on St Mary's Road, Dartford Road and Wansunt Road. Neighbouring places we cover for window mastic include 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). We also work in nearby towns such as 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).
Local landmarks in Coldblow
Locally, jobs take us to homes and businesses close to 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. Other landmarks nearby include Stone Castle (5 miles east) and Bexley Museum (0.7 miles north). Green spaces nearby include Wansunt Pit and Summer Hill.
Work for landlords, hotels and businesses
We also work for property managers and facilities teams in Coldblow and across Greater London. Several sites can be quoted together.
We regularly work with letting and managing agents. Send the address, what’s needed and the access arrangements and we’ll give you a quote.
Also near Coldblow
Other services in Coldblow
What happens on the day
Every visit runs the same way: we look at the joints together, mask and protect the surrounding surfaces, carry out the job and clear up. Most jobs take anything from an hour or two to a full day, depending on how many frames there are. 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.
- First we look at every frame and agree the list.
- The old mastic is cut out and the surfaces cleaned back.
- Where gaps are deep, backing rod goes in first.
- A flexible, weatherproof sealant is applied in a colour to suit the frame.
- We clear up and check every joint is fully closed.
Before we arrive
- Let us know if you’ve seen damp or leaks
- Move anything stored near the joints
- Tell us about access, such as stairs, a lift or high-level joints
Getting a quote
If you are in Coldblow and need window mastic, phone 0345 464 0079 or email us. Tell us what the problem is and where, and you’ll get a clear quote before any work starts.
Related advice
Coldblow: your questions answered
Can you do window mastic in Coldblow?
Yes. We work across London and the South East, and Coldblow is part of that. Just ring 0345 464 0079 or drop us an email with a few details of the job, and we’ll give you a clear price.
Can parking be tricky for a visit in Coldblow?
It can be, so it helps to tell us about permits, visitor bays or off-street space when you book. The visit is then planned around what’s available.
How long should I leave it?
Cure times vary by product and the temperature. We tell you how long to leave it before we go.
Do you work for landlords and businesses?
Yes, we do. We work in homes, commercial premises and hotels.
How many windows can you do in a day?
A handful of frames is a short visit, while a whole house takes longer. We confirm the timing with your quote.
Can I paint over the new sealant?
Not generally, if it’s silicone. Tell us your decorating plans and we’ll pick a sealant to suit.
Can you match the sealant to my frames?
Yes. Grey and black frames get grey or black sealant, and wood-effect frames usually suit brown.
What do you need from me for a quote?
A short description and the location, plus pictures if you have them. We will ask anything else we need to know.