Resealing Windows and Doors: Window and Door Mastic
Cracked, shrunken or blackened mastic around a frame lets in draughts, damp and rain. Our team specialises in resealing windows and doors for homeowners, landlords, property managers and contractors.
What fresh window mastic does for a building
The bead of window mastic around a frame closes the gap between the frame and the wall. Over time sunlight, frost and movement make it harden, crack and pull away. Once that happens, water runs behind the frame, plaster stains, reveals grow mould and rooms feel colder.
Window mastic replacement is one of the simplest ways to make a building more weathertight. Done properly, it also tidies up the whole elevation, because a straight, even bead in the right colour makes old frames look sharp again.
Signs your window and door mastic needs replacing
It is worth booking a reseal if you notice any of the following:
- Gaps, splits or cracks in the bead around frames and sills
- Mastic that has gone hard, brittle or chalky
- Draughts around closed windows or doors
- Damp patches or staining on reveals and window boards
- Black mould along the internal seal
External sealant around frames should flex with the building. If yours has stopped doing that, it has stopped protecting the wall.
Every type of frame, inside and out
We reseal windows and doors of all types:
uPVC windows and doors
uPVC window sealant in white, grey, black, anthracite or woodgrain shades.
Aluminium and composite
Window frame sealant for aluminium windows, composite doors, bifold and patio doors.
Timber frames
Flexible sealant that copes with timber movement and can be painted where needed.
New build plots
Window and door mastic on new build plots for housebuilders, sealed plot by plot.
Commercial buildings
Commercial window sealant on offices, schools and shops, from ground floor to high level.
Internal seals
Silicone sealant to window boards and internal reveals to finish the job inside.
How we go about resealing windows
The same careful steps on every frame.
Cut out
All old window mastic removed, not sealed over.
Clean and dry
Frame and wall cleaned, dust removed and surfaces dry.
Back and prime
Backer rod in deep gaps, primer on porous masonry where needed.
Seal and tool
New sealant applied and tooled to a neat, consistent bead.
Homes, landlords and commercial sites
Homeowners call us when draughts or damp start showing around frames, often after a hard winter. Landlords, letting agents and property managers use our team to reseal whole blocks or estates in one programme, which keeps costs and disruption down for tenants.
On the commercial side, we reseal windows and doors on offices, schools, shops and industrial units, working from ladders, towers or MEWPs as the height demands. Our director holds IPAF and PASMA cards, and we carry £5m Public Liability cover.
Products, colours and how long it takes
Most homes are straightforward:
- Low modulus sealant for external use. Usually take one day to reseal.
- Colour chosen to match your frames from our sealant colour charts
- Silicone, modified polymer or polyurethane sealant chosen for each frame and wall
We use and apply Arbo, Sika, Dow and Everbuild products. For commercial buildings, we follow the window or façade specification. We are also currently carrying out external window frame perimeter sealing at Salisbury Square, the new City of London law courts.
Insured & pre-qualified
Peace of mind for homeowners, builders and main contractors.
- £10m Employer’s LiabilityInsurance cover
- £5m Public Liability & Professional IndemnityInsurance cover
- Constructionline Silver member
- CSCS Skilled WorkerSealant Applicator (NVQ Level 2)
Over 20 years in construction
Products we use
Professional-grade sealants and adhesives from leading manufacturers.
Brand names and logos are trademarks of their respective owners and are shown to identify products we use. No endorsement is implied.
Neat lines, right colour
Window and door mastic: common questions
Can new mastic go over the old?
No. Sealing over old mastic traps dirt and moisture and fails quickly. We always cut out the old bead first.
Is learning how to reseal windows a realistic DIY job?
Small internal joints can be, but external resealing needs the old mastic fully removed, the right sealant and a clean tooled finish, often at height. Our team does it quickly and neatly.
Do you reseal windows for landlords and managing agents?
Yes. We work on rented homes, blocks of flats and commercial buildings, and can coordinate access with tenants.
Where do you cover?
We reseal windows and doors across London, the South East, the Midlands, the East of England and the South, including Bedfordshire, Hertfordshire, Buckinghamshire, Northamptonshire and Cambridgeshire.
Windows letting the weather in?
Send a photo of your frames on WhatsApp, email office@pioneersealants.co.uk or call 01234 607 252, and we will tell you what is needed.
- Opening hours
- Monday – Friday8:00am – 6:30pm
- Saturday9:00am – 4:00pm
- SundayClosed
