Mr Mastic · South East, London and Scotland
Window and door mastic
Failed mastic around windows, doors, sills and patio doors cut out and replaced with a weatherproof sealant that suits the frame and the wall.
- Cracked or shrunken mastic around the frame
- Draughts coming in around windows and doors
- Rain getting in at the frame edge or under the sill
What window & door mastic involves
The mastic around a window or door frame closes the gap between the frame and the wall. Over time it hardens, cracks and pulls away, and that is where draughts and rain get in. We cut the old mastic out, clean back to sound surfaces, fill deep gaps with backing rod and apply a weatherproof, flexible sealant chosen for the frame and the wall it meets.
We work across the South East, London and all of Scotland from our base in Crawley. Every job comes with our one-year guarantee, and we’re fully insured and an ARBOMaster approved applicator.
Problems we put right
- Cracked or shrunken mastic around the frame
- Draughts coming in around windows and doors
- Rain getting in at the frame edge or under the sill
- Old mastic that has gone hard, black or come away
- Gaps left after new windows were fitted
Where we work
- uPVC windows
- Aluminium frames
- Timber windows & doors
- Patio & French doors
- Window sills
- Composite doors
How it works
- We check each frame and agree which windows and doors need doing.
- We cut out the old mastic and clean the frame edge and wall back to sound surfaces.
- Deep gaps are filled with backing rod so the new sealant is the right depth.
- We apply a weatherproof, flexible sealant in a colour to suit the frame and tool it neatly.
- We clear up and check every joint is fully closed before we leave.
Inside and out
The outside joint keeps the weather out; the inside joint between frame and plaster stops draughts and finishes the reveal. We can do either or both.
Matching the colour
White, brown, anthracite grey, black and clear sealants are all available, so the new joint suits uPVC, aluminium, timber and composite frames.
Why it’s worth doing now
Old frame mastic shrinks, hardens and cracks. Draughts come first, then rain finds its way round the frame and under the sill, which can lead to damp patches on the reveal and rot in timber frames. New mastic closes the gap before that happens.
What affects the quote
We don’t publish set prices, because every job is different. Call or email us with a few details and we’ll give you a clear quote before we start. The main things that affect it are:
- How many joints, rooms, windows or metres of joint there are
- How much old sealant or grout has to come out, and how many layers
- Mould, damage or movement that needs dealing with first
- Access: stairs, height, ladders or work outside
- The product the joint needs (sanitary, exterior, fire-rated, glazing or sand mastic)
- For commercial sites, working hours and phasing
What a good quote includes
- All the old sealant removed, not sealed over
- The product named for each joint
- How long the guarantee is and what it covers
- How long before the area can be used
- How your home or building will be protected
- Who is doing the work, and that they’re insured
Aftercare
Check the joints once a year, especially on walls that face the weather. Don’t pressure-wash directly at the frame edges, and let us know if you see gaps opening after building work nearby.
What customers say
Rated 4.9 on Google from 180+ five-star reviews. Read the reviews on Google.
“Called for a bathroom reseal and the mastic man showed up on time with all the right equipment. Brilliant attention to detail. The sealant looks perfect and they kept everything tidy.”
“We had old mastic that needed replacing throughout our kitchen and bathrooms. The mastic man professional was knowledgeable, quoted fairly, and delivered excellent quality work. Highly recommend!”
“Professional mastic man service from start to finish. They assessed the work properly, gave a clear quote, and executed the job perfectly. Very satisfied with the results.”
Window and door mastic: common questions
How many windows can you do in a day?
It depends on access, the state of the old mastic and the size of the frames. We’ll tell you how long your job will take when we quote.
Can you do upstairs windows?
Yes, where they can be reached safely. Tell us about access when you get in touch and we’ll plan for it.
Will new mastic stop draughts?
If the draught is coming in around the frame, yes. If it’s coming through the window seals or a failed hinge, we’ll tell you.
Is the work guaranteed?
Yes. Every job comes with our one-year guarantee.
Do you give a price before you start?
Yes. Call or email us with a few details and we’ll give you a clear quote, so you know the price before any work starts.
Are you insured?
Yes. Mr Mastic is fully insured, and we’re an ARBOMaster approved applicator.
Page updated 26 October 2026
Near you
We cover the South East, London and Scotland. Find window & door mastic in your town:
- London
- Crawley
- Brighton
- Guildford
- Chelmsford
- Colchester
- Southampton
- Reading
- Oxford
- Edinburgh
- Glasgow
- Aberdeen
- Dundee