Mr Mastic · South East, London and Scotland
Fire-rated sealant
Fire-rated and intumescent sealant applied to gaps, door frames and service penetrations, following the product manufacturer’s tested details.
- Gaps around pipes and cables through fire-resisting walls
- Ordinary sealant used where a fire-rated product is needed
- Door frames with open gaps behind the architrave
What fire-rated sealant involves
Where a pipe, cable or frame passes through a fire-resisting wall or floor, the gap around it has to be sealed with a product tested for that job. We apply fire-rated and intumescent sealants to the manufacturer’s details for the gap size and substrate. We don’t carry out fire risk assessments or certify buildings, so we work from your assessor’s or designer’s requirements.
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
- Gaps around pipes and cables through fire-resisting walls
- Ordinary sealant used where a fire-rated product is needed
- Door frames with open gaps behind the architrave
- Damaged or missing fire sealant after other trades
- Joints flagged on a fire risk assessment or survey
Where we work
- Service penetrations
- Door frames
- Linear gaps
- Pipe & cable gaps
- Plasterboard & masonry
- Flats & HMOs
How it works
- We go through the gaps on your list or survey and check sizes and substrates.
- Old or unsuitable sealant is removed and the gap cleaned.
- Backing or fill is fitted where the product’s tested detail calls for it.
- Fire-rated or intumescent sealant is applied to the right depth and tooled.
- We record the locations and products used so you have them for your records.
Who decides what’s needed
Your fire risk assessor, designer or building control tells you which gaps need fire stopping and to what rating. We apply the product to that specification.
Scotland and England
Scotland’s building standards and England’s building regulations set out fire requirements differently. We follow the specification you give us and the product’s tested details.
Why it’s worth doing now
Gaps around pipes, cables and frames in fire-resisting walls and floors can let fire and smoke spread between rooms and flats. They are often opened up by other trades and never closed again, which is why fire risk assessments and surveys so often flag them.
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
Keep a record of where fire-rated sealant has been used, and make sure any trades who drill through those walls later know they must reseal with a suitable product. Don’t paint or cover the sealant with anything not approved by the manufacturer.
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.”
Fire-rated sealant: common questions
Do you do fire risk assessments?
No. We apply fire-rated sealant to the requirements set by your assessor, designer or building control.
Is intumescent sealant the same as fire-rated sealant?
Intumescent sealants expand in heat to close a gap. They’re one type of fire-rated sealant; the right one depends on the gap and what passes through it.
Can ordinary silicone be used to fill a fire gap?
Not where a fire-rated seal is required. It has to be a product tested for that application.
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 fire-rated sealant in your town:
- London
- Crawley
- Brighton
- Guildford
- Chelmsford
- Colchester
- Southampton
- Reading
- Oxford
- Edinburgh
- Glasgow
- Aberdeen
- Dundee