Best Intumescent Fire Sealant for Electrical Safety: 2025 Expert Review
Oli at OR Electrics
18th Edition Fully Qualified Electrician
Most homeowners don't give a second thought to the holes drilled through their walls for cables, but as an electrician, I see them as potential hazards. When we upgrade a Consumer Unit (fuse box) or run new circuits, we inevitably breach fire barriers. If those gaps aren't sealed properly, a fire in one room can spread quickly to another.
In Leeds, particularly in our older housing stock and HMOs, fire compartmentation is critical. Using standard caulk or filler isn't enough; you need intumescent sealant. This specialist material swells up when exposed to heat, crushing the cables and sealing the hole to prevent smoke and fire from passing through.
I've tested various sealants over the years to ensure my work meets BS 7671 and Building Regulations. In this review, I'm sharing the three products that offer the best reliability, adhesion, and value for ensuring your home remains safe.
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Specs vs. The Real World
The Spec: "Standard Decorators Caulk"
"Fills the gap and looks neat when painted."
Has zero fire resistance. In a fire, it will simply fall out, allowing flames and smoke to travel through cable runs. Always check the label says 'Intumescent'.
The Spec: "Expanding Foam"
"Great for filling large voids quickly."
Most standard builder's foam is flammable. Unless it is specifically 'Fire Rated' (usually pink) and intumescent, it can actually act as a fuel source. Use sealant for smaller cable entries.
My Top 3 Recommendations
Three options to cover different needs and budgets
Everbuild Everflex Fire Mate Intumescent Acrylic Sealant – Fast Curing – Permanently Flexible – Fire Resistant – White – 295ml
Everbuild
This is the tube you will likely find in almost every electrician's van in the UK. Everbuild creates a reliable, compliant seal that is easy to apply and smooth out. It is perfect for sealing around the cable entry points of a new consumer unit.
The Good
- Excellent swelling properties (expands to 150%)
- Fast curing (tack-free in 15 mins)
- Good acoustic reduction (average 24dB)
The Bad
- Can be messy if you don't use a smoothing tool
- Requires a standard mastic gun (not included)
Installer Tip:
When sealing around cables entering the back of a metal consumer unit, apply a generous bead from the inside before the unit is fully screwed back. It ensures the rear cable entry is airtight and fire-stopping compliant.
Priced at £4.88 at the time of writing
Check Price on AmazonBond-IT FS4 Fireshield Fire Seal Heat Intumescent Sealant - Fire Proof 4 hrs - White (25)
Bond It
For larger projects, such as a full HMO rewire in Headingley where every room boundary needs sealing, consistency is key. This Bond-It sealant offers professional-grade adhesion and a solid 4-hour fire rating. The bulk availability ensures you don't run out halfway through a compliance job.
The Good
- Professional trade quality compound
- Excellent slump resistance (stays in the gap)
- Consistent 4-hour fire protection rating
The Bad
- Buying 25 tubes is excessive for a single DIY job
- White colour only in this specific pack
Installer Tip:
This product has excellent 'non-slump' properties. It is ideal for vertical expansion joints or conduit entries in ceilings where cheaper sealants might drip before curing.
Priced at £44.26 at the time of writing
Check Price on AmazonVitcas Intumescent & Acoustic sealant– Acrylic Sealant - Heat Resistant Sealant – Quick Drying - 4 Hour Fire Rating
VITCAS
In Leeds' back-to-back terraces, noise transfer is almost as big a complaint as heat loss. Vitcas excels here by combining fire protection with superior acoustic damping. It adheres brilliantly to uneven surfaces, making it perfect for old brickwork or lath and plaster walls.
The Good
- Dual purpose: Fire stopping and sound damping
- Halogen-free formulation (safer in a fire)
- Adheres well to older, dusty substrates like brick
The Bad
- Slightly pricier per tube than standard options
- Quick drying time means you must work fast to smooth it
Installer Tip:
If you are sealing gaps around door frames or shared party walls in a terrace, use this. The acoustic damping really helps reduce neighbour noise, giving you a double benefit alongside the safety compliance.
Priced at £7.99 at the time of writing
Check Price on AmazonFrequently Asked Questions
Why do I need intumescent sealant for my consumer unit?
Can I just use normal decorator's caulk?
How long does fire sealant take to cure?
Is this required for landlords in Leeds?
Do I need a professional to apply this?
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