A gap around a cable, conduit or service entry can look like a simple problem: there is an opening, so fill it.
In practice, choosing the right solution takes a little more thought.
Some openings need to be completely sealed. Others need to remain accessible for future cable changes or maintenance. Larger penetrations may need support behind the sealing material, while ventilation openings such as weepholes need to continue doing the job they were designed to do. Fire-rated penetrations introduce another set of requirements altogether.
From a vermin-proofing perspective, even relatively small openings can matter. Victorian Department of Health guidance notes that mice are capable of squeezing through gaps as small as 8 mm.
The best place to start is therefore not with the product, but with the opening itself.
Start by understanding what the opening needs to do
Before selecting a sealing or barrier product, consider a few practical questions:
What services pass through the opening?
How large and irregular is the remaining gap?
Is the opening indoors or exposed to weather?
Will cables, conduits or services need to be accessed again?
Does the surrounding joint need to accommodate movement?
Does the opening need to retain ventilation or drainage?
Is the penetration part of a fire-rated wall, floor or other building element?
Is the main objective environmental sealing, vermin exclusion, or both?
The answers can point towards very different solutions.
It is also worth remembering that gaps in the building envelope can have consequences beyond pest entry. CSIRO research into Australian homes identifies uncontrolled air leakage through gaps and poorly sealed building elements as an ongoing building-performance issue. Appropriate sealing can therefore contribute to controlling unwanted airflow as well as closing potential access points.
Small and irregular gaps around cables and conduits
Cable entries rarely produce perfectly shaped openings. Multiple cables, conduit edges and existing services can leave irregular spaces that are difficult to address with rigid components.
Where the opening is relatively small and future access may be required, a mouldable, non-hardening compound can offer a practical solution.
RectorSeal Duct Seal Compound, for example, can be shaped by hand around cables, conduits and irregular openings. Unlike a curing sealant, it remains pliable, allowing it to be removed or adjusted if the installation needs to be accessed again.
This type of solution can be particularly useful around electrical conduits, cable entries, boxes and service penetrations where the ability to re-enter the opening is valuable.
The important characteristic here is not simply that the material fills the gap. It is that it does so without permanently locking the installation in place.
When a curing flexible sealant makes more sense
Other openings need a more permanent flexible seal.
Construction joints and service penetrations can experience movement caused by temperature changes, vibration, building movement or differences between adjoining materials. In these situations, a curing elastomeric sealant may be more appropriate than a removable putty.
Adheseal HiFlex Construction Plus is one example. The Australian manufacturer specifies it as a hybrid MS polymer sealant with ±50% movement capability, UV resistance and compatibility with a range of construction applications.
A flexible curing sealant is therefore better considered where the installation needs:
a durable cured seal
accommodation of joint movement
resistance to external weather exposure
adhesion to suitable construction substrates
a more permanent finished joint
There are also specialised curing sealants designed specifically around rodent exclusion. These products add pest-resistant characteristics to the sealing function and may be appropriate where vermin resistance is a primary consideration.
The important point is that a general construction sealant and a rodent-exclusion sealant do not necessarily perform the same role, even though both may be applied from a cartridge or sausage.
Larger openings may need support
As openings become larger, simply applying more sealing material is not always the most practical approach.
A large or deep penetration can provide limited support for a compound or sealant, particularly where multiple services pass through an irregular opening.
This is where a support product can become useful.
VerMesh Sealant Support is intended to provide a physical backing across larger openings so that an appropriate sealing material can be applied where it is needed rather than being pushed unnecessarily into the void.
The principle is straightforward:
Support the opening first, then apply the appropriate sealing material.
This can help create a more controlled installation and reduce unnecessary material usage.
The exact arrangement will always depend on the opening, services present and the sealing product being used.
Sometimes the answer is a barrier, not a seal
Not every vermin-proofing problem requires the entire opening to be filled.
In conduit openings or irregular access paths, it may be more practical to introduce a physical barrier that restricts pest movement while still allowing the installation to remain accessible.
Flexible barriers such as VerFlex can be shaped around conduits and irregular openings, providing another option where complete filling of the space is unnecessary or undesirable.
This distinction is useful:
Sealing closes an opening.
Supporting helps another material close an opening.
Barrier protection restricts access without necessarily filling the entire void.
Understanding which of those outcomes is actually required makes product selection much easier.
Ventilation openings should still ventilate
Weepholes are a good example of why every opening should not simply be sealed.
They form part of the building's cavity ventilation and drainage system, so blocking them completely can interfere with their intended function.
Where the objective is pest exclusion, a purpose-designed screen is a more appropriate approach.
The Weepa Protector Weep Hole Screen is manufactured from marine-grade 316 stainless steel and is designed to fit existing brick-wall weepholes while excluding mice and a range of other pests. Weepa specifies the Protector for openings between 7 mm and 17 mm wide in standard 75 mm brickwork.
Importantly, Weepa has also commissioned Australian research into airflow through its weephole products. Its testing reported no measurable airflow restriction under typical wind-flow conditions and less than 1% restriction under the extreme conditions tested across its current product range.
That illustrates an important principle:
Effective exclusion does not always mean completely closing an opening.
Sometimes the correct solution is one that prevents pest access while preserving the opening's original function.
Fire-rated penetrations are different again
Where cables, conduits, pipes or other services pass through a fire-resisting building element, the penetration should not be treated as an ordinary gap.
Fire performance depends on the complete tested arrangement, including the building element, service type, penetration configuration and firestop products used.
Australian building guidance recognises service penetrations as potential paths for fire spread and references tested systems under standards including AS 4072.1 and AS 1530.4.
Products such as Metacaulk FRS Fire Rated Putty Stick are specifically designed for firestop applications, but they must be used as part of an appropriate tested system rather than simply substituted for a general-purpose sealing product.
For fire-rated penetrations, the question should therefore not be:
“What can I use to fill this hole?”
It should be:
“What tested system applies to this penetration?”
A quick guide to matching the solution to the opening
Small irregular gaps around cables
Key consideration: Future access and irregular shapes
Typical solution: Mouldable, non-hardening compound
Service penetration or construction joint
Key consideration: Movement, weather exposure and durability
Typical solution: Flexible curing sealant
Rodent-prone gap or penetration
Key consideration: Pest-resistant sealing
Typical solution: Rodent-exclusion sealant
Larger unsupported opening
Key consideration: Supporting sealing material across the void
Typical solution: Support mesh with suitable sealing product
Open conduit or irregular access path
Key consideration: Physical exclusion without necessarily filling the opening
Typical solution: Flexible physical barrier
Existing brick weephole
Key consideration: Pest exclusion while maintaining ventilation
Typical solution: Purpose-designed weephole screen
Fire-rated wall or floor penetration
Key consideration: Maintaining required fire performance
Typical solution: Approved firestop system
This is a general guide rather than an installation specification. Opening size, substrate, services, environmental exposure, manufacturer requirements and applicable building requirements should always be considered when selecting a solution.
Start with the opening, not the product
There is no single product that is right for every cable entry, conduit or service penetration.
A small cable gap that needs future access presents a different problem from an external construction joint. A large unsupported penetration is different again. A weephole needs to continue ventilating, while a fire-rated penetration needs to maintain the required performance of the building element.
The practical approach is to understand the opening first:
What needs to be sealed? What needs to remain accessible? What needs support? What needs ventilation? What needs physical exclusion?
Once those questions are answered, choosing the right product becomes much simpler.
Rat Out brings together practical sealing, support and barrier solutions for cable entries, conduits, service penetrations and other vulnerable openings, with a focus on products that suit real installation conditions.
Different openings. Different challenges. Practical solutions.