What Can Rats Chew Through
What Can Rats Chew Through? A UK Homeowner’s Guide
What can rats chew through? If you have discovered gnaw marks, damaged pipework or a suspicious hole around your home, you may be surprised by just how much damage a determined rat can cause.
Rats have powerful front teeth and are capable of gnawing many of the materials commonly found in UK homes.
Wood, plastic, expanding foam and some softer building materials can all potentially be damaged by rats. They may also enlarge an existing weakness around brickwork, pipes, doors or ventilation openings.
However, there is an important distinction.
A rat does not necessarily create an entry point from scratch. Very often, it discovers an existing weakness and makes it larger.
At RodentKill, this is why we concentrate on finding how rats are entering a property rather than simply controlling the rats already inside.
Why Do Rats Gnaw?
Gnawing is normal rat behaviour.
A rat's front incisors continue to grow throughout its life. Regular gnawing helps keep these teeth worn down.
Rats may therefore gnaw objects they encounter while exploring, nesting or trying to reach food and shelter.
They may also gnaw around an existing opening to make it easier to pass through.
This is particularly relevant around:
- Pipe penetrations
- Doors
- Air bricks
- Floorboards
- Kitchen units
- Plastic drainage components
- Service ducts
- Damaged brickwork
If you are unsure where rats are entering your property, read our guide to where rats are getting into your house.
Can Rats Chew Through Wood?
Yes. Rats can gnaw wood.
Timber is found throughout UK properties, particularly in older houses with suspended wooden floors.
Potentially vulnerable areas include floorboards, skirting, timber around doors, sheds, decking and wooden structures beneath floors.
However, finding gnawed timber does not automatically reveal the original entry point.
A rat may already have entered beneath the property before damaging the wood.
Can Rats Chew Through Plastic?
Many plastics can potentially be damaged by rats.
This matters because modern properties contain a considerable amount of plastic pipework and other plastic building components.
Possible targets include:
- Waste pipes
- Water pipes
- Plastic ventilation components
- Storage containers
- Flexible ducting
- Plastic air vents
- Food packaging
Any suspected damage to water, waste or drainage pipework should be properly investigated.
Can Rats Chew Through Expanding Foam?
Expanding foam alone should not be considered reliable rat proofing.
It is useful for many building applications, but it is relatively soft compared with proper rodent-resistant materials.
A determined rat may be able to damage foam, particularly when it has been used to fill an existing access route.
This is why simply filling a suspected rat hole with expanding foam may provide only a temporary solution.
More importantly, you need to establish where the rat came from before sealing internal openings.
Our guide to rats entering around pipes explains why gaps around services can be particularly important.
Can Rats Chew Through Plasterboard?
Plasterboard should not be relied upon as a rat-proof barrier.
If a rat is already inside a wall cavity, service void or other concealed area, relatively soft internal building materials may be vulnerable to damage.
This can sometimes explain mysterious holes appearing inside cupboards, behind kitchen units or around boxed-in pipework.
If you hear movement inside walls, see our guide to rats in wall cavities.
Can Rats Chew Through Brick?
Sound, intact bricks are considerably different from wood, foam or plastic.
However, rats do not necessarily need to chew through a complete brick to exploit a wall.
They may find weaknesses associated with:
- Missing mortar
- Damaged brickwork
- Cracks
- Openings around pipes
- Broken air bricks
- Previous building alterations
A small existing defect may therefore be much more significant than it initially appears.
Can Rats Chew Through Concrete?
Good-quality, intact concrete provides a much more substantial physical barrier than softer materials such as timber, plastic or foam.
Again, the important issue is often not whether a rat can simply chew straight through a solid concrete slab.
It is whether the concrete already contains a weakness.
Look for gaps around pipes, deteriorated edges, cracks, construction joints and openings created during previous building work.
In some properties, the actual rat entry route may also be underneath the concrete rather than directly through it.
Can Rats Damage Electrical Cables?
Yes. Rodent activity around electrical wiring should be taken seriously.
Rats may gnaw cable insulation, potentially exposing wiring and creating an electrical hazard.
If you discover damaged electrical cables, avoid handling exposed wiring and arrange for the electrical installation to be assessed by a suitably qualified electrician.
Can Rats Chew Through Metal?
Suitable metal materials are generally far more resistant to rat damage than plastic, foam or timber.
This is why metal mesh and purpose-made rodent-resistant products are commonly used during professional proofing.
However, simply placing a piece of lightweight mesh over an opening does not automatically make it rat-proof.
The material, aperture size, strength and method of installation all matter.
A poorly secured grille may simply be pushed aside.
Can Rats Chew Through Air Bricks?
The air brick itself is not always the problem.
Older or damaged air bricks can contain openings that allow rodents access beneath a suspended floor. Damage around the surrounding mortar or brickwork can also create a route.
Air bricks should not simply be blocked because they perform an important ventilation function.
Instead, appropriate proofing should prevent rodent access while maintaining ventilation.
Read our complete guide: Can Rats Get Through Air Bricks?
Can Rats Chew Through Drain Pipes?
Drainage is particularly interesting because rats already use sewer and drainage networks as travel routes.
A rat problem involving drains does not necessarily mean a rat has chewed through an entire drainage pipe.
Existing defects can be much more important.
These can include:
- Cracked pipes
- Displaced joints
- Collapsed sections
- Damaged inspection chambers
- Open redundant connections
- Poor previous repairs
A rat may use one of these defects to leave the drainage system and reach the ground or void beneath a property.
If rats repeatedly return despite pest control, our Professional Rat Drain Survey can investigate accessible underground drainage for possible entry routes.
Why Filling the Hole May Not Solve the Rat Problem
This is one of the most important things to understand about rat proofing.
The hole where you see the rat may not be the place where it originally entered the property.
For example, a rat could potentially travel:
Damaged drain → ground beneath house → sub-floor void → gap around kitchen pipe → behind kitchen units.
Filling the kitchen pipe gap deals with only the final part of that route.
The original underground entry point remains open.
Alternatively, a rat might enter through a damaged air brick, travel beneath several rooms and emerge somewhere completely different.
This is why successful rat proofing starts with investigation.
Do Not Automatically Seal Every Rat Hole
If rats are already inside a building, immediately sealing every opening you find can sometimes create another problem.
A trapped rat may search for an alternative route and potentially enter another part of the property.
A more systematic approach is:
- Confirm rat activity.
- Establish where rats are travelling.
- Identify the likely original entry point.
- Control rats already present.
- Repair or proof the entry route appropriately.
- Monitor for further activity.
What Materials Are Best for Rat Proofing?
There is no single material suitable for every rat entry point.
The correct repair depends on the building and the location of the defect.
Professional proofing may involve suitable metal mesh, masonry repairs, rodent-resistant sealants, replacement ventilation products, door protection or repairs to damaged drainage.
The objective should be a durable repair that suits the building rather than simply filling the opening with whatever material happens to be available.
Why Do Rats Keep Chewing Through My Repairs?
If rats repeatedly damage repairs, consider why they are so determined to use that particular location.
It may be an established travel route.
There could also be food, water, shelter or another concealed area on the opposite side.
Most importantly, the rats may still have unrestricted access to the structure from somewhere else.
Repeatedly repairing the final hole without finding the original entry point can become an endless cycle.
Finding the Original Rat Entry Point
Finding gnaw damage tells us something useful: rats have been active in that location.
It does not necessarily tell us how they entered the property.
A proper investigation considers the whole building.
This can include:
- External walls
- Air bricks
- Doors
- Pipe penetrations
- Drainage
- Inspection chambers
- Sub-floor voids
- Wall cavities
- Kitchens
- Extensions
- Lofts
- Previous building alterations
At RodentKill, our Rat Entry Investigation is specifically designed for difficult and recurring rat problems where the original access route is unclear.
What Can Rats Chew Through? The Bottom Line
Rats can damage an impressive range of materials.
Wood, plastic, expanding foam, plasterboard, cable insulation and other relatively soft materials may all be vulnerable to gnawing.
More substantial materials such as sound masonry and appropriate metal barriers provide much greater resistance.
But concentrating only on what rats can chew through misses the bigger issue.
The most important question is how the rat reached that location in the first place.
If rats keep returning after treatment or repeatedly damage your proofing, there may be another entry route that has not yet been identified.
RodentKill specialises in investigating difficult rat problems, including structural entry points and underground drainage.
Rats keep coming back? Stop treating the symptoms and start investigating the route.
Book a Rat Entry Investigation with RodentKill
Frequently Asked Questions
Can rats chew through expanding foam?
Expanding foam alone should not be considered robust rat proofing. Rats can damage relatively soft materials, so a more durable repair may be required.
Can rats chew through concrete?
Sound concrete provides a substantial barrier. However, rats may exploit existing cracks, gaps, edges and openings around services rather than attempting to pass directly through solid concrete.
Can rats chew through plastic pipes?
Rats can damage some plastic materials. Any suspected damage to water, waste or drainage pipes should be properly investigated.
Can rats chew through walls?
It depends on the wall construction. Rats may damage softer internal materials and exploit existing weaknesses around brickwork, floors, cavities and service penetrations.
Can rats chew through metal mesh?
Suitable rodent-resistant metal mesh is considerably more resistant to gnawing than plastic or foam. However, the mesh must be appropriate for the application and securely installed.
Why do rats keep coming back after I block the hole?
You may have blocked an internal travel route rather than the original entry point. Rats could still be entering elsewhere through drainage, air bricks, pipe penetrations or another structural defect.
Should I block a rat hole immediately?
Not necessarily. If rats are already inside the structure, sealing the wrong opening could trap them or cause them to search for another route. The infestation and entry route should ideally be understood first.
