TECHNICAL | PPC100 August 2020

Following on from his demonstration at PPC Live 2020 in Harrogate, Pestology’s Gulliver Hill talks to PPC about all things proofing.

Proofing is about denying a pest access to its environment, but to be successful the process must consider two things:

• How the target pest species perceives its environment
• The physical capabilities and behaviour of the target pest species.

The majority of proofing works target rodents but in reality restricting access to food, shelter and warmth is a successful strategy to assist with insect treatments and bird works too.

Anyone can block a hole to stop a pest getting from A to B.

But a professional pest proofer will know which holes to proof, how to proof them and will use a combination of products to achieve this.

Yes, builders and handymen can carry out proofing but it’s rarely successful without the constant guidance of a pest controller. They don’t know things like how the target pest is accessing a given area and what the target pest is physically capable of.

Consistently effective pest-proofing is therefore best done directly by a pest controller where possible.

Laying the foundations

The foundation of rodent proofing has always been a backing material and an adhesive filler to then hold this in place – wire wool or mesh (backing material) and expanding polyurethane foam (adhesive filler).

Logic is that the wire wool or mesh is what stops the rodent in terms of gnawing, pushing and pulling, and the expanding foam is what holds it all in place.

This has been the approach for over thirty years but, while effective when done correctly, it has a lot of limitations and doesn’t cover the wide range of scenarios encountered across various sites.

It also limits the price point for a proofing exercise, as ultimately the customer is paying for products and a skillset available to most people.

Expanding foam is a very difficult product to apply neatly and has the equivalent density of polystyrene.

This limits its use to ‘back of house’ (out of sight) areas, for example, locations under kitchen units or under baths. Its fragility will encourage any rodents that encounter it to test its physical limitations.

In fact, so weak is the ability of expanding foam to stop rodents that its best use is to give us a visual clue as to where the rodents are coming from!

Simply apply under kitchen units and in a day or so holes will emerge indicating the rodents’ current preferred routes.

Wire wool is essentially finely chopped strands of mild steel which is very susceptible to damp conditions and atmospheric moisture, which can turn it into an orange mush in as little as a few weeks.

On the market

Better backing materials include pest-specific products on today’s market such as Xcluder fabric and Vermiguard mesh, which won’t corrode or degrade due to their stainless steel content and have more ‘spring’ to them, to tightly fill nooks and crannies.

Better adhesive fillers are silicone mastics – these don’t expand but this is a good thing, as you can be sure the backing material is fully covered and very neat finishes can be achieved.

They will also adhere to virtually any surface, are non-flammable, virtually inert, won’t degrade, and fully seal the odour trails and tiny wind movements that rodents use to locate the hole.

Note that silicone mastics are very different products to caulks. Caulks are much less adhesive, shrink when they cure, and large lumps can remain soft in the middle for many days, both of which make them very vulnerable to rodent attack. Decorators’ fillers also suffer the same attributes.

Some products such as Mousestop actually rely on the ‘soft centre’ characteristic to deter rodent attack, on the basis that a soft product interferes with the rodent diastema and is less attractive to gnaw.

Products such as linseed oil putty (a glazing product) mimic this characteristic. However where this may be effective in certain low-pressure situations, personally I’ve seen this fail on too many occasions to be deemed a trusted approach.

This concept also relies on a large lump of the product being present, as it is accepted that the rodent will gnaw some aspect in attempted passage – large lumps aren’t likely to please the customer in open areas and the application is generally unsightly.

A good backing material properly installed and fully sealed in place with a silicone mastic is a very durable and resilient solution for high-pressure access points, and can be adapted for both ‘back of house’ (out of sight) and ‘front of house’ (in view) locations to meet client expectations.

Some products mix the backing material with the adhesive filler (such as silicone mastic with chopped wire wool inside) but these are typically expensive and limit the flexibility of a separate backing material with adhesive filler.

Often the holes are too big to be filled with an adhesive material alone, and only the backing material has enough rigidity to span the gap.

From indoor to outdoor

External proofing needs to have the same considerations as internal proofing in terms of back of house, front of house, low-pressure hole, high-pressure hole.

But additional thought should be given to UV stability and weather resistance as well.

Cements and mortars are generally shunned by the modern pest controller but, from what I’ve seen and heard, they were used far more frequently by pest controllers of yesteryear.

These people seemed to actively engage the pest environment with gusto, incorporating crushed glass and other additives, to strengthen and differentiate their product.

Many modern pest technicians from today are on foot with only a rucksack or mobile in a tiny van, so portability is paramount. But I do think the reliance on products that come squeezed from a tube has blinkered our approach.

Many types of cement and mortars come ready to mix in small buckets, available from any of a number of local DIY outlets that now commonly exist.

You just add half a litre of water and briefly mix, to give a quick curing thixotropic product with excellent long-term rodent resistance.

Polyester resins are sometimes called ‘plastic cement’ and are widely used in the construction industry. 

They essentially consist of two parts that mix together (often automatically in the tube nozzle) and rapidly cure to give an incredibly strong and durable material.

Products such as cement and polyester resins are usually strong enough to be used without backing materials and can be used in damp greasy environments (around manholes covers, basements etc).

An understanding of these products greatly opens up the range of proofing scenarios any pest technician can tackle.

A slippery slope

Sometimes proofing doesn’t involve directly stopping a rodent’s movements with a lump of something – it can indirectly stop a rodent’s movements by representing a surface they
can’t cross.

Climbing is an inherent activity to all rodents and is the aspect most underestimated or ignored by everyone else outside the industry.

In any given infestation scenario, rodents will be climbing; they rely on grip and traction to achieve this so sometimes these factors can be removed to limit their ability to explore and exploit the environment.

Aluminium plates are too smooth for rodents to pass on vertical surfaces and can be installed in thin sections to act as ‘slip strips’ to stop climbing rodents.
They can be cut with shears and bent by hand so are easy to install, typically adhered with a film of silicone mastic.

Even pinning back a hanging cable or moving a bottom shelf a little higher can stop rodents accessing an area, and this approach often requires nothing more than a couple of cable ties and the knowledge of how high the pest can jump or what it can climb.

The construction and engineering world has a huge array of fascinating products currently utilised in applications far removed from the pest world.

Once we have awareness of these products, there is a wide crossover to our day-to-day objectives of stopping rodents getting from A to B.

And getting from A to B is key to any pest causing a problem for our customers, often critical to the survival of that pest population itself. The more we can do to limit or prevent this, the more successful our intervention will be.

Do you have a technical query about proofing?

Don’t forget, members get free technical advice from our team.

technical@bpca.org.uk

Source: PPC100