Expanding foam sealant keeps rodents out

There are two types of expanding foam sealant: polyurethane products and latex-based products.

When you wake up at 4:00 a.m. hearing something scratching, do you simply assume it's a nearby relative who should bathe more often? If so, your home may be a target for local rodents searching for winter lodgings. There's an old saying, "When nights get nippy, rodents get an address". Every fall, the average mouse sacrifices his integrity, kiting off a fellow mammal's heating bill instead of shivering in a tiny frigid grass hut under the snow.

At this time of year rodents are motivated, and creative. A mouse can skitter through a quarter-inch slit in a wall. A rat can reliably shimmy through an opening the size of a quarter. Lots of rodents enter through gaps in the wall around cable, conduit or pipes. Cracks in your foundation, mortar that needs re-pointing, holes in siding (or pieces missing entirely) are favourite portals for furry hooligans.

And once they're inside, they high-five each other along freeways between floors, up and down pipes, under sinks, inside walls, between cupboards, through drawers and behind appliances. And here's something else to watch out for; once they're warm and cozy, they relax. They let down their guard emotionally and have sultry mouse parties that lead to fertility accidents. So allowing rodents to enter your home means condoning promiscuity, and we all remember the health class about that.

How can you tell if rodents are setting up camp in your home? You may recently have said one of the following telltale sentences:

"Hey honey, the stupid cat is staring at the basement ceiling again."

or

"Okay, who spilled all the little black seeds in the pantry?"

or

"Woah, this bar of soap had corners last night, and now it's round; must be the humidity."

Now, keeping rodents out of the house in the first place is much easier than getting them to leave once they're inside. The traditional way to stop rodents from entering your domicile is to stuff steel wool into visible cracks and holes. Rodents don't like chewing steel wool. It hurts their fillings. But they often manage to muscle their way through steel wool so it's not a reliable barrier. Fortunately, nature has recently given us an alternative, with some help from giant chemical corporations. I'm talking about expanding foam sealant, and lots of it.

There are two types of expanding foam sealant: polyurethane products and latex-based products. Both types fill gaps and holes that are too large to pack with caulking. Polyurethane foam cures to a rigid but porous texture, similar to an ossified Cheesy, and can be sculpted (with a bread knife) to a suitable shape. Latex foam cures to a spongy non-sculptable texture, but while it is still setting up it can be tooled, shaped or moulded, giving you lots of texturing options. Both latex and polyurethane foams stick to almost anything including wood, aluminium, masonry, galvanized steel, plastic, rubber, drywall, glass and, based on experience, SKIN.

You can use expanding foam at this time of year to rodent-proof your house. Fill cracks and holes under sinks, in and around your foundation, chimneys and siding. Apart from discouraging rodents, foam has cosmetic potential. For example, my garage was missing a corner piece of aluminum siding. I tried to get a replacement corner but they don't make them anymore, so I applied polyurethane foam and waited overnight for it to cure. Then I sculpted a new corner and painted it to match the siding. Oh baby.

More great things about expanding foam sealant:

• Foam acts as a form-fitting barrier to the elements, and has no nutritional value so it doesn't attract insects or rodents.
• Foam doesn't support the growth of mould or fungus in damp conditions.
• It doesn't smell badly as you're using it, or after it's cured.
• Many brands of foam are free of volatile organic compounds that pollute the environment.
• Foam efficiently seals air leaks that compromise the energy-efficiency of your home.
• Foam sets up quickly, fills large voids, deadens sound, is airtight and water resistant and conforms to any shape as it expands.
• Foam can (and should) be painted after it's fully cured to protect it from UV light, which causes discolouration and deterioration.

If you haven't used expanding foam before, go with a low-expansion variety. (The label will indicate whether it's high- or low-expansion.) If you choose a high-expansion foam, use it with an extremely subtle touch. It expands 200-300 percent over a couple of hours. In other words, you only need to squirt in 35 -50% of what you think you need. If you overdo it, you'll have pendulous glops of uncured foam spilling out of crevices, rolling down your walls and spreading itself around like a bad soprano. It cleans up with acetone but not easily, so don't let it get to that point. Also, on the label the manufacturers always print a cryptic cautionary note: "Once the foam has cured, no known chemical will dissolve it. Remove by sanding." If the foam is on your skin, good luck with the sanding part. I'm still smarting.