A spider here and there in your basement is normal, but if you have lots of cobwebs in your basement, you have a problem that needs addressed. You could just spray insecticide in your basement to kill the spiders, but this is only a temporary fix and it adds poisonous chemicals to your home. What you need to do is change the conditions that allowed the spiders to thrive.
“Why are spiders happy to live and raise their spider families in my basement?”
Like any creature, spiders need to eat. A plentiful spider food source will quickly give you a large spider population.
“What are my spiders eating?”
Insects of course! Typically, these spiders are eating mites that live in the dark moist corners of your basement. Take away this food source and the spiders will go.
“So, I have to get rid of the mites to get rid of the spiders? How do I do that?”
Mites too will thrive if there is a plentiful mite food source. These mites eat mildew and mold. Essentially, you have a small ecosystem in your basement. Take away these mini mite gardens and the ecosystem will collapse causing all these unwanted creatures to leave.
“Great! How do I get rid of my mini mite gardens?”
Moisture is the key! Mildew and mold cannot grow without a high level of moisture. Moisture is at the bottom of the food chain in our little ecosystem. Lower the humidity ( moisture in the air ) in the basement and our little ecosystem will collapse, the spiders will leave, and your house will be cleaner and healthier.
“Awesome, what is the best way to lower the humidity in my basement?”
For a long-term solution, it is most important is to eliminate or reduce sources of moisture entering your basement. Are your gutters working properly? Are your downspouts dumping water at least three feet from your home? Does the ground around your home slope away from the house? Do you have plastic over or under the gravel in your crawlspace and is it in good shape? Addressing these issues will go a long way to resolving the problem.
Next, you should be heating and cooling your basement ( including the unfinished basement and crawlspace ) along with the rest of your house. This will circulate the air in your basement preventing a moisture build up. You may have closed your basement vents to save on your heating and cooling bill, but this can set up the conditions for the spider ecosystem above. Make sure all the heating vents are fully open in the unfinished part of the basement and the crawlspace. Don’t have any vents? You may want to hire an HVAC contractor to add them for you.
This may not be enough. You may need to add a dehumidifier to your basement. A dehumidifier pulls this unwanted moisture out of the air. Set the dehumidifier to 55%. Humidity below 60% will not allow mold and mildew to grow. Configure the dehumidifier to drain continuously to your basement floor drain. You will need a short garden hose for this. If you have an old garden hose that leaks or is chronically twisted, cut off the length you need ( typically about three feet ) from the female end of the hose ( the end that connects to your house ). The female end will connect to the dehumidifier, stuff the other end in the basement floor drain. If you choose to use the dehumidifier’s built in bucket instead, you will quickly forget to empty it and the dehumidifier will stop pulling moisture out of the air.
Have spiders in your basement? Lowering the humidity in your basement is the key to a spider free, cleaner, healthier basement.
This article was written my Jim Maurer, a home inspector in the Columbus OH area. Have questions about the article or know someone who needs a home inspection? Call Jim at 614-431-2300.