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How To: Keep Critters Out of Your Crawlspace

how-to-keep-critters-out-of-your-crawlspaceDo you know who lives underneath your house? Do you want to know? Old houses are often home to a lot of unwanted visitors in the crawlspace and these unwanted pests can cause major damage to things like ductwork, electrical and plumbing. You need to find an attractive way to keep them out. And just for fun, I’m going to see how many synonyms I can come up with for “critters” (that’s 1).

Old houses were often built with a crawlspace especially in warm climates to allow for cool air to pass underneath the house. This construction was done one of two ways usually, though there are always exceptions.

The first was a masonry stem wall built all the way around the perimeter of the crawlspace with small vents spaced throughout to allow for ventilation. The second is commonly referred to as pier and beam construction, which is simply a series of masonry piers spaced around the underside of the house with structural beams resting on top of them which carry the load of the house.

Both of these methods create openings into the crawlspace, which need to left open for proper ventilation, but sealed off to animal visitors.

Pier and beam construction poses a particular problem for keeping critters out of your crawlspace since there are so many openings to cover, whereas stem wall foundations have relatively few openings to protect.

The Lattice Solution

The solution to the problem with pier and beam foundations is two fold and the first is the decorative part, foundation lattice. Foundation lattice is a historically appropriate addition to any pier and beam foundation and it works great to keep the larger pests out. There are a ton of creative options you can use to dress up your house.

There are the standard designs of vertical, checkerboard, and diagonal checkerboard, but the layout is completely up to you and your creativity. Just make sure the spacing is tight enough to keep the cats and opossums out.

If you want to build some yourself, you can read my tutorial on How To Build Historic Lattice, which tells you everything you need to know.

Stopping the Smaller Animals

Lattice itself won’t keep all the troublemakers out. You also need something to keep the smaller more troublesome pests out like rats and mice. Did you know that a mouse can fit through an opening just 1/4″ wide? It’s true. That’s why they get into attics and crawlspaces so easily.

Lattice would have to be a solid piece of wood in order to keep them out, not to mention the fact that they can chew through wood. So what do you do? Two things:

  1. Hardware Cloth – This handy material is like insect screening on steroids. It is a wire mesh that comes in 1/4″ and 1/2″ sizes and it should go over any openings into your crawlspace or attic. It’s metal, and so the critters can’t chew through it and when it’s installed behind the foundation, lattice it’s barely noticeable.
  2. Fill Small Holes – Get out the caulk gun and wood filler and fill in any gaps in your siding and trim. Patch knot holes, caulk joints, anywhere larger than 1/4″ needs to be filled in if you want the varmints out.

Also, keep in mind that these little beasts will burrow under the dirt a little if they really want in, so just running your hardware cloth the ground level may not be sufficient. We typically install our hardware cloth about 8-12″ below the dirt to make sure no one and nothing is getting in unless it packed a shovel.

Other Areas of Concern

While the crawlspace is the biggest problem with these critters getting in, there are also spots like the attic that cause problems. It’s easy to miss 1/4″ holes in your house, especially from 20 feet up.

If you really want to keep everyone and everything out of your house, then go through it and look for any and every way that these boogers can find a way in.

Check eaves, cable lines, power drops, plumbing penetrations. Really anywhere they could get in you need to think of it before they do and seal it off.

Best of luck keeping the home safe, and in case you were counting, that was 7 different words for critters!

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19 thoughts on “How To: Keep Critters Out of Your Crawlspace

  1. My house sits on a steep grade toward the rear. In the rear, the grade slopes so sharply away from the foundation that the bottom of the foundation is visible in some places. Consequently, it is easy for rats to tunnel underneath it and get into the crawl space, which is large and not at all level. I have no expertise, but I’ll start with my own suggestion.
    . 1) Lay hardware cloth onto the slope behind the foundation extending perhaps 20 feet out–secured to the foundation with a ribbon of concrete along the rear foundation and also sealing any pipe openings. I see that the cloth would need to be buried to a certain depth.
    . 2) On the other side of the foundation, inside the crawl space, make the ground level for at least 10 feet away from the foundation and lay a 3″ deep concrete slab there.
    . 3) Continue to snap-trap rats while the fix is being installed, and thereafter, until I catch no more.
    It seems unlikely that a critter would know enough to tunnel for 30 feet to reach the crawl space (unless he saw the building plans!). But perhaps this won’t work. Any comments would be appreciated.

  2. need someone to come out and seal the crawl space so that this animal

    leaves and never returns. I need someone to seal the crawlspace.I live in Island Lake, IL. 60042


  3. We have concrete vents under our 1940s era home. I have seen critters go in. Some of the vents meet concrete in the carport and others are ground level with the yard. Exterminators have helped, but not permanently. HOW would this screen work on the concrete vents? How would one attach to the concrete?

  4. What’s the best way to make sure the critters are out of my crawl space before I try to seal it up? Mine is totally enclosed – they are digging under the foundation to get into it.

  5. In order to prevent entry, you must bend the hardware cloth outward to a 90 degree angle underground as burrowing animals will look for the bottom of the barrier however the bend will foil them.

  6. I have siding and only 4 inches at the highest point. Anything affordable and easy? I am a senior citizen and will have to do this by myself. I can’t use anything but a hand saw? I just want to keep the dog out from under my house. Any ideas or suggestions for this ole granny!

    1. I am having the EXACT same situation. I just bought a house that has pier and beam foundation, with only portions of the crawl space open (6-8 inches). My insurance company say the did not know the space was open so they canceled on me. I was given a new insurance company but they will come inspect in a few weeks so I have to figure out how to enclose it and what the heck do you use?? Lord, I don’t have much money but it has to be done. Any suggestions?? Joan Jan 11, 2020 4:02 pm

  7. Can’t believe I stumbled on this post. I’ve had the hardware cloth rolls sitting around for 6 months while I’ve been pondering whether I really wanted to go this route. Glad to see someone else has actually thought of doing this on a house. Everyone here wants to plaster (or, one handy man wanted to use mobile home metal panels on my craftsman house!). I’m afraid to enclose because, no matter how many vents I put in, the result will be a heck of a lot more humidity under there and hence far greater mold potential. Thoughts on my mold paranoia? Has 23-gauge quarter-inch hardware cloth really worked for the long term? I’m in 102-degree Texas.

    1. It works great and has been tested for he long term. Don’t use chicken wire it’s too large of gaps in the metal. Use stuff that is either 1/4″ or less spaces to keep everything out but still get the airflow you need.

  8. Scott,
    I have critters under my deck (low – 2′ off the ground) in the back of the house. I tried some smelly stuff along the deck, but it doesn’t help.
    I have hollow concrete from stairs on the front of my house. I see where some “critter” has dug down to get behind them.
    I’m at a loss! What can I do for these two areas!!???

  9. I got these metal replacement vent covers i got from Lowes i put them on the outside of the house but the raccoons and opossoms pull them off and get under the house. What should i get i want a permanent fix?

  10. Do I call a handyman or is there a certain company that specializes in coming out and closing up all the openings especially on a peer and beam house

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