Tunneling critters under foundation

pinkpaulaFebruary 1, 2013

Our house was built in 1910. It was constructed on brick pillars which extend at least a foot underneath the ground. Some time in the past 40 years, a previous owner filled in the gaps between the pillars with cement block and painted the whole foundation to make it look cohesive. The cement block sits directly on top of the ground.

A couple of weeks ago we noticed tunnels going underneath the cement block portions of the foundation. Then, something obviously died in one of our walls---what a smell!

We called our pest control company. They determined that in order to keep the rats or chipmunks from tunneling under the cement block, a trench one foot wide and one foot deep under the ground level would have to be dug around the entire perimeter of the house and filled with cement. In addition, we are going to have an entire house exclusion done to fill in any access areas other than the foundation. They are also setting numerous traps to eliminate any existing rodents.

My question to all of you old house owners is, Have any of you had this cement trench done and, most important, did it stop critters from tunneling under your foundation?

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I'd consider the other option: since the cement blocks aren't load bearing as they have no footings whatever, remove them. This will eliminate a hiding place for the vermin, and negates the expensive remedial measures proposed, beside sealing up gaps in the flooring system of the house itself.

    Bookmark   February 1, 2013 at 2:44PM
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Columbusguy1, Possibly, but then larger animals like stray cats and dogs, raccoons, etc. could easily get underneath the house. Also, the house would look very unattractive on brick pillars in the middle of a really nice neighborhood. And, the tunneling rodents would still have their tunnels.

    Bookmark   February 1, 2013 at 6:57PM
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Fori is not pleased

Rats and chipmunks don't really tunnel. I'd get a new pest company. It sounds like they are trying to contain bamboo.

The animals aren't going to die there very often. Just be sure they can get out.

    Bookmark   February 1, 2013 at 10:39PM
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I'm with Pinkpaula - if nothing else, the block would provide a good barrier against wind and weather. Keep it.
From my experience the pest company is correct. You will have to have some sort of barrier to stop the tunneling. It's possible to use other products, but most are either temporary (rotting, rusting, etc) or more expensive. A depth of a foot is probably the least you can do and be effective as most rodents don't go much deeper than that, but can get about that far down. Cement is a good way to go and that width is perfectly adequate (if not a bit much), I would think, without knowing your geographic area.
I'm going to ask a friend that worked in an old house area with an extermination company what she thinks... tomorrow, at a better, more polite hour. :)

    Bookmark   February 1, 2013 at 10:44PM
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fori, I didn't think rats and chipmunks made tunnels either until I did a Google search on the subject. They, along with voles and gophers, can do incredible damage to yards, driveways, and foundations. Our lab is going crazy sniffing around the openings to the tunnels, so we know something is in there. I just hope the cement barrier, along with traps, gets rid of the problem. One dead rodent inside a wall is one too many!

ging, We live just south of Atlanta. I would appreciate knowing what your friend has to say about the cement. Thanks!

    Bookmark   February 1, 2013 at 11:41PM
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Rats tunnel. Skunks tunnel. No need for critters to die to create odours.

ColumbusGuy is right that the proposed concrete under the blocks is a bandaid on a bandaid. That's usually bad.

Why not take this opportunity to assess the foundation overall and determine what your preference would be - so you don't want bare pillars, but do you want something other than concrete block? Does the house need its support, or perimeter drainage, or anything related addressed? If so, better to address the whole thing at once than to spend a few thousand on something you'll be dismantling in a few years.

If you do just want to close off the existing block walls, then there are cheaper ways to do it than pouring concrete. For example, you can dig down and put big stone tiles vertically (for a similar problem under our shed we used counter off-cuts that we pick up locally for free) or concrete slabs (24x24 perhaps). This option has the trench being dug beside the concrete blocks, not under them, is probably cheaper, and is both solid and readily reversible if you decide someday to, say, lift the house or need to augment the original pillars.

Karin L

    Bookmark   February 3, 2013 at 9:03PM
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Hi Pinkpaula,
Haven't forgotten about you - had all the tornado trouble here (north of Atlanta) and my friend has been uber busy. I will try to find out something tomorrow.
Talk to you soon,

    Bookmark   February 4, 2013 at 9:27PM
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Karin L. You suggested that "the trench be dug beside the concrete blocks, not under them". This is exactly what we are going to do. It is less labor intensive than taking out the concrete blocks,digging a new footing, and replacing the concrete blocks. The crew is coming tomorrow to dig the trench; then they will fill it with concrete.

Ging, Atlanta has had its share of bad weather lately. I do hope your friend will say that the concrete trench works effectively. Thanks for remembering this topic.

    Bookmark   February 5, 2013 at 12:29AM
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Hi Pinkpaula!
She got back to me! This is her response.

'The pest company's suggestion is the most permanent fix to the problem. A more temporary (but still fairly long lasting) option is to dig the trench at least one foot down and use heavy gauge wire. There is a type of heavy gauge bitty wire (chicken wire) that is used in cementing and other construction applications which has very tiny holes however, many chipmunks and very small mice would still be able to get through it, that's why the cement is really the best option. Any uglier but also fairly long-lasting and more effective method would be heavy gauge tin buried a foot deep and extending up above the existing block. It would be place underneath the house not on the outside where people could see it and would need installed as flush to the block as possible so they couldn't get between it and the block.'

I imagine this is too late to be particularly useful, but I thought you still might like to hear it. Best to you and hope all those 'pesty' problems cease.

    Bookmark   February 5, 2013 at 10:31AM
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Ging, I was relieved to get your input. I feel that we made the right decision to use the concrete trench. NOBODY wants to go to bed at night thinking that "something" is tunneling under their bedroom---and the problem, left unattended, would certainly get worse, possibly becoming a health issue.
I'd like to post a before and after picture on the same page, but I can't figure out how to do it. I have to post two entries.

    Bookmark   February 5, 2013 at 3:29PM
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After, but before final cleanup:

This is what was done all around the perimeter of the house. The crew we hired was good. They got here at 8:30 this morning and should be finished by 5:00 this afternoon. They are smoothing the surface of the concrete right now,and they will finish with cleaning up the yard and placing pine straw in the planting beds.

I must say, I do admire those who do physical work for a living.

    Bookmark   February 5, 2013 at 3:36PM
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Very nice. So glad it all seems to be going swimmingly. Hopefully, all will be quiet and peaceful 'below'. :)

    Bookmark   February 5, 2013 at 3:43PM
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