I have lived in my house since 2007. I have a large crawlspace (dirt floor, ranging in height) where I have a nice woodworking shop.

In 2011 the shop became infested with fleas, but not the upstairs. Two rounds of flea bombs got rid of them but they came back this year. There is no food or water source for them in the crawlspace.

I imagine that another round or two of flea bombs would get rid of them this time too. Is there any way of getting rid of them permanently? As there is no food or water source for them this seems doable, but I can't think of how.

3 Answers 3


The fleas are most likely lying dormant (deep) in the dirt floor, below where the bombs/sprays will get to.

Couple/few options:

  1. Pave it.
  2. Soak the floor 2' down with a chemical like bleach.
  3. Diatomaceous Earth.

Number 1 is most permanent, #2 is dangerous as all get-out (and probably illegal), whereas #3 is cheap and safe.

Diatomaceous earth is (basically) fossilized algae powder. You spread it on a surface and it will absorb fats out of the waxy outer protection on bugs like fleas, mites, etc. when they land on it or walk across it, dig through it, etc.

Once those fats are gone, the pest dehydrates and dies.

It'll take some time and effort applying and re-applying, but it's cheap at about $40-50 for a 50lbs bag of "Food Grade".

Doing an Internet search for "Diatomaceous earth" and "Fleas" and you'll finds lots of direction on using it for your application.


My suspicion is that you have cats around. Fleas had to catch a ride to get under the floors. Fleas do not dine on "food" that can be removed, just blood in living creature--most familar fleas prefer cats--thus are called cat fleas. The conditions you describe, and the location in a crawl space suggests cats living, hiding, even birthing there, especially when conditions (like seasonal) are (in)conducive. Try treating again, then use louver/hardware cloth to cut of paths, like through vents, for cat admission. If the cat(s) is a pet, use of adult flea kill treatment (like Advantage) can provide some help; possibly enough to do the trick. Inside the house with indoor cats it is very effective because fleas "find" and jump on the cat for a meal (and to be killed...and to lay eggs, which later drop of and hatch...which is likely or at least possibly the cause of your secondary infestation. The fumes wiped out one generation but not egg-housed next generation). Dead adult fleas cannot reproduce. Infestation goes away. But it could be somewhat less effective for a free ranging cat. But can't hurt to try, and the cat will get a benefit no matter. If dog--much less likely--basically the same--keep it out of crawl space, treat it with adult flea kill product.

  • There are no cats to my knowledge, I did have a mice problem earlier in the year though. I didn't think of cats sneaking in though, thank you! Oct 23, 2012 at 14:25
  • You might recall from history that rodent borne fleas were a primary vector in the spread of plague (bubonic plague) during the Black Death that wiped out much of Europe. So, be it mice or cat or both, recommend a program to safeguard the crawl space and control any mammal invaders. Maybe a pet cat, too, (treated as I mentioned) to help "monitor" for mice and sweep up fleas. Asforeliminating residual infestation (similar to post1 bt cheaper,less laborintensive wouldbeto cover thearea well with soapy/detergent water. (case in point: the killing agent in flea shampoo is the plain shampoo part.
    – Lex
    Oct 25, 2012 at 4:57
  • If repeated applications and cat don't clear the infestation, then see what advice and price exterminator can offere...then post 1 well worth considering. It would be of interest to see testimonials for that approach of @techie007
    – Lex
    Oct 25, 2012 at 5:02

The cycle of fleas is 10 days. when I have a heavy infestation, I treat, wait 10 days and treat again and then do it again. In one house, I battled the fleas for months but the only thing that got rid of them was to put Sevin Dust on the carpet, then rub in with a broom, then wait and vacuum. I had to do this twice. Sevin dust is very toxic so wear a mask. Flea larvae and defecation is also toxic. I am allergic to flea larvae. It is not pleasant. I can only imagine what an outbreak would be like if you can actually see the fleas. Good luck with that.

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