Rat Slabs for pest control?
My Crawl Space has been invaded. Being near a creek I have a problem with rats following the mole tunnels and, together, they have brought in nearly a cu. yd. of soil through the visqueen vapor barrier along with their other “house-warming gifts”. I am hoping to solve the problem by installing what I’ve come to learn is a rat slab. This is a retro-fit so I was plannning to use 4ft square frames of 2x2s on top of intact 6 mil vapor barrier. I am thinking I can then trolley in 5 gallon buckets and complete as much as my back will tolerate each weekend. I don’t know if I need to do anything special around the poured-in-place piers or what I should do at the foundation perimeter. Except for where the soil is, moisture has not been a problem. Any advice that would shorten the learning curve?
Replies
Like Mark says, this is a job for a pump. Mixing and hauling that much concrete in pails is an unbelieveable amount of work.
If you really must do without a pump, think about some sort of chute that would at least direct the concrete into the space so you can distribute it from down there.
Before you go the 5-gallon bucket route, figure out how many you have to do. A 5 gallon bucket (filled to the brim) is about 4 square feet at 2" (but of course you want a MINIMUM of 2" and will probably average 3" or more overall). 1000 square feet would be 250 5-gallon buckets, 500 buckets half-full, 750 half-full buckets at 3" depth.
While you're figuring, calculate the wt. of 5 gal of concrete...
I don't know the poundage, but I couldn't lift it comfortably (and be able to do anything with it) and doubt the handle would hold either.
Then again, I'm old and used up.
Yeah, a half-bucket's about the most I can carry standing upright. Hauling it around in a crawl would be a real chore.
At the very least one would want to work up some sort of plank slide, or better still a trolley.
crawl space freight..
I have several 8-10' long sections of
roller beds that snap together for a fairly mobile continous conveyer. A plywood sled with a guide rope on either end will move material pretty easy in buckets. I have also built a sized to suit plywood box with a drop front for other occaisions.
With someone on each end you can move soil out or building material in pretty easy. Well, anyway easier than dragging/shoving buckets. On a flat piece of plywood you can sled yourself in and out as well, a in a pleasant style compared to crawling.
Never had to build a rat slab but have done a few pier addition and footing repairs this way.
The roller beds were bought at plant auctions and such over the years, buying new would require some number crunching.
And to think how much (little) more it would have cost at the time of new construction to do it right the first time. A concrete Pumper might work if i could get the arm in the front door, into the coat closet, through the floor access, and miss the main sewer stack running through the middle of the access. And that's only if the concrete truck and pumper can somehow hover above the septic field. I think I'm *&*&547^%! Actually the trolley sounds like a good idea, especially with a skateboard left behind when the kids went off to college. As long as I've got a broad enough base to keep it from tipping that should accelerate the transit but I'm still trying to drop another handling step from the process. Maybe making a Plywood mud cart that would hold enough to fill out each 4ft square cell. I'm not sure of the why for three inch thick slab, the only need I have is vermin control, does that require greater than 2" of concrete?
The reason you figure three is that you're aiming for two, but you want to err on the side of thicker, not thinner. An inch thickness+/- is not much when you're froming up for concrete. (But is there really that much difference between 500 buckets and 750?)
You might consider another approach. I would guess that you could use some sort of wire mesh, either hardware cloth or expanded metal.
(And for pumping I'd be inclined to knock a hole in the foundation wall. I'd be even more inclined to do so if I was hauling buckets.)
Get the pump with a hose, usually towed behind a pickup truck. Then you are just dragging a hose into the crawl. Start pumping at the far end, screed as you go. You should be done in a short period of time. I did that on a garage, that was converted to a bedroom. I wanted the floor level instead of a 4" step down. Be aware, it is going to get hot in there so you do not have much time to work the concrete. Screed as you go. The heat of the reaction in a closed space will build up pretty fast.
And to think how much (little) more it would have cost at the time of new construction to do it right the first time. A concrete Pumper might work if i could get the arm in the front door, into the coat closet, through the floor access, and miss the main sewer stack running through the middle of the access. And that's only if the concrete truck and pumper can somehow hover above the septic field. I think I'm *&*&547^%! Actually the trolley sounds like a good idea, especially with a skateboard left behind when the kids went off to college. As long as I've got a broad enough base to keep it from tipping that should accelerate the transit but I'm still trying to drop another handling step from the process. Maybe making a Plywood mud cart that would hold enough to fill out each 4ft square cell. I'm not sure of the why for three inch thick slab, the only need I have is vermin control, does that require greater than 2" of concrete?
The trolley's a great idea. If that's too expensive another solution is to build a square wooden box of 2X's and plywood, 6-8" deep that will accept the bottom of a 5 gallon bucket snuggly. On the bottom of the box install 4 wheels, as big as you can get (the bigger the wheel, the easier the rolling) and still have the gig with a bucket in place fit in the space and be able to tip it to pour out the concrete. The wheels should be able to spin 360D. Get some 1/4" plywood and use that to make rolling the gig easier. Reposition the plywood as needed.
Also, regarding the pump (which is actually the best solution), have you considered making some temporary openings in the foundation wall to accept the pumping pipe? Never measured one of those pipes but it looks like 8" ought to do it.
Doug
concrete barrier
I have the similar situation, although no rats but other burrowing animals. Also I only have about 20'x20' area. I was thinking first layer of metal lathe to discourage then a layer of durock sheets - the concrete only sheets, not wood fiber plus cement. I was wondering, however, if rats may be able to chew through these sheets?
If you can use the sheets, but the ground was too rough, could the sheets be roughly tied together with wire and the overlapping joints filled with mortar? I was thinking of chain mail armor. Hope it helps.
Either expanded metal mesh or the cement board should work, both together would be overkill. The only trick with either is to assure the joints (and outer edges) aren't vulnerable. With the mesh you can overlapp a little and fasten them together with wire or hog rings, then maybe pour concrete along the outer edges.. Cement board would be trickier.
The mesh would be hell to crawl on, though.
(Of course, expanded metal runs about $50 a 4x8 sheet, and you'd need about 15 of them.)
There is nothing that rats cannot chew thru if they have incentive to get to the other side
My aunt had rats chew through her concrete foundation. My guess is it was a weak or poorly mixed batch of concrete. My uncle built the house himself up a holler in Kentucky and I know they were poverty stricken so he may have skimped on the portland, but I was still impressed with the rats chewing ability. My aunt calls them mountain rats, they might be a different species from the Norway rats, or just healthier.
Rats will find a way thru all those multiple joints in the 2x2 forms.
There is no need to be neat as a pin with a rat slab, as long as the surface is troweled smooth enuf to keep from taking off all your skin as you crawl on it later.
So hire it done and be finished in a day, or just do it bit by bit without bother with forms.
If it was me, I'd hire a pumper on a trailer and just gitter dun