Preventing rats in cleaned out crawl space

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  #1  
Old 01-24-19, 02:45 PM
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Preventing rats in cleaned out crawl space

I have a small crawl space (under 500 sq. ft underneath a room addition) as the rest of the house has a basement. Anyways, rats have been in there before and it was much worse than I thought. They not only got into the insulation around the ductwork but also got above the batt insulation. Anyways, I am getting everything removed, disinfected, and any openings sealed up and then reinsulated. This section does not have a foundation so I plan to dig down 6 inches or so up against the plywood skirting and fill it with concrete to prevent any future rats from digging under it. Once that is all in place, I am looking for ideas for ongoing pest control. I am not going to hire anyone to come out and set traps so would it be advisable to just constantly leave some snap traps inside it? Any other ideas?

A deck surrounds the room above so the crawl space access is under the deck (but with at least 3-5 feet clearance so you can walk around it easy enough). The ground outside the crawlspace is just dirt and part of it has plastic over it. Would it be better suited to get rid of the plastic and put pea gravel or crushed rock under the deck instead? Id on't know if that will deter anything but I remember reading somewhere that rats don't like digging in pea gravel.
 
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  #2  
Old 01-25-19, 07:29 AM
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I never did like plastic on the ground when it was on the exterior of the structure as it traps moisture and allows almost waterproof harborage for rodents and insects. I personally would remove that unless there was a compelling reason otherwise.

As far as pea gravel, my thoughts are that it would need to be quite deep to discourage digging. If it's not deep enough they will simply get to the soil underneath and dig burrows. It needs to be deep enough so that it collapses on them well before they find the ground so I think that depth of pea gravel would be prohibitive and might not work anyway. Could turn out to be a waste of time and money and effort.

Keeping traps set with the bait/lure being freshened regularly is always a good idea. Having exterior grade rodent baiting stations in crawl and under deck would also have value but the bait needs to be kept fresh on a regular basis.

Is there still rat activity? If so, any idea where they are living and what their food and water sources are? Dealing with them at their harborage and food sources would be the ideal way to prevent them from traveling to your house but it if's on neighboring properties then that may not be viable.
 
  #3  
Old 01-25-19, 09:21 AM
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I don't know why the plastic was there. Maybe to keep it from getting muddy? But that actually probably gave them a nice water source as well because the water would collect on it during the rainy season I would probably want to put some type of rock there anyways just to keep it nicer under there. How thick of pea gravel would help? If it is too much, I might just put a thinner layer of crushed rock just to keep it a little cleaner.

I don't know if the rodents are active. They were definitely living in the insulation around the ductwork and even up above the batts under the floor. I can see how they got up there easily because someone tacked plastic sheathing under the joists so they had a nice way to travel up there! When I get that all removed, I will see if they found any live rats. I know at one point they got in there by digging under the plywood skirting around the posts which is why I dug down a little and poured concrete over half of it and will continue to do the rest. I did throw a couple traps in there recently and only caught a mouse. Once they remove everything, it will be pretty open so there would really be no place for them to hide if they are in there.

I think you replied to my other post about them being in the attic and that is the only place I know for sure they are now. The place where I hear them is actually above this room with the crawlspace so at least the guys will seal any holes if there are any through the floor/wall. I can't imagine there would be anything big enough for a rat to get up to from floor to ceiling through the wall, but that chimney I mentioned is right in that same area so I think they are climbing up it somehow. What do you recommend for the snap traps? Peanut butter? As far as the exterior bait stations, I just but some of those Tom Cat black boxes with the green bait. Shortly after I did it, I had a dead smell in my house, particularly near one of the heat vents. While most of the ducting is metal under that section of house, there is one flex duct so it is possibly they got into that. Regardless, that is going to get replaced and I am having the ducts sealed and cleaned.

Sorry for the long post, but since you have a lot of knowledge, I figured I would ask a little more. Do rats tend to come in go? For example, last winter I heard some in the attic too and I caught a couple but then I didn't hear anything all summer. Same with the crawl space. Do they just come back when it gets cold out? Where else do they usually live? Underground? I can't think of the typical food sources because we have no pets. Thank you again for all your help.
 
  #4  
Old 01-25-19, 09:48 AM
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I don't know if the pea gravel would work but it seems to me that it would have to be 10-12" deep. As resourceful as rats are, they may still clear an area and burrow anyway. They are survivors. It's all they have to do in life. That's why I commented that it may be a waste of time, material and money.

AS far as bait for snap traps, peanut butter can be good, but "slim jims" or "beef sticks", "beef jerky" in 1" lengths or so are very good. They can be tied to the trigger if that works better. Thread or dental floss, thin wire, etc.

Could there be a food source at neighboring properties that are 100-200 yards away? They may not feel safe living near the food source but feel (felt) safe using your property as harborage. They easily travel that distance for food and then back to safe harborage. Pet food, bird food, poorly stored garbage, animal barns, dog house, etc are all atractive to rats.

https://www.domyown.com/rat-bait-stations-c-21_333.html

These are examples of exterior and tamper proof rat stations. They are large enought to allow rat entry. I don't think the smaller tomahawk stations will allow rats. These are expensive but required if you were to hire someone. You could make your own too. Any material that would protect the bait from weather would be good enough. Lengths of 4" or bigger PVC pipe can work as a crude bait station too. Make sure it doesn't roll or wobble. Inside the crawl you could just place them on plastic or something to keep the rodenticide off the ground to keep it drier. Make sure no dog accidentally gets in as they can quickly ingest bait blocks.
 
  #5  
Old 01-25-19, 10:31 AM
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Ok, forget the pea gravel idea then! I will remove the plastic though and maybe just put a thin layer of rock down so it is not too muddy there when I have to go in and out. I have never tried meat but I will give it a try. How about raw bacon? Does that work too? Those boxes you shown are not too expensive an look pretty sturdy so maybe I will get a few of those. The ones I bought before are found here https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 One time I found one upside down a few yards away so maybe a rat flipped it over? They are pretty large. They came with a ton of bait so will that work in those boxes you showed or is it different? Is it better to put the bait outside of the crawlspace rather than inside so they don't die inside?


Just thought of this too...I only dug down about 6 inches and poured some concrete. Is that deep enough?
 
  #6  
Old 01-25-19, 01:30 PM
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Your Tomcat box is bigger than I thought and they do advertise it for rats. Any bait and formulation such as meal, blocks, pellets, etc will work. If they are eating the Tomcat than keep using it.

Bacon would be a good choice, too, raw or cooked.

The "flipped over" bait box was probably flipped over by a raccoon or opossum or some such animal. It's ok to put bricks or rocks on top of them but in cold weather do it gently as they get brittle and can crack. Sidenote: if they crack, duct tape will work well to close the crack and keep rainwater out.

As far as whether to put them in or outside of crawl space, even if exterior only baiting is done, they could still die inside if they are entering/exiting. In my own house with mice, I do have bait inside and I take the chance of getting a bad odor and it has happened to me. The odor of a dead rat is way worse as it is a larger animal.

If you do buy the exterior bait stations see which ones you could put a rat snap trap inside. Some companies are doing only trapping and they use the bait statioins to protect the traps and keep non-target animals away.

You could bait outside and trap inside too, which would minimize but not eliminate the chance of them dying inside.

I don't know if six inches of concrete depth is good enough or not. Rodents will burrow against the side of even deep foundations and simply live there because of the structure and possible warmth that radiates. In any case, this is much better than you had and it will force them to expose themselves if they do that and you can deal with them then.
 
  #7  
Old 01-26-19, 01:52 PM
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Great. I have just neglected this too long and hopefully if I keep up with now, it should cut them down. Since you know what you are talking about, I want to run one more thing past you. As you see from my first post, I am getting my crawl space cleaned out under this room. I got a good bid from one place, but another place wanted to just tear everything out first and get on their pest control service for $350 or whatever. I am not going to go with that, but it gave me an idea. First of all, this room looks like it was built over the structure of an existing deck because there is 2x4 decking, then a subfloor which looks to be about an inch, and then hardwoods. I was thinking of just having them remove all the insulation and leaving it without, at least for now, to make sure there are no rats. I am also curious to see if may even be warm enough without insulation with all that solid wood down there. Do you think it is a good idea to leave it bare and see how it goes? I would still have them insulate the ductwork, but is there something I can put over that too to keep them out? Maybe like wrap the whole insulated duck with some chicken wire with very small holes or some type of still mesh?

As far as pest control services, I imagine they are pretty knowledgeable and know what to look for, but do they just basically place traps and bait just like I would? Thanks again.
 
  #8  
Old 01-26-19, 02:32 PM
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As to leaving it bare and without insulation, that choice will be easier when seeing what the rodent evidence looks like in the torn out insulation and if live rats are noted, etc. It wouldn't be wrong to leave the insulation out for a while. This would be a good time to inspect all the wood for mildew, mold, etc too.

The existing ductwork is metal if I'm understanding this as you are talking about insulating it. I'd be surprised if rats could chew through the metal duct so it might be overkill to wrap them in hardware cloth, though 1/4" hardware cloth would be a good material.

Pest control services would bait and trap much like you're doing. Some do exclusion which would be a big dollar amount but it sounds like you're onto that pretty well. The rodenticide baits that they would use are the same as over the counter as far as active ingredient. The brand names may/may not be different.

Continue with the baiting/trapping and judge the results. You are gaining knowledge and experience as this goes forward.

Rats are neophobic, meaning a fear of new things, especially the older rats. Sometimes trappers will "pre-bait" snap traps until the rodent accepts it confidently. Then they set the trap with the same bait in it.
 
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Old 01-26-19, 02:50 PM
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Yes, it is metal duct, but right now they had gotten into the insulation around the metal duct. I just don't want them messing with the new insulation. Maybe I will just get it all removed now and leave it open and see how it is. I can always do it later. Maybe I will even tack that hardware cloth under the joists after the insulation is in place then they can't get in there for sure. With rats having been up in it for who knows how long, I am sure there are a lot of voids so it is probably like not having any insulation up there now! Thanks for all your help. Now I just need to get them out of the attic and I will be set. I put some traps up on the roof where I think they are getting into so we'll see how that goes. I know they can climb up vertical walls, but they can't go upside down, can they? I have eaves on all sides so if they go up the wall, can they go upside down under the eave to get to the roof? I am thinking no so there really only a couple of areas (chimney and a canopy I suppose they could climb up onto). I also have no tree branches touching the roof. Do rats just sleep all day and then come out at night to get food?
 

Last edited by dm888; 01-26-19 at 03:38 PM.
  #10  
Old 01-28-19, 12:24 PM
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HI again. Sorry for all the questions and postings in two different places, but I want to make sure I get this right. Let me know if you think this is a good plan:

I will have the insulation contractor just remove all of the insulation, vapor barrier, etc. from the crawl space and ducts, sweep up all the droppings, deodorize, etc. They have included in their quote to do duct sealing as well and with rebates from the energy company, it ends up being under $100 so I'll have them do that too. One of the ducts from the main one is a flex duct that is about 15' so they are going to replace that too, as I can see some of the insulation was chewed so they may have even gotten inside. They are also going to seal up any holes they find around the perimeter above ground level and lay down a new vapor barrier. I am going to hold off on insulating the floor for now, but they probably should insulate the ducts or that will lose a lot of heat, right? Before they start sealing any holes, I will take a look or have them see if there are any holes that may go up through the wall above and into the attic. If so, I will leave them unsealed for now. You mentioned that mice are ok to trap inside, and since I did catch a mouse in the crawlspace, what is the largest size hole you would seal up (assuming it is just big enough for a mouse)? Once it is all cleaned up, I will continue digging a concrete trench around the skirting and place several traps and bait inside and out. What do you think, place a trap every 10 feet around the perimeter inside? Assuming I can't find where they may have entered the crawlspace, would it be a good idea to leave a small opening to allow them to leave the crawl space in case they are in there? Would they just keep going around the perimeter until they found it? Sorry so long winded, but I just want to get this right. Thank you again for all of your advice. I really appreciate it.
 
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Old 01-28-19, 03:50 PM
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Yes, go ahead and protect the ducts/flex-ducts right away. No potential harm in that. Good to hold off insulating the floor until accurate assements can be made. We may learn nothing helpful, but that still is an answer.

Mouse traps every ten feet are a good spacing; better than what most people do. As far as sealing up holes, please realize that rats and mice will use the same holes. Holes that are smaller than a quarter will be mouse holes though.

If after the insulation removal you think that there may be rats still inside, then I'd leave an opening for them to get out, but the kicker is that rats could still get in. I'd make that decision or think more about it after insulation removal and re-assment.
 
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Old 02-08-19, 10:54 AM
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They are coming today to clean out the crawl space and reinsulate the ducts, but leaving the floors uninsulated for now. If they do happen to run across rats in there that scamper out, they will probably try to come back later and look for their nest, right? What happens when a nest is disturbed? Do they move on or try to rebuild in the same place? Do I want to start placing traps immediately, or leave unset traps for now? There has been snow out which is rare for around here, and it is supposed to snow a lot tonight. That may be useful because in a different area in my yard, I saw a bunch of little footprints leading to a dugout hole in the ground. Anyways, I am a little worried what they might find in there now and if they may scatter or try to come back. I will report back later.
 
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Old 02-08-19, 02:49 PM
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Ok, they are all done. They only encountered one big rat up in the joists but were unable to kill it. It ran off to the corner and at first didn't get out because they saw it again but then after making the final sweep and spraying down everything they did not see it. I did see an opening above the plywood in the area it ran off too so maybe it got out there. I left that opening and just put some paper towels in it to see if it comes back and set 4 traps inside and 2 right outside the crawl space along with a bait box. We did not see any holes going up to the walls or into the basement but the noise that was heard in the wall one time was down low so it is possible it was scratching the wall inside the crawlspace or the floor and maybe wasn't in the wall. Anyways, I was afraid they would find a big nest in there so I guess one is pretty good. In your expertise, would something that got disturbed like this try to come back? At least I can see if there are any droppings or anything since it is clean.
 
  #14  
Old 02-09-19, 07:44 AM
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Rats are neophobic, meaning fear of new things, unlike mice. Being disrupted, especially on a large scale like this could very well chase these rats away for good. Re-iinfestation from new rats that have no memory/history of these events will be possible.

Don't let up, keep traps set like you have and move or add more as your learn more. I don't know if I'd place unset traps now as a strategy may be to not have them get used to anything and play on the neophobia to keep them away. The old rats are more neophobic than the younger rats so just because some stay away, the younger ones, lower on the pecking order, may return of their hunger and lack of haborage requires them to.

In the long run for effective rodent control, I would want to know where other rats are living in the neighborhood, what brought them to that area, do the conducive conditions still exist, etc. As neighboring rat populations increase, the over flow (the young rats) will periodically search for new food and harborage as the older rats are dominant and territorial. There is no social order in that they would feed each other or share politely. The "alpha" rats get what they want first and maybe they take it all. They will fight the younger ones which is why there will be young rats searching the neighborhood for new food and harborage.
 
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Old 02-14-19, 11:46 AM
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It has been almost a week and nothing set off the traps inside. The funny thing is I put 4 brand new snap traps inside with peanut butter and 2 outside. I had one of those T-rex plastic traps that had been laying outside that I had some salami in a few weeks ago that hadn't even been set and I just figured I'd set it and leave it outside. Guess which one had a rat in it today? LOL I guess it likes old meat that had been sitting around. It was a huge rat too so maybe it is the one they saw. Maybe I will wait a couple of weeks and if there is no activity on the inside traps, I will start sealing up holes. I think I better put the outside traps in a box or something because unfortunately I caught a little bird in one. There has been quite a bit of snow this week so I don't know how that affects the rats. Anyways, we'll see what happens.
 
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