Rat proofing - how deep to bury hardware cloth?

[My Three Chicks]

Hi. I have a good sized coop and run for my 6 (soon to be 8!) girls. It's secure and predator proof. But I didn't take rat proofing fully into consideration when it was built.
The coop/run sits on dirt and this last spring we had a rat problem. It's under control now but I was thinking about making it rat proof byburying hardware cloth around the entire perimeter of the coop/run which is 8' x 22'.
How deep do I need to bury the hardware cloth down vertically to prevent them from digging underground and into the run?
Anything else I should consider?

Attached are a couple of photos.

 

[aart]

Do you have any anti-digging mesh around the cop and run already?
Were the rats digging under to get in or.....?
I've read at least a foot deep for rats, but really not sure.

 

[My Three Chicks]

Do you have any anti-digging mesh around the cop and run already?
Were the rats digging under to get in or.....?
I've read at least a foot deep for rats, but really not sure.

I don't have any anti-digging mesh that spreads out from the perimeter of the coop/run.

The rats were both digging from just outside the run, under the wood, then popping up right on the other side. But they were are also digging from directly underground where their burrow holes would show up in the middle of the run.

 

[perkolator]

Horizontal anti-dig skirting would be pretty easy to add vs all the work it would take to dig down for a vertical barrier

 

[My Three Chicks]

Horizontal anti-dig skirting would be pretty easy to add vs all the work it would take to dig down for a vertical barrier

That would definitely be easier, but I think since they are creating underground burrows they just have a path deeper underground and coming up from under the run.

 

[LaurelC]

Do you have any anti-digging mesh around the cop and run already?
Were the rats digging under to get in or.....?
I've read at least a foot deep for rats, but really not sure.

I had 1/4" hardware cloth buried ~18" and the rats tunnelled under it. The most effective way would be to fully enclose the bottom top and sides of the run in 1/4" mesh.

 

[My Three Chicks]

I had 1/4" hardware cloth buried ~18" and the rats tunnelled under it. The most effective way would be to fully enclose the bottom top and sides of the run in 1/4" mesh.

Wow yeah that's what I was afraid of, that they dig down quite deep.
So you mean like putting mesh wire across the floor of the run and up the side to meet up the wood/wire of the existing walls?

 

[LaurelC]

Wow yeah that's what I was afraid of, that they dig down quite deep.
So you mean like putting mesh wire across the floor of the run and up the side to meet up the wood/wire of the existing walls?

Yeah. I was never able to beat them without a big expensive overhaul to the design as the top 4' of our run was 2x4" wire mesh that the rats could easily get through if i were to enclose the bottom of the run with hardware cloth. The rats were a big enough issue that we eventually got rid of the chickens, and when we sold our house a few years later to move somewhere rural, we ended up having to drop ~$4k to have all of the insulation and vapor barrier replaced in our crawl space as the rats were splitting their time between the chickens and the house's crawl space. It didn't help that our soil was fine sand that was very easy to excavate. The pest control folks said that there's really not anything to do to stop them except trapping.

 

[perkolator]

If you think they're tunneling in from deeper to get in the middle of the structure, then covering the floor is probably your next option if you want to stop that. I did HC underneath the floor of my coop, because in the old setup the rats were using mole tunnels to get in, and rodents promote the rattlesnakes that I don't want around my kids - my HC is buried about 6-8" below grade so the chickens are less likely to dig down to it

 

[Nicole Bee]

If you think they're tunneling in from deeper to get in the middle of the structure, then covering the floor is probably your next option if you want to stop that. I did HC underneath the floor of my coop, because in the old setup the rats were using mole tunnels to get in, and rodents promote the rattlesnakes that I don't want around my kids - my HC is buried about 6-8" below grade so the chickens are less likely to dig down to it

This may be a really dumb question, (chicken newbie here!) but can you lay hardware cloth down on the ground rather than burying it? Perhaps use wood shavings or hay over the hardware cloth for the chickens?