Chicken Run. Stumped on what I should do.

[Bock-Bock-Bagock]

I got an old shed that I'm converting to a chicken coop and run. I'm getting to the point where I will build the run itself now. I'm a little stuck on how I should build it. Mainly the base of the run. I was considering putting down a row or two of cinder blocks for the wood parts to sit on top of and keep the wooden frame from contacting the ground and rotting over time.
As it stands now, the whole area is on top of about 6 inches of softball sized rocks covered in crusher run. I will still put hardware cloth down to keep animals out.
I'm looking for any advice on building the frame on the ground versus elevated. I do want to have about 6-8 inches of dirt/bedding in the run space. So I was thinking of elevating the run to keep it off the ground and give me the space to have dirt for the chickens to dig and play in. I was thinking of maybe using railroad ties, but I'm not sure if that's toxic for the chickens to be around.
Any tips or advice is welcome.

 

[Ridgerunner]

I personally have no problems with railroad ties. The chemicals they use now are a lot safer than the ones they used to use. If they are weathered railroad ties even better.

I'd also have no issues with using treated wood to touch the ground. That's what it is designed for.

You can pour a concrete footing or use cinder blocks to raise it above the soil. I'd want to anchor it down so the wind doesn't blow it off.

When I built my run I used treated posts with wire mesh. No horizontal wood at the bottom. I used wire mesh "aprons" at the bottom for dig protection.

 

[Ted Brown]

There are two kinds of treated wood: ground contact; non ground contact. If you choose to use it make sure you purchase ground contact specified boards only.

Like @Ridgerunner I did not use wood around the bottom of my run. After 5 years of being covered with earth or ... the hardware cloth began to fail at the welds and break apart, particularly when groundhogs decided that the food inside looked tasty. I had to add new horizontal aprons, this time using 1/2" x 1" 16 gauge HC. At the same time I added 2x6 PT boards around the bottom sides so that the wall portions were separated from the mulch+ that is on the run base.

Note that I have a covered run and the ground on which run & coop is sand and gravel so drainage is very good.

I recommend doing things correctly the first time. Either concrete or ground contact PT can be used. As recommended above if you use the blocks make sure the run is secured to the ground in some manner.