Do you use cork roadbed on yard tracks?

I do use the cork.  Only because I like the uneveness.  I have two set's of tracks that are right out of my office window that run through a gravel parking lot in a warehouse area.  They are considerably higher than the gravel lot. 

I covered my entire switching layout with Homasote. Then raised the mainline and siding with more homasote and/or cork. All the industry tracks are on top of the base layer of homasote creating 3 different levels of track, just like the real world.

Most yard tracks are ballasted with small crushed rocks, significantly smaller than mainline ballast, and covered up to the rail for the most part. Depending how you plan to ballast the yard tracks, it will just require more ballast whether or not you use cork. If you have QB or Homasote as a base, I would attach the yard tracks directly to that. Just my opinion. 

You can see all these yard tracks are "burried" in the dirt. When we walk around in the yards, the ground is level with the top of the ties. We just have to step over the rails.

I had planned to use roadbed on all main and sidings with the yard tracks flat on the board. As stated, to get the uneven look, that you see in real life. Most yards are blackish or grimy looking while the main is gray or newer looking when compared to the yard.

Frank

I will be using Fastrack for my whole layout, and I did consider using another track for my yard and sidings.  I decided I to stay with Fastrack everywhere to save cost since I already own a very large amount of it.  

What I will do is in the yard I will fill ballest between the tracks up to the track level and also glue in ballast between the rails.  Since I will be modeling winter, I will also have the ground covered in dirty snow in the yard.  This should help it look more realisitic.

As for my mainline, I havent decided how I will make it higher then the yard tracks, but it doesn't need to be much higher.

I "submerge" my Yard tracks by installing 3/16" Foamboard over the layout's base material. This brings the "ground" nearly up to tie top. I use oil/soot stained dark ballast. The rest to achieve the Yard track look is taken care of by the scenic dirt and other ground cover. It took a lot of cut and fit due to the many angles created in my Yard but I like the result. Mine is a Service Yard as opposed to a train makeup and car storage yard. It has Sand, Coaling, Water, Diesel Fuel and Switch Towers, Ash Pit and Engine House. I enter and exit bi-direction off 084 and 072 end curves of the inner mainline.

Dewey I doing the same thing on my switching layout. I love to see a pic or 2 of yours. 

Email photos sent.