New Build Basement Root Cellar

Hi!
Newbie here, grateful to have found Permies!

We are rebuilding our family home from the ground up. Original house has a dirt floor Root Cellar with access from Basement.  With additions, the root cellar will probably have a concrete floor.  I have been reading to increase my knowledge on how to build, best practices, etc.  I have many questions!  

How big should it be for a family of 4-6, with sink & electricity?
Should I have a drain installed for easy cleaning?
I've heard that mold could be an issue with concrete, any suggestions here would be awesome!
I am hoping to start canning also.  Would a room in front of the Root Cellar be a good idea?  I think it could act as a buffer room for the Root Cellar.
What devices in addition to the thermometer, hygrometer would be a good investment?
What are the best materials to use for shelving/storage?

Thank you in advance for all of your help!

Cool project and welcome to Permies Jodi!

I think that you can keep your humidity higher in the root cellar with a dirt floor.  I lime washed my cement block walls and that seems to have helped with mold.

I had wooden shelves but they got funky so I'm using plastic ones now.

Having a dryer canning storage area outside the root cellar is a great idea.  Remember that squash, onions, garlic and a few other things like it cool but dry so they might fit in that room as well.

A sink in there would be neat, there is a risk that a root cellar will freeze so that might be a problem.  

Size wise I'm thinking 8' by 10' is plenty for storage and moving around.  

Thank you so much for the great advice.  We have to go with a cement floor.  Wondering if a flor drain would be good for clean out.
Also the builder wants to put up a water/thermal barrier around foundation would the be a good idea for the Root cellar?  

Mike Haasl wrote:Cool project and welcome to Permies Jodi!

I think that you can keep your humidity higher in the root cellar with a dirt floor.  I lime washed my cement  walls and that seems to have helped with mold.

I had wooden shelves but they got funky so I'm using plastic ones now.

Having a dryer canning storage area outside the root cellar is a great idea.  Remember that squash, onions, garlic and a few other things like it cool but dry so they might fit in that room as well.

A sink in there would be neat, there is a risk that a root cellar will freeze so that might be a problem.  

Size wise I'm thinking 8' by 10' is plenty for storage and moving around.  

Depending on where you live, I'd be tempted to ask them to skip the insulation in the area where the root cellar will be.  Unless you're in a very frigid area (colder than me in northern WI), an uninsulated basement wall or corner will help your root cellar get cold enough.  Too cold is fixable by cracking the cellar door.  Too warm is hard to fix.

Consider a limecrete floor instead of a concrete floor that contains cement.
The lime crete breaths.

The reason for the bare dirt floor is to let moisture from the ground to help keep the humidity up in the root cellar.  A different porous floor would work, as long as the builder doesn't put plastic under it.  They often do that under cement floors and it wouldn't help to have a dirt floor with plastic 8" under it...

Here i only cover the walking area with material who do not let pass humidity, the rest of the cellar is bare earth.

If you have to have a concrete floor, you can wet the floor periodically to increase humidity.