Generally the whole warehouse

Generally the whole warehouse floor is at boxcar/traier height with a removeable dock plate between the car and warehouse floor to handle the forklift.

Barry.

In this day and age most

In this day and age most warehouses are built at loading dock height with the intention of loading/unloading trucks , boxcars are usually an afterthought...unless you use a lot of boxcars.

If your just loading and unloading boxcars , its not that critical , you can place the warehouse at ground level and unload outside with an external ramp (you see this with lumber because its going to an open air shed)  , or you can place the warehouse at standard loading dock height and use an external platform or shed to load / unload.

Keep mind most modern warehouses built at dock height will have an extra roll up door with a concrete ramp so fork trucks can get down to ground level , to be able to move pallets between buildings and production facilities. So you can use any combination you want that will fit your space / budget / convenience  ,

if its trucks unloaded a lot of them will build at ground height, and cut the ground in front of the dock , so that trucks back down hill into the dock. The problem is that when it rains you end up with a pond in front of the dock.

Its really up to you

An example

Here's Monson Paper in Springfield, MA:  https://goo.gl/maps/Wc9Mnjfvgrzwjjmx6

They've taken advantage of a slight slant of the land so that floor level in the warehouse is the same as ground level on the office side of the building, but on the rail siding side it's high enough to line up with car floors.  You can find the following photos on the Monson Paper website:  http://www.monsonpaper.com/home.html

Floor height

Would depend on the type of building and the terrain. If the ground slopes the loading dock ground might be lower than the other end of the building. On level ground they might grade a depression for the loading dock         (then add a drainage system),or they might make part of the building floor lower then ramp up for the loading dock area. All kinds of possibilities so best to search for photos of the type of industry you want to model , like the paper warehouse Ken posted ....DaveB

Four foot works in most cases

Four foot works in most cases for train or truck.

rich

Thank you for the replies

I should have mentioned that I am building a more or less modern era mainly switching layout but I want the buildings to look large enough to warrant rail service. The buildings will be shallow depth and just just feature the railroad side. I can't find any kits that look substantial enough but should be easy enough to scratch or bash.

The info above gives me some ideas to have a variety of buildings so thank you all.

Bagal

Modern Rail-Served Warehouses

Here's a prototype examole that will give you an extra spot for varied loads, ranflging from boxcars to flatcars with equipment loads. It's a railcar-height open loading dock between two rail-served warehouses. Both have overhead doors on the other side of the wall, allowing forklift access, and the deck is truck-height so stuff can be either unloaded and brought into the warehouse, or transloaded directly onto a railcar. This means to spot could be used as a sort of team track as well. Modeling would be super easy, as the gate doesn't need to actually open - though that would be a nice detail, especially if a flat car were spotted in front of it...