It would depend on the buildings

If the buildings are showing their front then you should have a road for access. If they are showing a loading platform or loading doors then they need to be near the tracks. If they are showing their back without RR access then you could have a little space with a fence between tracks and building.

would you have them touch?

It depends on the scene I'm trying to create. Is it a busy city area where the buildings would be built touching or is it a rural scene where they had room to space the buildings, or is it something in between like a suburb location?  As for the use of N scale background buildings it might look okay if they are not placed right against the larger HO scale buildings but something like 80% of HO might look better if you are scratch building them. I have a scene on my layout with an HO scale 87:1 bridge in the background about 3 feet from my S scale 64:1 winery building and it looks okay. I suggest standing in your layout aisle, viewing the area from your operating position and arrange some cardboard building mock ups in different pattern till you find something that works for you....DaveB

Very similar layout concept

Hi there...thought I would throw my 2 cents your way...

I am also running a switching HO layout - two moduless on industrial strength roll around shelving in the shape of an 'L'...one is 3 feet deep, and one is 20" deep...both are 8 feet long - but that makes the 20" deep module 11 feet long. (the 'L')

OK so now after all that.. the buildings for most of the businesses are on the 3 foot deep module....I chose to space my buildings after the move to North Las Vegas 8 months ago.  Before I had a few butted against one another but that was because I was trying to (force) get more buildings on the layout which in the long run I just didn't need.

top picture shows the separation of buildings which is currently how it will stay...bottom is before the move after the layout was "complete" (they never are face it)...and running switchers. Pictures show at least three buildings side by side

Separation allows you to insert roads and accesses to the businesses to fill out the scene:

And then when I have open back ground I use building flats I create from leftover parts and sides of buildings I did not complete building.  Like above.

I know some folks use N scale to depict distance for the back ground - but you have to consider, how much distance would you really see depending on the height of the view.  my layout is at a comfortable height for me which is almost street level.  56" actually above the floor.

I am still working of the back drop on the lengths of both modules, so there is a lot of work to be done.

Hope that helps

Pix in the first post.

It seems I didn’t post the pics correctly on the first post. Maybe an admin can give me an assist. There are two pictures showing the buildings I’ve already built to go along the back wall behind the yard which will be on the viewer side.

most if not all of the buildings have loading docks/loading doors.

Pic...

Here you go: 

Randy

Thanks Randy!

That’s the second pic, the right side. Does the first pic work?

Apparently I uploaded the 2nd pic twice, that may teach me to do this on my phone.

Negative space scenery

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There is another topic open now about negative space scenery. 

https://model-railroad-hobbyist.com/taxonomy/term/7

The concept to let some open space between building or between scene by making open scenery or any kind of opening which cut away the overwhelmed  scene we often produce.

Yes one of the  factor of the overwhelmed scene is space, by the way we need to use any square inch to put models or trains.

Back to this topic, for sure along a yard many real building are all against each other, but....

If you look carefully on old pictures you will quickly notice a big amount of open space resumed by streets or small open surface or even demolished buildings.

Here you can find numerous pictures of "wall yard building"  with open space    www.shorpy.com

It's not very difficult to model such scene and the opening could be also kind of vista of further or behind country giving the illusion the open space exist behind the wall of building .

Isolate each building from each other give a kind of patchwork not realistic, but blocs of a few building separate by some open space or vista is really natural.

The famous trick of John Allen with the use of mirrors is particularly appropriate in this case, like a tunnel or a bridge with a street which connect the front scene to the back scene.

Vegetation is also important in such scene and also help to make open space or something different in the wall of building.

So a full wall of building seems to me overwhelming and behind to be convincing , even if it's seems impressive.

My original notion

was to leave some space between several groups of buildings. Then two things happened;

I started shopping "picture" background buildings, and they were often "touching".

I ended up with to more buildings and felt the urge to "cram" them all in, as they have no other place on the layout, only in this 10 foot section.

I leaning back to leaving some space, we'll see what appears in those spaces.

More examples of what you've done is appreciated.