Its in the Detail
If you're thinking of having a go at making some buildings like these, here's the measurements I use.
I'm using 5mm foamcore. All my buildings have a base to them for improved rigidity and warp-resistance. You tend to need this when you're using old foamcore you've had stored in your loft for years.
Of course, the other benefit to this is that you have a boardwalk raised 5mm above the gaming surface already. I use a standard measurement of 5cm per floor of a building at 28mm scale. Doors are 3.5cm high by 2cm wide. I match windows to this height, normally 1.5cm wide and 2 cm deep. Of course this all depends on what building you're going for. My shop windows are 4.5cm high. I simply raise the door to this height by adding a window above it.
Planking on the boardwalk is done in 5mm strips. These are glued on individually. This creates more definition as befits well worn wood. The wooden panelling on the doors is simply done by pressing hard with my pen on a single piece of cardboard. That's a much neater and uniform result. Of course, the difference is only really visible when painted.
As to the weatherboarding, I cut strips to measure the building 1cm deep. These are then placed on top of each other staggered at 5mm intervals. I use a black pen to mark out my buildings and a red pen to mark the 5mm intervals for the weatherboarding.
Oh, don't forget to add 5mm to the height of the ground floor to compensate for the height of the boardwalk!
Of course, these days 28mm has really replaced the old 25mm scale. And thanks to the variety of manufacturers out there it really covers anything from 25-32mm toe to eye on the miniatures. M buildings will be used with Artizan Designs and Perry Miniatures. If you're using these buildings for Malifaux the above dimensions should be fine. However, if you're using those 'heroic scale' miniatures you may need to add 5mm to all heights. I find it much easier to have some painted and based miniatures to hand to check the compatability between the figures you intend to use with the scenery while you're making it.
For the record, I made some old west buildings about a decade ago. They were used for Wargames Foundry miniatures. Back when 25mm was 25mm. Things sure were smaller back then. Needless to say they won't be appearing in this project!
Hope this is helpful...!