u/arrozvegano

Hi everyone,

I'm an architecture student from South America working on the structural concept for a small single-story house built with wood framing. The house is elevated above the ground on reinforced concrete pier footings, so the floor framing also serves as the structural platform for both the interior floor and an exterior deck.

My initial floor framing layout was:

• Main beams spanning between the concrete piers in one direction.
• Floor joists at 16" (400 mm) on center running perpendicular to those beams.
• Structural sheathing (OSB) over the joists.
• Wood-framed walls sitting on top of the floor platform.

During a review, my professor suggested that I should also include primary beams (or major girders) in the perpendicular direction instead of relying only on the joists. His reasoning was that this would make the platform much stiffer and prevent movement or twisting of the structure.

I'm trying to understand the structural reasoning behind this recommendation.

My questions are:

• Are there any general rules of thumb regarding beam spacing, girders, blocking, bridging, or diaphragm action for this type of platform?
• Is it common practice to create a two-way beam grid in elevated wood-framed houses?
• Under what conditions are joists alone sufficient, and when are additional girders needed?

I'd also really appreciate any books, design guides, framing manuals, or other technical resources that explain the structural behavior of elevated wood floor systems.

Thanks in advance!
*first picture is the reference of what i want to achieve