On simple floors you can frame straight from the walls. But as a layout grows — more columns, repeated bays, a need to coordinate precisely — a structural grid becomes the backbone of the drawing. It sets out where the structure lives and gives everyone a shared way to point at a spot. This primer explains what the grid and its columns communicate, and when to use them.

If you are still getting comfortable with the drawing, how to read a floor framing plan gives the wider picture, and the floor framing plan guide is the full reference.

What the grid is

A structural grid is a set of setting-out lines running in two directions. By convention, one direction is labelled with letters (A, B, C…) and the other with numbers (1, 2, 3…). The lines themselves are usually drawn light or dashed — they are reference geometry, not physical members.

The power of the grid is in its references. A point at the intersection of line B and line 2 is "B-2". That single label locates a column, a connection, or a dimension precisely, and means the same thing to the designer, the engineer, and the crew.

Bays

The spaces between grid lines are bays. Bay dimensions — how far apart the grid lines sit — set the rhythm of the structure and influence how far beams and joists must span within each bay. Regular, sensible bay spacing tends to produce efficient framing; awkward bays force larger members or extra supports.

Columns

Where loads need to come down away from walls, columns appear, typically at grid intersections. On the plan a column is a small filled or outlined square or circle. Each column gathers load from the beams that frame into it and carries it down. Reading from beam to column to the level below shows you the vertical load path.

Setting grid spacing in a preliminary layout

In Framing Plan you can turn on the structural grid to set out lines and place columns at the intersections, and set the grid spacing in millimetres to suit the structure. A few practical pointers for the preliminary stage:

  • Keep bays as regular as the layout allows — consistent spacing simplifies framing.
  • Align grid lines with bearing walls and major openings where you can, so structure and architecture agree.
  • Treat the grid as a coordination tool, not a constraint to fight — it should make the plan easier to read, not harder to draw.

When you do not need a grid

Plenty of residential floors never need a formal grid. A single rectangular room, framed wall-to-wall, reads perfectly well without one. Reach for the grid when you have repeated columns, multiple bays, or a plan large enough that precise coordination starts to matter. On a small plan, you can skip the grid step entirely — see how to draft a preliminary floor framing plan.

Keep it preliminary

Grid layout, column positions, and bay sizing all feed structural design, but the final grid and column scheme is engineering work. Use the preliminary grid to communicate intent and coordinate the layout — and have a qualified engineer confirm the structure for your project.

Try it

Switch on the grid, set your spacing, and drop columns at the intersections to see the bays take shape. Open the framing studio to lay out a structural grid in the browser.