What Is a Column Grid?

A common convention runs letters across one axis and numbers across the other, so no intersection is 'B-B.' The side of the plan where A starts should be the same on every sheet. A plan that is rotated relative to the rest of the set should say so, loudly.

Skipped letters, such as omitting I and O because they look like 1 and 0, are a firm convention. Stay consistent. Adding grid A.5 between A and B is the usual way to insert a line without renaming the building.

Columns often sit on grid intersections, but not always. A column offset from the grid should be dimensioned from the grid, not left visually 'close.' The structural plan is the authority for where the column is. The architectural plan should match.

Transfer beams, sloped columns, and circular grids break the simple story. They still need names and dimensions. A radial grid should say how angles are measured.

Backgrounds given to engineers should include the current grids and their dimensions. A mechanical shaft called 'near grid C' is not located. 'Centered on C-4, 2 feet toward D' is located.

If architecture inserts a grid and does not reissue backgrounds, the engineer's sheets will not show it. Coordination starts with a grid check, before the ducts are drawn.

Overall dimension, then bay dimensions, should add up. A string that does not add is a drawing error of the expensive kind, because layout crews start from grids. Publish one chain. Do not dimension the same bay differently on the architectural and structural sheets.

Establish the origin. A grid dimensioned from a property line on civil and from a column on architecture, with no tie between them, will float when the surveyor lays it out.

Survey control and the grid have to be tied on the site plan or a dimension plan. After layout, walls and embeds are measured from that control. A late grid shift moves embeds, openings, and steel.

As-built grids that drifted are recorded. Pretending the as-built matches the design grid hides a problem the next phase will hit.