The grid lines represent the centerlines (or specific faces) of the main load-bearing columns and walls. They are the reference point for all dimensions.

• Alphanumeric System: Typically, numbers (1, 2, 3...) run along one axis (e.g., across the top of the plan), and letters (A, B, C...) run along the perpendicular axis (down the side).
• Grid Bubbles: The alphanumeric designations are enclosed in circles (bubbles) at the ends of the grid lines.
• Column Location: A column located at the intersection of Grid A and Grid 1 is referred to as "Column A-1". This nomenclature allows instant identification on site and in schedules without ambiguity.
• Sub-Grids: If an intermediate beam or minor column is added between main grid lines, a sub-grid with a decimal or prime notation is created (e.g., Grid 1.5, or Grid A').
• Expansion Joints (EJ): In very long or complex structures (like L-shaped or U-shaped buildings), grid lines often indicate a deliberate physical gap in the structure (an expansion joint). This allows different sections of the building to move independently during an earthquake or thermal expansion, preventing catastrophic cracking.

• Design Criteria: Lists the specific building codes (e.g., National Structural Code of the Philippines - NSCP 2015), the assumed Seismic Zone (e.g., Zone 4, high seismicity), the basic Wind Speed (e.g., 250 kph for severe typhoon areas), and Soil Bearing Capacity (e.g., 150 kPa).
• Material Strengths: Defines the required properties of materials.
  • Concrete Compressive Strength: e.g., f'c = 21 MPa (approx. 3000 psi) at 28 days.
  • Reinforcing Steel Yield Strength: e.g., fy = 275 MPa for Grade 40 rebar, or fy = 414 MPa for Grade 60 (high tensile).
  • Structural Steel Grade: e.g., ASTM A36 for wide flange beams.
• Standard Construction Practices: Minimum concrete cover requirements for different exposures, lap splice lengths, hooking details, and the minimum time required before stripping formwork (e.g., 14 days for suspended slabs).

A top-down view of the building's substructure, cut below the ground floor slab. It shows the elements that transfer the building's entire weight safely into the earth.

• Isolated Footings (F1, F2): Square or rectangular concrete pads supporting individual columns. They are typically drawn with dashed lines if they sit entirely beneath a slab-on-grade.
• Combined Footings: A large, often rectangular pad supporting two adjacent columns, usually required when a property line prevents an isolated footing from being centered under an exterior column.
• Mat Foundation (Raft): A massive, continuous thick slab covering the entire footprint of the building, used when soil bearing capacity is very low or column loads are enormous.
• Wall Footings (WF): Continuous concrete strips supporting load-bearing masonry walls (CHB) or concrete retaining walls.
• Grade Beams / Tie Beams: Heavy reinforced concrete beams connecting the footings or column bases at ground level. They do not carry floor loads; their primary purpose is to tie the foundation together to resist differential settlement and immense lateral seismic forces.

Top-down views showing the layout of the primary horizontal load-carrying members at each specific floor level (e.g., "Second Floor Framing Plan").

• Columns (C-1, C-2): Shown in cross-section (usually as solid black squares or hatched rectangles) located at grid intersections. The column size often decreases on upper floors.
• Beams and Girders (B-1, G-1): Girders are massive primary beams that span directly between columns. Beams are secondary members that span between girders or walls to break up large floor areas. They are drawn as solid lines indicating their width.
• Slabs (S-1, S-2): The horizontal floor plates. The framing plan indicates the slab thickness (e.g., t = 125 mm) and the direction of load transfer.
  • One-Way Slab: Supported primarily on two opposite sides. Bending occurs mainly in one direction (the shorter span). Indicated by a straight double-headed arrow symbol spanning the short direction.
  • Two-Way Slab: Supported on all four sides with an aspect ratio (Length/Width) less than 2.0. Bending occurs significantly in both directions. Indicated by crossed double-headed arrows.
• Slab Elevations: Often indicated with symbols like +3.20m or -0.05m. A drop in elevation is critical for bathrooms (to accommodate plumbing pipes beneath the tiles) or balconies (to prevent rainwater ingress).

• Column Schedule: The most vertical of schedules. It lists the column mark (e.g., C-1), its dimensions (e.g., 400x400mm), the number and diameter of main vertical bars (e.g., 8 - 20mm $\phi$), and the size and spacing of the transverse ties (e.g., 10mm $\phi$ @ 100mm on center). It tracks how the column size and reinforcement change from the foundation up to the roof.
• Beam Schedule: Lists the beam mark (e.g., B-1), dimensions (Width x Depth), and the reinforcement required at three distinct zones: the Left Support, the Midspan, and the Right Support. This is because the bending forces (moments) change drastically along the length of a beam. It details Top Bars, Bottom Bars, and shear Stirrups.
• Footing Schedule: Lists dimensions (Length x Width x Thickness) and the rebar required, typically noting "Both Ways" (e.g., 16mm $\phi$ @ 150mm O.C. B.W.) indicating a grid of steel at the bottom of the footing.