Amogh N P
✦ In loving memory of Amogh N P — Architect · Designer · Visionary ✦
A foundation under construction — footing reinforcement cages, a plinth beam and timber formwork in the trench: the structure the foundation plan sets out, before any backfill.
Unit IIArchitectural Detailing and Working Drawing

Foundation, Plinth & Structure

Setting out the footings, the DPC that stops damp, and drawing reinforcement.

≈ 40 min + studio task

The foundation plan is a setting-out drawing — the mason pegs the columns from it before any backfill, so it is dimensioned to the column grid, not wall faces. Learn the isolated, strip and raft footings; the plinth beam, filling and the all-important damp-proof course (DPC) at plinth level above ground; the column-footing junction with its L-bent dowels; and the conventions for representing RCC reinforcement — covers, hooks and the bar bending schedule. Explore the key figures with the construction-detail tool.

Learning objectives

By the end of this lesson, you will be able to — mapped to the course outcomes for Architectural Detailing and Working Drawing:

1
CO2 · Apply

Draw a foundation plan as a setting-out drawing, dimensioned to the column grid.

2
CO2 · Apply

Detail isolated/strip/raft footings, the plinth beam, filling and plinth protection.

3
CO2 · Apply

Position and detail the DPC and anti-termite measures at plinth level.

4
CO6 · Apply

Represent RCC reinforcement correctly — cover, hooks, dowels and the BBS.

Setting out the structure

Footings & reinforcement

The foundation plan sets out to the grid; the footing detail shows the pad, PCC, mesh and L-bent dowels with the right cover; and you represent the steel with hooks and a BBS.[1, 4, 5]

Isolated footing — section PCC 100 mm, M10 bottom mesh (both ways) dowels: 90° L-bend cover 50 mm Dowels lap with the column bars above; never draw straight dowels with no anchorage bend.
DiagramAn isolated RCC footing section — pad with bottom mesh on a PCC course, column dowels with a 90-degree L-bend, and clear cover

A setting-out drawing

Drawn looking down on the footings before backfill: the column grid, each footing marked (F1, F2…) and keyed to a schedule, the plinth-beam layout, and centre-to-centre dimensions for the mason to peg out. Levels of footing bottom and plinth-beam top are critical. Dimension to GRID CENTRES — columns must sit on the engineer's grid, not the wall faces.[1]

Representing reinforcement stirrups @ 150 c/c · 135° hooks main bars: 4-16ø Bar Bending Schedule markølengthno. You represent the steel, not design it: show cover, hooks and a BBS (IS 2502 / SP 34).
DiagramHow RCC reinforcement is drawn — bold main bars, closed stirrups with hooks, callouts and a bar bending schedule
The plinth defence layer

Plinth, DPC & anti-termite

The plinth beam ties the columns; the DPC at plinth level above ground stops rising damp; and anti-termite treatment plus plinth protection complete the defence.[2, 3, 5]

DPC — position is everything wall DPC 40–50 mm M15 plinth ground level ✓ above ground, full width rising damp blocked here A DPC below ground cannot stop rising damp; never bridge it with mortar or plaster.
DiagramThe damp-proof course at plinth level, above ground and across the full wall width, stopping rising damp

The base of the wall

The plinth beam is an RCC tie beam at plinth level connecting columns and carrying the superstructure wall — detail its section (e.g. 230×300 mm), bars and stirrups, and top RL at plinth. Below, the plinth filling is compacted earth/sand in layers, topped by a PCC bed and the ground-floor slab. Plinth height is commonly 450–600 mm above ground.[5]

Interactive

Explore the details

Pick a junction — footing, DPC and more across the course — and read its key India-correct figures and detailing note.

Construction details · pick a junction

Isolated footing

Unit II
Cover 50 mm (IS 456)PCC 100 mm, M10 (1:4:8)PCC projects ~50 mm beyond pad

Bottom mesh both ways; column dowels with a 90° L-bend resting on the mesh, lapping with column bars above.

Figures are India-correct standard practice — read the exact value off the relevant IS code / NBC for your case.

Isolated vs raft, and cover

At a glance

AspectOneThe other
SoilIsolated footing: good bearingRaft: weak / low-bearing soil
FormIsolated: discrete pads at columnsRaft: continuous slab under all
ReinforcementIsolated: bottom mesh per padRaft: top & bottom mats overall
DPCMyth: anywhere at the baseReality: at plinth, ABOVE ground, full width
CoverFooting: 50 mmColumn 40 · beam 25–30 · slab 15–20 mm
Vocabulary

Key terms

PCC

Plain Cement Concrete — an unreinforced levelling/blinding course below footings and floors.

Dowel / starter bars

Column bars anchored into the footing to splice with the column reinforcement above.

DPC

Damp-Proof Course — a horizontal barrier at plinth level stopping rising damp.

Plinth beam

An RCC beam at plinth level tying the columns and supporting the walls.

Nominal cover

The specified clear distance from a concrete surface to the nearest bar (footing 50, column 40).

BBS

Bar Bending Schedule — a table of bar mark, shape, size, length and quantity.

Apply it

Studio task

Draw a foundation plan (dimensioned to the column grid) and a 1:20 isolated-footing section for a small framed building: show the pad, the PCC levelling course, the bottom mesh, the column dowels with their L-bend and lap, the cover (50/40 mm), and the plinth beam. On the wall section at plinth, position the DPC correctly above ground, full width, and note the anti-termite treatment.

Check your understanding

Self-assessment

1. The DPC at plinth must be positioned —

2. Nominal cover to reinforcement in a footing per IS 456 is typically —

3. Column starter (dowel) bars in a footing should be detailed with —

In a nutshell

Recap

The foundation plan is a setting-out drawing — dimension to the column grid, not wall faces.
Footings: isolated pads (good soil), strip (under walls), raft (weak soil) — all on a PCC levelling course.
The DPC sits at plinth level, ABOVE ground, full wall width, continuous — never below ground or bridged.
The column-footing junction needs L-bent dowels on the bottom mesh, a lap above, and the right cover.
Represent reinforcement with bold main bars, hooked stirrups, dimensioned cover and a BBS (IS 2502/SP 34).
The evidence

References & further reading

  1. [1]BIS, IS 962 — Architectural and Building Drawings (foundation plan conventions).
  2. [2]BIS, IS 6313 — Anti-Termite Treatment in Buildings.
  3. [3]BIS, IS 3067 — design/construction of DPC; standard Indian plinth practice.
  4. [4]BIS, IS 456:2000 — Plain and Reinforced Concrete (cover, anchorage, splices).
  5. [5]SP 34 / IS 2502 — Handbook on Concrete Reinforcement and Detailing; Rangwala, Building Construction.

Further reading

  • BIS — IS 456:2000 and SP 34 (Reinforcement Detailing).
  • S.C. Rangwala — Building Construction (foundations, DPC, plinth).
  • Francis D.K. Ching — Building Construction Illustrated.

Sources gathered and fact-checked June 2026. Published values vary by source, sample and method — treat as indicative and confirm against the cited standard before structural use.