Technical Drawing · Lesson 11

Foundations, floors, walls, openings, stairs, roofs, plans, sections and symbols

WAECNECO

What the syllabus asks

WAEC: WAEC/NECO Technical Drawing, Building Drawing items BD1–BD8 (tools and materials; foundations; floors; walls; openings; stairs; roofs; construction details; working drawings; symbols and abbreviations). Standards cited by WAEC: BS 1192 (now superseded). (Not a JAMB UTME subject: Technical Drawing is absent from JAMB’s official IBASS e-syllabus list.)

NECO: WAEC/NECO Technical Drawing, Building Drawing items BD1–BD8 (tools and materials; foundations; floors; walls; openings; stairs; roofs; construction details; working drawings; symbols and abbreviations). Standards cited by WAEC: BS 1192 (now superseded). (Not a JAMB UTME subject: Technical Drawing is absent from JAMB’s official IBASS e-syllabus list.)

What you will learn

Identify building drawing types, scales and tools.
Describe and draw foundations, floors and walls in section.
Represent doors, windows and stairs in plan, elevation and section.
Calculate stair and roof dimensions.
Draw construction details with correct material symbols.
Produce floor plans, elevations and sections with dimensions and title blocks.

Key points

Know the drawing types and their scales.
Strip foundation under walls; DPC ≥ 150 mm above ground.
Ground floor layers: hardcore, blinding, DPM, slab, screed, finish.
Block sizes and about 9.25 blocks per m².
Doors show swing arcs; openings listed in schedules.
Stairs: 2R + G 550–700; goings = risers − 1.
Roof rise = half-span × tan pitch.
Details at 1 : 20 to 1 : 5 with material symbols.
Plans dimensioned in three chains outside.
Always add north point, scale and title block.

Start here: Building drawing: purpose, tools and drawing types

Building drawing communicates the design of a building to the client, the planning authority, the builder and the tradesmen. In Nigeria, a set of drawings must be approved by the state physical planning or development control authority (for example the Lagos State Physical Planning Permit Authority or the Abuja Development Control) before construction, and the builder works from them on site. WAEC Paper 3 Section B offers a building drawing option; Paper 1 Section B has ten building questions for candidates who choose that option.

Tools (BD1)

The usual drawing instruments (td1) plus: architect’s scale rule with 1 : 50, 1 : 100, 1 : 200 and 1 : 500 scales; templates for doors, sanitary fittings and furniture; drafting film or tracing paper for prints; and increasingly CAD software (AutoCAD, ArchiCAD, Revit). On site, the builder uses a measuring tape, line and pegs, spirit level, builder’s square and the 3-4-5 rule (td2) to set out the drawing.

Types of building drawings

Drawing	Typical scale	Shows
Site (location) plan	1 : 500 or 1 : 1250	Plot, boundaries, building position, access, north point
Floor plans	1 : 100 or 1 : 50	Walls, openings, rooms, dimensions
Elevations	1 : 100 or 1 : 50	External appearance of each side
Sections	1 : 50 or 1 : 100	Vertical cut through foundation, walls, floors, roof
Details	1 : 20, 1 : 10, 1 : 5	Construction of junctions (eaves, lintel, sill, stair)
Roof plan	1 : 100	Ridges, hips, valleys, falls, gutters
Foundation plan	1 : 100 or 1 : 50	Trench layout and widths

Working drawings

The full set needed to build is called the working drawings, supported by a specification (written description of materials and workmanship) and a bill of quantities (measured quantities for pricing). Structural, electrical and plumbing (mechanical) drawings are produced by engineers and coordinated with the architectural drawings.

Standards

WAEC cites BS 1192 (metric) for building drawing practice. BS 1192 has been superseded: its information-management role is now covered by BS EN ISO 19650, and drawing conventions for construction by BS EN ISO 7519 and BS 8888-related ISO standards. The conventions taught here remain the ones examiners expect.

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Practice questions

1. The commonest walling unit for houses in Nigeria is the

sandcrete block
burnt clay brick
timber panel
steel sheet

Show answer

A: sandcrete block
NIS 87 sizes 450 × 225 × 225 and 450 × 225 × 150 mm.

2. The standard “9-inch” sandcrete block (NIS 87) measures

400 × 200 × 200 mm
450 × 225 × 150 mm
300 × 150 × 150 mm
450 × 225 × 225 mm

Show answer

D: 450 × 225 × 225 mm
The 6-inch block is 450 × 225 × 150 mm.

3. The damp-proof course in a wall is placed at least

at foundation level
at lintel level
150 mm above finished ground level
50 mm below ground level

Show answer

C: 150 mm above finished ground level
Standard figure (UK Approved Document C).

4. A comfortable stair satisfies 2R + G between

150 and 220 mm
550 and 700 mm
300 and 450 mm
700 and 900 mm

Show answer

B: 550 and 700 mm
UK Approved Document K guidance.

5. Floor-to-floor height 2 850 mm with 16 risers gives a rise of about

178 mm
190 mm
160 mm
150 mm

Show answer

A: 178 mm
2850 ÷ 16 ≈ 178 mm.

Key words

Working drawings: Full set of drawings for construction.
Specification: Written description of materials and workmanship.
Bill of quantities: Measured quantities for pricing.
Strip foundation: Continuous concrete strip under walls.
Raft foundation: Slab under the whole building.
Pile: Column carrying loads to firm strata.
DPC: Damp-proof course in a wall.
DPM: Damp-proof membrane under a slab.
Hardcore: Compacted fill under a floor.
Screed: Sand–cement layer under a floor finish.
Lintel: Beam over an opening.
Ring beam: Concrete band tying the top of walls.

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