← Estimating & Costing · MP Vyapam Sub Engineer Civil

Chapter 2 of 12

Detailed & Abstract Estimate

In the MP Vyapam Sub Engineer Civil syllabus under Estimating & Costing · 2 parts

Principles & Types of Estimates · Building Estimates — Long Wall-Short Wall & Centre Line Methods

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📑 Contents (12 sections)

Part 1 of 2

Principles & Types of Estimates

Last reviewed 16 Sept 2026 · 8 min read

What is an estimate?

An estimate is a calculation of the probable cost of a project before construction, prepared from drawings, specifications and current rates.

Purposes

Determine the approximate cost for deciding feasibility and obtaining administrative approval and financial sanction.
Arrange funds and budget allocations.
Invite tenders and compare bids (bill of quantities).
Plan quantities of materials, labour and equipment and schedule procurement.
Control expenditure during execution; prepare valuation of existing properties.

Data required

Drawings — plans, elevations, sections, detailed drawings.
Specifications — general and detailed (quality of materials and workmanship).
Rates — schedule of rates (e.g. CPWD/State PWD DSR) or analysed rates for items.
Site information — soil, access, leads for materials, local conditions.

Approximate (preliminary) estimates

Prepared quickly for feasibility and administrative approval, before detailed drawings exist.

Method	Basis	Formula / remarks
Plinth area method	Cost per unit plinth area of similar buildings in the locality	Cost = plinth area × plinth area rate; plinth area measured at floor level including external walls; separate rates for different floors/specifications
Cubic content (cubical) method	Cost per unit volume of similar buildings	Cost = volume × cubic rate; volume = plinth area × height (e.g. from floor/plinth level to top of roof) — better than plinth area for buildings of different heights
Service unit (unit base) method	Cost per unit of service provided	e.g. per bed (hospital), per student (school), per seat (theatre), per classroom, per km (road), per tonne of storage
Typical bay method	Cost of one typical bay (between column lines) in repetitive buildings	Cost = cost of one bay × number of bays (+ adjustments for end bays) — factories, warehouses, halls
Approximate quantity (bill) method	Approximate quantities of major items (e.g. per running metre of wall including foundation, superstructure, finishes) × rates	More accurate than area methods

Additions to building cost (commonly allowed as percentages of building cost when detailed estimates are not available): water supply and sanitary installations, electrical installations, and other services (often of the order of several per cent each), plus contingencies and supervision charges.

Detailed estimate (item rate estimate)

Prepared from complete drawings and specifications for technical sanction and tendering.

Steps

Details of measurements — each item of work is measured (number, length, breadth, height/depth) from drawings and quantities computed as per standard modes of measurement.
Abstract of estimated cost — quantities of each item multiplied by rates to get amounts; items grouped (earthwork, concrete, masonry, finishing etc.).
Additional provisions on the total:
- Contingencies — for unforeseen items and minor variations (commonly about 3–5%).
- Work-charged establishment — wages of staff employed specifically for the work (e.g. work supervisors, chowkidars) (commonly around 1.5–2%).
- Tools and plant, quality control, petty supervision, centage charges (departmental charges for design and supervision in deposit works) as per departmental rules.
Report explaining the need, design basis, specifications, rates adopted, cost and sources of funds.
Drawings and specifications attached.

Other types of estimates

Estimate	Purpose
Revised estimate	A detailed estimate prepared again when the sanctioned estimate is likely to be exceeded beyond permissible limits (as per departmental rules), or when there are material deviations from the original proposal — requires fresh sanction
Supplementary estimate	For additional works found necessary during execution that were not part of the original estimate
Annual repair (maintenance) estimate	For routine yearly maintenance — whitewashing, painting, minor repairs — often a small percentage of the capital cost
Special repair estimate	For major repairs beyond routine maintenance (e.g. re-roofing)
Complete estimate	Total cost of a project including land acquisition, buildings, services, roads, compound walls, establishment, etc.
Quantity estimate (quantity survey)	Only quantities of all items (used in tender documents as the bill of quantities)
Project estimate	Consolidated estimate for a large project with sub-works

Part 2 of 2

Building Estimates — Long Wall-Short Wall & Centre Line Methods

Last reviewed 16 Sept 2026 · 7 min read

Methods of estimating walls

In a building, walls and their foundations have the same cross-section along their length, so quantities are found by multiplying length × cross-sectional dimensions for each layer (excavation, concrete bed, footings, plinth and superstructure). The difficulty lies in corners and junctions, where quantities could be double counted or omitted.

1. Long wall–short wall method

Walls in one direction are treated as long walls and those at right angles as short walls.

FormulaLong wall–short wall lengths (for each layer of width b)

Long wall length (out-to-out) $=$ centre-to-centre length $+$ one breadth $b$
Short wall length (in-to-in) $=$ centre-to-centre length $-$ one breadth $b$

The breadth $b$ is the width of that particular layer (trench width, footing width, wall thickness), so the lengths change from layer to layer.

Quantities for each layer are computed separately for long walls and short walls.
Simple and less error-prone for rectangular buildings; laborious for buildings with many walls.

2. Centre line method

The total length of the centre lines of all walls is multiplied by the cross-sectional dimensions of each layer.

FormulaCentre line method

Quantity of a layer = (total centre line length - junction deduction) \times b \times h

At each T-junction (where a cross wall meets a main wall), deduct half the breadth of that layer ( $b /2$ ) from the total centre line length for each junction — because the overlap would otherwise be counted twice.
At corners (L-junctions), no deduction is needed — the extra length on the outer side balances the shortage on the inner side.
At a cross (+) junction of walls, deduct one full breadth (two halves).

Quick and suitable for buildings with walls of uniform section and many junctions (after applying deductions carefully).

3. Partly centre line and partly cross-wall method

Main walls are computed by the centre line method, and cross walls by in-to-in lengths — used where walls have different sections.

Sequence of items in a building estimate

No.	Item	Unit
1	Earthwork in excavation in foundation trenches	m³
2	Lean concrete (e.g. 1 : 4 : 8 PCC) in foundation bed	m³
3	Brick/stone masonry in foundation and plinth (footing steps)	m³
4	Damp-proof course at plinth level	m²
5	Filling in plinth (sand/earth) and floor base	m³
6	Masonry in superstructure (with deductions for openings, lintels, embedded RCC)	m³
7	RCC work — lintels, chajjas, beams, columns, slabs	m³
8	Formwork for RCC items	m²
9	Reinforcement (from BBS)	kg
10	Flooring — base concrete and floor finish; skirting	m², m³
11	Plastering — internal walls, external walls, ceiling	m²
12	Doors, windows, ventilators — frames and shutters, fittings	m², no.
13	Roof treatment / waterproofing, parapet, coping	m²
14	Whitewashing, distempering, painting	m²
15	Steps, sunshades, rainwater pipes, miscellaneous	as applicable
16	Water supply, sanitary and electrical installations	lump sum/%
17	Contingencies, work-charged establishment	%

Worked estimate — single-room building

Worked ExampleEstimate of a single-room building

Data:

Internal room size 5.0 m × 4.0 m; walls 300 mm thick in superstructure; height of superstructure (floor to roof slab bottom) 3.0 m.
Foundation: trench 0.9 m wide, 1.0 m deep below ground level; PCC 1 : 4 : 8 bed 0.9 m wide × 0.2 m thick.
Brick masonry footings: first step 0.6 m wide × 0.3 m; second step 0.45 m wide × 0.3 m; plinth wall 0.3 m wide × 0.6 m (up to plinth level).
Openings: one door 1.0 m × 2.1 m; two windows 1.2 m × 1.2 m; RCC lintels 0.3 m wide × 0.15 m deep with 150 mm bearing on each side.

Centre line lengths: long walls c/c $= 5.0 + 0.3 = 5.3$ m; short walls c/c $= 4.0 + 0.3 = 4.3$ m Total centre line length $= 2 (5.3 + 4.3) = 19.2 m$ (four L-corners, no T-junctions → no deduction)

1. Earthwork in excavation $19.2 \times 0.9 \times 1.0 = 17.28 m^{3}$ Check by long wall–short wall: long walls out-to-out $= 5.3 + 0.9 = 6.2$ m (×2 = 12.4 m); short walls in-to-in $= 4.3 - 0.9 = 3.4$ m (×2 = 6.8 m); total 19.2 m ✓

2. PCC 1 : 4 : 8 in foundation $19.2 \times 0.9 \times 0.2 = 3.46 m^{3}$

3. Brick masonry in foundation and plinth

First step: $19.2 \times 0.6 \times 0.3 = 3.456$ m³
Second step: $19.2 \times 0.45 \times 0.3 = 2.592$ m³
Plinth wall: $19.2 \times 0.3 \times 0.6 = 3.456$ m³ Total $= 9.50 m^{3}$

4. Damp-proof course (at plinth level) $19.2 \times 0.3 = 5.76$ m², less door opening $0.3 \times 1.0 = 0.30$ m² → 5.46 m²

5. Brick masonry in superstructure

Gross: $19.2 \times 0.3 \times 3.0 = 17.28$ m³
Deduct door: $1.0 \times 2.1 \times 0.3 = 0.630$ m³
Deduct windows: $2 \times 1.2 \times 1.2 \times 0.3 = 0.864$ m³
Deduct lintels: length $= (1.0 + 0.3) + 2 (1.2 + 0.3) = 4.3$ m → $4.3 \times 0.3 \times 0.15 = 0.194$ m³ Net $= 17.28 - 0.630 - 0.864 - 0.194 = 15.59 m^{3}$

6. RCC lintels $4.3 \times 0.3 \times 0.15 = 0.194 m^{3}$

7. RCC roof slab (120 mm thick, resting over walls, no projection) $(5.0 + 0.6) \times (4.0 + 0.6) \times 0.12 = 5.6 \times 4.6 \times 0.12 = 3.09 m^{3}$

8. Internal plaster (12 mm) on walls Internal perimeter $= 2 (5.0 + 4.0) = 18.0$ m → gross $= 18.0 \times 3.0 = 54.0$ m² Door (2.1 m²) and windows (1.44 m² each) are between 0.5 and 3 m² → deduct on one face (taken on the inside face here): $2.1 + 2.88 = 4.98$ m² Net internal plaster $= 49.02 m^{2}$

9. External plaster (on superstructure) External perimeter $= 2 (5.6 + 4.6) = 20.4$ m → $20.4 \times 3.0 = 61.20 m^{2}$ (no deductions on this face under the one-face rule for these openings)

10. Ceiling plaster $5.0 \times 4.0 = 20.00 m^{2}$

11. Flooring Floor area $= 5.0 \times 4.0 = 20.00 m^{2}$ (base concrete and finish computed from thicknesses)

The abstract of cost then multiplies each quantity by its rate (from the schedule of rates) and adds contingencies and other provisions.

Worked ExampleDeduction at T-junctions (centre line method)

If an internal cross wall (same foundation section) is added across the room of the example (c/c length 4.3 m), find the centre line length for the excavation layer.

Solution. The cross wall meets the long walls at two T-junctions. For the 0.9 m wide trench, deduct $2 \times \frac{0.9}{2} = 0.9$ m. Centre line length $= 19.2 + 4.3 - 0.9 = 22.6 m$ (a different deduction applies to each layer according to its breadth)

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