Everything on this page is taken from the chapter notes — nothing new is introduced. Use it the night before the paper; follow a link back to the chapter whenever a line needs its derivation.
1Units and modes of measurement
| Item | Unit | Item | Unit |
|---|---|---|---|
| Earthwork, concrete, brickwork | m³ | Plastering, pointing, painting | m² |
| Stone masonry, well steining | m³ | Damp proof course | m² |
| Reinforcement steel | kg (or quintal) | Honeycomb brickwork | m² |
| Iron grills, gratings | kg | Shuttering, formwork | m² |
| RC sunshade (chajja) | running m | Doors and windows with frame | m² |
| Cornice, skirting, railing | running m | Wood work in beams, posts | m³ |
| Pipes, kerbs, edging | running m | White washing, distempering | m² |
2Deduction rules
| Where | Rule |
|---|---|
| Brickwork — openings | Deduct openings over 0.1 m² (1000 cm²). Smaller ones are ignored. |
| Brickwork — bearings | Bearings of lintels, beams and posts up to 500 cm² (0.05 m²) in section are not deducted. A section is an area, not a volume. |
| Brickwork — plates and chajja | Bed plates, wall plates and chajja bearings up to 10 cm depth are not deducted. |
| Brickwork — slab bearing | The bearing of an RCC slab on a wall is never deducted. |
| Plastering | Opening up to 0.5 m² — no deduction. 0.5 to 3 m² — deduct one face. Over 3 m² — deduct both faces, but add the jambs and soffit. |
| Concrete | Deduct openings and embedded steel only when they exceed the same limits; reinforcement volume is never deducted from concrete. |
3Taking out quantities
Three ways to reach the same quantity. The centre-line method is fastest, the long wall – short wall method is the safest when walls differ in thickness.
| Method | Length used |
|---|---|
| Long wall – short wall | Long wall = centre-to-centre length + one width (out to out). Short wall = centre-to-centre length − one width (in to in). |
| Centre line | One total centre-line length for the whole building, then − ½ × width of that item × number of junctions. |
| Crossing / bay | Used for repetitive framed bays; take one bay and multiply. |
A junction is where THREE walls meet — a plain closed rectangle has none, and a single partition creates two. The centre-line length is not found once and reused: the deduction is half the width of each item, so a 70 cm footing, a 50 cm wall and a 30 cm wall all give different lengths. In the long wall – short wall method a partition counts as a short wall.
4Types of estimate and the standard percentages
| Quantity | Value |
|---|---|
| Contingencies | 3 to 5% of the estimated cost |
| Work-charged establishment | 1.5 to 2% |
| Departmental charges | 10 to 15% |
| Revised estimate needed when | cost exceeds the sanctioned amount by more than 5% |
| Benefit–cost ratio | annual benefit ÷ annual O&M cost; must exceed 1 |
| Contingency and establishment | computed on every sub-head except land |
| Work value | scheduled items only — excludes contingency, establishment and tools & plant; it is the amount put to tender |
5Earthwork and road formulas
For a section of formation width B, depth D and side slope s horizontal to 1 vertical, on level ground:
That bracketing is the answer to “compare the three methods”: the prismoidal value always falls between the mid-sectional and the mean-sectional value.
On side-lying (hill) ground with cross slope 1 in r and side slope 1 in s, taking b = B/2:
The s·b² term is the one that is usually dropped; leaving it out makes the area about 2% low.
Zero (balance) point — where cutting changes to filling, at distance x from the section of depth d when the next section at distance L has height h:
Slopes are rates, so they average harmonically, not arithmetically. Widths are lengths and average arithmetically.
Canal lining — measured on the wetted perimeter:
6Material constants
| Quantity | Value |
|---|---|
| Bricks in brickwork | 500 per m³ (modular 190×90×90, 200×100×100 with mortar) |
| Brick flat soling | 50 bricks per m² |
| Mortar in brickwork | about 23% of the volume of masonry |
| Mortar in rubble stone masonry | about 32% |
| Cement bag | 50 kg ÷ 1440 kg/m³ = 0.0347 m³, so 28.8 bags per m³ |
| Dry volume factor — concrete | 1.54 (Nepali practice: wet + 50 to 55%) |
| Dry volume factor — mortar, plaster | 1.30 (wet + 30 to 35%) |
| PCC 1:3:6 with brick ballast | dry factor 1.60 |
| Water cement ratio | 0.50 for concrete, 0.80 for plaster; specifications cap mixing water at 30 litres per bag |
| Floor concrete | add 10% for unevenness of the base before the dry-volume factor |
| Steel unit weight | w = d²/162 kg per metre |
Cement, sand and aggregate for 1 m³ of finished concrete:
| Mix | Cement | Sand | Aggregate |
|---|---|---|---|
| 1 : 1.5 : 3 | 8.064 bags | 0.42 m³ | 0.84 m³ |
| 1 : 2 : 4 | 6.336 bags | 0.44 m³ | 0.88 m³ |
Both rows are just 1.54 ÷ (sum of proportions), shared out. For 1:2:4 the sum is 7, so cement = 1.54/7 = 0.22 m³ = 0.22 × 28.8 = 6.336 bags, sand = 2 × 0.22 = 0.44 and aggregate = 4 × 0.22 = 0.88. Learn the method, not the table.
Materials from a finished quantity — the standard 5-mark question:
Two checks before you write the answer: bricks should come to about 500 per m³, and mortar to about 20 to 25% of the masonry. If your figures fall far outside those, look for an arithmetic slip.
7Analysis of rates
The analysed rate is built in four heads and quoted excluding VAT:
The water charge is 1% of (materials + labour). Of the 15%, roughly 10% is profit. 13% VAT is added later, in the summary of cost, not in the analysed rate. No profit is allowed on departmentally supplied materials, but their carriage from the godown is added. Cement carriage is computed on weight in kg, not on the number of bags.
8Valuation and depreciation
C = original cost, S = scrap or salvage value, n = life in years, i = rate of interest as a decimal, m = present age.
Total depreciation when the building is m years into an n year life:
Do this as one division. The tabulated sinking fund coefficient is tiny (of the order of 0.0000488 for 80 years at 10%), and rounding it to three significant figures moves the answer by more than 1%. Check the formula by putting m = n: it must give D = C.
| Term | Meaning |
|---|---|
| Year's purchase (YP) | the number of years' net income that equals the capital value; for a perpetual income YP = 1 / i = 100 ÷ rate per cent |
| Capitalised value | net annual income × YP |
| Scrap value | value of the material alone when dismantled, about 10% of cost |
| Salvage value | value at the end of the useful life, sold without being broken up |
| Obsolescence | loss of value from a change in design, fashion or use; there is no method of calculating it |
| Standard rent | net return + outgoings; about 7% on the building and 6% on the land |
| Easement | acquired by 20 years of uninterrupted enjoyment |
| Land | never depreciates — it usually dominates the value of an old property |
| Nepali land unit | 1 ropani = 16 aana |
Development method — the most a builder can pay for raw land:
Two different areas: the income comes only from what can be sold, but the improvement cost and the final division are over the whole area taken — the owners are paid for the land that becomes road as well.
9Checks worth doing before you hand in
| Check | Expected range |
|---|---|
| Steel in RCC | 80 to 120 kg per m³ of concrete, or 4 to 6 kg per m² of built-up area |
| Bricks | 500 per m³ of brickwork |
| Mortar | 20 to 25% of the volume of masonry |
| Lintel length | clear span + 2 bearings; bearing = thickness of the lintel, minimum 12 cm |
| Beam in a framed building | measure the depth below the slab (500 − 125 = 375 mm), or the flange is counted twice |
| Septic tank proportions | length : width from 3:1 to 6:1, width 0.75 to 1.8 m, liquid depth 0.9 to 2.1 m |
| Manhole cover | 0.45 × 0.45 = 0.2025 m² — over 0.1 m², so it is deducted |