Construction Thumb rules
What Is Thumb Rule?
First of all, we have to understand what is a Thumb Rule.
Thumb Rules are known as an approximate method, you must remember that This method can never be accurate or never gives you exact results, but you can use them just for approximate results to take quick decision-making in the construction field whenever needed. Thumb rules enable you to make smart & quick decisions whenever needed.
These Thumb Rules are very essential for every civil engineer, Site engineer, civil supervisor or a site in charge, etc while making quick decisions on site.
We can use the Thumb Rules for almost every construction industry calculation like manpower estimation, concrete calculation, brickwork calculation, the material requirement for plastering, wastage calculation, etc.,
There are many Thumb Rule For Civil Engineers that we used in construction work. So, Let us learn about some extensive Thumb rules that are most frequently and popularly used by engineers on the Construction site for various activities. If you get to benefit from it then please share.
Thumb Rule 1:
Thumb Rule For Excavation
Excavation Quantity – 3 x Footing Concrete Quantity
Let’s take an example,
Footing Size – 2 x 1mtr.
Depth of Footing – 3mtr.
So, Concrete Quantity of footing = 2x1x3 = 6m3.
Then, Excavation Quantity – 3 x Footing concrete quantity
– 3 x 6 = 18m3.
Prove that:-
Always Consider Offsets for excavations
Length of Footing – 0.5 + 2 + 0.5 = 3mtr.
Width of Footing – 0.5 + 1 + 0.5 = 2mtr.
Depth of Footing – 0.100 + 3 = 3.1mtr.
Then, Excavation Quantity – L x B x H
– 3 x 2 x 3.1 = 18.6m3.
(The actual excavation quantity is nearby the thumb rule quantity)
Thumb Rule 2
Thumb Rule For Concrete
if you know the plan area Concrete volume can be easily calculated
As per the thumb rule Concrete volume required = 0.038m3 per square foot of plan area.
Let’s take an example,
Thus if the floor plan of a house is 40 X 20,
then the total plan area= is 800 sqft
Quantity of concrete per square foot = 0.038 m3
Then, the Volume of concrete – 800×0.038
So, the Volume of concrete – is 30.4m3 (for any structural members area).
Thus Total concrete quantity required to build an 800sqft house is – 30.4m3
Thumb Rule 3:
Thumb Rule For Steel Quantity Required for Slab, beam, footing & columns.
For residential buildings – 4.5 to 4.75kg/-Sqft.
For commercial buildings – 5 to 5.50kg/-Sqft Or 80 to 150kg/m3.
For Tall mass heavy structure project – 6 to 8kg/-sqft
This Rcc steel estimation qty is not so accurate, If you want more accurate results, Consider BN Datta’s recommendations as shown below …..
(Bar Bending Schedule Part-1) Kindle Edition.
This Ebook is specially designed for Freshers Civil Engineers. Recommended for Quantity Surveyors & Billing Engineers. Here You Can Learn All the Basic concepts & Formulas for Bar Bending schedules (BBS).
B.N Dutta’s recommendation as per IS code
Percentage of Steel in Structural Members
i). Slab – 1% of total concrete Volume.
ii). Beam – 2% of total concrete Volume.
iii). Column – 2.5% of total concrete Volume.
iv). Footing – 0.8% of total concrete Volume.
For Example,
Slab having dimension – 5m x 4m x 0.15m (L x B x D)
Total Concrete volume – 3m3
According to B.N Dutta’s recommendation, Steel quantity in Slab – is 1% of total concrete Volume.
So, Required Qty of Steel in Slab = Concrete Volume x Density of steel x 1%
= 3m3 x 7850 kg/m3 x 0.01 = 235kg.
Thumb Rule 4:
Thumb Rule for Shuttering Work
Shuttering is required for pouring concrete & the shuttering work is called by another name “Form Work” because it gives a uniform shape and smoothness to the concrete. so that it helps to shape the concrete. Shuttering is an important part of building construction.
Generally, Shuttering Cost – 15 to 18% of total construction cost.
Suppose, Total Structure Cost – is Rs.2Lakh.
So, Total Shuttering Cost – 15 to 18% of 2lakh = Rs.30,000 to 36,000/-
The Thumb rule for shuttering work is listed below.
Type of Concrete Element | No of Times Sqm Per cubic meter |
Foundation | 2 to 3 times of concrete volume |
Column | 11 to 13 times of concrete volume |
Beam | 11 to 12 times of concrete volume |
Slab | 6 to 8 times of concrete volume |
or 2.4 times Plinth Area.
For example, if the concrete quantity is 1 m^{3}, then
Area of Shuttering is 1 x 6 = 6m^{2}
Components of Shuttering:-
Shuttering Ply, Battens, Nails, shuttering oil & binding wires are the components of Shuttering.
i.) Shuttering Ply quantity Calculation by Thumb rule
Suppose,
Shuttering Ply size – 2.44 x 1.22 x 0.012mm.
No. of Ply Sheets required = 0.22 times of shuttering area
Let, the Area of Shuttering = 5m2.
So, Shuttering Ply Required = 0.22 x 5 = 1.1m2.
ii). Battens Quantity Calculation:
Battens have different widths but we usually use shuttering batten having a length & width of 75mm x 40mm.
Batten Quantity = 19.82 x No. of Ply Sheets
Let, Construction required 32 Ply sheets
So, The Total quantity of Battens required = 19.82 x 32 = 634 Nos. Battens.
iii.) Nails quantity Calculation by Thumb rule
In 1m2 Shuttering = 75gm nails are required.
In 1m2 Shuttering = 75gm bolts are required.
Example:
10m2is total area of shuttering, then Binding wire required = 75 x 10 = 750gms
iv.) Binding wire quantity Calculation by Thumb rule
In 1m2 Shuttering = 75gm binding wire is required.
Example:
10m2is total area of shuttering, then Binding wire required = 75 x 15 = 750gms
v.) Shuttering oil quantity Calculation by Thumb rule
Shuttering oil is used to de-frame or de-assemble from the concrete easily. Oil is applied on the surface of ply or metal plates for easy removal of shuttering.
Oil Required – 0.065 x total area of shuttering.
Let’s take an example,
Suppose, Shuttering Area = 15m2
So, Oil Required = 15 x 0.065 = 0.975 or 1ltr.
(or)
For every 15m^{2} of shuttering 1 liter of shuttering oil is consumed.
Thumb Rule 5
Thumb rule for removing Shuttering
Shuttering should be removed only after the member has attained suitable strength. The below table mentions detail about the removal of shuttering duration.
Sr. No. | Member of Structure | Days |
1. | Sides of foundation, column, beams, and walls | 2 days |
2. | Sides of span larger than 4.5 meter | 14 days |
3. | Sides of span shorter than 4.5 meter | 7 days |
4. | Sides of beams and arches up to 6-meter span | 14 days |
5. | Sides of beams and arches from 6 m to 9 m span | 21 days |
6. | Sides of beams and arches above a 9-meter span | 28 days |
Thumb Rule 6
Thumb rule for concrete work
Thumb rule for the quantity of cement/sand/Coarse aggregates and fine aggregates in different grades for 1 m3.
Concrete Mix | Cement In Bags | Aggregates In Cum | Sand in Cum |
M – 5 (1:5:10) | 2.77 bags | 0.96m3 | 0.48m3 |
M – 7.5 (1:4:8) | 3.41 bags | 0.94m3 | 0.47m3 |
M – 10 (1:3:6) | 4.44 bags | 0.92m3 | 0.46m3 |
M – 15 (1:2:4) | 6.34 bags | 0.88m3 | 0.44m3 |
M – 20 (1:1.5:3) | 8.06 bags | 0.84m3 | 0.42m3 |
M25 (1:1:2) | 11.09 | 077 | 0.39 |
Thumb Rule 7
Thumb Rule For Plastering
Sr. No. | Plastering Type | Ratio | Plaster Thickness (mm) | Cement (Bags/m^{2}) | Sand (m^{3}/m^{2}) |
1. | Internal wall Plaster | 1:3 | 15 | 0.16 | 0.017 |
2. | External Wall Plaster | 1:4 | 20 | 0.17 | 0.024 |
3. | Ceiling Plaster | 1:2 | 12 | 0.17 | 0.012 |
4. | Rough Plaster | 1:5 | 16 | 0.11 | 0.020 |
Thumb Rule 8
Thumb Rule For Flooring
The quantity of cement required for laying flooring can be calculated based on the thumb rule given below.
Sr. No. | Type of Flooring | Thumb Rule for cement |
1. | Marble Flooring | 0.3 Bags/m^{2} |
2. | Marble Skirting | 0.025 Bags/m |
3. | Marble Glading | 0.27 Bags/m^{2} |
4. | Terrace Flooring | 0.3 Bags/m^{2} |
5. | Granolithic Flooring | 0.25 Bags/m^{2} |
6. | Mangalore Tile | 0.35 Bags/m^{2} |
7. | Ceramic Flooring | 0.3 Bags/m^{2} |
8. | Vitrified Tile Flooring | 0.28 Bags/m^{2} |
9. | Vitrified and ceramic tile dado | 0.25 Bags/m^{2} |
10. | Anti-skid Flooring | 0.28 Bags/m^{2} |
Thumb Rule 9
Thumb Rule For Cement Masonry Quantity
Cement Masonry Type & Mix | Cement Qty in Bags | Cement Qty in Kgs |
200mm in Cement Masonry work of Ratio 1:6 |
0.124Bags/m^{2} | 6.2Kgs/m^{2} |
150mm in Cement Masonry work of Ratio 1:6 |
0.093Bags/m^{2} | 4.65Kgs/m^{2} |
200mm in Cement Masonry work of Ratio 1:4 |
0.206Bags/m^{2} | 10.3Kgs/m^{2} |
150mm in Cement Masonry work of Ratio 1:4 |
0.144Bags/m^{2} | 7.2Kgs/m^{2} |
100mm in Cement Masonry work of Ratio 1:4 |
0.103Bags/m^{2} | 5.15Kgs/m^{2} |
Thumb Rule 10
Thumb Rule For Cement Sand Masonry Quantity In Brickwork
The thumb rule for Brickwork for different mix ratio thicknesses of brickwork along with cement sand required are given below.
Sr. No. | Brickwork | Mix Ratio | Mortar Thick (mm) | Cement Qty (Bags/m^{3}) | Sand (m^{3}) |
1. | 100 mm thick | 1:4 | 10 | 0.15 | 0.035 |
2. | 200 mm thick | 1:6 | 10 | 1.4 | 0.30 |
3. | 200 mm thick | 1:5 | 10 | 1.7 | 0.25 |
4. | 200 Blockwork | 1:5 | 10 | 0.15 |
0.02 |
Thumb Rule 11
Thumb Rule For Masonry wall Mortar Quantity
If, Mortar Ratio – is 1:4
A 100sqft wall consume
Cement bags – 2Nos.
Sand – 24Nos. Bucket.
And, 1 bag of cement containing – 3 bucket
So, Cement Bucket – 6 Nos.
Sand Bucket – 24 Nos.
Thumb Rule 12
Thumb rule for Masonry wall Bricks Quantity
A 100sqft wall consume
Brick 9’’ – 950 -1000 bricks.
Brick 4’’ – 450 – 500 bricks.
But Always order 50 to 100 bricks extra for wastage.
Thumb Rule 13
Cement bags quantity in Concrete Slab
Let’s Take an Example,
Slab Area – 900Sqft
So, Cement Bags – 9 x 7 = 63 Bags.
Let’s take another example
Slab Area – 1300sqft
So, Cement Bags – 13 x 7 = 91 Bags.
Thumb Rule 14
Find the depth of the Foundation by the Thumb rule
As per IS Code – 1080 – 1982
Depth of foundation for a multistory building.
5% to 10% of the height of the building.
For example,
No. of the floor – 17Nos & overhead tank height 3mtr.
Ground to first-floor height = 4.2mtr.
1st to 17th floor – 3mtr.
So, Total Height of Building – 4.2 + (17 x 3) + 3 = 58.21mtr.
So, the depth of foundation may be as per thumb rules.
Total building height x 5 to 10%
= 58.21 x 5% = 2.91mtr or, 58.21 x 10% = 5.82mtr.
It depends on the soil condition.
Thumb Rule 15
Labor Productivity by Thumb Rule
Labour output per day in construction activity can help to estimate the number of labor required to perform a particular work or task.
Manpower productivity estimates are shown below:
Brickwork – 1 mason + 1 Labor + 1 Female labor = 1.25m3 or 45cft ( for 8 hrs).
Block Work 4″ – 1 Mason + 1Male Mazdoor + 1Female Mazdoor – 8 Sqm
Block Work 6″ – 1 Mason + 1Male Mazdoor + 1Female Mazdoor – 8 Sqm
Block Work 8″ – 1 Mason + 1Male Mazdoor + 1Female Mazdoor – 10 Sqm
Wall Plastering – 1 mason + 1 Labor = 10m2 or 107sft ( for 8 hrs).
Ceiling Plastering – 1 mason + 1 Labor = 8m2 or 85sft ( for 8 hrs).
External Plastering – 1 mason + 1 Labor = 8m2 or 85sft ( for 8 hrs).
Carpenter Shuttering Work – 1 skilled + 1 unskilled = 4m2 ( for 8 hrs).
Bar Binder – 1 skilled + 1 unskilled = 150kg ( for 8 hrs).
Tile Work – 1 mason + 1 Labor = 10sqm ( for 8 hrs).
Painting Work – 1 Skilled Painter = 600 sqft
Earth digging – 5 male labor + 4 female Labor = 1000cft ( for 8 hrs).
From the above standard labor productivity in construction, we can calculate labor requirements and estimations.
Thumb Rule 16
Bricks Required in 1 m3
500 Nos. (For standard sizes bricks).
Thumb Rule 17
Mortar Required for 500 Bricks
0.25m3.
Thumb Rule 18
Concrete Qty = Area x thumb rules
Area – Total Built-up Area ( Plinth area x No. of Floors).
For Commercial – Area x 0.5m3
For Residential – Area x 0.2m3
Thumb Rule 19
House Construction Cost by Thumb rules
Civil Structural works cost – Rs.1200/-sqft.
Finishing work cost – Rs. 650/-sqft.
Thumb Rule 20
Painting cost by thumb rules
2-layer putty + 2 Layer paint coat.
Rs. 18 to 20/-sqft.
Thumb Rule 21
Flooring
Marble Rate – Rs.100 to 120/-sqft.
Granite Rate – Rs.20 to 22/-sqft.
Thumb Rule 22
Electricals
Rs.70 to 120/-sqft For materials (A rough guide).
Rs.15 to 32/-sqft for labor.
Thumb Rule 23
Cement Required per m3
M10 – 210kg
M20 – 320kg
M25 – 340kg
M30 – 380kg
M35 – 410kg
M40 – 430kg
M45 – 450kg
Thumb Rule 24
Anti–termite treatment
The chemical’s name is chlorophyrifac 20%.
Diluting 5ltr of chemical with 95ltr of water and usage is 7.5sqm per ltr.
To provide 1’’ dia. Hole and 1-foot depth Use 7.5sqm per ltr.
Thumb Rule 25
Thumb Rule for Water Proofing
Sr. No. | Water Proofing work | Thumb rule |
1. | Waterproofing for sunk slab | 0.23 Bags/m^{2} |
2. | Waterproofing for walls | 0.23 Bags/m^{2} |
3. | Waterproofing for toilets | 0.65 Bags/m^{2} |
Thumb Rule 26
Vitrified tile flooring
0.28 cement bags/sqm.
Thumb Rule 27
Ceramic tile flooring
0.28 cement bags/sqm.
Thumb Rule 28
Daddo tile flooring
0.27 cement bags/sqm.
Thumb Rule 29
AAC Blocks – 12.5Nos/sqm.
Thumb Rule 30
Wall Putty
– 14 to 15sqft/-kg (For 2 Coats).
– 8 to 12sqft/-kg (For 3 Coat).
Thumb Rule 31
Primer
– 120 to 140sqft/-kg (For 1 Coat).
– 70 to 90sqft/-kg (For 2 Coats).
Thumb Rule 32
Labor cost for painting
– Rs.10 to 15/-sqft.
Thumb Rule 33
Cement Consume for Plastering by thumb Rules
For External Plastering – 8.75kg/m2.
For Internal Plastering – 4.5kg/m2.
Ceiling Plastering – 0.11bags/m2.
Thumb Rule 34
Labor required for Demolishing by thumb Rules
PCC (1:2:4 or 1:3:6) for 1m3 – 2 Labors (8hrs).
RCC (Lead 50mtr) for 1 m3 – 4 Labors (8hrs).
Brickwork (Lead 50mtr) for 1 m3 – 2Labor (8hrs).
Removing Mortars for 10m3 – 4 mason & 25 labors with (cleaning & stacking).
Thumb Rule 35
Labor required for Masonry by thumb Rules
Brickwork :- 7.55sqm – 1 mason + 1 man labor + 1 Women labor (for 8hrs).
Block work :- 12m2 – 1 mason + 1 man labor + 1 Women labor (for 8hrs).
DPC :- 100m2 – 5 mason + 6 man labor (for 8hrs).
Thumb Rule 36
Cement Consume for Marble flooring – 0.3bags/sqm.
Thumb Rule 37
Thumb Rules For Contractors
i). Floor-to-floor height should be a minimum.
ii). Use repetitive formwork & Ms shuttering.
iii). Use the Standard size of Columns.
iv). Adopt a uniform column layout.
v). Use the same beam bottom & beam depth.
vi). Use high-strength concrete in column eg.M30.
vii). Use high early strength concrete.
vii). Use locally available materials.
viii). Use the commonly available size of bars and spirals
ix). Eliminate bent bars where possible
x). Use the largest bar size that satisfies the design considerations
xi). Avoid the congestion of steel
Thumb Rule 38
Thumb Rules to calculate materials qty. for house construction.
Let, Built-up Area – 1000sqft
i). Cement – Built-up Area x 0.4
= 1000 x 0.4 = 400bags
ii). Sand – Built-up Area x 0.816
= 1000 x 0.816 = 816 tone or 51m3.
iii). Aggregates – Built-up Area x 0.608
= 1000 x 0.608 = 608 tone.
iv). Steel – Built-up Area x 4
= 1000 x 4 = 4tone.
v). Paint – Built-up Area x 0.18
= 1000 x 0.18 = 18ltr.
vi). Flooring – Built-up Area x 1.3
= 1000 x 1.3 = 1300sqft (with skirting).
vii). Bricks – Built-up Area x 25
= 1000 x 25 = 25000Nos.
Thumb Rule 39
Thumb Rules to Find Depth of Beams
According to ACI Code – 318 -14 (Table no. 9.5A)
Depth of beam in inch = Length of a beam in feet
For Example,
Length of beam = 5mtr. Or 5 x 3.28 = 16.40 feet
So, the depth of the beam = 16.40 inches.
Thumb Rule 40
Thumb Rules for Design beam size
Depth of beam = Effective Span / 12
For Example,
Length of Span = 5mtr or 5000 / 12 = 417mm
or, depth of beam = 16.40 inches.
Thumb Rule 41
Thumb Rules for Design Slab size
As per IS 456,
i). Simply supported Slab–Span/30
ii). Continuous Slab – Span/30
iii). Cantilever Slab – Span/7
This is applicable for slab span 10mtr or less than 10mtr only not for more than 10mtr.
Thumb Rule 42
Standard data for tolerance
i). Accuracy of measuring equipment in batching plant
i). cement – +_2%
ii). Aggregates – +_3%
iii). Admixture – +_3%
iv). Water – +_3%
v). Mixing time – 2 minutes for 1 mixing.
Thumb Rule 43
Standard data for tolerance
ii). Tolerance on steel diameter in length
i). 0 – 25mm – +_0.5%
ii). 25 – 35mm – +_0.6%
iii). 35 – 50mm – +_0.8%
Thumb Rule 44
Standard data for tolerance
iii). Tolerance on steel weight per meter
i). 0 – 10mm – +_0.7%
ii). 10 – 16mm – +_0.5%
iii). 16mm & above – +_0.3%
Thumb Rule 45
Standard data for tolerance
iv). Tolerance for cutting length.
i). When the specified length is not given = _+75mm.
ii). When the length is given for cutting L = _+50mm.
Thumb Rule 46
Thumb Rules In Building Construction Cost
Sr. No. | Material/ Work | Thumb Rule |
1. | Cement | 0.5 Bags/sqft |
2. | Steel | 3 to 5 Kg/sqft |
3. | RMC | 0.05 m^{3}/sqft |
4. | Blockwork | 12.5 no./m^{2} |
5. | Electrical Cost | ₹ 150/sqft |
6. | Plumbing Cost | ₹ 140/sqft |
7. | Fire Fighting Cost | ₹ 55/sqft |
8. | External Development Cost | ₹ 94.5/sqft |
Thumb Rule 47
Thumb rules for construction cost
The average cost of Construction based on the quality of construction is shown below.
Sr. No. | Construction based on Quality | Thumb Rule |
1. | Basic Quality Construction | 1200 Rs./Sqft |
2. | Medium Quality Construction | 1850 Rs./Sqft |
3. | High-Quality Construction | 2500 Rs./Sqft |
Thumb Rule 48
Requirement of standard materials and standard calculations in buildings Construction
Description | Thumb rule (% of Total Cost) |
Cement | 16.4% |
Sand | 12.3% |
Aggregate | 7.4% |
Steel | 24.6% |
Painting material | 4.1% |
Tiles | 8% |
Bricks | 4.4% |
Window | 3% |
Doors | 3.4% |
Plumbing | 5.5% |
Electrical | 6.8% |
Sanitary | 4.1% |
Thumb Rule 49
Percentage of Work stages and standard calculations in buildings Construction
Sr. No. | Work | Cost |
1. | Excavation and Filling Earthwork | 0.5% |
2. | Foundation | 5% |
3. | Damp Proof Course | 1% |
4. | Brickwork | 34% |
5. | Roofing | 20% |
6. | Flooring | 6% |
7. | Doors and window | 16% |
8. | Plastering | 10% |
9. | White Washing | 2% |
10. | Miscellaneous | 5.5% |
Thumb Rule 50
Cost of building general thumb rules
Sr. No. | Work | Thumb Rule |
Cost of Material and Labour |
||
1. | Material Cost | 70% of Building Cost |
2. | Labour Cost | 30% of Building Cost |
Direct and Overhead Cost |
||
1. | Direct Cost | 85% building cost |
2. | Overhead expense | 15% of Building Cost |
Foundation and Superstructure |
||
1. | Cost of Foundation | 15% of Building Cost |
2. | Cost of Superstructure | 85% of Building Cost |
Thumb Rules for construction is an experienced base data, not collected from any books So, please don’t consider it accurate but it is an approximate figure. If we have missed anything please do let us know to update!
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