Minimum Standards for Structural Design | RCC Structures



Thumb rules for Structural Design | RCC Structures

I highly recommend use of advanced structural design software like ETabs or Staad Pro for design of structures. This is very important. There are so many variables in design of a structure that no minimum standards can be accurate. This guide can be used for design of very small structures, maybe up to G+1 floors. But I would still recommend use of professional software. Every structural designer should learn these software. Use of manual methods is outdated. Manual method is only used for checks. Real design is done with the help of computers, with very advanced design concepts like pushover analysis, seismic analysis, wind loads simulation and many advanced methods.

You can hire me for your structural design need. Contact me.

Design of RCC Structural Components

In this article, I will discuss the minimum standards that can be followed for the design of RCC structural components of a structure, such as columns, beams, slab and foundation. We will also discuss the minimum safe standards for the reinforcing bars that are to be used for the design of the above mentioned Structural Components.

Minimum cross-sectional dimension for a Column: is  9″x 12″ (225 MM x 300 MM) which is the minimum recommended size. I have designed hundreds of buildings, and never had the misfortune of any structural component ever failing due to loads. I always use M20 grade concrete for construction, as it is the minimum recommended grade of concrete is IS 456:2000. Please don’t skimp on the quality of concrete. The minimum steel in a 9″ x 9″ column is 4 bars of 12 MM with stirrups of 8 MM steel rings at a distance of 150 MM centre to centre. In a 9″ x 12″ column, I add two more bars, to take the total to 6 bars of 12 MM diameter. This design can be safe for up to G+1 floors. But there are a lot of other factors involved.

Also check out:

Thumb rules for making a Column Layout

Construction on Site | Design of RCC Structures

Construction on Site | Design of RCC Structures[/caption]

Minimum RCC beam size should not be less than 9″x 9″ (225MM X 225MM), with an additional slab thickness of 125 MM. I generally use a minimum of 4 bars, with 2 bars of 12 MM thickness in the bottom of the beam, and 2 bars of 10 MM at the top of the beam. I maintain a concrete cover of 40 MM. I recommend use of M20 grade of concrete (1 part cement : 1.5 parts sand : 3 parts aggregate : 0.5 parts water).

Minimum thickness of RCC slab I recommend is 5″ (125MM) because a slab may contain electrical pipes embedded into them which could be 0.5″ or more for internal wiring, which effectively reduces slab depths at certain places, causing cracking, weakening and water leakage during rains. So, a minimum thickness of 5″ should be maintained.

Minimum size of foundation for a single storey of G+1 building, where soil safe bearing capacity is 30 tonnes per square meter, and the oncoming load on the column does not exceed 30 tonnes, a size of 1m x 1m should be used. Minimum depth of footing should be atleast 4′ below ground level. It is recommended to go to depths up to had strata.

Reinforcing bar details (minimum)

1. Columns: 4 bars of 12mm steel rods FE 500

2. Beams: 2 bars of 12 mm in the bottom and 2 bars of 10 mm on the top.

3. Slab

a) One Way Slab: Main Steel 8 MM bars @ 6″ C/C and Distribution Steel of 6 mm bars @ 6″ C/C

b) Two Way Slab: Main Steel 8 MM bars @ 5″ C/C and Distribution Steel of 8 mm bars @ 7″ C/C

4. Foundation: 6″ of PCC layer comes first. Over than, a tapered or rectangular footing of 12″ thickness is minimum. Steel mesh of 8 mm bars @ 6″ C/C should be laid. In a 1m X 1m footing, this would consist of 6 bars of 8 mm on both portions of the steel mesh.

119 thoughts on “Minimum Standards for Structural Design | RCC Structures”

  1. If I use #2-16mm dia at bottom and #2-12mm dia at top of a beam then can I take the width as 130 mm and depth as 350mm of th beam. Is it safe?

    • Depends on the span, imposed loads, point loads. I have used 150mm beams in a few locations in my projects, but only in very rare instances where 230mm beam would be a problem. I would not recommend it.

  2. Hi there!
    Can I use 2 rods of thickness 16 mm and 2 rods of thickness 12 mm in my roof beam of dimension 12×10 inch?

  3. Just want to ask.i built my house step by step.my mason made 11 column for 2 storey house.each column has 6 16mm RSB with a ring of 10 mm.is it safe column?for 2 storey house?

    • There are a lot of unknowns. It would have been better to get structural analysis done by a professional engineer to be sure. It can even save money, as you can prevent over-engineering in your structural elements too.

  4. Hai sir
    I am a civil engineer I constructed the house 516.5 sqft. 7nos of 9″x9″ pillar having 4 nos of 12 mm and 2nos of 9″x1′ columns with 4 nos of 12mm and Middle of column is 2 nos of 10mm the footing dimension 4’*4’*1′ and it is 6.5 feet below the ground level. Corner 1pillar is located on the one side because of some place problems. The distance between these columns are in x direction is 9’and in y direction is 12’and 11′ ,8.5′ now I have a plan to construct one more floor that is g+1 is it safe whether it’s is not safe please gives the reinforcement details.

    (Note:I provide 1′ of plinth beam 3″of sill and 1’of lintel lintel same as plinth beam and all the beams are L crinked and All footings having 4″ L crinked.1st lift column is same as super structure )

    • Depends on the area of the slab. In most of my projects, I use 5″ thick slabs. Minimum steel is 8MM @ 150 MM C/C. For larger slabs, my calculations lead me to increase steel to 10 MM bars. Sometimes, I even have to go to 5.5″ or 6″ slab thickness, but it is very rare.

  5. Hai my plot size is 22×39 and engineer plan for g+1 column size 12″ ×9″ and rod is 12mm×6 No’s for 15 no column and ground beam size 15″ ×9″ and rod is top is 3×12mm bottom is 3x16mm it is OK or modify help me

  6. New construction g+2 10″ x10″ columns and beams M 20 4 -12mm and 2-10mm tmt rebars base plate and RCC plinth 5′ height 5″ thickness aligned with a tie beam
    Up to floor level columns aligned with tie beam would rest on a reverse base plate (floor leval) embossed by a steel sheet and separated by a steel sheet embossed column bottom and the corner of the superstructure will be designed to allow movement of the superstructure by 6″ then restricted to isolate seismic energy flowing into the structure the metal sheets is used with a view to reduce friction the structure would be g+2 dimensions 20’x 48′ spacing and span 12 &10′ request advice if I should go ahead with this innovative idea remember our zone is highly earthquake prone it is no doubt that it would be somwhere around 7.5 to 8 Richter scale as the structure will not be anchored is there a chance of toppling ?

    • I would recommend you get the design from a professional structural designer. It is dangerous to take risk in high earthquake prone regions. You can get a good structural designer at around Rs 5 per square feet. It is worth it.

  7. BenzuJK :
    I would suggest you to hire a certified civil engineer for the job.

    Can u please help me.

    Im constructing a g+2 building in red clay area, the plinth area is 1450 sft. My contractor told that he is using 12mm 10 mm and 8 mm steel rods for foundation and taking depth of 7 feet. if in the future shall we build 2 more floors on this, kindly suggest immediately please.

    • Designing a structure is a complicated process. Don’t depend on a contractor please. Get detailed drawings from a competent structural designer.

  8. Dear sir/madam,
    We r designing for g+1 building residential and have total area 158sqmtr and slab near about 3000sq ft and total pillars 22 at 11 ya 10ft distance some r 12*9 and sm r 9*9 inches) and beam 12mm. Kindly tell me is it safe construction?

  9. Hi,
    Is it safe column size of 250 x 350 with 6no 12mm rod for g-2 building??
    Please share your mail id as I would like to share the foundation drawing with you.

  10. Dear Sir,
    I have made my house. it is parking + 3 floors. It is made in 1800 sqft. it is built on 17 coloumns. 11 columns are 15×9″ and rest 6 coloumns are 9×9″. The concret mix used in coloumns, beams and slabs are 1:1.5:2.5. Also the balconies are 31feet length and width 6 feet without any support or beam. is the balconies safe ? please reply me. some friends say i should put coloumns under the balconies. is it really required.

  11. My house(20ft by 45 ft) have G+1 floors and have 4 columns of 9 inch by 12 inch having two 16mm bar + four 12 mm bar.
    Beam of 9 by 9 having 12mm and 10mm bar and 6 inch thick slab.

    Is this construction good?

  12. Hello

    i am constructing G+1 House , Area plot size is 25 Feet X 62Feet & construction place are 20.7″X54.5″.

    Total column 18 Number, each one column distance 10 feet and below, i am using 12 mm bar 8 Number for each column, can you reply , is it enough?

    Regards
    mohamed Hanifa

  13. hello …i observed number of sites in which engineer used a column of six inches width and other dimension as 18 inches …am also civil engineer but never seen such columns used what ur comment about

    • They might use it in rare cases, but generally I would avoid it. I have used 6″ columns and beams in lift wells and staircases, where I am forced to use 6″ walls, and cannot afford a 3″ column or beam projection into the limited staircase area. But if there is space, I never go below 9″ width.

  14. hai sir this is aravind. i am a civil engineer. now my 1st project is going on. i am design the 1st lift column 225mm x 225mm the footing size is 4 x 4. each dirction the columns are placed in the distance of 10 feet c /c is it safe or not for g+1 story plz rply…..

    • In my opinion, please don’t go below 225MM X 300MM for column and beam size. It gives better stability, and 3″ extra concrete is worth it.

  15. Madam…..Can i use Your Given Dimensions of Columns,beams,Slabs and Foundation For G+1 Building.Provided that the Soil present is purely Sand .And i m not sure that the concrete will be properly Handled.Please do tell me the depth of foundation and center to center distance between successive columns.
    Regards and respect.

  16. Dear sir/madam, can you tell me the load carrying capacity of 10″*10″ square column with 6# of 16mm rod, but the concrete mix ratio is just 1:3:6(M10). Thanks in advance..

    • Minimum concrete strength to be used according to IS 456:2000 is M20 concrete. There are no calculation formulae for M10 concrete.

  17. Sir/Madam, I want to extend my Chajja/Loft by 3ft towards the compound and I’ve put 3 columns with distance of 15 feet . The existing Chajja is of 2ft width and 25 ft length. The 3 columns are of 6″*6″ with a finishing of 9″. Is it OK if I go for a beam of 9″*9″ of 16 mm rods at the top and 12 mm rods at the bottom? And how many rods I’ve to use for top and bottom?

  18. Sir/Madam, I want to extend my Chajja/Loft by 3ft towards the compound and I’ve put 3 columns with distance of 15 feet . The existing Chajja is of 2ft width and 25 ft length. The 3 columns are of 6″*6″ with a finishing of 9″. Is it OK if I go for a beam of 9″*9″ of 16 mm rods at the top and 12 mm rods at the bottom?

  19. Hlo sir all the details are very very useful for me.i have a big doupt .can u clear me pls. For example i want to design a small building how to design each part of rcc for slab to foundation and how to calculate loads.

  20. Respected sir
    I am constructing G+2 FLOOR.1400 Sq ft area having 16 columns sizing 10 x 15 ” ( 4 x 12 mm and 2 x 16mm iron rod)
    Plinth Tie beam Size 10 x 12 “(4 x 12 mm )
    Lintel tie beam size 10 x 10 “(4 x 12 mm ) as per architect
    kindly advise is it sufficient ?
    regards rituraj utkarsh

  21. hi madam
    i am using 9″x12″ column for a span of 14′ by 10′ 12mm rod size 8 nos for a G+1

    floor building. Will 9″x12″ be sufficient?

  22. Dear Sir,
    i am planning to G=1 Building total 750 Sq.ft.
    COLUMNS
    square column size 9″x9″ (14 square columns) reinforcement 4 nos of 12mm and 8mm Ties. circular column 9″ dia (4 circular columns for portico) reinf. 6 nos of 12mm and 8mm Ties. (1:1.5:3)
    BEAMS,
    All are Square beams size is 9″x9″ Reinf. 4 nos of 12mm top and bottom (2 top and 2 bottom) and stirrups 8mm (1:1.5:3)
    SLAB,
    We fellow two way slab thick 5″ reinf. 8mm @ 5″ and 8mm @ 7″ spacing

    • Hello Nazir,

      There are thumb rules for designing buildings. Every building requires a unique structural design. I would strongly recommend you to hire a certified structural engineer. This is not something to be done by a lay person. Let me know and I will direct you to our paid design service.

  23. I am building a house of size 1400 sqft. with load bearing walls and rcc roof. As per building codes in my area rcc foundation belt above rubble foundation and rcc lintel band are must. One engineer suggested that adding one additional rcc band just like lintel band below the window level called still band will give added protection in case of earthquake. Is it true?

    • Yes, for a load bearing structure, use of sill bands is a good idea. Very minimum increase in cost, but really holds the building together.

  24. I am constructing my house now with a 12mm steel and column depth is 6 feet. now I plan to increase the height from plinth beam to lintel height from basement to 10 feet, due to increase the floor level 3 feet from PB/
    it looks PB to floor 3 feet and the lintel from PB 10 feet and from PB to ceiling 13 feet, it is safe to construct.?

  25. i want to construct a G+3 building in a plot size of 38×33 sq.feet for class room purpose havind diamention of 33feet×35feet and i didn’t want to give any pillers in between. please suggest the size and number of pillers and beams in this structure.

    • Hi Abhishek,

      Structural design depends on the location, soil and the design of the building. It is therefore not possible to answer this question. It would be best for you consult a structural engineer.

  26. Hello,
    I am using 9″x12″ column for a span of 14′ by 15′ for a G+1 floor building. Will 9″x12″ be sufficient?

    • Are you an Engineer? If not, then please get a professional to design it. You want your family to survive after you have moved into that house.

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