Column is a vertical structure that starts from a base footing mat and grows vertically upwards. It transfers the building load to the ground. It is to be placed keeping in mind the architectural aspects such as windows, doors, openings etc. Columns emanate from a footing and grow upwards vertically.
Column starter box
What you need to know?
A column is normally 6 inches or 8 inches in depth and 1.5 to 3 feet in width depending on strength and load factors.
A column depth of 6 inch or 8 inch also impacts the wall thickness[before plastering]. Normally a 6 inch wall is constructed when you use solid blocks for construction in residential buildings.
If there is a mismatch in column depth and wall depth there will be unnecessary projections in the wall where the wall and columns meet. So it is better to keep in mind the wall thickness you plan the column thickness and discuss with architect and structural engineer if any concerns.
Column length is not an issue most of the times as it merges with the wall in line.
Column normally consists of [even number] 6 or 8 or 10 vertical rebars of different diameter[based on structural load calculations]. They are bound horizontally by a lesser diameter rebar in box/square shape and tied using binding wire. The horizontal spacing is as described in drawings[4 to 8 inches]. See picture for more details.
Normally the diameter of vertical bars remain unchanged throughout the length of the column all the way till top floor. If two rods are joined normally a overlap[ check with structural, its normally 50 times diameter] is recommended which translates to couple of feet based on rod diameter. This overlap is mandatory.
A rebar is of 39 feet in length bent in U shape. It is not a good idea to erect this entire length at once. So the barbender normally cuts this into half so that it can be easily managed. Else the rebars will be hanging in air and bend considerably.
A column starter box is used to make a protrusion on a flat surface such as plinth beam, after roof mould and so on. This is a way to pour manageable proportion of concrete and also ensure further straight continuity of the column. Once a starter box is used and starter, now its easy to place the bigger column box ontop of it since it acts like a glove to the bigger column box.
A column box is a framework which is used to pour concrete into and results in a neat column. Column boxes are subject to small leakings and should be ensured to have minimum leakage. Oil/Grease is smeared on the inside of column box to ensure smooth removal once concrete is set.
A finished column after using column box
Hope the information presented clears some aspects. Here is a more complete list of articles. Do read about them
10 thoughts on “Understanding RCC – structural RCC columns”
Dear Naveen,
Your posts are very helpful in gaining knowledge in construction.
Please help me in knowing some facts about residential construction.
I am planning to construct a house for self in Bangalore. Please clarify the following
1. Please tell me how much quantity of steel, cement, sand and aggregates are required for rcc slab concrete for residential house consruction for ground plus one floor . Also what should be the diameter of steel rods used.
2. How much quantity of cement, sand, steel and aggregates required for rcc column concrete. what should be the diameter of steel rods used.
3. What is the ratio of cement, sand, and water for plastering concrete mixture.
overall I want to calculate the materials required for constructing a 1700 sqft house. ground floor and a room in first floor.
It will not be possible to calculate entire cost without knowing your structural drawing. Structural drawing will give you the details of diameter of rebars. So you will have to use all information in my blog to do that. I have mentioned how to calculate using drawings in below blogs of rcc. Please have a look..Thank you
Hallo sir my name is Radha we have a new construction going with a column with 4 ft ( 8inches t)unfortunately a metal fabricator has drilled into the column to accommodate his staircase and we have currently stopped the process due to fear of the collapse due to this silly thing they did
Can you please advice how yo correct the same regards
Please get a structural engineer. He will inspect it and suggest changes.normally they drill into beams for stair case etc. So if you have doubts get a structural engineer. He should not charge much. Look-up on just dial. Thanks
Sir thank you for question. You will need a structural engineer to decide on placement and size of column. Please dont skip hiring a structutal engineer for design of columns, roof and beams. Thank you.
hello, this is ashwini. If we are providing 6″ columns for g+3 30×40 house .i should provide beam of 6″ width ? but minimum width is 9″.. any suggestions for this .The client wants 6″ blocks only because of this constrain we are going with 6″ x 18″ column sizes
Dear Naveen,
Your posts are very helpful in gaining knowledge in construction.
Please help me in knowing some facts about residential construction.
I am planning to construct a house for self in Bangalore. Please clarify the following
1. Please tell me how much quantity of steel, cement, sand and aggregates are required for rcc slab concrete for residential house consruction for ground plus one floor . Also what should be the diameter of steel rods used.
2. How much quantity of cement, sand, steel and aggregates required for rcc column concrete. what should be the diameter of steel rods used.
3. What is the ratio of cement, sand, and water for plastering concrete mixture.
overall I want to calculate the materials required for constructing a 1700 sqft house. ground floor and a room in first floor.
Regards,
V.Ravikumar
Thank you Ravikumar for your nice words. Sir
I understand your concern..
Please check all RCC related data here..
http://naveenadisesha.in/house-construction-in-bengaluru/
It will not be possible to calculate entire cost without knowing your structural drawing. Structural drawing will give you the details of diameter of rebars. So you will have to use all information in my blog to do that. I have mentioned how to calculate using drawings in below blogs of rcc. Please have a look..Thank you
Hallo sir my name is Radha we have a new construction going with a column with 4 ft ( 8inches t)unfortunately a metal fabricator has drilled into the column to accommodate his staircase and we have currently stopped the process due to fear of the collapse due to this silly thing they did
Can you please advice how yo correct the same regards
Please get a structural engineer. He will inspect it and suggest changes.normally they drill into beams for stair case etc. So if you have doubts get a structural engineer. He should not charge much. Look-up on just dial. Thanks
Dear Naveen post is awesome & knowledgeable please if you can will you explain more about Interior Designing Fundamentals would Love to hear from you.
Thank you for your kind words and encouragement . Sure will update the same once I have some clarity. And update you on it.
4 inch by 16 inch column are using for 2 story house. is it sufficient for house?
Sir thank you for question. You will need a structural engineer to decide on placement and size of column. Please dont skip hiring a structutal engineer for design of columns, roof and beams. Thank you.
hello, this is ashwini. If we are providing 6″ columns for g+3 30×40 house .i should provide beam of 6″ width ? but minimum width is 9″.. any suggestions for this .The client wants 6″ blocks only because of this constrain we are going with 6″ x 18″ column sizes
Beam can be six inch but it has to be decided based on structural engineer load calculations.