A Civil Engineer is a blog to help you be expert

We share ideas, articals and practical experience for costruction related professionals. Find out more...


Why you should suubscribe?

  • We share pracactical experience.
  • Easy to understand tutorials.
  • And, wee help you to be an expxpert
// // Leave a Comment

4 Easy Steps for Making Column Stirrup

A rcc column has two types of bar. One is longitudinal bar and another is horizontal bar.

As horizontal bar we use stirrups and ties in column. Stirrup also has some other name in construction sector. Such as ring, shear reinforcement, etc.

For making stirrup for column you have to calculate the cutting length of bar for stirrup, you have to calculate the number of stirrups and you have to determine the size of stirrup.

You can do this in 4 easy steps.

4 Easy Steps for Making Column Stirrup

Making column's stirrup involves following 4 steps of work.

  1. Determine the size of stirrup
  2. Calculating cutting bar length for stirrup
  3. Calculating the number of stirrups
  4. Bending the bar in stirrup's shape


1. Determine the Size of Stirrup



column stirrup making, column, stirrup, ring, shear reinforcement

See the above image. The column size is 20" x 40". We know the concrete clear cover for reinforcement of column is 1½".

So the length of stirrup will be 40"-2x1½"=37" and width will be 20"-2x1½"=17".

So the size of the stirrup is 37"x17".

2. Calculating Cutting-Bar-Length for Stirrup


Before cutting the bar you have to calculate the cutting bar length for the stirrup.

There are two terms - actual bar length and cutting bar length.

The actual bar length of stirrup is,

2 x length + 2 x width + 2 x hook's length

= 2 x 37" + 2 x 17" + 2 x 3"

= 114" or 9.5'.

Let's discuss a little about hook length.

Hook length is calculated by a formula that is 6db (diameter of bar).

So the hook length for 10mmø bar is,

 6 x 10 = 60 mm. 

But length of hook should not be less than 75mm (as per code).

So the hook length for the stirrup is 3" (75mm = 3").

The actual bar length of the stirrup is 9.5'. But the cutting bar length will be less than the actual bar length.

column stirrup making, column, stirrup, ring

See the above image. That is our stirrup. The stirrup has three 90° bend and two 135° hook.

For each bend, the length of bar will be reduced. There is a certain formula to calculate the reduced length for bend.

The formula needs various calculation process. I'll write about the formula some other day in this blog. So subscribe via Email to get it in your inbox when it happens.

Below I'm giving a chart for reduced length for a 90° bend for different diameter of bar.

10 mmø bar - 1"
12 mmø bar - 1¼"
16 mmø bar - 1½"

Since, we are using 10 mmø bar for our stirrup so the cutting bar length will be,

9.5' - 3 x 1" (bend deduction is ignored for 135° bend).

= 9'-2"

So, you have to cut 9'-2" length of 10mmø bar.

That means, cutting bar length for the stirrup is 9'-2".

3. Calculating the Number of Stirrups


Making column stirrup

See the image above. There are two types of spacing for stirrups. One is S1 and another is S2. S1 is spaced 4" c/c and S2 is spaced 8" c/c.

S1 is provided in the bottom ¼th portion and top ¼th portion of clear column's length. S2 is provided in the middle half portion of clear column's length.

Clear column's length means the height of column between the top of floor to bottom of beam.

You also should provide 2 numbers of stirrup for column into beam-column joint.

Now let's calculate the numbers of stirrups for column.

The floor height is 10'. 

Beam height is 2'

Clear height of column is,

= floor height - beam height

= 10' - 2'

=8'

Number of stirrups are,

= 4'/4" + 4'/4" + 2 + 1 (1 bar should be added for getting the correct number of stirrups.)

= 27 nos.

4. Bending the Bar in Stirrup's Shape

You can use stirrup-making-machine for large project where vast quantity of stirrups are required.

But, we often make stirrups by hand in our project.

For making stirrups by hand you need a stand and a handle.

making column stirrup

See the above image. That is a hand-made stand and a handle. You can make stirrup with these tools.

Just place the rod in the stand and bend the rod with the handle. You have to go for trial and error method to get the desired size of stirrup. Also don't forget to make the hook angle at 135°.

Symbol used in this post
" - inch

' - foot

° - degree

db - diameter of bar

nos - numbers

ø - diameter

c/c - center to center distance


Your Turn
How do you make stirrup bending stand? How do you make the handle? How do you calculate the deduction length for bend of different dia bar?

Read More
// // 1 comment

10 Easy Steps to Construct a Isolated Footing

There are various types of footing can be constructed for a building. It is structural engineer's responsibility to decide which type of foundation is to be constructed for a building.

As construction professionals, our responsibility is to properly construct footings as designed or suggested in structural drawing.

In this post I'll show you how to construct a isolated footing for a residential building. You can do this in following 10 easy steps.

10 Steps to Construct a Isolated Footing

Follow the steps below to construct a isolated footing.

1. Positioning Footing Location

Footing layout sheet of structural drawing shows dimension related to grid line to place the footing on ground. See the image below.


Mark the footing on ground as shown in the drawing.

2. Earth Excavation

Excavate a trench on earth for the footing. The size of trench should be 1' bigger in both side than the footing size. In the above image we have a footing size of 4' x 5'. For this footing you have to make a trench size of 5' x 6'. It is done for placing and removing shutter easily.

The depth of trench will depend on the earth condition or suggested in the drawing.

3. Preparing the Base

Depending on the soil condition of the base you may require to make brick-flat-soling or cement concrete at footing-base. It is also suggested in the structural drawing.

Read More:
A Checklist for Brick Flat Soling

Sometimes brick-flat-soling isn't suggested in the structural drawing. If you found the base soil isn't suitable enough to construct the footing without brick flat soling then consult with structural designer.

4. Making Form-work

Make form for the footing as specified size. You can use wooden shutter or steel shutter for this purpose. Place the form as showed in the footing layout sheet of structural drawing.

Read More:
Types of Formwork Materials

Check the dimension of form and check if it is properly placed related to grid line. Also make the form-work leakage proof.

5. Placing Reinforcement

I assume you have the required materials for the isolated footing available on the project.

Cut the steel reinforcement as required sizes and provide L-bend  as shown in the structural drawing. You can make the reinforcing net for the footing separately and place in footing position later or you can place the reinforcing bar directly on footing position and bind them there.

One important thing sometimes not shown in the drawing is that - in which direction main reinforcement of footing should be placed - in short direction or in long direction?

In footing, placing main reinforcement doesn't follow the short direction rule. It is related to position of column on footing. Read the following post to know about this.

Placing Main Reinforcement of Footing

6. Providing Cover Block

It is very important to maintain concrete clear cover ont only in footing but also in all RCC members. Provide required cover block in bottom and sides of footing to keep the reinforcing net in position.

7. Placing Column's Reinforcement

Neck column reinforcement should be placed before pouring concrete into footing. Because neck column's reinforcement sits on the bottom reinforcement of footing.

8. Pouring Concrete

Check again the footing and column are properly placed. Check the form of footing is leakage proof. If everything is perfect then move to pouring concrete.

If the concrete volume is large or if you make several footings to cast at a time then you can go for ready-mix concrete. Otherwise you can cast your footing with machine mix concrete. In that case you have to order and stacked the required concrete ingredients on the job-site before.

9. Removing Formwork

On the next day remove the form of footing. If any small honeycomb appears on footing's surface repair those properly. If checked the formwork properly major honeycomb won't appear.

If major honeycomb somehow appeared on the footing then you have to consider breaking the footing and reconstructing.

10. Back Filling

If everything is ok then fill the trench with soil and compact.

Now what? I think, you noticed I back-fill the footing's trench before constructing neck column. Don't do this. Yes. Before back filling you should construct the neck column.

Tour Turn:
If you have anything to say, write it in the comment section below.
Read More
// // Leave a Comment

Estimate the Neck Column's Reinforcement With these 8 Easy Steps

For complete estimating and costing solution of a construction project we always use computer aided software like Contractor's office. It is time-saving and accurately deliver us what we want.

But for our day to day construction activities, we always do this manually on the project to find the required materials for our tasks.

In this post I'll show how you can estimate the required reinforcement for neck column in 8 easy steps.

As we know a neck column has two types of bars. One is longitudinal bar and another is stirrup.

Longitudinal bars are those which are vertically places in column and stirrup are those which are horizontally provided around longitudinal bars.

So we'll estimate both types of bars in following 8 easy steps.

8 Easy Steps to Estimate Neck Column's Reinforcement

Let's start with the longitudinal bar first.

1. Determining the Number of Longitudinal Bar

Summarise the numbers of same diameter bar separately.

See the image below. There are different diameter of bars in the column section.


estimating, steel reinforcement, neck column
Neck Column: Not scaled and designed

From this image we have found

25mmø bar - 4 nos
20mmø bar - 6 nos

2. Determine the Length of a Longitudinal Bar 

It is not practical to place the longitudinal bar more than 20' long. Another thing to consider is that the full length of a bar is about 40 feet. If you cut them at middle you'll get 20 feet long bar.

So the length of longitudinal bar for the neck column is 20'.

3. Calculating total length of Longitudinal bars

To find the total length of longitudinal bars multiply the length of each bar with the total number of bars of same diameter.

Total number of 25mmø bar = 4 nos
Total numbers of 20mmø bar = 6 nos
Length of each longitudinal bar= 20'

Total length of longitudinal bars 
25mmø bar= 4 x 20' = 80'
20mmø bar= 6 x 20' = 120'

4. Calculating the Weight of Longitudinal Bar

To calculate the weight of bar you should know the unit weight of different diameter bar.

Read the following post to know how to calculate the unit weight of steel reinforcement.

How to Calculate the Unit Weight of Steel Bars

From the above post, we found the unit weight of,

25mmø bar = 1.172 kg/ft, and
20mmø bar = 0.750 kg/ft.

Now multiply the total length of bar with unit weight to find the total weight of bar.

25mmø bar = 80 x 1.172 = 93.76 kg. Say, 94 kg.
20mmø bar =120 x 0.750 = 90 kg.

Now let's move for estimating stirrups of neck column.

5. Determining the Number of Stirrup

To find the number of stirrup you need to know the length of neck column and the spacing of stirrups.

The length of neck column is the distance between the top face of footing and the bottom face of grade beam. Let's assume, neck column length is 5'.

We can find the stirrups specification from the above image. That is 10mmø [email protected]"c/c.

Now divide the neck column's length with the stirrup's spacing.

That means,

=5'/4"+1 (1 additional number should be added)
=16 nos

6. Determine the Length of a Stirrup's Bar

The neck column size we found from the above image is 43" x 23".

That means, the length of column is 43" and width of column is 23".

If we deduct the concrete clear cover from both side, the length of stirrup will be 43"-6"= 37" and width is 23"-6"=17".

The length of bar for a stirrup is,

2 x length of stirrup + 2 x width of stirrups + 2 x hook's length.
= 2 x 37" + 2 x 17" + 2 x 3"
= 114" [12"=1']
=9.5'

7. Calculating Total Length of Bars for Stirrups

To calculate the total length of bars multiply the numbers of stirrups with the bar length of a stirrup.
Total numbers of stirrup = 16 nos
Bar length for a stirrup= 9.5'
Total length of bars = 16 x 9.5 = 152'

8. Calculating the Weight of stirrups

To calculate the weight of stirrup's bar just multiply the unit weight of 10mmø bar with the total length of stirrup's bar.

Unit weight of 10mmø bar = 0.188 kg/ft
Total length of stirrup's bar= 152'
Weight of stirrups bar= 152 x 0.188=28.58 kg, say 29 kg.

So, the required steel reinforcement for the neck column is,

"25mmø bar = 94 kg
20mmø bar = 90 kg
10mmø bar = 29 kg"

Symbol I used in this post
ø - diameter of bar

c/c - center to center distance

' - foot

" - inch

ft - foot

kg - kilogram

nos - numbers

Your Turn:
If you have any query about this post please share in comment below.
Read More
// // 1 comment

How to Place Steel Reinforcement of Neck Column

As neck columns carry the load of whole building those should be constructed with caution.

What is Neck Column?

The column between footing and grade beam is called neck column. It's also called short column.

In today's construction world almost all columns of a building are designed as reinforced concrete column and steel reinforcement is the backbone of any reinforced concrete member.

In this post I'll describe how to place steel reinforcement of neck column.

Steel reinforcement also expressed as rebar or MS bar or simply rod. Whatever you call this I'll call this steel reinforcement in this post. So that you don't be confused.

Column is constructed on footing. There are various types of footing. No matter whichever footing you are constructing column on, the procedure is same. In this post I'll construct a column on a isolated footing. After learning this you can place steel reinforcement of neck column on any type of footing.

Steel reinforcement of neck column is placed on the bottom reinforcement of footing. Some footings have two layer of reinforcement. One layer is placed in bottom and another layer is placed on top of the footing. Some footing has only one layer of steel reinforcement that is placed at bottom of the footing. Neck column's reinforcement is directly placed on that bottom reinforcement.

Neck column, steel reinforcement

See the above image. There are 3 footing and 5 grid lines. See how the the footings are shown related to grid line. In structural drawings book there is a sheet titled footing layout. On that drawing you will find the details dimension for placing footing.

In the structural drawing book there is also a column layout drawing sheet. On that drawing you'll see how column is placed related to grid lines.

Ok we studied the drawing. Now let's start the work.

In this post I'll not discuss about how to place the footing reinforcement. I assume you've already placed the bottom reinforcement of footing.

Now we'll place the steel reinforcement of neck column.

Let's take F3 footing for example.

In the image it is clearly showed that how the footing should be placed related to grid line and how the column is placed related to footing. In that we found that column is placed 1'-2" and 1'-4" inside from outer face of footing. Now follow the following steps to place the steel reinforcement of neck column.

steel reinforcement, neck column

Placing Steel Reinforcement of Neck Column

Placing steel reinforcement of neck column involves following three steps -

  1. Positioning a stirrup on footing reinforcement
  2. Binding Column's skeleton separatly
  3. Placing column's skeleton on the Stirrup

  1. Positioning a Stirrup on Footing Reinforcement


  • Make a stirrup of 1'-6½"x 3'-2½" size and place that on the bottom reinforcement of footing as shown in the above image.
  • Here I would like to clear one thing that clear cover for reinforcement is 1½ for the column above ground. But it'll be 3" below ground. In that case the stirrup size should be 1'-5"x3'-1½". But I didn't make that size of stirrup. Why? Because I checked the column dimension for above floor. The column size is not changed for upper. In this case the column size for neck column will be 23"x43" even that isn't specified in the drawing. But the stirrup size will remain unchanged.


To know more about the clear cover of reinforcement read the following post.

Concrete Cover for Reinforcement Bar


  • Now check the dimension. It'll be 1'-5½" from short face of column to short face of footing and 1'-3½" from long face of column to long face of footing. You can also use plumb bob to check the position of that stirrup related to grid line.

2. Binding Column's Skeleton Separatly



  • Now place main reinforcement of column. For that you first have to bind the column's main reinforcement with sstirrups in a separate place.
  • The main reinforcement specified in the drawing (above image) as 30-25mmø bar for the column. You need to bind those main steel reinforcement with the column's stirrups to make skeleton of neck column.
  • The length of steel reinforcement bar we buy from the supplier is about 40 feet. You can't place this so long bar in column. So, cut those rod at middle so that you can place them easily.
  • You have to make 90 degree bend of 1'-6" length at one side of each bar as specified in the drawing (above image).
  • Now tie all the main reinforcement with stirrups in a separate place. Stirrup should provided as per drawing ( I didn't shown them in the image above, you'll find them in the column layout of structural drawing).

3. Placing Column's Skeleton on the Stirrup


  • After completing the binding process you can now place that column's skeleton on the stirrup which we placed on the bottom reinforcement of footing in step-1.
  • Now tie that column's skeleton with the footing reinforcement.
  • Again check the column position related to footing or grid line. It is better to check the column position related to grid-line than related to footing.
  • To keep the skeleton of neck column in its position provide enough support.


Now you can move to next step that is shuttering of column.

You can read the following post to know about the column shuttering procedure.

Basic Construction Process of RCC Column

Neck column positioning is very important because if it is shifted somehow your whole building will be shifted. So check the column position carefully.

Your Turn:
You saw the bend of column's main reinforcements are spread outside. But now-a-days, some structural designers suggest that those should be placed in opposite direction. What do you think about that?
Read More
// // Leave a Comment

How to Calculate the Unit Weight of Steel Bars

There is a formula to calculate the unit weight of steel bars. I'll come that point later.

Why do we need to know the unit weight of steel bars?

When we estimate the steel bars for a Reinforced Concrete member we get the length of that as a result. For example, 1000 feet 20mm ø bar or 500 feet 16mm ø bar, etc (ø - symbol of diameter).

But steel bar suppliers measure the steel bars as weight. So we have to order them in weight for purchasing. The weight of steel bars can be expressed in kg or quintal or ton.

1 quintal = 100 kg
1 ton = 1000 kg or 10 quintal

Now come to the point.

How to calculate the weight of steel bars

How to Calculate the Weight of Steel Bars

We often use a formula for Calculating the weight of Steel Bars.

The formula just converts the length of steel bars to weight. We can also use this formula to know the unit weight of steel bars of different diameter.

The Formula: D²L/162

Where,

D = Diameter of steel bar in millimeter
L = Length of steel bars in meter

Understanding the Formula

We know, the weight of a material is,

= Cross sectional area of the material x Length of the material x Density of the material

For steel bar this is also same.

Weight of steel bars= Cross sectional area of steel bar x Length of steel bar x Density of steel bar.

That means,

W = A x L x ρ

Where,
A = Area = πD²/4 
π (pai) = 3.14
D = Diameter of steel bar in millimeter
L = Length of steel bar in meter
ρ (Rho) = Density of steel bar = 7850 kg/m³

Therefore,

W = 3.14 x D²/4  x L x 7850

But there are two conflicting unit in the formula. Those are millimeter for D and m for ρ (Rho).

We have to convert either D or ρ to same unit.

Let's convert D from millimeter to meter.

1 millimeter = 1/1000 meter

Lets implement this to the formula,

W= 3.14 x D²/(4x1000x1000) x L x 7850

= D²L/162

Using this formula we can calculate the weight of steel bars.

You May Want to Read:
Types of Estimates in Building Construction
How to calculate materials for different-ratio concrete

Calculating Weight of Steel Bars When Length is in meter

Keep in mind that you always use D as millimeter and L as meter in this formula.

Lets see some example.

Example-1:
How to calculate the weight of 100 meter long 16mm ø bar?

In this example,

D= 16mm
L = 100 m

So,

W = D²L/162

= 16² x 100/162

= 158 kg (approx)


Answer: Weight of the 100 meter long 16mm ø bar is 158 kg.

Example-2
How to calculate the weight of 100 m long 20mm ø bar?

In this example,

D = 20mm
L = 100 m

So,
W = D²L/162

= 20² x 100/162

= 247 kg (approx)

Answer: Weight of the 100 meter long 20mm ø bar is 247 kg.

Unit weight of steel bar per meter

Unit Weight of Steel Bar When Length is in Meter

If you put 1 meter length for each diameter of steel bar in the formula then you'll get the unit weight.

Let's see.

W = D²L/162

Unit weight of,
  • 10mm ø bar = 10² x 1/162 = 0.617 kg/m
  • 12mm ø bar = 12² x 1/162 = 0.888 kg/m
  • 16mm ø bar = 16² x 1/162 = 1.580 kg/m
  • 20mm ø bar = 20² x 1/162 = 2.469 kg/m
  • 25mm ø bar = 25² x 1/162 = 3.858 kg/m

If you multiply the length of estimated bars with this unit weight you'll get the total weight of steel bars for your reinforced concrete member.

For example, total weight of 1000 meter long 25mm ø steel bar is,

1000 x 3.858 = 3858 kg.

So far we have seen the unit weight for each diameter of steel bar in meter basis. That means weight of bar per meter.

But what if you estimate the steel bar length in foot. What will be the formula to calculate the steel bar's weight if the length of bar is in foot?

You May Want to Read:
Concrete Cover for Reinforcement Bar
Types of Rebar Support in RCC Member

Calculating Weight of Steel Bars When Length is in Foot

Again,

Weight = A x L x ρ

= 3.14 x D²/(4 x 304.80 x 304.80) x 222

= D²L/533

Where,
D = Diameter of bar in mm (1 foot = 304.80 mm)
ρ (Rho) = 7850 kg/m³ = 222 kg/ft³ (actually it is 222.287 kg/ft³)

Keep in mind that you always should use D as millimeter and L as feet in this formula.

Unit weight of steel bar per feet

Unit Weight of Steel Bar When Length is in Foot

If you calculate 1 foot length of any diameter of steel bar you will get the following result and that will be the unit weight of steel bars per foot length.

Unit weight of,

  • 10mm ø bar = 10² x 1/533 = 0.188 kg/ft
  • 12mm ø bar = 12² x 1/533 = 0.270 kg/ft
  • 16mm ø bar = 16² x 1/533 = 0.480 kg/ft
  • 20mm ø bar = 20² x 1/533 = 0.750 kg/ft
  • 25mm ø bar = 25² x 1/533 = 1.172 kg/ft

If you multiply the estimated length of steel bars with these unit weights you'll get the total weight of steel bars.

For example,
Weight of 1000 feet long 10mm ø bar is,

1000 x 0.188 = 188 kg.

Your Turn:
If you have any query about this post then ask me in the comments below. I'll reply as early as possible.
Read More
// // Leave a Comment

How to Estimate Materials for Isolated Footing

Companies often use Software for estimating the project cost. They more often do this for biding purpose.

But we are construction professionals and working on field level. So we can't always use software for estimating materials for the small part of a building. Sometimes it is impossible to construct the whole part of a building at a time because of the critical condition of the project.

Let me clear this.

Suppose, there are 30 numbers of isolated footing in a building. Whatever the reason, sometimes we can not make the all 30 numbers of footing ready for casing. At that situation, we just make 3 or 4 numbers of footing ready for the casting. And it is not economical to cast this small quantity of concrete with readymix. So we always prefer machine mix concrete for this purpose.

For constructing footing of a building you have to have plan before starting the task. You have to estimate the materials for footing. You have to make purchase requisition for materials and ensure the required materials are available on the project.

The question is, what is isolated footing and what are the materials required for a isolated footing?

Isolated footing is a shallow type footing. It normally holds one column on it. To know more about the types of footing read the following post -
Various Types of Foundation

Materials Required for Isolated Footing

For constructing a isolated footing following materials are required -

  • Shutter Material
  • MS Rod
  • Binding Wire
  • Cover Block and Chair
  • Concrete

Shutter Material for Isolated Footing

Most of the time wooden shutter materials are used for the isolated footing. Sometimes steel shutter materials are also used. We will use wooden shutter for this purpose, at least in this post.

Isolated footing, estimating isolated footing, materials for isolated footing


Isolated footing, estmate of footing,

How to Estimate Wood for Shuttering Isolated Footing?

See the above picture. The length of footing is 5 feet, width is 4 feet and height is 1 feet. To make the shutter for side-A of the footing you'll need 4 feet long and 15 inches height wooden plank.

Our footing height is 1 feet. Then why we use 15 inches height wooden plank? Because we will fix the shutter below 3 inches from the bottom of footing.

Then the required wooden shutter for side-A is,

4' x 15" = 5 sft (12" = 1 feet, sft= square feet)

We'll use 1.5" thick wooden plank.

So the volume of the wood is,

5 sft x 1.5" = 0.63 cft (cft= cubic feet)

Wood is always measured as cubic feet.

For the side-C we'll require the same quantity of wood as side-A.

Now, lets calculate the wood for side-B.

Length of wood for side-B is, 5'-3". But our footing length is 5 feet then why we'll require 5'-3" long shutter? Because we'll join this shutter with the side-A's and side-C's shutter. The thickness of side-A and Side-C shutter is,

1.5" + 1.5" = 3"

Therefore,
Length of side-B shutter is 5'-3" or 63"
Width of side-B shutter is 1'-3" or 15"
Thickness of shutter is 1.5"

Then,
volume of side-B shutter is,

63" x 15" x 1.5" = 0.82 cft (cft= cubic feet).

Side-D also require the same quantity of wood as side-B.

So far, we have found -

Required wood

For side-A = 0.63 cft
For side-B = 0.82 cft
For side-C=side-A=0.63 cft
For side-D=side-B=0.82 cft

Total wood= A+B+C+D= 2.92 cft

We will require 2.92 cft wood for making shutter for the isolated footing. If you don't find required size of wood then you'll need some 2" x 1.5" size wooden plank for making shutter.

We estimated required wood for one isolated footing. If you have 30 isolated footing of different sizes calculate the required wood for each one using same technique we applied here. Total them all and make purchase requisition for the required wood.

Now we'll estimate the MS rod for the isolated footing.

How to Estimate MS Rod for Isolated Footing?

See the above picture. There is a instruction for rod placement. That is [email protected]"c/c both way.

It means 12mm diameter bar should be placed at the distance of 4" centre to centre.

The length of our isolated footing is 5 feet. The clear cover of reinforcement is 3 inches for one side. For both side it is 6 inches. So we have to place rod for 5' - 6"=4.5'.

Requires number of rods are, 4.5' divided by 4".

That means

4.5'/4"= 13.63 numbers.

Say 14 nos.

You have to add one more number of rod for starting point.

So total required number of rod is 14+1= 15 nos.

Now we have to calculate the length of rod. We'll place the rod along short-side (4' side).

So the length will be

4' - clear cover of both side + hook (90 degree bend)  length of both side.

= 4' - 2x3" + 2x6"
= 4' - 6" + 12" (12" = 1 feet)
= 4.5'

So total length of all 15 numbers of bar is

15 x 4.5'
= 67.5 feet

Now we'll calculate the rod for long-side of the isolated footing.

By following the above method,

Number of rods,

= 3.5'/4" + 1

=11.61

Say 12 nos

Length of rod,

= 4.5' + 1'

= 5.5'

Total length of rods for long-side of isolated footing,

= 5.5' x 12

= 66 feet

Total rods for the isolated footing = 67.5' + 66'

= 133.5 feet.

Say 134 feet

You have to add 10% more rod with the estimated rod during ordering for purchase.

You may not order rod as running feet. So you have to convert them in kilogram or ton.

Read More:
How to Calculate the Unit Weight of Steel Bars

Oh. One more thing, you have to order rod for short column also. Because rebar of short column should be placed before casting footing.

I'll write about estimating rod for column some other day here in this blog. So subscribe our Email newsletter to get the update when it happens.

Summary of MS Rod Calculation
For rods along short-side

Numbers of rod= 4.5'/4" +1= 14.64 say, 15 nos.

Length of rod= 4' - 6" + 1'= 4.5'

Length of total rods=15 x 4.5=67.5'.

For rods along long-side
Numbers of rod= 3.5'/4" + 1= 11.61 say, 12 nos.

Length of rod=5' - 6" + 1' = 5.5'.

Length of total rods=12 x 5.5=66'

Total rod for the footing= 67.5' + 66'=133.5'

You'll need a 10mm Ø bar for binding the main rod of the footing. The length of the binder is,

2 x 4.5 + 2x 3.5= 16'.

So, total required rod is,
  • 10mm Ø bar= 16', and
  • 12mm Ø bar= 133.5'

Binding Wire for Isolated Footing

For binding rods you need binding wire. We need 9 kg to 13 kg binding wire for 1 ton of rod. You can estimate average 10 kg binding wire per ton of rod. So estimate total binding wire depending on required rod.

Cover Block and Chair for Isolated Footing

To keep the rod in place and maintaining concrete clear cover you should provide either cover block or chair for bottom and cover block for side. Cover block should be placed at 2 feet distance.

You'll need 8 numbers of cover block for sides and 5 numbers of cover block/chair for bottom of the Isolated footing.

Read More:
Types of Rebar Support in RCC Member
17 Technical Terms about Reinforcement a Construction Supervisor Should Know

Concrete for Isolated Footing

The size of our isolated footing,

Length - 5 feet

Width - 4 feet

Height - 1 feet.

Volume of concrete for the footing is,

5 x 4 x 1

= 20 cubic feet.

If you want to estimate ingredients for the footing first know the ratio of concrete suggested in the structural drawing. Then read the following post.

How to Calculate Materials for Different-Ratio Concrete

I've just shown the estimating technique for one isolated footing here. You may have many footings of different sizes in your project.

Follow the same technique to estimate materials for all the isolated footings of your project and sum up them to order materials for purchase.

Some symbols and terms I used here in this post

'- Foot symbol

" - Inch symbol

Ø - Diameter symbol

1' = 12"

Sft - Square feet

Cft - Cubic feet

Nos - Numbers


Your Turn
Do you have any question about this post?
Do you want to share anything else about this post?
Please share in comments...
Read More
// // Leave a Comment

Completion: The 8th Work Phase of a Building Construction, bct9

When I started this tutorial series I had a plan in my mind that I'll describe every point of a residential building construction process from a construction professional's point of view. For that purpose, I first divided the whole construction process into 8 work phases. Each work phase is a summary post of different tasks of a building construction. After that I will go in-depth details of every tasks so that a construction professional, even novice, can understand the complete building construction process easily.

With this post, I have reached the last work phase of building construction. And our last work phase is Completion.

Building construction tutorial


Completion: The 8th Work Phase of a Building construction

Actual building construction ends before this completion phase starts.

When I was in school, teachers alway advice us to finish the writing 20 minutes before the exam ends. So that we can check the exam sheets if there were any mistakes.

Completion of the building construction is like that. And it is done to check if there is anything wrong in that. It also include some important task. If I summarise all it'll look like below -

  • Final Touch
  • Cleaning
  • Landscaping and Planting
  • Final Inspection
  • Hand Over

Final Touch

Various works are done in final touch stage. Those are as following -
  • If there is any spot on painting that is repaired.
  • If any cracks found on plaster surface those are repaired.
  • If found broken tiles on any location that is replaced.
  • If any defect found on wooden door that is repaired or replaced.
  • If any defects found on window grill, aluminium or window's glass those are repaired.
  • If there are any leakages on water supply line that should berepaired.
  • If any leakage found on drainage line that is repaired.
  • If any fault found on electrical connection those are repaired.
  • If any problem found on door lock and window lock that is replaced.
See your finished project through home owner's eye and check if there is any fault or defect and repair those. This is called final touch.

Cleaning

During the whole construction process we left many dust, dirt and rubbish in the project. Those are cleaned in this stage. It can include following tasks -
  • Cleaning the dirt from tiles surface which we left during working and walking on those.
  • Cleaning the rubbish which we accumulate during brick work plastering work.
  • Removing shutter materials which you used during construction.
  • Sell wooden, steel and aluminium cut pieces available in the project.
  • Sell paint buckets and others scraps.
  • Clean surrounding of the project.
  • Cleaning also includes removing tools and machine like generator, cutting machine, welding machine, hoist etc.

Landscaping and Planting

In this stage of building construction you have to perform the following tasks -
  • Levelling the surrounding of the project.
  • Paving work arround building.
  • Planting or gardening around building or on roof as instructed by architect.

Final Inspection

In this stage of construction you have to do some tasks with the local government authority and it is the part of handover process. A project manager as a contractor's representative performs following task in this stage -
  • Prepare set of plan known as the "as build plan". As build plan is the plan which shows exactly how the facilities were constructed and they also shows the all changes to the original construction plan. Local building officials will follow this drawing during examining the project.
  • Collecting completion certificate from the government officials. In this process local building officials check the building if it is built as per code. If everything is satisfactory they will give the completion certificate.

Hand over

This is the last stage of building construction. In this stage final cost is prepared for the project. If any payment is pending that is collected from the building owner. And finally all documents is handed over to the owner.

Different country follows different rules and regulations for handing over the projects. So it may differ in your country.

Your Turn
Do you have experience handing over a building project? How did you do that? Please share in comment so that we can get knowledge from that.

Read More
// // Leave a Comment

7 Cement Tests to Justify Its Quality

Producing large quantity of cement with quality is practically impossible.

So when you buy cement there is certain possibility of quality variation in cement. That is why it is essential to test the cement to know its quality not only you paid for this but also to forestall the possibility of a failure through the use of defective material.

The main qualifications demanded of a cement in civil construction are strength, permanency of structure and a rate of setting suitable to the demands of the work.

To determine these qualification both chemical and physical tests are done. But chemical tests aren't more important than physical tests. So I'll discuss about physical tests here.

Cement test

7 Cement Tests to Justify Its Quality

The physical tests which are generally performed to determinethe acceptability of cements are -

  1. Fineness Test
  2. Consistency Test
  3. Setting time Test
  4. Soundness Test
  5. Strength Test
  6. Heat of Hydration Test
  7. Specific Gravity Test

1. Fineness Test

Fineness is the mean size of cement grain. Fineness test is done to measure the mean size of cement grain.

The finer the cement the surface area for hydration will be large and it increases the strength of cement. But the fineness varies in different types of cement.

Following three methods are applied to test the fineness of cement

  • Sieve method
  • Air Permeability method
  • Sedimentation method

2. Consistency Test

This test is done to estimate the required water quantity to form a normal consistency cement paste. It is defined as the percentage of water required for the cement paste.

3. Setting Time Test

Cement has two types of setting time, one is initial setting time and another is final setting.

Initial setting time is the state of cement mortar or concrete when it starts to become stiffen and unworkable.

Final setting time is the state when cement mortar or concrete has become fully unworkable.

Two methods are used to find the initial and final setting time of cement

  • Vicat needle method, and
  • Gillmore needle method

4. Soundness Test

Soundness of cement means it doesn't undergo large volume change after setting. Large changes in volume produce cracks, disintegration and distortion, ultimately leading to failure. So it is very important to test the soundness of cement.

To test the soundness two methods can be applied.

  • Le-chatelier method
  • Autoclave method

5. Strength Test

Cement has two types of strength - compressive strength and tensile strength.

To know the compressive strength and tensile strength of  cement following tests are performed -

Cement mortar cube test (for compressive strength)

  • Briqutte test (for tensile strength)
  • Split tensile test (for tensile strength)

6. Heat of Hydration Test

Cement produce large amount of heat during hydration process. When large amount of concrete volume is poured the inner temperature is greater than outer surface of concrete. Because outer surface is exposed to weather. Thus surface shrinks rapidly than the inner and tends to produce cracks. That is why it is important to test the heat of hydration of cement.

Following test is performed to know the heat of hydration of cement

  • Calorimeter method

7. Specific Gravity Test

Specific gravity of cement is a comparison of weight of a cement volume to the weight of same volume of water.

  • Le-chaterlier flask is used to test the specific gravity of cement.

Source: IS-4031

Your Turn
Which test do you think is more important to jusify the cement quality? Share in comments..
Read More
// // Leave a Comment

Finishing Work in a Building Construction Project, BCT8

If you are a regular reader of this blog then you know how I design this building construction tutorial series. There are 8 work phases and finishing work is the 7th work phase of that tutorial series.

Typical finishing work of a building construction includes plastering, tiles work, painting, wooden work, metal work, electrical and sanitary fixture fitting, lift installation etc. etc.

But in this tutorial series there is a masonry work phase which includes plaster work, tiles work etc. So I exclude those items from finishing work phase.

There is also a work phase which is called services work phase. Services work phase includes electrical fixture fitting, sanitary fixture fitting etc. So I excluded those items also from finishing work phase. So the rest of the finishing item are painting work, wooden work, aluminium work and metal work. And these are the work-items of our finishing work phase.

Building construction tutorial, Finishing work

Finishing Work: The 7th Work Phase of Building Construction

Following are the items for finishing work -

  • Painting Work
  • Wooden work
  • Aluminium Work
  • Metal work

Painting work

Paint is done on following surface of the building -

  • Interior wall and ceiling
  • Exterior wall,
  • Metal and 
  • Wooden surface.

Read the following post to know more about the paint.

Types of Paints Used in Building Construction
Types of Paint Finishes

Wooden work

We mostly use wood in building as

  • Door shutter
  • Door frame, etc


Read the following post to know more about wood.
About Wood: All You Need to Know As a Construction Professional

Aluminium work

Aluminium is mostly used in following parts of a building


  • Window
  • Door
  • Curtain wall. Etc

Metal work

The following item of a building we define as metal work in our construction tutorial series -

  • Window Grill
  • Railing
  • Gate, etc

We have discussed 7 work phases of this tutorial series so far. One work phase is left, that is completion. I'll discuss about this within short time. So please subscribe via Email to get that as it happen.

Your Turn
Have I missed anything here? Please share in comments...
Read More
// // Leave a Comment

Procedure of Mixing Mortar

Correct procedure of mixing mortar can save you money and time. So it is essential for a construction professional to learn the procedure of mixing mortar.

Before knowing mortar mixing procedure let's first see the ingredients of mortar.

Ingredients of mortar depends on the type of mortar. Generally, mortar ingredients are binding materials, sand and of course water.

Widely used binding material for mortar is cement.

So we'll mix cement, sand and water for our mortar.

Now the core question is what should be the proportion of ingredients of mortar?

It depends on the purpose of the use of mortar.

Suppose, when we use the mortar for brick laying purpose the mixing ratio of cement and sand is normally 1:4. But you can't use this proportion for honey-comb repairing purpose. The proportion will be different for honey-comb repairing.

But that is the another topic. I'll discuss about mortar mix ratio some other day. Now we'll focus on the procedure of mixing mortar.

So far we have found from above discussion that the general mortar ingredients are
  • Cement
  • Sand
  • Water

Procedure of Mixing Mortar

Mortar mixing procedure involves four steps of operation -
  1. Selection of ingredients
  2. Measuring the ingredients.
  3. Batching mortar
  4. Mixing Mortar

1. Selection of Ingredients

We normally use Portland cement in mortar. Portland is not a brand name it's a type of cement.

Sand of mortar should be fine grade, clean, sharp and free from organic materials. We normally screen the sand before using in mortar.

Water for mixing mortar should be fresh drinking water.

2. Measuring the Ingredients

Ingredients of mortar are measured by volume. Suppose, the ratio of mortar is 1:4. That means one part cement will be mixed with four-part of sand. But how to measure?

The easiest way is to measure by cement bag. One bag cement should mix with four bag sand. But measuring sand by bag is time consuming. That is why we use fera for this purpose. The volume of a fera is equal to half bag of cement. So for one bag cement we mix two fera of sand. And that is the easiest way we found so far.
Mixing mortar

Now water. How much water is needed for one bag cement?

It depends on various things. Such as weather condition, quality of sand, purpose of using mortar, etc. By not going to technical terms you should focus on the consistency of mortar. So add small quantity of water at a time to dry mortar-mix to get the desired consistency.

3. Batching Mortar

You don't need to prepare whole required amount of mortar at a time. Suppose 5 masons are working together to make brick wall on a floor. They will work full day long. They will consume, for example, 38 cubic feet of mortar. But you should not prepare whole amount of mortar at the beginning of the day. You should prepare mortar several times in a day. It should bedone for the shake of the quality of mortar.

Read More:
How to Estimate Ingredients for 3" Brick Masonry Wall?
How to Estimate Materials for 5" Thick Brick Wall

However, mortar can be mixed by hand or by machine.

Machine mixing is done in large project. But for building construction project we rarely use machine for mixing mortar.

The procedure is same for both hand mixing and machine mixing. Only a difference between them is, hand mixing is done on a floor by shovelling whereas machine mixing is done by a machine.

4. Mixing Mortar

Follow the simple steps below for mixing mortar -
  • Choose a clean, even and dry place for mixing mortar. Sometimes, finding even and clean place is a bit difficult. In that case, use one or two plain sheet for this purpose.
  • Spread required quantity of sand on that place.
  • Put required cement on spreaded sand.
  • Now mix those throughly in dry condition with a shovel till the mix gains cementious color.
  • Add small quantity of water and mix again with shovel. Follow this step until the mixer gain desired consistency and workability.
Now a days, there are readymix mortar available to buy. You can use those for your small-size project. The procedure of mixing readymix mortar is same as we described above. But it doesn't need to add sand in readymix mortar.

Your Turn
I didn't personally use readymix mortar. If you have an experience please share in comments below.
Read More