I am of the opinion that building contractors and engineers spend too much money on bungalow foundation, especially in the DPC ( over site concrete).

My analysis here will be focusing on structural design and cost estimations of different bungalows foundation of different soil type such as dry, waterlogged, sandy etc. I will also be looking at the commonly used foundation typed for bungalows such as strip foundation, wide strip with reinforcement, pad footings, combined pad, continuous footings and extreme cases raft foundation for bungalows.

I will start by enumerating the steps that need to be followed why building a bungalows foundation from structural points of view and also considering cost.

1. Site clearance
2. transverse survey and the leveling of the site by a land survey or a civil engineer using either total station or theodolite
3. the setting out of the building
4. Excavation of foundation trenches
5. Foundation footings( popularly called blinding).
6. Setting of foundation if any in the case of pad footing, combine or continues foundation
7. setting of foundation wall or substructures wall.
8. filling of the foundation
9. preparation of the filled foundation for DPC by compaction
10. Formwork for DPC
11. Placement of oversite concrete on the prepared foundation.

I will start here explaining each of the steps listed below with simple arithmetic calculations of equilibrium, cost and with pictorial view of work done in the past.

What is site clearance: in a simple language, it is the removal of bushes, trees, and all other unwanted structures or material on site. materials such as site dump, unwanted sand or gravel etc. It also involved the removal of top vegetable soil of at least 150mm deep into the ground in other to allow for work to be done a solid surface.

How can site clearance be done:
There are two ways in which it can be done, namely;
1. Mechanical ways
2. Manually

1. mechanically: by using a grader to remove this unwanted site materials. This method is faster and cost effective over a large area of building land. I mostly recommend this type clearance for a big to medium project of 1 plot ( 50' x 100 or 15m x 30m) and above.
Most client are scared to use this method because of the perceived cost implication but in reality it offers more values for money because of the following advantages.

1. It offers wider coverage of work over a shot period of time.
2. It help to grade site uniformly, make access road to site and help to get rid of vegetable soil of 150mm above ground level.
3. Condemned soil from top soil removal can further be used to filled the foundation where laterite or other feeling materials are expensive.

Cost implication:
It cost about N60,000 - N80,000 to get a grader in Port harcourt
it cost about N30,000 - N 50,000 to get the vehicle that will bring it to site.
fuel cost of about N20,000
Total of = N110,000 ( minimun)
Total of = N 150,000 ( maximum)

2. manual method: This involve the used of crude implement like cutlass, hoe, rake and shovel to remove the bushes, unwanted materials and top vegetable soil of a building construction site.
This method is cost effective over a small area of land like half a plot for a 2 bedroom or 1 bedroom flat. It is cheaper and more labour intensive than the mechanical method. it is recommended for a small building project like a two bedroom or one bedroom flat on half a plot of land.
It cost about N20,000 or less to prepared a land for two bedroom flat bungalow using this method.

Item 2: Land survey; Land survey is important because it allows the builder/engineer understand the following information;
1. Understand the relative height of the site with respect to an ordinance benched mark already in existence
2. It enable the building line of the building to be known
3. It will also help to control the drainage of the building and the site in future.

Most building owners don't do this item 2 because fear of cost or ignorant but it reality, it is relatively cheap to do.
For a small building project, it cost about N10,000 to rent a theodolite or N20,000 to rent a Total stations for one day and the operator/surveyor/engineer is paid around N10,000 making a sum of N30,000 ( maximum).

Item 3. setting out : setting involve the transferring of information on the structural drawings, architectural drawings and servicing drawings into the ground for construction of a house to be possible.

Setting out can also be done using the following two method:
1. It can be done manually
2. It can also be done using surveyors instrument like total station or a theodolite.

For most bungalow with dimension of building less than 20m in both width and length, manual method can safely be use.
materials for a typical setting out
1. peg
2. Line
3. profile board ( 2 x 2'' soft wood)
4. nail ( 3'', 2'' and 11/2'' nail)
5. Builder's square, plumb, meters rule, tabe etc.

How to estimate materials for setting out
to get number of pegs required;
1. Get the perimeter of the building.
2. increase the perimeter by 25%
3. divide the perimeter by 2 ( i normally spaced my pegs @ 2m c/c)
4. since there are 20 pegs in a bundle and a bundle cost about N1,200. the result from 3 above is further divided by 20 to get the number of bundle and the result is multiply by N1,200 to know the cost of peg.


to get number of profile board ( 2 x 2'' soft wood)
1. using the result of 2 above, divide the result by 3m ( since 2 x 2 comes in 3.6m )
2. since each 2 x 2'' soft wood cost about N200, multiply the result in above by N200 to get the cost of profile.

in summary, it cost about N40,000 for materials and workmanship to set out a typical three bedroom flat bungalow


a typical profile board

ride on sir..ur student eager to learn..

Item 4: foundation excavation; this involve the removal of soil along the path of the building wall as drawn on the architectural plans and structural plans as the case may be. For a simple bungalow, a foundation layout showing the width of excavation ( girth) is used to carry out this operation.

1.width of foundation excavation or trench = to 3 x width of the block to be used for the building
e.g, for a bungalow built with a 150mm ( 6'') on relatively solid soil, width = 3 x 150 = 450mm
for a bungalow built with 225mm (9''), width = 225 x 3 = 675mm

for a poorer soil of low bearing capacity ( water lodged and sandy soil).
width = weight of wall per unit length/ bearing capacity = w/qu (N/m/N/m2)
where the weight of wall per unit length = unit weight of block wall plus finishes x height of wall.

some strip foundation for a bungalow can be reinforced if the soil is poor.

2. Depth of foundation for a simple bungalow ( strip foundation)

I sent you an email.Pls can you go through it and send reply to same address.Thanks.

Shawls:
I sent you an email.Pls can you go through it and send reply to same address.Thanks.

I will check sir....thanks

Cost of excavation: the rate of excavation is around N1000- N600/m depending on the location of the project.

Bill of quantity is prepared in cubic meters but labourers are paid per meters. you will need to work out the discrepancy.
1 cubic meter of a trench of the following dimensions 675mm x 900mm x 1000mm can be converted into a linear measurement = 0.6075cubic meters will be 0.6m for the perimeter billing.

well done..what is the thickness of strip foundation footing for 6" and 9" wall.

nwabuwa:
well done..what is the thickness of strip foundation footing for 6" and 9" wall.

IT DEPEND ON THE NATURE OF THE SOIL.
FOR 9" BLOCK ON A NORMAL SOIL ( Qu between >|100kN/m2) = 225mm ( 9"
FOR 6" BLOCK ON A NORMAL SOIL = 150mm

Nice analysis, this kind of article is somehow scarce on Property section of NL this days. I am happy to read this as I know this will help potential builders, clients and students. pls ride on.

But, just a little observation, the cost of setting out/pegging in item 3 is 40k does this include excavation or just pegging alone. Just asking for clarification.

Thanks

Aventures.

Aventures:
Nice analysis, this kind of article is somehow scarce on Property section of NL this days. I am happy to read this as I know this will help potential builders, clients and students. pls ride on.

But, just a little observation, the cost of setting out/pegging in item 3 is 40k does this include excavation or just pegging alone. Just asking for clarification.

Thanks

Aventures.

here in port Harcourt, it is the cost of setting out ( pegging )
here is the breakdown for a three bedroom flat
1. pegs = 4bundles ( @N1000/bundle = N4,000)

2. profile board = 30 nr of 2 x 2" ( N200/nr = N6,000)

3. builder's square, line, plumb and nail = N10,000

4. transportation = N5,000

5. Labor cost = N5,000 ( 1 carpenter and 1 labor)

6. Professional charges = N 10,000

TOTAL = N 40,000

OP,good job you are doing.
Alternative building technologies lessons will also be appreciated in this analysis class.

abdulwastecx:

here in port Harcourt, it is the cost of setting out ( pegging )
here is the breakdown for a three bedroom flat
1. pegs = 4bundles ( @N1000/bundle = N4,000)
2. profile board = 30 nr of 2 x 2" ( N200/nr = N6,000)
3. builder's square, line, plumb and nail = N10,000
4. transportation = N5,000
5. Labor cost = N5,000 ( 1 carpenter and 1 labor)
6. Professional charges = N 10,000
TOTAL = N 40,000

Thanks for the clarification

mix ratio for foundation footing for bungalow should either be 1:3:6 or 1:2:4 for normal soil.
i prefer 1:2:4 ( 1 bag of cement : 4 head pan of sand or 1 wheel barrow of sand : 8 head pan of gravel or 2 wheel barrow of gravel). reason been that the foundation of bungalow is very important because it help to distributes the wall load to foundation adequately.
A typical foundations supporting a three bedroom flat or its equivalent should have the following features

1. minimum thickness of 100mm ( 4'') and should not more than 225mm (9'') thick on a strong soil for economy reason.
2. the sharp sand should not be too smooth and free from clay and other dirt which may reduce the strength of concrete
3. the gravel should be preferably 3/4 ( 20mm) thick and must be free from dust.
4. the water for mixing should be drinkable and free from salt and other chemical contamination
5. the water-cement ratio must not be greater than 0.6.


mode of calculating the volume of concrete for foundation footings ( strip foundation).
1. get the sum of the total gird of the substructure, let say 'P' = 50 ( example)
2. get the width of the foundation, say 450mm (18'') for 150mm ( 6" wall and 675mm ( 27" ) for 225mm (9" wall
3. Assume a thickness of say 150mm for 6" wall and or 225mm for 9" wall.
4. convert all your dimension to 'm'
5. hence volume, v =50x 0.45 x 0.15 = 3.375m3
6. increase the volume by 25% to cater for shrinkage and wastage. =1.25 x 3.375= 4.05m3

using mix ratio 1:2:4
part of cement = 1/7 x4.05 =0.58m3
since the density of ordinary Portland cement s 1506kg/m3
and i bag = 50kg
hence, no of bags = 0.58 x 1506/50 =17.4bags ( 18 bags aprox.)

part of sand = 2/7 x 4.05 =1.16m3
since the density of sharp sand is 1600kg/m3 and a tonne of sharp sand is 1000kg
hence, 1.16 x 1600/1000 = 1.856tonnes ( 2 tonnes aprox.)

part of gravel = 2 x 1.16 = 2.32m3
since the density of gravel is 2400kg/m3 and a tonne of gravel weight 1000kg
hence, 2.32 x 2.4 =5.57tonnes ( 6 tonnes )

part of water using water cement ratio of 0.6
weight of water = 0.6 weight of cement = 0.6 x 18 x 50 =540kg
volume of water required, from density = mass/volume
making volume subject, volume = mass/density
where density of water = 1000kg/m3
hence, volume of water required = 540/1000= 0.54m3
since,1m3 = 1000liters
volume of water required = 540 liters

Please can you drop your email address.

Thanks

Akinbaba:
Please can you drop your email address.

Thanks

jwastecx@gmail.com

I have been away from the property section due to work. I am back to continue my analysis.

item 6.
sub structural block wall: this is part of the building that is built below the floor level serving as part of the foundation.

It is normally built with either hollow 9" block or 6'' block ( but i prefer 9" block).
the strength of the block should be within 4 - 1N/mm2


how to calculate the number of block required for a particular foundation.
1. get the perimeter of all the sub structural wall
2. get the height of such wall ( mostly 3ft or 900mm)
3. get the product of (2) and (1) to get the area of the block required
4. multiply the result in (3) above by 1.25 ( which is 25% to cater for breakage of block
5. since there are 10blocks in a 1m2 area of wall. multiply the area from (4) by 10 to get the number of blocks.

mortar for the block wall using 1: 6 (one bag of cement to 12 head pan of sharp sand)
number of cement required for every 60blocks in 1 bag


workmanship for block work,
9" block is been set for 50-70N per block and 6" goes for N40-N50 per block

oga nice work where have you been it's almost over a week now

i have been a bit busy sir, now i am back.

Item 8 :Filling of the foundation to required height
This is done after the completion of the foundation block and casting of foundation column( if any). the most preferable soil for foundation filling is laterite or sandy soil in area with no laterite ( south southern states like rivers and bayelsa).

after filling the foundation should be left for a period at least one week during raining season to be compacted by rain or properly wet and compacted manually with rammer of mechanically with a compactor.

DPC also known as over site concrete is a structural element that is made up of membrane, and concrete layer reinforced with light reinforcement mostly 5mm iron mesh to avoid cracking of the concrete layers.

The thickness of this oversite concrete vary from say 3" to 6'' ( depending on the financial strength of the client and the nature of the site).
The mix ratio popularly used vary from 1:2:4 to 1:3:6 ( the use of 1:3:6 for bungalows built on considerable solid soil with properly compacted laterite filling of the foundation). for a simple bungalow a depth of 4"(100mm) or 75mm (3" can be used provided the laterite filling is properly compacted.

the membrane popularly used is polythene and the polythene serve the proposed of preventing moisture from rising through the foundation wall to the super structural walls above, such moisture rise when not prevent can cause swollen and pilling of finishes like plastering and paint on the super structure.

picture below of a typical membrane, mesh and the over site concrete

i am open to any question

abdulwastecx:
item 6.
sub structural block wall: this is part of the building that is built below the floor level serving as part of the foundation.

It is normally built with either hollow 9" block or 6'' block ( but i prefer 9" block).
the strength of the block should be within 4 - 1N/mm2


how to calculate the number of block required for a particular foundation.
1. get the perimeter of all the sub structural wall
2. get the height of such wall ( mostly 3ft or 900mm)
3. get the product of (2) and (1) to get the area of the block required
4. multiply the result in (3) above by 1.25 ( which is 25% to cater for breakage of block
5. since there are 10blocks in a 1m2 area of wall. divide the area from (4) by 10 to get the number of blocks.

mortar for the block wall using 1: 6 (one bag of cement to 12 head pan of sharp sand)
number of cement required for every 60blocks in 1 bag


workmanship for block work,
9" block is been set for 50-70N per block and 6" goes for N40-N50 per block

Sir Abdul, please check that No.5... I think it should be "... multiply the area from (4) by 10 to get the number of blocks".

You are good,bro.

So my Brother pls what is the estimated total cost for a foundation of 4Bedroom bungallow on a dry land.?

laplace19:



Sir Abdul, please check that No.5... I think it should be "... multiply the area from (4) by 10 to get the number of blocks".

You are good,bro.

thanks sir for the correction..

Icon4s:
So my Brother pls what is the estimated total cost for a foundation of 4Bedroom bungallow on a dry land.?

setting out = 40k
excavation = 80 - 100k ( with a depth of 600mm and width of 450 or 675mm)
blinding concrete = 250k ( assuming 15k/cubic meter)
block work blocks both materials and workmanship= 500K
some foundation side columns = 80k
filling = base on site condition
dpc of 100mm thick (4" = 350k

TOTAL WITHOUT SUPERVISION FEE AND FILLING = 1.35m ( for a very solid job)

abdulwastecx:


thanks sir for the correction..

Original corrected...

Hajji M.

abdulwastecx:
DPC also known as over site concrete is a structural element that is made up of membrane, and concrete layer reinforced with light reinforcement mostly 5mm iron mesh to avoid cracking of the concrete layers.

The thickness of this oversite concrete vary from say 3" to 6'' ( depending on the financial strength of the client and the nature of the site).
The mix ratio popularly used vary from 1:2:4 to 1:3:6 ( the use of 1:3:6 for bungalows built on considerable solid soil with properly compacted laterite filling of the foundation). for a simple bungalow a depth of 4"(100mm) or 75mm (3" can be used provided the laterite filling is properly compacted.

the membrane popularly used is polythene and the polythene serve the proposed of preventing moisture from rising through the foundation wall to the super structural walls above, such moisture rise when not prevent can cause swollen and pilling of finishes like plastering and paint on the super structure.

picture below of a typical membrane, mesh and the over site concrete

Abdul, is there any setback to the structure if I wait till after roofing, plumbing and electrical work before doing the oversite concrete job