How To Calculate Materials In Concrete Foundation.
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Using images 1 and 2 above and in a bid to also demystify the raft foundation cost, this article will deal extensively on how to calculate your concrete materials like cement, sand and granite that you will use for the foundation.
Often time concrete are mostly mixed in 1:2:4 ratio, when you see such specificationit simply means one bag of cement to four headpans of sand and eight headpans of granite.
Notice that first number represent a bag of cement which is equivalent to two headpans, hence the sand is taken as four headpanss and the granite represented by 4 in the ratio is taken as eight headpans.
Going by this knowledge it is easy for us to do a very fast calculation at least to be close to what we might need on site.
To do this calculation, add the sum of ratio 1+2+4=7
Calculate the cubic volume of concrete for foundation.
Going by the previous article the total lenght of trench was taken as 65.6m
Height of concrete beam is 1.1m or 1100m from image 2
And width is 0.225m or 225mm
therefore total volume of concrete beams =65.6m x 1.1 x 0.225 =16.236
Now divide 16.236 by the sum of the ratio which is 7
16.236/7=2.31943m3
Taking a constant, the volume of a bag of cement is 0.035m3
Divide 2.31943 by 0.035
=66 bags of cement to do all the concrete beams , however don’t forget that cement and sand will also be used for the blinding before the concrete beams are placed .
For the sand reqd.,multiply 2.31943m3 by 2 to know the volume since it is in ratio of 1:2:4
Therefore volume of sand requires =4.63886m3
If we take volume of a tipper as 3.8m3 then
4.63886/3.8=1 1/2 trip of 5 tons tipper for the concrete beam.
For the granite use the same ratio of 1 bag of cement to 4 headpans of sand to 8 headpans of granite
So for granite reqd, multiply 2.31943m3 by 4 to know the volume since it is in the ratio of 1:2:4
therefore volume of granite requires=9.27772
If we take volume of a tipper as 3.8m3 then,
9.27772/3.8=2 1/2 trips of granite (Disregarding water and and other attending expenses
If one bag cost N1,800, then 66 bags =N118,800
And if one trip of sand is N15,000
then 1 1/2 trips =N22,500
And if one trip of 5 tons of granite=N30,000
then granite cost needed =2 1/2 x N30,000
=N75,000
Total=N118,800 + N22,500 + N75,000
=N216,300
For the german floor or oversite concrete-
Multiply the lenght by breadth by the thickness or width of the plan from image.
Add 3.825 +3.95 +1.375 +1.25+4.975+1.25=16.625
Add 3.825+2.910+3.825=10.560
So multiply the sum for the volume=16.625 x 10.560 x 0.2
=35.112m3
To know the number of cement required divide 35.112 by the sum of the ratio which is 7
=35.112 / 7
=5.016m3
Taking a constant, the volume of a bag of cement which is 0.035m3,
divide 5.016m3 by 0.035
=143 bags of cement for the german floor or oversite concrete.
Apply the steps above for the sand and granite,
For sand,
Multiply 5.016 by 2=10.032, now divide by 3.8m3
=3 trips of 5tons sharp sand
For granite,
multiply 5.016 by 4=20.064, now divide by 3.8m3
=5 1/2 trips of 5 tons granite
So if one bag of cement cost N1800
then 143 bags of cement will cost N1800 x 143 =N257,400
And if one trip of sand cost N15,000
then 3 trips of 5 tons sharp sand =N45,000
And if one trip of 5 tons granite cost =N30,000
then 5 1/2 trips of 5 tons granite =N165,000
So total for concrete excluding other attending materials
=N216,000+257,000+45,000+165,000
TOTAL=N683,400
This is hard to understand I believe but you can still study it by bits.
August 19th, 2009 at 2:39 pm
This is great insight coming from you, Odion. You took all concrete technology & estimating and mashed it all into a single whole. Good job, man!
June 23rd, 2010 at 10:53 am
kidly re-explain your calculations on oversite concrete. The one i saw is for the beam which i really don’t get, becos the total bags of 66bags is not straight. thanks.
June 26th, 2010 at 10:19 am
Yes, I am about to update these calculations for easier understanding. thanks
July 18th, 2010 at 6:40 pm
Hello Odion,
Could you pls give me total estimate of blocks, cements, sand, & granite that will be needed to complete a three bedroom bungalow with kitchen and store. Kindly note that i have already completed the foundation. I look forward to your favourable reply.
Thank you.
August 9th, 2010 at 6:55 pm
bumping into ur site is joy to me. ur artcles sure helps contractor architects like me.
August 9th, 2010 at 7:34 pm
Thanks for your comments. I am happy you like the site.
August 9th, 2010 at 7:35 pm
I will write comprehensively on it soon but will forward a sample to you.
Thanks
August 12th, 2010 at 2:45 pm
good job and well done
August 18th, 2010 at 5:22 pm
the 66 bags for the ground beams need be checked again pls. thank you.
August 18th, 2010 at 5:48 pm
Yes I agree I need to recheck this. Though the formular is right but I think the total length of the trenches is not 65m. Thanks for your observation.
October 12th, 2010 at 7:57 pm
this is a well done job!
October 26th, 2010 at 7:01 pm
GOOD JOB.so wat about d labour rate.pls explain.
Thank
October 30th, 2010 at 5:50 pm
this is a very goog job and more explanatory hoever i will like you to take a step further by explaining paint calculations.
January 29th, 2011 at 12:37 pm
sir, honestly no doubt you are a great man and blessing to the building world, thanks for caring young generation like our along. More grease to your elbow. Thanks.
February 16th, 2011 at 9:20 pm
Thank you so much Emma.
I am a young Mechanical Design Eng. based in the US. I am getting ready to embark on a small housing project for my family in the east.
I am very happy to come across your writings. I wish to prepare myself with all the tools I need to come out of this with less stress; I understand there are many other Naija factors that are inevitable.
With your blog; it think I will not be a total mugu.
March 28th, 2011 at 6:16 pm
your calculation is only based on raft foundation. wat abt if u want to get the required quantity of matl for a simple bungalow, and a decking excluding ur above explanation for raft fdn. n thnks for ur good work
April 19th, 2011 at 3:40 pm
you have dymistifed the problems of taking off and estimating.More power to your elbow
May 2nd, 2011 at 11:13 am
Brother,rhanks for all your efforts.
The word concrete beam is a little confusing for me.I thought you were describing foundation for a bungalow on a solid ground.
Please explain.
May 18th, 2011 at 6:58 am
No concrete beam is basically for a raft foundation which is mostly for a waterlogged or weak soil and also for storey buildings. I will paste a picture of one soon to explain further.
May 18th, 2011 at 6:59 am
Thank you sir.
June 30th, 2011 at 3:49 pm
pls this is mind blowing thanks for a job well done
wat abt reinforcement calculation
August 2nd, 2011 at 1:49 pm
guys keep on traying
August 3rd, 2011 at 10:25 am
,love what u ve done in this page,informing us who are learners to understand concrete technology.pls am still not clear with the explainaton.like is it that the perimeter of the rooms or of every compactment is sum up to give the total lenght of the room or compactment. which in turn is multiplied by the thickness of concrete floor by what that i dont understand pls explain. (2) many of these suppliers will tell u six tiers of truck of sharpsand is 25TONS and if its true,how do u convert to volume of that truck i.e m3.pls am an ND holder in civil engineering and since i know nothing of concrete technology pls enlighten me.
September 29th, 2011 at 10:07 pm
You just helped me today. Have been trying to make estimate for a job for some days now. Thank GOD i came across your blog. Thanks man.
October 1st, 2011 at 7:44 pm
Thank you for the wonderful job you ve been doing may God reward you infolds.Pls i will need more explanation on the calculation for oversite concrete, i try to follow the one you gave but got conffused bcos of the beams but i honestly enjoy and understand the caculations for the numbers of block.Pls use an example of a three bedroom bungalow. once again thank you.
October 2nd, 2011 at 10:21 pm
I will work on that .
Thanks
October 2nd, 2011 at 10:21 pm
Thanks I am happy u find the article useful.
October 5th, 2011 at 4:40 pm
To be sincerely sir,my first come cross thing on construction material you are did more than enough, this is just the begin. may God bless your understand. thanks
October 5th, 2011 at 4:44 pm
but footing is not including in your calculation how?
December 28th, 2011 at 8:39 pm
infant this is encouraging,but i want to has a question that is possible to build a house with councrete,cement,sand only?i mean without bricks,along side with the partition.
February 17th, 2012 at 6:21 am
Thanks for the patience used in explaining this view.It’s a good explanation.Bravo and GOD bless us!
February 18th, 2012 at 8:46 pm
Kio
February 18th, 2012 at 8:49 pm
It’s nice but b4 d concrete works you have to consider some things first
April 3rd, 2012 at 3:30 am
am greatly impressed by the contents of this site
April 3rd, 2012 at 7:55 pm
Footing is not included but is same process for the calculations.
May 12th, 2012 at 10:24 am
its okay .continue my brother, God bless u