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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.

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!

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.

Yes, I am about to update these calculations for easier understanding. thanks

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.

I will write comprehensively on it soon but will forward a sample to you.

Thanks

bumping into ur site is joy to me. ur artcles sure helps contractor architects like me.

Thanks for your comments. I am happy you like the site.

good job and well done

the 66 bags for the ground beams need be checked again pls. thank you.

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.

this is a well done job!

GOOD JOB.so wat about d labour rate.pls explain.

Thank

this is a very goog job and more explanatory hoever i will like you to take a step further by explaining paint calculations.

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.

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.

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

you have dymistifed the problems of taking off and estimating.More power to your elbow

Thank you sir.

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.

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.

pls this is mind blowing thanks for a job well done

wat abt reinforcement calculation

it is hard to udarstand

guys keep on traying

,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.

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.

Thanks I am happy u find the article useful.

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.

I will work on that .

Thanks

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

but footing is not including in your calculation how?

Footing is not included but is same process for the calculations.

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.

Thanks for the patience used in explaining this view.It’s a good explanation.Bravo and GOD bless us!

Kio

It’s nice but b4 d concrete works you have to consider some things first

am greatly impressed by the contents of this site

its okay .continue my brother, God bless u

I am very happy to have come across this site. I really have a lot to read and learn. Thanks for the work you are doing to help others. God bless you.

nice job, but i think ur quantities does not have provision 4 waste. ur estimates will not b sufficient on ground. u should allow minimum of 25% 4 waste.

Arc. Odion,

Many thanks for your good job.

God bless you richly.

On profit, what do you assume and how do you include that.

Regards,

Arc. James Awosina, mnia

Dis ????§ a great job i must confess cos av been searchin for an opportunity †? learn dis estimation and costing until I came across dis blog. Keep on with †?? ???? work brother Emma.

Hey it’s great job, & i can add some thing important which is a factor of safety ranges from 1.2 to 1.6 depending on type/condition tipper,site location, workmanship,etc….

thnx

thanks

I have got more confidence to confront my job now. Thanks for the exposition. God bless you real good.

I really appreciate ur effort cos dis is original practical one u av ur drawing with u just follow d procedure. It just a good thing for site QS dat dnt really nid to carry BOQ all around d site…….Good work man.

Once u av ur drawin wit u no nid of BOQ just follow d procedure…..gud work

Thank you very much for all you have been doing, i am confident that i would be able to start somthing on my site. What i have learnt on this site is beyond measure, May GOD bless you. Pls can you do this same estimate for a four bedroom bungallow on a fairly stable soil using either the dimension you used in calculation of blocks n cement?. I am a liitle confused abt this beam thing. Once again, You are GODs SENT.

@Banki, thank you, you need a plan before you can do that hence we will be doing estimate without any base we will refer to which can not work for most plans.

I must say i’m grateful, keep it up

U’v jst set the pace for us to follow. U re gud leaders

@Gabriel, Thanks bro.

How come you put n and sum number? what does that mean?

Excellent Site

If teachers could explain things like this in the classroom, we would all enjoy being engineers, all they do is to scare you. I really enjoy you site, you are good.

Thanks Kwesi.

This is good and well understandable.

this is really a great work thanks and God bless you for the information

pls can u enlighten us on how to calculate for 1 3 6 ratio

thumps up….

dude ur doing a great job….

itz very detailed nd informative….

This is really a nice work, and it will also help the Nigerians to build their houses without any problems.

Thanks

well done emma. let me add something. u av not included shrinkage value of vol. x 1.5. do that and check ur results with this standard value for 1m3 of 1:2:4 compacted concrete requires 6.2 bags of 50kg cement, 0.43m3 of sand and 0.86m3 of granite.

Thank you sir. I will have to add the shrinkage value really because some people are afraid they may give quotation and won’t like to explain further more to client. Once again thanks.

Nice material estimate sir, let me add to ur calculation please let them also know that 16.236m3 is just the volume of concrete excluding percentage shringkage and waste for the work. There is a need for shringkage and waste depending on effective accuracy of the measured work. Thanks

Your articals are impresive and educative,thanx

thank you for infarmation sir

pleases kindly let me know a rough estimate of bags of cement needed for the lintel work of a three bedroom bungalow thanks

IM doing a foundation with a 100mm depth, its 6.5 meters x 5.5 meters for a garage that it built with panels to sit on top of the foundation. Can you give me an estimate of the material i will need and do you think the depth should be greater. This is my neighbours choice..??

i speak authoritatively as a member of rics and niqs that the above calculation is wrong.

on a ratio mix of 1:2:4 agg you have 6bags/cubic metre of concrete, this also include waste i.e 1/7 X 28.8bags X 1.45(ADD 45% WASTE AND SHRINKAGE)= 5.8BAGS

WHILE SAND IS RATIO OF SAND 2/7 X 1.45 X 1.42(WEIGHT OF SAND TO TONNES)

SAME FOR GRANITE

Thanks for your contribution Diran.

Iam gr8ful for the bold step @ emma. Pls why do u have to multiply the volume of the whole body by the ratio to get d sand and granite this adrin is very good but showing us how those constant numbers were derive will help and can I get Diran phone number pls

Pls amma u re correct there by multipling wth unit of cement as 1/7 of vol.now do mean that 3.8m3 is 5tonne? Pls explain 1 1/2 tipper bcoos so many tipper out there wth diffnt names

infact! Ur head dey there,i respect ur intelligence.ure 3much brotherly

i realy comend ur effort for such expensive fact. pls am confused by d 1:2:7 , can u pls expanciate?

keep up d gud work. god bless u.

@ Diran pls can u simplify ur contributions

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Good work and nice contributions…. Howerer, its noteworthy that when preparing a BOQ from the plan, the formula used applies but more emphasis on safety, wastage and shrinkage should be considered to quote the material requirements. For the costing, its of utmost importance that the cost of labor charges and material be adopted as obtainable in the proposed site location. This is to avoid under-estimation or an outragous BOQ. Thanks…

emma well done

Emma. U ar doing a great job. Well done. Pls can u explain how to calculate water cement ratio in simple terms?

Emma, how can i get the building contractors manual?

I think you missed something. You didn’t subtract the quantity of reinforcement bars to be used. Unless you are dealing with plain concrete, which i don’t think is right to have raft foundation without reinforcement to transfer the load. When you consider the quantity of reinforcement to be used, the quantity of cement and aggregate will reduce. Nevertheless, you did a nice job

Thanks for all the info on building construction shared.

I do have a question regards to reinforcements – my question is how could one determine the sizes of reinforcement to be use in reinforced concrete slab.

thanks 4 ur contribution in the construction org.

God bless you.

This is your first article am reading. It is great and it is a light in the darkness. Thanks so much.

Though a Structural Engineer like me will not totally agree with this calculation, it is a way out of desert. With maximum respect, try to incorporate void and waste into the calculation. Thanks.

Welldone, u’re one of our best lecturer in our institutn in naija. u’ve explained so simple and easy!

U’re one of our best lecturer in our higher institution! U’ve made the ‘JAMB’ of estimating simple and self-done.

How to calculate raw material of concrete.

Slab size 120′ x 56′ x 1/2″

Raw Material (Cross Agg + Sand + Cement)

U are doing a great job. Well done. pls how can i see you one on one.

Good day sir. please i wish to know the original scale used in auto card 2002.

I tried using ur formular to calculate an oversite concrete of 26.7m by 9.9m by 0.75m….but got an outrageous 809 bags of cement…how come?…pls I’ll be looking forward to ur reply..

I am a fresh graduate of Quantity surveying,sound in Quantity surveying practices.l will appreciate 1f anybody on this site can link me to any construction firm.contact 08138509216

I’m a structural Engineering student and truly greatful to you. This has reduced my stress on concrete calculation, I grabed all you did, more power to your able.

Emma,could you throw more light on what the figures below represent please.? 3.825,3.95,1.375, 1.25, 4.975, 1.25 (16.625) and 3.825, 2.910, 3.825,(10.56)

Good work man.but u forgot about shrinkage of concrete which is about 30% which is very important. So update ur estimate

well done job

its a good information. thanks.

thank you for your material caluculation

nice work. but can we say, if one bag of cement = 2headpans, in mix ratio cant we use say 2:8:10 as we practically use on site? or we say 1headpan of cement: 4headpans of sand: 5headpans chippings?

Emma, you are doing a great work. please keep it up. In simple terms, how can I calc. water cement ratio.

U are great man thanks

well done for work, thanks

I really accept the way of calculating materials but I suggest that there is a need of adding percentage for waste as well as shrinkage, since the input in concrete is not equal to output due to shrinkage factor

Your work have given me a solution to my concrete and aggregates estimation problem thanks man.

Pls tell me a building job I am free in Laber rate me