# Decking or suspended Concrete floor Estimate

Planning for your decking is one area people spend too much of time because of the finances involved but we can as well prepare our minds for the probable costs by doing a rough estimate ourselves from the plan. This will help you to plan ahead and also save cost.

For the plan above,

Estimation will start from the bamboo studs, other materials can also be used but bamboo is cheaper and commonly used.

BAMBOO- Bamboo are spaced at 0.6m or 600mm or 2ft apart in most construction of normal decking height  , so for the plan, we are taken the plan to be a perfect rectangle of 29m by 13m.  29m being the longer side, divide by 0.6m

=48pcs of bamboo studs to span one row of 29m

For 13m ,divide also by 0.6m=22 pcs of bamboo studs to span one row in 13m side.

To know the total number, simply multiply (48 by 22)pcs=1056 pcs

But each length of bamboo from the market can cut 2 pieces, so divide 1056 by 2=528pcs of bamboo.

PLANKS-Wood planks of 1” by 12” are most commonly used in decking, plywood can also be used but for this article we are working on 1” by 12” planks.

We need the planks for the table on which the concrete decking will seat, and to calculate that , consider the size of a plank first, which is 3.6m by 0.3m or 12” by 1” . So surface area of a plank is 3.6m by 0.3m=1.08m2

Now calculate the surface area of our decking from plan which is 29m by 13m=377m2

Now divide 377m2 by 1.08m2 to know the numbers of planks needed=350 planks.

You also needs the planks that will go round the wall and serve as a support for these planks. To do this, calculate the total length of walls, for this sample is taken as 275m, but you need the planks to board at both sides of each wall i.e 275m multiply by 2=550m.

Also divide this length by the length of a plank of 3.6m=153 planks

(The one needed for staircase not included),

Total plank is 350+153=503 planks

2”by3” wood also has to run across the lines of the bamboo studs to support the decking table too.

Assuming the 2 by 3 wood goes crosssectionally under the table along the same path with the bamboo, multiply 13m by 48=624m, divide that by 3.6 =173pcs of 2” by 3”.

For other bracing works on site, is advisable you add half of the sum to the sum above i.e (173/2)+173=260 pcs of 2by3

Also consider paying for nails, binding wire and labour.

IRON RODS-Iron rods can’t be calculated without the structural plan, so this is based on experience and assumptions to give us a close idea of what the reinforcements will be.

The iron rods are laid from one end to the other and crossing each other to form a netlike look which depends on the structural designs . But for our sample, we want to assume the spacing for each rod is at 200mm or 0.2m intervals, calculating for the 13m side,

13 divide by 0.2m =65pcs. Now multiply 65pcs by the length the iron rods are expected to span which is 29m.=1885m

Divide 1885m by 12m (which is length of iron rod in the market)

So you’ll need to buy 157 pcs of either 10mm or 12mm iron rods from the market as the design specified.

For the 29m side ,divide 29m by 0.2m =145 pcs, then multiply 145pcs by the length the iron rods are expected to span which is 13m=1885m

Divide 1885m by 12m(which is length of iron rod in the market). You’ll need to buy 157 pcs of either 10mm or 12mm iron rods from the market as the design specified . Note that we arrived at same result for both sides because we are using perfect rectangle and also adopting spacings of 0.2m for both, in a design spacings varies most time. Allowance must also be left for 0.6m return of these iron rods from the edges when laying them, hence the length ought to be taken as (29m+1.2m) and (13m+1.2m) to accommodate the extra irons needed for the returns.

Consider paying for binding wire and labour also.

CONCRETE– To form the concrete paste we need to buy granite, sharpsand, cement, of course water (lol)

Please check this article and its comments for the calculations on concrete http://buildingcontractorsecrets.com/2011/07/how-to-calculate-the-numbers-of-bags-of-cement-in-the-foundation-of-a-simple-bungallow-from-a-building-plan/ ,  some factors won’t be considered here , so for a concrete of 29m by 13m with concrete thickness of 6” or 150mm or 0.15m, multiply 29 by 13 by 0.15 to get the volume =56.55m3

For the ratio of concrete mix 1:2:4 aggregate, multiply 56.55 by 6.18=353 bags

For sand multiply 56.55 by 0.434=25m3

A cubic meter of sand weighs 2.08 tonnes , therefore for 25m3 you’ll need 2.08 x 25=52 tonnes of sand.

For granite, multiply 56.55 by 0.868=50m3

A cubic meter of granite weighs 2.4 tonnes

So 50 x 2.4 =120 tonnes of granite.

An architect with decades of experience

1. Ifelola says:

Good Job, keep it up brother.
NB:The weight of solid granite ranges between 2.4 T to 2.7T, howerver when granite is crushed, the voids reduces this to about 1.67T, we might need more than d calculated value. Thats why a full 30T full truck of crushed granite is about 18 tons
Cheers bro.

2. Ifelola says:

Good Job, keep it up brother.
NB:The weight of solid granite ranges between 2.4 T to 2.7T, howerver when granite is crushed, the voids reduces this to about 1.67T, we might need more than d calculated value. Thats why a full 30T full truck of crushed granite is about 18 cubic meters.
Cheers bro.

3. emma says:

Thanks Ifelola.

4. ayodeji says:

happy to fine this website, thank you sir.

What a good work…..thanks bro!

6. olawale says:

A wonderful job which it’s benefit is
unlimited indeed you made a name but u may not know now. Sir you are a pride in the construction industry now and for the oncoming generation in the industry.

7. Kola says:

Thank u for the good job you are doing. God will reward u. Sky is yr limit. You deserve National award for selfless service you are rendering to the Nation.

8. Eric Bioh says:

What is the 6.18,0.434 and o.868. can you tell me more about those formula

9. Nurudeen says:

Fantastic ideas I love it great work, pls don’t relent your best is yet to come.

10. doyin says:

Good job,may GOD increase your wisdom.

Best Regard.

11. akeem says:

@ mr emma/ ifelola,
Sir, I must commend u both for the great job u r doin here.
pls, am a quantity surveying student and I need clarification on certain things here.
Based on the conversion factor u highlighted here, it means d 3.81m3 tipper of sand has a tonnage of abt 8tons. pls, confirm if dats wats obtainable.Also, comin down to our local context,pls help with the following:
4 tyres…….what’s d sand/gravel vol and tonnage?
6tyres……….. same
8 tyres………..same
All other types of tipper tyres dat I dnt knw.
Lastly, how many headpans/wheel barrows is contained in the 3.81m3 tipper?
I need to knw all dis in order to further aid my understanding.
Thanks and God bless sir.

12. akeem says:

@ mr emma/ ifelola,
Sir, I must commend u both for the great job u r doin here.
pls, am a quantity surveying student and I need clarification on certain things here.
Based on the conversion factor u highlighted here, it means d 3.81m3 tipper of sand has a tonnage of abt 8tons. pls, confirm if dats wats obtainable.Also, comin down to our local context,pls help with the following:
4 tyres…….what’s d sand/gravel vol and tonnage?
6tyres……….. same
8 tyres………..same
All other types of tipper tyres dat I dnt knw.
Lastly, how many headpans/wheel barrows is contained in the 3.81m3 tipper?
I need to knw all dis in orde!, to further aid my understanding.
Thanks and God bless sir.

13. Rita Aileen Okpokam says:

Cheers. I finished my building in record time (22 months). It is a beautiful place. I look at it and can hardly believe I virtually project managed it. Thanks for all your tips and sound advice. Would have sent a picture but will look like I am showing off. Leave it to your imagination.

14. engr bosun says:

nice calculation.keep it up bro

15. Ibrahim says:

nice wk

16. ugoeze ifeyinwa says:

Pls i will like to have an idea on how much it will cost me to do a fence on my 2 plots of land at ibeju lekki

17. okunola funminiyi says:

how did you come accross 353 bags of cement for concrete, cld u pls share more light on how you get that 6.18 by 56.55