Difference in Cement cost between Local Fundi mix ratio vs. specified ratio.

Difference in Cement cost between Local Fundi mix ratio vs. specified ratio.

In Kenya, majority of the local construction developers who have no full architectural and structural engineering services rely on the local fundis and foremen to guide them on the mix ratios for cement, sand and ballast.

The local fundi mix ratio is usually 2 bags of cement for 4 wheelbarrows of sand to 8 wheelbarrows of ballast.

This represents a ratio of 1 to 4 to 8.

The specified mix ratio of for exposed Reinforced concrete is 1 to 2 to 4.

This represents 2 bags of cement to 1 wheelbarrow of sand to 2 wheelbarrows of ballast.

2 bags of cement make up 1 wheel barrow.

Example. 170m2 residential house.

Calculations when the house construction has used cement ratios of 2 bags cement to 4 wheelbarrows of sand to 8 wheelbarrows of ballast will be as below.

FOUNDATION
BLINDING
CEMENT BAGS 14.98
SAND 3,630.77
BALLAST 5,990.77
STRIP FOOTING
CEMENT 88.85
SAND 21,538.46
BALLAST 35,538.46
FOUNDATION WALLING

2000 stones

CEMENT

29.17

SAND

12,376.00

RING BEAM
CEMENT 25.38
SAND 6,153.85
BALLAST 10,153.85
SUPERSTRUCTURE WALLING 3800 stones
CEMENT 41.71
SAND 17,696.00
BALLAST 10,267.57
ROOF 2000ft
FLOOR SCREED
CEMENT 23.76
SAND 5,760.00
WALL PLASTER
CEMENT 41.25
SAND 17,500.00
WALL KEYING
CEMENT 6.50
SAND 2,756.25
TOTAL
COST KES
CEMENT 271.60 190,119.00 190,119.00
SAND 87,411.33 87.41 87,411.33
BALLAST 61,950.65 61.95 99,121.03
TOTAL 376,651.36

 

271 Bags of cement costing KES 190,000 will be used in total.

 

Calculations for the same house using specified ratios of 1 to 2 to 4 will be as below

FOUNDATION
BLINDING
CEMENT BAGS 27.81
SAND 3,371.43
BALLAST 5,562.86
STRIP FOOTING
CEMENT 165.00
SAND 20,000.00
BALLAST 33,000.00
FOUNDATION WALLING

2000 stones

CEMENT

38.90

SAND

11,786.67

RING BEAM
CEMENT 47.14
SAND 5,714.29
BALLAST 9,428.57
SUPERSTRUCTURE WALLING 3800 stones
CEMENT 41.71
SAND 17,696.00
BALLAST 10,267.57
ROOF 2000ft
FLOOR SCREED
CEMENT 23.76
SAND 5,760.00
WALL PLASTER
CEMENT 41.25
SAND 17,500.00
WALL KEYING
CEMENT 6.50
SAND 2,756.25
TOTAL
COST KES
CEMENT 392.07 274,450.41 274,450.41
SAND 84,584.63 84.58 84,584.63
BALLAST 58,259.00 58.26 93,214.40
TOTAL 452,249.44

 

392 bags of cement will be uses, costing KES 274,000.

this represents a 30% increase in cost of cement.

This represents a 16% increase in overall cost of concrete.

For most local constructions whereby developers engage fundis without architectural and engineering consultations, this is the amount of % savings they usually aim to get.

This method of achieving savings can be compared to an own goal since once structural defects check in, they are unrepairable and can result in the loss of the complete building, usually costing millions of shillings.

Developers should engage their architects and engineers in other methods that can result in the same % savings without compromising structural integrity.

Francis Gichui Kamau, Architect.

0721410684

 

Francis Gichuhi (692 Posts)

Architect Francis Gichuhi . B.Arch. University of Nairobi. Registered Architect, Kenya. Member, Architectural Association of Kenya. Contacts. email info@a4architect.com. Telephone +254721410684


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  4 comments for “Difference in Cement cost between Local Fundi mix ratio vs. specified ratio.

  1. October 19, 2016 at 7:56 am

    “The specified mix ratio of for exposed Reinforced concrete is 1 to 2 to 4. This represents 2 bags of cement to 1 wheelbarrow of sand to 4 wheelbarrows of ballast.”

    To me it looks like this ratio is 1:1:4

    • October 19, 2016 at 10:01 am

      1 wheelbarrow of cement is 2 bags of cement. yes..there is a typo there, thanks for notification.

    • Maina Eric
      December 17, 2016 at 2:37 pm

      Why don’t you just use a common measuring container. Like a bucket.
      I personally don’t like wheelbarrows in measuring ratios.

  2. Peter Oeri
    November 16, 2016 at 6:26 am

    Thanks alot for your information. I intend to put up a small retail shop in a remote rural shopping centre whose dimensions are let’s say 20 ft by 24 ft. The ground is flat red soil which doesn’t require much but just a trench for foundation. Assuming simple flat roofing is preferred, approximately how much sand, bricks and cement might I need? Bricks here in Kisii measure around 2ft long.
    Thanks

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