Apr 19

Composite Rate Build Up for Foundations – Approximate Quantities in Elemental Estimate Layout

Composite Rate - Foundations

Composite Rate Build Up – Foundations

The Elemental Estimate layout and grouping of items will be used in this example. There are principles that you have to follow when building up composite rates for Approximate Quantities. We are going to illustrate a composite rate build-up for Foundations:

Excavate trench 600mm wide and 700mm deep, with 200mm thick concrete footings, 230mm foundation brickwall 800mm high and facebricks on plinth 300mm high.

Step 1

First, you have to determine the Group unit of measurement. When you are measuring Foundations in Elemental or Approximate Quantities estimating, the group unit of measurement is the metre (m).

Step 2

The second step is listing all associated Bill items that can be mapped to Foundations by length. These are:

  • Trench Excavation – (m3) Rate – R27.50
  • Risk of collapse/Earthwork support – (m2) Rate – R2.00
  • Compaction – (m2) Rate – R5.00
  • Ant Poisoning to bottoms and sides of trench – (m2) Rate – R7.00
  • Backfilling  – (m3) Rate – R35.00
  • Cart-away surplus material from excavations – (m3) Rate – R30.00
  • Concrete footings – (m3) Rate – R1200.00
  • One Brickwall in Foundations  – (m2) Rate – R235.00
  • 150mm wide Brick reinforcement – (m) Rate – R2.50
  • Facings on plinth area – (m2) Rate – R50.00
  • DPC – (m2) Rate – R7.00

Step 3

Since your Group unit is the metre (m), you should convert the Bill item rates to Cost per Metre.

Rate Build Up

GROUP – FOUNDATIONS

Rate – Cost Per Metre (m)  Rands Rate – Cost Per Metre (m)  Rands
1m of Trench Excavations:    
600 x 700 x 1000
0.6 x 0.7 x 1 = 0.42m3
0.43m3 x R27.50 = R11.83 11.83
1m of Earthwork Support:    
(700)2 x 1000
(0.7) 2 x 1 = 1.44m2
1.44m2 x R2.00 = R2.88 2.88
1m of Compaction:    
600 x 1000
0.6 x 1 = 0.6m2
0.6m2 x R5.00 = R3.00 3.00
1m of Ant Poisoning:    
Bottom 600 x 1000 = 0.6 x 1 = 0.6m2
0.6m2 x R7.00 = R4.20 4.20
Sides (700)2 x 1000 = (0.7)2 x 1 = 1.4m2
1.4m2 x R7.00 = R9.80 9.80
1m of Backfilling:    
600 – 230 = 370
700 – 200 = 500
370 x 500 x 1000
0.37 x 0.5 x 1 = 0.185m3
0.185m3 x R35.00 = R6.48 6.48
1m of Cart-away from Excavations:    
700 – 200 = 500
500 x 230 x 1000
0.5 x 0.23 x 1 = 0.115m3
0.115m3 x R30.00 = R3.45 3.45
1m of Concrete Footings:    
600 x 200 x 1000
0.6 x 0.2 x 1 = 0.12m3
0.12m3 x R1200.00 = R144.00 144.00 185.64
1m of One Brickwall in Foundations:    
800 x 1000
0.8 x 1 = 0.8m2
0.8m2 x R235.00 = R188.00 188.00
1m of 150mm wide Brick reinforcement:    
1m = R2.50 2.50
1m of Facings on plinth area:    
300 x 1000
0.30 x 1 = 0.30m2
0.30m2 x R50.00 = R15.00 15.00
1m of DPC:    
230 x 1000
0.23 x 1 = 0.23m2
0.23m2 x R7.00 = R1.61 1.61 207.11
Composite Rate – FOUNDATIONS 392.75  

The composite rate for FOUNDATIONS is R392.75 per metre.

**Bill items which cannot be mapped to the Group unit (m) are measured separately. These are:

Site Drainage:

  • Keeping excavations free of water (item)

Extra over excavations:

  • excavating in soft rock (m3)
  • excavating in hard rock (m3)

Elemental Layout and Grouping

Items which go into the element FOUNDATIONS and components Unreinforced Strip Footings and Brick and Block Walls are stated in the description:

 
 

 

Unit Quantity Unit Rate Cost/m2 Subtotal Cost
FOUNDATIONS

 

Unreinforced Strip Footings:

 

Mass concrete footing 700x300mm, excavation 1m deep, risk of collapse, cart-away, backfilling, compaction, blinding and ant proofing.

 

m 65 185.64 12,066.60
Brick and Block Walls:

 

One brickwall in foundations 1m high , brick reinforcement, finishes and DPC

 

m 65 207.11 13,462.15
Subtotal FOUNDATIONS M2 25,528.75