Example 1
o
In order to construct a square metre of the
blockwall, the following are required:
o
Materials: [Blocks-13 Nos; Mortar (1:3) head pans-3
Nos; Water – 1 bucket]
o
Labour: [Mason-1No; labourer – 1 No]
o
Equipment: [None]
o
Overhead [site expenses 20%; head office
expenses 10%]
o
Markups [risk 5%; profit 10%]
o
The table below summarizes the calculation for
the price for construction of a square metre of blockwall.
|
|
Requirements
|
Qty
|
Price per Unit (Tshs)
|
Amount
|
|
Materials
|
Blocks
|
13
|
1000
|
13000
|
|
Mortar
|
3
|
600
|
1800
|
|
|
Water
|
1
|
200
|
200
|
|
|
Labour
|
Masons charge
per blocks
|
13
|
150
|
1950
|
|
|
Labourer
charge per blocks
|
13
|
90
|
1170
|
|
Machine
|
-
|
|
-
|
-
|
|
Total direct
costs
|
18,120
|
|||
|
Site overheads
(20%)
|
3,624
|
|||
|
Main office
overheads (10%)
|
1,812
|
|||
|
Total costs
|
23,556
|
|||
|
Risk 5%
|
1,177.8
|
|||
|
Profit 10%
|
2,355.60
|
|||
|
Rate per m2
|
27,089.40
|
|||
Example 2
The following
information is available to an estimator who is required to build up a unit
rate for 1:2:4 concrete for foundation using volume batching. This information is then used to illustrate
how this unit rate is built up and adjusted to be entered in the bills of
quantities as a balanced bid unit rate estimate.
A Costs
of Resources
Cement
o
Cost per tone ex-factory (loaded free) ….
200,000/=
o
Delivery to site by hired 7ton lorry km ….
200/= per ton-km
o
Distance – factory to site …. 20km
o
Unload and site and store …. 7
men @ 1 hour @ 1350/= per
hour per lorry load
o
Wastage due to breakage …. 2.5%
o
Density of cement …. 1442kg/m3
Aggregates
o
Cost per m3 ex-quarry (loaded free) …. 13,500/=
o
Delivery to site by 7ton (5 m3) lorry …. 200/= per ton-km
o
Distance-quarry to site …. 18km
o
Labour banking at site …. 3
men @ 1hour @ 1350/= per
hour per lorry load
Sand
o
Cost per m3 ex-quarry (loaded free) …. 11000/=
o
Delivery to site by 7ton (4 m3) lorry …. 200/= per ton- km
o
Distance quarry to site …. 25
km
o
Labour banking at site …. 2
men @ 1hour @ 1350/= per hour per lorry load
B Mixing
(Using mixer with output 3m3/hour)
Mixer
o
Hire rate 8,350/= per hour, including fuel
o
Efficiency 75%
Vibrator
o
Hire rate 4,300/= per hour, including fuel
Skilled labour
o
1 mixer operator @ 1700/= per hour
o
1 skip attendant @ 1200/= per hour
General labour
o
Cement 1
o
Sand 2
o
Aggregate 3
6 @ 1350/= per hour
Allowing
for 30% shrinkage of concrete in place, a 20% overhead and a 10% profit, what
would be your balanced bid unit rate estimate per m3, assuming that
water is priced in the preliminaries.
C Unit
rate build up
Cement
o
Cost per 7ton lorry, ex-factory, 7 ton @ 200,000/ =
1,400,000/=
o
Cost of delivery to site per load, 7 ton @ 200/=
x 20 km = 28,000/=
o
Cost of unloading and sorting, 7 @ 1hour x
1350/= =
9,450/=
Sub total =
1,437,450/=
o
Cost of waste due to breakage at 2.5% = 35,936.25
Total =
1,473,386.25
o
Cost per
m3 = (1442kg x 1,473,386.25)/7000 =
303,517.57
Aggregates
o
Costs per lorry load, ex quarry, 5m3
@ 13,500/= =
67,500/=
o
Cost of delivery to site per load, 7 ton @ 200/-
x 18 km = 25,200/=
o
Cost of Banking at site, 3@ 1hour x 1350/= = 4,050/=
Total = 96,750/=
o
Cost per
m3 = 96,750/5 = 19,350/=
Sand
o
Cost per lorry load-ex-quarry, 4m3 @
11,000/= = 44,000/=
o
Cost of delivery to site per load, 7 ton @ 200 x
25km = 35,000/=
o
Cost of banking at site, 2 @ 1hour x 1350/= = 2,700/=
Total = 81,700/=
Cost
per m3 = 81,700/4 = 20,425/=
Mixing
Mixer
o
Hire rate 8,350/= per hour = 8,350/=
o
Efficiency 75%
o
Production per hour 3 x 75% = 2.25 m3 (productivity)
Cost per m3 = 8350/2.25 = 3,711.11
Labour
o
1 mixer operator @ 1,700/- per hour = 1,700/=
o
1 skip attendant @ 1200/- per hour = 1,200/=
o
6 general labour @ 1350/= per hour = 8,100/=
Total = 11,000/=
Cost per m3 =
11,000/2.25 = 4,888.89
Vibrator
o
Hire rate 4,300/= per hour = 4,300/-
Cost per m3 = 4,300//2.25 = 1,911.11
D Summary
1
m3 of cement @ 303,517.57 =
303,517.57
2
m3 of sand @ 19,350.00 = 40,850.00
4
m3 of aggregate @ 20,425.00 = 77,4 00.00
7
m3 (of concrete) Sub total = 421,767.57
Add 30% for shrinkage =
126,530.27
=
548,297.84
Cost per m3 = 551,092.84/7 = 78,328.26
Add: Mixer 3,711.11
Vibrator 1,911.11
Labour
4,888.89
Sub
total = 88,839.37
Allow
for 20% overhead 17,767.87
106,607.25
o
Add: 10% profit 10,660.72
o
Cost per m3 117,267.97
Say 117,268
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