e stimation 1 excavation 2 lesson 5. e xcavation 2 recap from excavation 1 looking at site plans...
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ESTIMATION 1Excavation 2 lesson 5
EXCAVATION 2
Recap from excavation 1 Looking at site plans
Desk top study Site Visit
Unit pricing of excavation Excavate to reduced levels Excavate trenches Disposal of water Removal of excavated material
EXCAVATION 2
Battering the slope of the excavation
EXCAVATION 2
Nature of the ground Weather conditions Proximity of in ground services Trench/excavation depth Previously disturbed ground
EXCAVATION 2
Earthwork support/shoring
EXCAVATION 2
Earthwork support/shoring The cost is influenced by
The nature of the ground and depth of excavation The type of excavation that needs shoring The material cost of the timber and the assessment
made on how many times it can be used. Sheet pile shoring is usually used today.
EXCAVATION 2
Unit cost for earthwork support Cost
The labour cost of fixing and removing the timber The material cost itself The number of times the timber can be used before it
is unfit for further usage
EXCAVATION 2
Unit cost for earthwork support Cost
The cost of the earthwork support is allowed by diving the initial cost of timber per m2 by the number of times it can be used
Cost of timber is $220/m2 of face of excavation Can be used 10 times Allowance for earthwork support = $220/10 = $22.00/m2 of face of excavation
EXCAVATION 2
Working space
EXCAVATION 2
Working space Area for tradesmen to complete their work May or may not be required- estimator to review
EXCAVATION 2
Schedule of Quantities for excavation
EXCAVATION 2
Schedule of Quantities Consider the type of plant to use and the nature
of the ground and quantities for excavation and disposal
Check the amount of excavation = the amount of disposal
EXCAVATION 2
Schedule of Quantities
The total excavation Topsoil 380 m2 x 0.275 = 105 m3 To reduced levels 246 m3 Trenches 38m3 Total 389 m3
EXCAVATION 2
Schedule of Quantities
The total disposal Topsoil 380 m2 x 0.275 = 105 m3 Filling to excavation 47 m3 Disposal off site 237 m3 Total 389 m3
EXCAVATION 2
Labour and machine constantsDigger (banksman the same constants)
Top soil –0.15 hr/m3 To reduced levels – 0.09hr/m3 To trenches – 0.14 hr/m3
Digger and roller (labourer the same constants) Working space allowance–0. 08hr/m3 Filling excavations – 0.08hr/m3
EXCAVATION 2
Labour and machine ratesDigger - $28.00/hrDigger + roller - $31.00/hrBanksman - $12.00/hrLabour - $12.00 hrHardcore
1.95 t/m3 = $10.00/t
EXCAVATION 2
Topsoil – 275mm deep
Digger 0.15hr/m3 x $28.00/hr = $4.20 Banksman 0.15 hr/m3 x $12.00 = $1.80 Sub total = $6.00/m3
Top soil 1 m2 x .0275 = 6 x 0.275 = $1.66/m2
EXCAVATION 2
Excavate to reduced levels
Digger 0.09hr/m3 x $28.00 = $2.52 Banksman 0.09hr/m3 x $12.00 = $1.08
Total $3.60/m3
EXCAVATION 2
Excavate trenches
Digger 0.14hr/m3 x $28.00 = $3.92 Banksman 0.14hr/m3 x $12.00 = $1.68 Labourer 0.14/m3 x $12.00 = $1.68
Total $7.28/m3
EXCAVATION 2
Working space allowanceExcavation as for trenches $7.28/m3
Assume 75% filling and 25% disposalDigger + roller (75% x 0.08hr/m3) = 0.06 hr/m30.06 hr/m3 x $31.00 = $1.86
EXCAVATION 2
Working space allowanceLabourers (2no) =(2 x 0.08) x $12.00 = $1.44/ m3Additional earthwork support – not pricedAdditional disposal (25% x 1 m3) = .25 x $15.80
= $3.95
Total cost of working space/m3 = 7.28 +$1.86 +1.44+3.95
= $14.53/m3
EXCAVATION 2
Working space allowanceWorking space is measured in m2 ( standard
allowance is 250mm wide)
Total cost of working space/m21 x .25 x $14.53/m3 = $3.63/m2
EXCAVATION 2
Filling with excavated material Assumed that transport over short distances can
be provided by a site dumper and an allowance for this has been included in the preliminaries
Digger +roller 0.08 hr x $31.00 = $2.48 Labourer (2 no) (2 x .08 x $12.00 = $1.92 TOTAL $4.40/m3
EXCAVATION 2
Hardcore filling
Hardcore materials 1.9t x $10.00 = $19.50 Waste 10% 0.19t x $10.00 = $1.90 Digger + roller .05 x $31/hr = $1.55 Labourer (2 no) (2 x 0.05 x $12.00) = $1.20
TOTAL $24.15/m3
EXCAVATION 2
Operational estimatingThis is form of estimating where all the resources
needed for part of the construction are considered together
Examples
Drain runs including excavation, earthwork support, bedding, pipework and backfill
EXCAVATION 2
What labour and plant is required ??
EXCAVATION 2
Operational estimating Forecasting anticipated durations of activities Resourcing Advise from construction managers and
subcontractors Estimator to provide a method statement so
construction staff can understand assumptions made when preparing the estimate
EXCAVATION 2
Operational estimating
Estimator collates a list of resources for each operation to calculate the cost
Estimator to provide a method statement so construction staff can understand assumptions made when preparing the estimate
EXCAVATION 2
Advantages Construction methods are selected which are
practical Programme of works included holidays, time of
year, facilities available which give a more realistic guide to the time needed for plant and labour
Alterations and repair works are priced globally not against each individual item which causes overpricing
The sequencing of works can be looked at before the project commences which make for more efficient resources.
EXCAVATION 2
Disadvantages If pricing a schedule of quantites it is difficult to
split the costs accurately against each items. Initial discussion with other team members is
necessary to provide the correct method statement and then implementing it once the works commence re Housing New Zealand rollouts
EXCAVATION 2
Comparison of pricing a schedule of quantities with an operational estimate (looking just at plant and labour)
Weighbridge foundation is priced based on the schedule
The site Foreman knows that a similar project took 2 weeks for 4 labourer, a return visit for 2 men to complete. A backactor and roller was needed for 3 days to complete the project
EXCAVATION 2
EXCAVATION 2
Labour 4 no x 2 weeks x 45 hrs x $15.00 = $5400.00 2 no x 2 days x 9 hrs x $15.00 =$ 540.00 TOTAL LABOUR $5,940.00
Plant 1 no x 3 days x 8 hrs = $ 840.00 TOTAL =
$6,780.00
EXCAVATION 2
Review the difference in the total costs and ask the question why??
Good check for labour constants
EXCAVATION 2
Hourly labour rates Standard code of practice to calculate the labour
rate Hourly rate = annual cost of employing an
operative/actual hours worked
EXCAVATION 2
Considerations Rate includes public and annual holidays Overtime working No of hours worked each week Trade supervision Skilled operatives in the area/resources Travelling time/ subsistence allowance _
Hamiliton Bonus payments Insurances
EXCAVATION 2
Plant rates Identify specific items of plant
Purchase for the contract Company owned plant Hire from an external source
Price sourcing Calculate from first principles Internal plant department rates Hirer’s quotations Published schedules
EXCAVATION 2
References Estimating and tendering for construction work –
Martin Brook
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