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