Estimating Seminar

Estimating SeminarDanielle Yoong . Chung Hui Ping . Tan Jing Yi Ng Wei LinQuestion 5You are currently working as a trainee at Taylors QS Consultant. You are required to provide an estimate for a medium cost housing development in Petaling Jaya based on a set of preliminary sketch drawings. You are given a day to complete the task.

Explain the various methods of estimatingSelect the appropriate method/s of estimating that you will apply for the task and justify your selectionKey WordsTrainee ( No Experience)Medium Cost Housing DevelopmentPreliminary Sketches DrawingOne Day to complete task

Methods of estimatingSingle rate estimatingMultiple rate estimatingSquare MeterDefinitionOne of the popular methods for estimating due to its simplicity.This method measures the gross internal floor area (GIFA ) and making rates derived from experience or data from past projects.GIFA = Area of a building measured to the internal surface of the perimeter walls at each floor level

RequirementAll floors must be included, no deduction made for stairwells, lift shaftsExternal works and non-standard are calculated separately

CalculationPrevious project construction cost / GIFA current project= cost per unit area

This can be apply to future projects to estimate their construction cost.

AdvantagesProduce an estimate quicklyA very minimum data required to estimateHas a huge amount of data is published based on square meter costEasy to communicate to layman

DisadvantagesCan be accurate only if very similar building is compared withSingle rate: Functional UnitDefinition: Commonly used by National Bodies such as educational and health sector.What is Functional unit?A method use to estimate cost based on the functional units of a project.

Unit cost:School-cost per pupil rate/ cost per classHospitals-cost per bedroomTheatre-cost per seatRequirements:a) Client has a budget set for the project.b) Project closely similar to the previous project.c) Experience or data from previous project.

How to obtain?Cost is obtained by comparing previous projects of similar nature and dividing the total cost by the number of functional units obtained. Calculation:

Example 1: A school cost MYR 5,000,000 and provided 1000 student places the functional unit cost is MYR 5000 per school place.

Example 2: From previous experience, the cost of a 50 bed hospitals has been constructed for MYR 60 millions (60,000,000). Hence, the unit cost = MYR 60 million/500beds=MYR120,000 per bed. Thus, estimated 40 bed wing hospital will be 400 x MYR 120,000=MYR48 million.

Advantage: Produces estimate very quicklyA minimum data requiredEasy communicate to layman

Disadvantages: Low level of accuracyNo breakdown of the single rate, not useful for cost control.

APPROXIMATE QUANTITIESApproximate quantitiesMeasured quantities based on item from the drawingMost reliable methodCompare cost when sufficient details availableTime involve: the whole project life cycle

measurementsubstructureSuperstructureExternal workInternal finishespreliminariesFitting and furniturecontingenciesAdvantagesDisadvantagesQuantities based on planned construction, not previous jobHigher chances of getting underestimates(solved with contingencies for small components, fitting, fixing)Allowance made on plan shape, height, type of ground and quality of finishes.Calculation: A cavity wall measured and priced with both skin included in the unit rate. The rate includes forming cavity, wall ties, plastering and pointing (according to the specification). If the previous project does not include plastering and pointing, adjustment must be made accordingly.Elemental Cost EstimatingDefinition Using the Elemental Cost Analysis (ECA) to estimate a building cost.

RequirementBasic size and shape of building (Preliminary sketch)Purpose and location of building Historical cost data of similar buildings constructed at the same general location

AdvantagesMore accurate than square meter methodOnly needs a very minimum information to prepare the estimate, hence can be used as early as feasibility stage of project

Disadvantages Faster but less accurate than approximate methodRequires access to ECA

Part BScenario 1If the trainee has access to ECA and knows how to utilize the information extractedElemental Cost Estimating is the most suitable method It takes into account all the elements of the buildingInformation is easy to find since its a typical medium cost developmentTakes a minimum time to complete the estimate since its only taking the GFA of one house and multiplying it to the cost per m2.Scenario 2If the trainee has no experience on using the ECA or have no access to itSquare meter method is most suitableA very minimum data requiredA lot of data are published based on cost per square meterVery straight forward, easy to understandQuestionsWhat are the factors to choose which method of estimating to use?Why is elemental cost more accurate than square area method?