Best Cost Estimating methods for the various design phases

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    Brianna Grimm

    Tyrone Bunyon absolutely! I am reading this information from the ARE5 Review Manual by Ballast. Page 10-21 in the Programming & Analysis section covers the first three methods listed and the last two methods are from pages 30-13 to 14 in the Project Planning section:

    • Project Comparison Method = Beginning Stages. The cost of the new project is estimated using the costs of past projects of similar scope and function. This method is often used when setting a budget or determining a project's feasibility. Accurate within 15% to 25%
    • Area Method = Prelim Design. This type of estimate is usually prepared when preliminary design is completed and the architect has a fairly good idea of the size of the project, its functional components, and the general level of quality or complexity. With this method of estimation, an average cost per unit of area (or volume) may be used, but the actual area (or volume) is more precisely known than in the project comparison method. Accurate within 5% to 15%
    • Assembly Method = SD. During schematic design, when more is known about the space requirements and general configuration of the building and site, budgeting can be based on major subsystems. Historical cost information on each type of subsystem can be applied to the design. Accurate within 10%
    • Parameter Method = DD and CD. Typically used during the design development phase and early stages of construction document production. It involves an expanded itemization of construction quantities and assignment of unit costs to these quantities. For example, instead of using one conglomerated sum for floor finishes, the cost is broken down into carpeting, vinyl tile, wood strip flooring, unfinished concrete, and so forth.
    • Unit Cost Method = Bidding. The project is broken down into its individual building components and the labor needed to install them. Contractors typically use this method of estimating when they are determining a bid or negotiated price for the project. It is the most accurate method, but it can only be used when the construction drawings and specifications are complete or mostly complete and all the requirements of the project are known.
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    Brianna Grimm
    • Area Method = prelim design 
    • Assembly Method = SD 
    • Parameter Method = DD and CD 
    • Unit Cost Method = bidding 
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    Tyrone Bunyon

    Brianna Grimm can you explain which each of these cost estimating methods means. 

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    Tyrone Bunyon

    Thanks for putting this together. I take PDD in March and have no idea what to expect. 

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    Brianna Grimm

    You are welcome! I am taking PDD for the second time on January 25th so I have been looking through these blog posts. A lot of people have mentioned Karin's Notes and Elif's ARE Questions. Additionally, I am skimming Ballast's Review Manual and watching Kevin Griendling's Pluralsight videos. I hope this helps some!

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    Tyrone Bunyon

    I am also confused on when to use cost estimating. It seems you can use Unit costs per sf at schematic design and unit cost as line items on the CD phase. Can someone explain? 

    Thanks

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