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Building Design

1-2-3 Revit: BIM and Cost Estimating, Part 2

7 Sep, 2006 By: AIA ,Rick Rundell

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Link BIM and cost-estimating solutions for more accurate estimates

Last month, I began a two-part series on how you can use the information in a BIM (building information model) to support cost estimating. I outlined approaches used to link BIM to cost solutions, and then gave an example of a design/build firm that uses an API (application programming interface) between Autodesk Revit and Innovaya's estimating solution to count and calculate materials directly from the Revit BIM.

This month, I'll highlight several other connection examples: a second API integration, a BIM to costing solution link using ODBC (open database connectivity) and outputting data from BIM to spreadsheets which are then used as input for costing. Although the integration strategies vary, all of these examples provide insight as to how information from BIM is benefiting architects, quantity surveyors, cost estimators and builders -- as well as their clients.

Linking Design Decisions to Costs
Oculus Inc. is a 30-person architectural, strategic facility planning, interior design and move-management firm with offices in St. Louis, Dallas and Chicago. From its 1994 inception, it has been committed to meeting voids in what traditional firms offer; helping their clients maximize the value of their investments by linking architecture to master planning, long-range forecasting, space planning and interior design. Integral to that commitment is the concept of architectural design linked to cost: informing their design decision-making process.

A longtime Revit user, Oculus immediately recognized BIM's potential for data-intensive applications such as facilities management and costing. According to Ron Reim, Oculus principal and co-founder, "BIM enables us to get better information about our projects, so we can give better advice to our clients."

Oculus recently started to use Autodesk Revit in conjunction with estimating software from U.S. COST, an Atlanta-based company that provides cost management and project control services and software. Oculus was already quite familiar with U.S. COST's estimating software, Success Estimator, as many of its outsourced cost estimates are developed with it and Oculus routinely (but painstakingly) checks those estimates against their design model -- verifying estimates for clients. So the company was closely tracking the API integration between Revit and Success Estimator (the commercial product is called Success Design Exchange), looking forward to replacing those manual checks with programmatic ones. Once the API link was complete, Oculus sent an architect, with a background in specifications and costing, to a U.S. COST training class and it has recently begun using Success Estimator and Design Exchange.

The company will still work closely with cost estimators on large projects, but by using Success Estimator internally, Oculus can quickly develop cost baselines for its Revit projects and deliver optimal designs that honor its clients' budgets. It can also produce quick cost estimates on small, fast-track projects, eliminating the delay associated with outsourcing and using the time and cost savings strategically, such as lowering fees and more front-end design time. In addition, it expects to capitalize on its new in-house costing capability for expanded design/build partnerships and projects.

"The ability to get dead-on counts from the Revit model has meant a huge improvement for timely, accurate costing," states Reim. "Now with the link between Revit and U.S. COST, we can use those quantities ourselves to develop our own cost estimates or streamline the verification of outsourced cost estimates."

The API integration between Revit and U.S. COST allows Oculus to develop its own cost estimates.

Scope Management using ODBC, Turner & Townsend Rawlinsons, one of Australia's largest construction and management consultancies, has a hands-on, can-do approach to new technology and are committed to improving its product through IT (information technology). One example of this commitment is its innovative use of IT solutions throughout the costing process, including the use of Exactal's flagship product CostX -- a popular Australian cost-estimating package.

To accurately estimate cost and variations as they occur, CostX features bi-directional ties into design solutions, including a recently released ODBC-based integration between CostX and Revit that Turner & Townsend Rawlinsons has quickly capitalized on.

Usually Turner & Townsend Rawlinsons are sent 2D electronic CAD files from clients that they import into CostX -- propagating any inaccuracies in the original drawings. But the company's clients that use Revit can now provide Revit views in DWG format and the Revit model exported to an ODBC database. The combination of dimensional data from the DWG files and attribute information in the ODBC database is automatically detected and reconstituted by Exactal's Revit integration, enabling the highest quality quantity surveys and helping to stem client dissatisfaction with scope creep.

According to Dave Liddle, quantity surveyor and principal of Turner & Townsend Rawlinsons, "Scope management requires tools to analyze change over time. We're constantly updating cost estimates during the design process -- comparing and evaluating pricing changes due to design changes." The Revit-to-CostX integration ties costs directly to dimensions or Cost Geometry to use Exactal's phrase. "We don't have to manually compare drawings and re-takeoff materials. The link between Revit and CostX automatically detects the changes and graphically displays the results, which allows us to easily see the areas that have changed and quickly re-cost the model," states Liddle. "The time savings allows us to do a better job estimating and reduces scope creep -- to the delight of our clients."

[Note: In July 2006, Exactal released a second Revit integration version based on Autodesk's DWF format, built to distribute CAD files and 3D models so intelligence of designs can be communicated even more easily and securely.]

Accurate Quantification with Revit and Excel
Founded in 1885, PB (Parsons Brinckerhoff) is one of the oldest continually operating consulting engineering firms in the United States. PB's St. Louis office offers professional services in architecture, landscape architecture, planning and program/construction management, and civil, structural, mechanical, electrical, plumbing, fire protection, environmental and geotechnical engineering. With a staff of more than 70, PB's St. Louis office provides services throughout the United States and is supported by the specialized expertise of PB's national service groups that are available as needed to assist the local staff.

PB's St. Louis office was an early adopter of BIM and has used Revit for all facets of building design for more than five years. They're committed to achieving their client's cost objectives and vigilantly heed the cost-estimating adage: the one who gets the low bid is the one who left something out. Thus, it relies on getting accurate quantities for accurate cost estimates: extracting quantities from the Revit BIM, outputting them to a text file, importing that to Excel and then sending the spreadsheet to estimators for costing.

The company typically produces at least two cost estimates, one at the end of schematic design and a complete estimate at the end of detailed design. The first estimate used to be quite general, based on standard rule of thumb square footage costs. "By using the quantities from Revit, we can get detailed estimates much earlier in the process," reports Tom Brooks-Pilling, director of architecture for the PB St. Louis office. "For example, the initial estimate may have included only allowances for finishes, but with the level of detail in Revit we can often replace allowances for actual quantities -- even during schematic design."

"We pride ourselves on preparing realistic solutions that fit our client's needs as well as their budget," explains Brooks-Pilling. "The quantification capabilities of Revit allow us to generate cost forecasts for decision-support, making it easier for us to meet our client's design and cost expectations."

To export a Revit schedule to Excel, select File / Export / Schedule (left), then name the file and select the file location and format (right) and click Save. Then import the delimited text file into Excel.

The First Step: Quantify
The first step of cost estimating is quantification, and the computable information at the heart of a BIM makes quantification effortless. BIM solutions don't generate automatic cost estimates by any means, but they offer significant advantages over traditional drawing-based systems by eliminating manual takeoffs. More accurate quantities of materials results in more accurate cost estimates. Reducing the quantification effort means estimators can more effectively apply their time and knowledge to higher value estimating activities. Architects also can use the information within the design model to easily double-check estimating quantities -- facilitating concurrent estimating during the design process.