Construction Costs During Design

As we discussed in previous posts, construction costs can be difficult to identify during the pre-design and design process. With the many moving parts and constant state of change, cost evaluations must be performed in stages. 

A deeper dive under the hood reveals that there are key pieces of information needed to perform these cost evaluations. This data includes the quantity of materials, product selections, labor cost, and unit cost for each element. This data gets to the heart of providing more accurate price evaluations early on.

 

 

Contractors During Construction

Believe it or not contractors have a big role to play during design just as architects and designers have a big role to play during construction. 

Our preference is to involve the expertise of a contractor as early as possible during the design and even in the pre-design phase if possible. The primary purpose of this practice is to understand construction cost as early as possible to avoid a design that is too expensive for you to build. 

We discussed in previous posts the different phases of the design process. It is important at the end of each phase to have a cost evaluation performed by the cost consultant/General Contractor before more time is spent making further design decisions. 

Cost Evaluation by Phase

As an owner, it is important to have certain expectations about costs at each phase. 

Pre-design (PD): Low amount of design information = Very Inaccurate cost 

Because there is very little information about the design the contractor and/or architect can only guess about the construction costs. By evaluating previous projects and comparing those previous costs to precedent imagery, only a general price per square foot range should be expected.  

Schematic Design (SD): Broad design information = Somewhat Inaccurate cost 

In SD we design the layout, shape, and overall aesthetic of the project. With the added information a cost consultant should be able to provide a more accurate cost per square foot range. 

Design Development (DD): Detailed information = Somewhat accurate cost

The DD process determines beam sizes, product selections, and more. This greater amount of detail allows for more accurate cost evaluations.

Construction Documents (CD): Completed Design and Drawings = Hard Bids

Now that all the information is available and communicated through drawings and specifications, the general contractor can distribute the drawing sets to the suppliers and sub-contractors for an accurate bid.  

Material take off and New Technology can offer a window into the costs of construction as early as the SD phase. 

Let’s discuss the material take-off technology used by many in the industry to help cost consultants provide more accurate estimates. This then provides owners with the information they need to make big design decisions as soon as possible.

Building Information Modeling (BIM)

Like so many things in the design world, most of them revolve around BIM technology. We wrote a few months ago about BIM; for a deeper dive into what BIM is, read our article. In short, BIM allows us to build your project digitally and embed data related to building elements in the digital model. That data can include area calculations, sizing information, model numbers, and even unit cost of materials and products. There are several BIM software options out there for architects. We prefer Archi-Cad because of its ability to play well with other tools on the market and its design flexibility.

 

BIM Workflow

 

Starting with the site, say we begin placing concrete footings inside the model. The BIM software will keep track of the amount of concrete being used in the project automatically and in the background. As we model the floor it keeps track of the floor area. As we place windows it tracks the quantity, type, and sizes. This goes for all elements and materials set up in the interface. With these material quantities, we can then report out all of the available information to the cost consultant or contractor estimating the project. The cost consultant can then apply cost unit data and labor cost based upon today’s market rates and determine the project price. Reports can then be issued to the client for approval.

Want to make a change? 

No problem, setting up the model correctly can allow for automatic updates the the materials and quantities in the take-off. 

 

Tip: Some firms offer cost evaluation as an additional service. Ask your architect if they have the capabilities of providing cost evaluation in-house.

Challenges in BIM Data

Keeping track of BIM data can sometimes be more overwhelming than actually modeling the project. Like design in general, the more time spent, the stronger the end result. At a certain point, time and design cost may not outweigh the benefit of the information itself. Knowing the balance between the data provided and the accuracy of it varies from project to project. Although the software will keep track of the unit cost, it can be time-consuming to collect that data in a useful manner.

Another challenge facing the BIM data is knowing the units and pricing per unit as it applies to the varying conditions in the design. Take our footing example above. We can easily find the cubic yards of concrete and the price per cubic yard with the raw BIM data. But what about the labor cost, the cost of the reinforcing steel, the excavation of the site. Sometimes it is hard to know where to draw the line and put the information to good use. The many moving parts and variations of conditions can sometimes be overwhelming. To combat those variations many firms use additional templates and spreadsheets like “ContraBIM.”

What is Contra BIM?

Contra BIM is an Excel and ArchiCAD template/workflow created by John Hallgarth. The product allows BIM models to output quantity and cost data in a more refined manner. The template organizes the data into CSI Master Format to provide a more standardized workflow. For a deep dive into the software check out his youtube channel.

Investing in Cost Evaluations

Knowing project costs early on is always in high demand. Investing in cost consultation can help you avoid surprises and make decisions related to the design. These added services of cost consultation can help decide between poured concrete versus CMU foundations. Between using one window manufacturer versus another. How about pitched v.s. flat roof? Anyone can find out the cost of one product versus another but how does it compare to the overall project price, and how can we use this information to make design decisions.

Our team is always investing in new technology to help our clients see the big picture of design and cost. Stay tuned for more posts related to cost and design technology.

© 2021 by Clements Wimsatt Architects PLLC

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