How Calculator Construction Costs Work #
The Calculator uses a “countywide base cost” for new construction (hard and soft costs), and a “local multiplier” to calculate the construction cost in each jurisdiction for each type of construction (conversions/modular).
Many jurisdictions have unique construction costs based on market conditions, topography and other factors. The Calculator allows you to adjust the base countywide construction costs using local multiplier. Learn more about researching and setting up your local construction costs below.
Researching Local Construction Costs #
In order to accurately set up construction costs for your jurisdiction it is important to get a sense of the average local construction costs in your community.
Below are some recommendations for how to do this:
- Based on your knowledge of local construction costs, pick an average cost per square foot for new construction that you think accurately reflects local conditions.
- Check with building staff who may have an idea of average construction costs.
- You could also reach out to local ADU contractors to get a better understanding of local construction costs or to confirm local construction costs.
It may be helpful to download and review the Cost Assumptions: Construction Costs + Finance/Rent Defaults Spreadsheet to learn more about the cost calculations before you start researching and developing your local construction costs.
Setting Your Local Construction Costs #
Once you have a good idea of the local average construction costs for your jurisdiction, follow the steps below to set your local construction costs with the local multiplier. These steps will help you develop a multiplier that accurately reflects construction costs in your jurisdiction.
Step 1: Adjust Your Local Multiplier #
- Download and open the Cost Assumptions: Construction Costs + Finance/Rent Defaults Spreadsheet.
- Use a scale from 0.5 (50%) to 2 (200%) play with the local multiplier to get a sense for how this affects your local construction costs.
- Pick a number that accurately reflects local conditions. Do not include land cost.
- Track the local multiplier you chose in the Onboarding Form.
- Adjust your local multiplier in the Admin Portal on the Jurisdiction Parameters Page.
Step 2: Test Your Local Multiplier #
Getting an accurate local multiplier may take some research and testing. We suggest setting up your Calculator and testing the project cost estimates on the front end of your jurisdiction calculator to make sure the local multiplier is producing reasonable project estimates.
- Adjust the local multiplier until you obtain outputs that are representative of your region.
- Check-in with your local building department for additional feedback and guidance.
Annual Countywide Updates #
Base construction costs are updated annually for all counties. When base construction costs are updated, your will receive a notice and reminder to review the new construction costs and reset your local multiplier as needed.
For more information about how these costs are set, please feel free to reach out to info@aduaccelerator.org.
If you think the countywide costs are off, reach out to us at support@aduaccelerator.org.