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Building design and construction process – step by step

Reasonable people may disagree, but here are the sequential steps in designing and building an ADU. This is an approximation of the steps for my ADU project, anyway. This was for an ADU built in Portland, Oregon. Slab on grade, stick frame construction—pretty standard ADU construction for this area.

**Get a PDF version of this step-by-step process, and a bunch of other resources about building an ADU on

Design Process

  • Funding
  • Brainstorm with other funder/executors
  • Talk to City Planner
  • Rough sketch some ideas with executors/friends
  • Talk to neighbors
  • Integrated Design Process
  • Interview architects (test them with some small space design questions: eg. What are a couple things that you would do to make a small space feel and act bigger? tall ceilings, join living/dining room, high windows, coupling functionality
  • Find builders and subs (ideally, you want to have identified a builder, plumber, mechanical, electrical subcontractor)
  • Architect draws up schematics for consideration
  • Have meeting- talk through design goals
  • Schematic refinement
  • 3D model (use SketchUp)
  • Develop drawings for City
    • Permit process- In Portland, processing takes 10 days for new construction, then another 10 days for corrections
  • Permits
Construction Process
  • Break Ground
  • Excavation
  • Foundation
    • Concrete Forms
    • Pour Foundation Wall
    • Concrete Slab Pour
      • Gravel
      • Water Barrier
      • Rigid Foam
      • Rebar (and PEX tubing for radiant floor heating)
      • Pour Concrete for Slab
  • Utilities
    • Sewer, Electrical, Water, Gas
  • Framing
    • Balloon Framing
    • Sheathing
    • Roof
    • Stairs
    • Windows
  • Roofing
  • Weather Resistant Barrier
    • Rain Screen
  • Rough Plumbing
  • Mechanical Sytems
    • HVAC
  • Lighting and Electrical
    • Ambient
    • Task
    • Accent
    • Perimeter
  • Air Sealing
  • Insulation
    • Spray Foam, Blown-in Insulation, or Batt Insulation
  • Drywall
    • Sheetrock, Mudding, Sanding, Primer
  • Siding
  • Flooring
  • Tiling
  • Painting
  • Cabinets, Shelving
  • Finish Plumbing
  • Finish Electrical and Lighting
  • Certificate of Occupancy
  • Modifications
  • Moving In

About Kol Peterson

Kol is an ADU consultant, advocate and author of Backdoor Revolution: The Definitive Guide to ADU Development. Read more here: and learn about building your own at Email at

11 comments on “Building design and construction process – step by step

  1. SAndeep
    December 23, 2012

    Thank you sir

  2. Muhammad.
    October 3, 2013

    This was extremely helpful. Really appreciate it.

  3. Pingback: The Second Coming of Detached ADUs in Portland | Accessory Dwellings

  4. Steve Jepson
    October 4, 2016

    Could you recomend an Eningeer in Portland, OR for a project like this? Why is Engineering not listed as one of your steps?

    • Kol Peterson
      October 8, 2016

      Steve, engineering is sometimes required, depending on the complexity of the construction. Engineering is done in conjunction with the design work prior to submission to the City for plan review. I don’t have any referrals for you.

      • Steve Jepson
        October 8, 2016

        It’s not so much the complexity of the construction that mandates engineering as it is meeitng siesmic and lateral resistance requirments for windloads. This is especially true of older structures being renovated into ADU’s since they may have never met these requirements in the first place, or the current Energy Code. Engineering and Energy Calculations, Noticicatoins to neighbors, Demolition Permits, waste disposal, Storm Runoff Plans, and more beaurocratic encumberances from the City are significant cost factors that can make or break an ADU project. Be sure you know the cost of all the time and nonsence you will be put through before you start. Perscriptive code solutions to meet the structrual and energy codes are not always the most cost effective.

      • Devon Mac Intosh
        June 14, 2018

        Engineers always have to be present in construction as they are the ones who make the construction work, they have to be on sight regularly to check the structure out and make further assumptions if need be, with their calculations.

      • Steve Jepson
        June 21, 2018

        Devon Mac Intosh
        June 14, 2018

        “Engineers always have to be present in construction as they are the ones who make the construction work, they have to be on sight regularly to check the structure out and make further assumptions if need be, with their calculations.”

        Nothing about that is true. No, they do not ever come to my project sites even if there was some reason to have some “Engineering”. It is built exactly per the Plans I make for permits. Further assumptions? No such thing. This is why a good set of Plans will always save you more than they cost you. You certainly do not need an Engineer and/or Architect for an ADU or Single Family Residence. These kind of buildings are exempt that requirement. As are Light Commercial projects up to 4,000 sqft and 35′ ( if I remember correctly). I have been making Custom Home plans and Light Commercial projects for more than 25 years, mostly here in Oregon and I have never had any Engineer who provided the Calculations visit even one job site. Ever.
        They typical disclaimer on their cover sheet says this: ** Engineer was retained in a limited capacity for this project. Design is based upon the information provided by the client, who is solely responsible for accuracy of same. No responsibility and/or liability is assumed by, or is to be assigned to the Engineer for items beyond those shown on these sheets.** They are not typically retained as the “Engineer of Record” for the Engineering they do for an ADU or Single Family Residence of any size. The Engineer or Architect of Record is required on buildings of “significant importance” like public buildings, large commercial buildings, factories…

  5. Yvette J Lafleur
    May 6, 2017

    Thanks so much this was helpful. Palo Alto ,California will be finally relaxing the restrictions on June 8th .This really helped I’m so Excited and freaking out a bit .My neighbor has one I love so will be talking wirh her alot.

  6. Mohamed Ashfaq Omar
    June 21, 2018

    Thank you kindly. Helped me construct a Project plan to use as a template.

  7. Newman.Ingrid
    February 14, 2020

    The power developed by a person with conviction is greater than the one who only has interest

Comments are closed.


This entry was posted on November 9, 2011 by in Design & Build and tagged .
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