Starting Your ADU

Improving and expanding on your greatest investment is a proven strategy to building long-term and secure wealth. While buying new property may not be in the cards for everyone, increasing the value of your home and it’s ability to generate income is not. ADUs, also called Granny Flats, Laneway Housing and Mother-law-suites, are a great way to meet long-term and secure financial goals. At Fleschner Construction we strive to ensure you’re a client who can make informed decisions for your project, so we have provided a guide to the uses and costs of an ADU. Cities like Portland have stated goals to increase density, so they have smoothed the process for homeowners to explore these development options. Now its your job to seize the opportunity, and we are hear to help.

Using Your ADU

The first step in building your ADU, before speaking to professionals, you must decide on what you’ll be us using your ADU for. Here are a few of the ways we have seen clients use theirs.

Common ADU Uses

  • Begin building rental income
  • Provide close or segmented family housing for love ones
  • A retirement investment in increase values

Types of ADUs

Now that you’ve decided on the main use of your ADU you can move towards choosing what type will meet your goals and work with your property and budget. 

These are just a few of the main types of ADUs:

  • Existing Living Area conversion in to seperate unit within home
  • Finishing or Remodeling a basement or attic area within home
  • New building/contruction
  • Adding to existing buildings (home addition or detached garage remodel/addition)

ADU Project Details & Costs

Building an ADU can range from an update to fully new construction. Depending on your property and the regulations you will have options when designing your project and settling on a budget. Below we have provided some rough numbers on the high and low ends of the for a space of about 800 to 1,000 SF.

Choosing between standard or batt insulation, number of stories, appliance quality, number of sinks/lights, energy efficiency etc. all have effects on the price. We have broken out each cost for you to mull over as you start your design and descion making process.

We are here to help you understand the details and reasons behind each line item. 


Here are the costs for all pre-construction and initial concrete work. Before any nails are hammered these steps must be taken to ensure your project is legal and has a good foundation for building

  • Permits: $3,000 – $6,000  (All trade and municipal permitting costs)
  • Excavation: $9,000 – $14,000 (Depends on lot condition, tree removal, leveling)
  • Footings and Retaining Walls: $25,000 – $35,000
  • Concrete Slab: $5,000 to $10,000

Trade & Exterior Work

All exterior framing and initial trade work is included here.

  • Framing & Rafters: $20,000 – $40,000
  • Siding: $10,000 – $14,000
  • Doors/Windows : $12,000 – $15,000
  • Roofing: $12,000 – $16,500
  • Plumbing Rough Ins: $11,500 – $15,000
  • Electrical Rough Ins: $12,000 – $18,000
  • Insulation: $6,000 – $11,000
  • Sheetrock/Taping/Texture: $8,000 – $11,000 


The prefabed portions of the projects, does not include built in furniture but that is always an option. 

  • Cabinets: $4,000 to $10,000
  • Tiling: $6,000 – $11,000 (Full tile bathroom and/or kitchen will be a huge factor in this)
  • Countertops: $3,000 – $6,000 (Material is a major factor, composite, stone, etc.)
  • Flooring: $2,500 – $8,000 (Material also a huge factor, laminate, wood, etc.)
  • Appliances: $3,000 to $8,000


Finish carpentry, a few more pre-fabbed additions and final trade work.

  • Trim Work: $3,000 – $7,000
  • Staircase & Railings: $2,000 – $8,000
  • Electrical Fixtures: $2,000 – $3,000  
  • Plumbing Fixtures: $1,500 – $2,500
  • Painting Ext./Int.: $3,000 – $5,000

ADU Information Government Resources

Understanding the municipal regulations your project will built under is part of this initial information gathering process any homeowner must go through. Here are a few links that will give you the information directly from the departments who will be making the decions. 

Let Us Build Your Dreams

If you have more questions, feel free to drop us a line anytime 503.386.7944