Accessory Dwellings

A one-stop source about accessory dwelling units, multigenerational homes, laneway houses, ADUs, granny flats, in-law units…

Words of Advice about the ADU Development Process, from Those Who Have Gone Before You

Recently, I conducted a brief survey of those who have attended one of my ADU classes.  Of those who had completed or nearly completed construction, I asked a question:

If you completed an ADU or are in the final stages of building one, what advice would you offer to prospective ADU owner-developers?

Sometimes, you can do research on your own googlecartoonusing Google. But, other times, it’s more useful to get advice from homeowner/developers who have already gone through the process. Below are the 25+ responses to that question.

  • Make sure you’ve set aside a significant chunk of time so the process is less stressful. Prepare to be patient with yourself and the contractor.
  • Spend a lot of time planning with your contractor, make all your decisions ahead of time, then let them build. This avoids change orders, keeps the project on budget and on time.
  • Take this course!! Note: We are using equity from sale of previous home, plus a standard mortgage for the newly purchased existing (main) home, as main source of funding. So equity is being used, but not a home equity loan. ADU is for aging family member (mother/mother-in-law).
  • Take your time with the planning and be sure to get a small space expert to help you with the design. Placement of water tanks, washer/dryer, closets, bathroom, etc. can be done well if you have someone who knows what they are doing. Stick to a small footprint. A lot can be done in a small space.
  • The City permit process is a bureaucratic quagmire (and expensive, too). Avoid it if you possibly can.
  • Please see:
  • Know what your project is from the beginning
  • Get multiple trades estimates or GC estimates for the entire project
  • Get in writing what your trades people are doing and what you are doing if you are GC-ing yourself
  • Know the cities rules!
  • It will take longer, and be more expensive than you originally think. Also, bid everything extensively.
  • It costs a lot more than $100k, think more like $180K to have it build and signed for you
  • I would want them to know doing it yourself is a lot harder than I thought, and nothing seems to get done as quickly as you’d hope. Dealing with the city is HARD.
  • I probably over built the house. Designer was overly cautious.
  • I discovered that even though I hired a general contractor to do the job, I was much more involved in the project than I thought I would be. I needed to make all of the design decisions, buy all of the fixtures, and (most importantly) watch for and point out mistakes made by my contractor or one of his subcontractors.
  • Have a contingency fund — in my case around 20% is needed.
  • Go slowly, work with a designer who has experience.
  • Give yourself more time then you think you’ll need. Know that it will be consuming but fun… at least so far!
  • Get the builder in on the design phase.
  • Find contractor and designer that you can trust
  • Find a good designer and you can save money with a drafter in lieu of an architect. If you use a designer/drafter team, you’ll need to make sure that one of them is competent to submit the plan set and shepherd it through the process with the City.
  • Everything will be more expensive and take longer than you initially planned for … so plan for that!
  • Do your homework. It’s more complicated than it may appear.
  • Do your homework and have a good plan in place before you start, but be prepared for the plan to change daily. Make sure you are working with a contractor with whom you trust completely, because they are the most important person in the whole process. Don’t cut corners and don’t waste time trying to save a couple of bucks by doing things yourself that some one else really should be doing.
  • Do it!

It is probably going to cost more than you think.

You are allowed to do most of the work yourself if you plan to occupy. (City will provide you with handy sheet detailing what you can and cannot do.)

For myself in the future, I may consider just finishing space (ie basement/attic) as opposed to the whole process of the ADU.

I’d also like to see some prefab designs or construction packages. As much as anyone likes to have a personalized design, it is overwhelming to make all the choices and if you want as a rental anyway, it may make sense to go with a cheaper option.

  • Be patient 🙂
  • Hire a designer!
  • Wow. educate yourself. and plan. plan. plan. and definitely consider a design build company to work with. in retrospect i feel that the pros outweigh the cons of hiring a design build company. at the very least hire an architect who works alongside a builder and have them collaborating from the jump start. and last but not least prepare yourself for the potential of dealing with tree representatives that work for the city and promote unreasonable tree code…


Admittedly, there’s some common cautionary advice themes here 🙂 !

  1. It’s going to take longer than you think.
  2. It’s going to cost more than you think.
  3. Plan to spend significant time/energy planning and designing the ADU in advance with skilled pros.

But, here’s one more anecdotal takeaway I have noticed from those who have completed an ADU. No one ever regrets having built an ADU. Indeed, for many homeowners, building an ADU is the most life-changing thing they’ve ever done to create flexibility and financial freedom in their lives. That additional little tidbit of advice may be useful for those who are considering whether to undertake an ADU project on their property.

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


This entry was posted on May 23, 2016 by in Opinion, Uncategorized and tagged .
%d bloggers like this: