Building An ADU? This Construction Scope Checklist Will Keep Your Bids Consistent

Construction Checklist For Building An ADU

Accessory Dwelling Units are becoming a very popular project in Los Angeles and surrounding areas.  Plenty of homeowners are considering building an ADU (see ADU definition here) to meet a variety of different needs, from housing aging parents to earning rental income to help pay their mortgage.  At the time that I’m writing this, there are over 14,000 ADU projects in the permitting and construction process in the City of Los Angeles alone. But, planning an ADU unit or garage conversion isn’t a simple undertaking, so it’s good to have as much knowledge and preparation as possible regarding what such a project requires.  

Here at GreatBuildz, a free service that connects homeowners in Los Angeles, Orange County, Ventura & San Diego with reliable general contractors, we help people every day with the details, scope, and costs that go into accessory dwelling unit and garage conversion projects – below is an overview of all the items required when building an ADU.  

How do I start planning an ADU?

When a homeowner is ready to start the process of building an accessory dwelling unit, they’ll likely look to either meet with an architect or a general contractor.

It’s good to speak with an architect to understand the costs that go into developing ADU plans, and also to make sure your project desires are realistic based on the city’s standards. Misunderstanding local regulations is generally the first and most costly building misstep. ADU standards vary often, so consult an expert before building. Permits and professional advice may seem expensive, but they’re worth it. An unlawful ADU on your property might make refinancing or selling your house difficult, so be sure your project complies with local ADU laws. It is also good to meet with a general contractor to get a better perspective of the process, ADU project costs, expectations, etc. for the entire project.

When you meet with general contractors, you’ll want to be as prepared as possible with your list of needs and requirements for the project. You will likely be meeting with multiple contractors to collect a few bids for your project, so you want to make sure each of them bid on the identical scope of work. The below ADU project checklist is a great place to start. Plan to get at least three bids with the hope that they are all within 10-20% of each other on total price. If you’re finding that some bids are significantly low or high compared to the average, you may want to get more contractor’s estimates.

You’ll want to ensure that your contractors provide you with an estimate based on all the specific items you want for your accessory dwelling unit. Start your ADU planning process by reviewing this checklist – cross off any items that you deem unnecessary and add any notes that are specific to your project.  Then, provide this checklist to every general contractor that is bidding on your project. This way, you’re more likely to get accurate bids that are “apples-to-apples”.   

ADU construction is a substantial investment, and it is not cheap. ADU estimates might vary significantly based on factors such as size, location, regulations, etc. Regardless of the specifics of your project, you should get a reasonable ADU estimate from your contractor. A good rule is to obtain three to five estimates from different ADU contractors prior to making a final decision. If all of the estimates are relatively comparable in price, it indicates that your project is ‘clear’ to each contractor and that their pricing is likely in line with the market. However, if your ADU estimates are inconsistent, it indicates that something is amiss. Either your project’s requirements are unclear, or some of your contractors’ estimates are unrealistically high or low. In this instance, obtaining other estimates will help you determine the job’s appropriate cost.

Keep in mind that a contractor can only give you an approximate, rough bid based on your scope or preliminary layout for your Los Angeles ADU. You won’t get an exact, detailed cost estimate until you have a full set of building plans completed. These plans are necessary to submit to the city in order to get a building permit and also provide the contractor the exact information needed for a detailed estimate.

Scope Checklist For Building An ADU

Building An ADU? This Construction Scope Checklist Will Keep Your Bids Consistent 1Typical Scope Checklist For Building An ADU – Contact Us For an Editable Version!

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If you review an ADU contractor bid and compare it with your scope checklist, you may find that there is something missing or unclear in their bid. This should be a trigger for you to ask the contractor why this item isn’t included. There may be a good reason the item isn’t necessary in this project or they may have just forgot about it. Most likely, a good contractor’s estimate will be comprehensive, but they may or may not always include the materials you’re expecting them to provide. For example, the contractor will almost never include or purchase kitchen appliances for you…and you need to keep that in mind when budgeting for items that aren’t included in the contractors estimate.

Let’s break this ADU checklist down by category so you can understand the significance of each section:


Every accessory dwelling unit or garage conversion will need a sewer line, water line, electrical connection, and gas line (unless your ADU is all electric).  It is likely that these utilities will be connected to different places around your house and will therefore need multiple trenches. This will be obvious to your contractor and should be clear in their bid.  You should be aware, however, the cost of installing utilities can vary significantly depending on whether these lines can be run (trenched) through dirt or need to be run under existing concrete areas, which will need to be cut out and later re-poured.    

Rough Construction

This includes the bulk of the construction that goes into the structure of the ADU and comprises many unique items, so it’s important to ensure every item you expect is in the contractor’s bid.  Furthermore, it is typical for most, if not all the materials in this category to be provided by the contractor (and included in their bid). Make sure to confirm this explicitly with your ADU contractor.

Most of the items in this section should be in your ADU plans and will be obvious in your bid.  However, there are also some items in this category that often get missed…so please review contractor’s bids carefully to ensure their inclusion.  Some examples of commonly missed items are: water heater, closet doors, recessed lights, gutters/downspouts, HVAC, baseboard & casing, and any roof water capture system if required by your city.    

Some of the materials in this category of building an ADU can be selected by the contractor and don’t need any input by the homeowner…things like concrete, lumber, drywall, etc.  However, there are many items where the homeowner can and should provide guidance, otherwise, the contractor will just use the cheapest materials available. Examples are roofing material, windows, doors, lights, flooring, HVAC unit, and even the water heater (ie. tankless). So, be clear with your contractor regarding any materials you want to select; this will help your contractor provide a more accurate price estimate.


An ADU kitchen is reasonably simple because there are very few components; the major ones being cabinets, countertops, and appliances.  However, planning the kitchen design is important. Some ADU plans have a detailed layout of the kitchen and others don’t. You’ll want to make sure to communicate to your contractor your exact expectations. 

That means

1) providing input regarding the style/materials you want, especially the cabinets and countertops

2) deciding on the specific layout and dimensions

You’ll want to start planning the space by selecting your appliances. Because an ADU kitchen is likely small, you should consider narrow appliances…fridge, range, hood, microwave, dishwasher, and also a small sink.  Depending on the dimensions of your appliances, the cabinets will be sized to accommodate these. For efficiency, consider using a microwave/hood combo installed directly above the range. If you have the space to install a small island, this can double as countertop space and a kitchen table/bar.

Building An ADU? This Construction Scope Checklist Will Keep Your Bids Consistent 2

You should carefully review which kitchen materials are included in each contractor’s bid.  Most likely, cabinets are included. Countertops and backsplash are either included or the estimate will indicate an ‘allowance’ (or maximum cost) that the contractor will spend on this material.  This means if you pick a more expensive type of countertop, you will have to cover the difference. Items that are usually not included in a bid are appliances, sink, faucet, cabinet knobs, etc. “Installing appliances” is an item that can often get missed, so make sure it’s in your bid if you expect your contractor to do this. 


When building an ADU, the bathroom is slightly more involved than the kitchen and requires more decisions & consideration from the homeowner.  Most items in the bathroom will require you to choose the exact material you want to use, including floor/shower tile, vanity, mirror, faucet, shower hardware, and even the toilet and tub (unless you just let the contractor decide).

Building An ADU? This Construction Scope Checklist Will Keep Your Bids Consistent 3

Because the bathroom requires so many material selections by the homeowner, the contractor’s cost for this part of the ADU can vary widely.  Every contractor will bid this differently, and therefore, it’s important to review each bid for inclusions/exclusions. Some contractors will note that the homeowner will ‘provide’ (ie. pay for directly) faucet, vanity, tub, tile, toilet, etc.  Other bids will include the cost of these in the form of an allowance. Further, some bids will include some of these items but not others. It’s rare to see consistency amongst these items in contractor bids, so it is important that you review and compare each bid.

A few items that often get missed in the bathroom are the glass shower door, exhaust fan, and recessed lights or sconces, so make sure these are included if you expect them. Also, be clear with your contractor if you want a tub/shower or just a walk-in shower.  If you decide on a walk-in shower, inform your contractor if you want tile or a shower-pan on the shower floor.       

Sitework & Misc.

Oftentimes, ADU plans only represent the structure itself and we forget about adding any items that may be needed outside the building. Whether you’re building an ADU to be rented out or for you and your family, you’ll likely want to create an enjoyable environment inside and out. So, if you think you need items like fencing, patio concrete, a walkway to the unit, landscaping, etc., make sure your contractor is aware and includes these in their bid.  

Fixtures & Finishes

These are items that are found throughout the ADU, all of which require the homeowner to make the material selection.  These include items like flooring material, light fixtures, doorknobs, etc. It’s important to carefully review each bid to determine if any of these materials are included or not. Usually, contractors do NOT include these materials in their price and expect that the homeowner will pay for them directly.  

Selecting the many materials that are required for building an ADU can take a homeowner quite some time and may include lots of internet shopping and visiting material stores.  A contractor or designer/architect can guide you on material selection, but if you decide to go it alone, do your best to make these selections as early as possible in the process.  Material delays are a common reason for ADU projects to take longer than necessary to complete.     

How can I compare pre-fab ADU with standard ADU?

A pre-fab ADU is built in a factory and delivered to the site and assembled in pieces. A pre-fab or modular ADU company should be able to tell you exactly what comes in and on the ADU structure, they are selling. This can make it easier on the client if they want a standard plan/model but doesn’t allow for a custom ADU size, plan, or layout. With a pre-fab ADU, your scope will be limited to the site work category needed to accommodate the ADU, including foundation, utility connections, landscape/hardscape, fencing, etc.

I hope this checklist will be a good starting point for you if you’re considering building an ADU. Once you take the time to go through this list and decide which items you’d like to include in your ADU project, you’re well on your way. It’ll be a good idea to print out a few copies of this checklist to give to each contractor you meet with. That way, you have more control over keeping each bid consistent. Every contractor has their own method of assembling a bid, so you will likely have to review each carefully, especially with regard to which materials are included or excluded in each respective bid.

GreatBuildz is a free service that connects homeowners in Los Angeles, Orange County, Ventura & San Diego with reliable, thoroughly screened general contractors and provides project support from start to finish. Submit your project to be connected with several fully vetted, trustworthy contractors who are experienced with ADUs. For more info, visit or call 818.317.3567 today.

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Hi, we're Paul and Jon - Co-Founders of GreatBuildz. We believe everyone deserves to find a great contractor, have a stress-free renovation, and enjoy their beautiful new space. There are so many contractors out there and it's often hard to tell the good from the bad... until it's too late. We started our company to help simplify your contractor search and help you have a stress-free renovation experience. We're always available to help, no matter where you are in the process. Click here to learn more about our story.

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