The following is a construction scope checklist we've developed during our ADU build. If you're building an ADU, please use this list as a guide; it will save you more than enough time and frustration to be worth the cost of this article (free!).
Section 1: Understanding ADUs
Section 2: How to Write an ADU Construction Specification
Section 3: ADU Construction Specification Checklist
Takeaway: A construction specification checklist makes it easier to get bids on a construction project like an ADU accurately.
Accessory Dwelling Units (ADUs) are small housing units, typically built on the same lot as single-family homes. By comparison, secondary units are larger structures that may be detached from the main house. ADUs can either be attached or detached from the main home but are typically smaller than a secondary unit.
Some of the most common types of ADUs include converted garages, basement apartments, and granny flats. ADUs can also be referred to as in-law units, backyard cottages, and granny flats.
This includes the bulk of the construction that goes into the structure of the ADU and comprises many unique items, so it's crucial to ensure every item you expect is in the contractor's bid. Furthermore, it is typical for most 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.
Rough Construction can include:
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 can plan for this by first determining where you would like each utility to connect to the main building. Once these locations are determined, you can plan around them.
Fixtures & Finishes
When building an accessory dwelling unit (ADU), it's important to ensure that your contractor has included all the essentials in their bid.
Although most contractors do an excellent job at including everything in their bids, sometimes a few items are overlooked. This is especially true when the homeowner is not experienced with construction projects.
Here are a few of these items that are often missed:
These are items 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 the homeowner to pay for them directly.
Sitework & Misc.
Access to the ADU:
Do you need to add any fencing, gates, or landscaping to block the view of the unit from the street? Will there be a walkway from the driveway or sidewalk to the ADU? What kind of surface will be used for the walkway? Concrete? Pavers? Gravel? Grass turf?
Will there be any outdoor lighting for safety purposes along the walkway, outside your ADU, or along your fence line? It's essential to include these in your plans for permitting, but it's a good idea to confirm this with your contractor.
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).
It's also important to choose a tile for your walls that will not only look good but be durable as well. A glossy tile or metallic finish can be slippery when wet. A matte finish may be a better choice.
If you choose a bathtub rather than a shower stall, it should be cast iron or enameled steel. These are much harder and more durable materials than fiberglass or acrylic.
Choose a toilet with a round bowl if you have limited space in your bathroom. The round bowls are usually two inches shorter than their elongated counterparts. Consider choosing a dual-flush toilet because they use less water than conventional toilets, which can help save money on your water bill.
If you're looking to add character to your ADU bathroom without breaking the bank, consider using decorative wallpaper or paint instead of tile for your walls.
If there is no kitchen layout plan in your ADU plans, you should create one. This can be done by measuring your existing kitchen or using software programs like Sweet Home 3D, allowing you to design your own kitchen virtually. Once you have designed your own or an existing kitchen on paper, you need to take that plan to a cabinet designer who will create detailed drawings of the proposed cabinets for you.
Some ADU plans have a detailed kitchen layout, and others don't.
ADUs are one of the more affordable, energy-efficient ways to add more space to your home. They're also relatively easy to build if you've got the right equipment and read up on safety procedures beforehand. The following construction checklist should help keep things in order while building any ADU.