This Step in the ADU Process Will Make or Break Your Project!

Step 2: Building Your ADU - Laying The Foundation | Step-By-Step Guide to Building an ADU
Welcome to the second step in Maxable's comprehensive guide to building an Accessory Dwelling Unit (ADU) - constructing the foundation. Whether you're planning to build a small studio apartment or a large 3 bedroom ADU, this video is your blueprint to beginning your ADU project on solid ground.
In this episode, we discuss:
- Preparing your lot for the foundation - digging the trenches and installing the vapor barrier to prevent moisture from the ground from seeping into the home.
- Installing the wood forms that create the boundary of the foundation and laying the necessary rebar steel for structural support
- An explanation of the underground plumbing needed for the ADU bathroom, laundry room and kitchen.
- Pouring the concrete for the footings and slab and forming the finish level of the ADU floor.
- The rebar steel sticking out of the finished concrete footing will create the “hold downs” that will secure the exterior walls of the ADU to the foundation.
- Floating the drying concrete into a nice smooth finish to create a level floor for the ADU.
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Is this the year you build the ADU of your dreams on your property? Taking the first steps is going to feel daunting, but when you're equipped with the right knowledge and resources from Maxable, building an ADU can feel like a breeze.
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Key moments
0:45 Preparing your lot for the foundation
1:06 Installing the rebar steel and wood forms
1:35 The foundation - footings versus the slab floor
1:57 Discussing underground plumbing
2:30 Pouring the concrete foundation
3:40 Leveling the concrete slab
4:06 Rebar “hold downs” that tie the foundation to the exterior walls
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WHAT IS AN ADU?
ADU stands for accessory dwelling unit. An ADU is a permanent additional housing structure built on a property that already has a main home or main structure. You may have heard them referred to as granny flats, casitas, guest houses, or in-law suites.
They can be built on a single-family lot or multi-family lot (duplexes count as multi- family). An ADU has its own entrance, separate from the primary house, as well as a kitchen, bathroom, and living space. Accessory dwelling units can be rented year-round and add a lot of value to your property.
They can be garage conversions, stand-alone units, attic or basement conversions, or be attached to the main house. ADUs are exceptionally flexible, and most owners find that their use for the unit evolves over the years. The main reason people build ADUs in California is to house a relative, usually a parent but often an adult child. The second most common use is to rent for additional income.
Don't forget to like, subscribe, and share this video to help others on their ADU journey. Your dream space is just a plan away!

[@Accordriven]

Quick question, in regards to the water line. My main house has a 3/4 inch water line. The plan is to pull from my line to supply the ADU. The water pressure already comes down when I'm showering and the sprinklers go on. I'm afraid pulling from a 3/4in water line will not suffice for the main house and the ADU. What are my options?

[@Maxable]

That would be a great question for a local contractor - reach out to our team via our website to get connected with qualified contractors for your project!

[@carlosr363]

That concrete is so wet I don't think it passed a slump test. Looks sketchy.

[@Maxable]

No slump test required for concrete with a compressive strength of 2500psi and below per LADBS

[@carlosr363]

@@Maxable Just because it's not required doesn't mean we don't do it and make sure the concrete isn't a slurry mess that will fall apart in a few years.