If you love your neighborhood in Foster City but need more space (or a smarter way to use your property), an ADU can be a great next step. A well-planned backyard ADU can create room for family, a private home office, or a long-term rental that supports your goals.

This guide breaks down what homeowners usually want to know, from accessory dwelling unit design and ADU floor plans to ADU zoning regulations, budgeting, and choosing the right ADU builders.

Benefits of building an ADU in Foster City

Homeowners explore ADUs for a lot of reasons, but the biggest benefits of building an ADU usually come down to flexibility and long-term value.

More usable space without moving
Multi-generational living (a comfortable space for parents or adult kids)
Rental potential and added property value
Privacy for guests, work, or hobbies

If you’re thinking about ADU rental income, the best results come from a plan that balances layout, privacy, and durable finishes.

Start with the right ADU floor plans

Great ADU floor plans are less about squeezing in rooms and more about making the space feel natural.

When you’re reviewing layouts, consider:

How you’ll use the unit (family, rental, office, guest suite)
Storage (it’s always the first thing people wish they added)
Natural light and ventilation
Noise separation and privacy
Outdoor access (especially for a backyard ADU)

A strong design-build team can help you compare options and tailor accessory dwelling unit design to your lot and lifestyle.

Backyard ADU vs. converting garage to ADU

In Foster City, two of the most common paths are building a new unit or adapting space you already have.

Option 1: Backyard ADU (new build)

A new backyard ADU gives you more freedom with layout and finishes.

Homeowners like it because you can:

Choose the best placement for privacy
Build a layout that feels open and bright
Create a true separate home experience

Option 2: Converting garage to ADU

Converting garage to ADU can be a smart option when the structure is in good shape and the layout works.

It can help you:

Reduce some structural scope (depending on conditions)
Move faster through certain phases of the build
Keep the project footprint compact

A qualified adu contractor will evaluate the existing slab, framing, utilities, and access to confirm feasibility before you commit.

ADU zoning regulations: what to check early

Before you fall in love with a layout, make sure you understand the ADU zoning regulations that apply to your property.

Common items to confirm include:

Setbacks and lot coverage
Height limits
Utility connections
Parking requirements (if any)
Fire separation and access

Because these rules can affect both design and budget, it’s worth working with an adu contractor who can guide you through the process and keep the plans realistic.

Planning for ADU rental income

If your goal is ADU rental income, think like a future tenant.

A few practical design choices that help:

A real kitchen with good storage
A comfortable bathroom layout (not cramped)
Sound control (insulation, windows, doors)
Private entry and outdoor space
Durable finishes that hold up over time

The right ADU floor plans can make a big difference in how rentable the space feels.

Granny flat construction: a friendly way to add family space

Some homeowners call it an ADU, others call it a granny flat. Either way, granny flat construction is often about creating independence without losing closeness.

If you’re building for family, prioritize:

Easy access (wider doorways, minimal steps)
Good lighting
Comfortable storage
Quiet separation from the main house

ADU financing options (how homeowners typically approach it)

There are several ADU financing options, and the right one depends on your goals, timeline, and current mortgage.

Common approaches include:

Cash savings
Home equity-based financing
Construction financing

Your builder can help you estimate a realistic project range so you can choose financing with fewer surprises.

How to choose ADU builders near me (without guessing)

Searching ADU builders near me will give you a long list. The best way to narrow it down is to look for a team that can handle the full process and communicate clearly.

Green flags to look for

Proven experience with Foster City permitting and builds
A clear pre-construction process (design, budgeting, permitting)
Transparent scopes and allowances
A portfolio that matches your quality expectations

Questions to ask any ADU builders

Do you handle accessory dwelling unit design and permitting, or only construction?
Have you completed converting garage to ADU projects?
How do you estimate costs and manage change orders?
What’s your typical timeline for granny flat construction or a new backyard build?
Who is my day-to-day point of contact?

Ready to build an ADU in Foster City?

Whether you’re planning a backyard ADU, exploring converting garage to ADU, or designing for ADU rental income, the best next step is a site visit and a plan that fits your property.

If you’re looking for experienced ADU builders and a reliable adu contractor to guide the process from design through construction, EDR Design Build can help you map out the right approach, with clear communication and craftsmanship you can feel good about.