ADU Floor Plans 400 sq ft
Our 400 sq ft ADU designs are perfect for homeowners who want to add a compact, functional living space without a large footprint. Whether it's for guests, rental income, or your own cozy retreat, we make small feel big.
Starting from:
$ 100,000
Plan Overview
Efficient 400 sq ft ADU Plan for Compact Living
1 bedroom
1 bathroom
0 garages
1 story
Benefits
Why Choose a
400
Square Foot
ADU Layout
Compact Fit
Fits comfortably on most backyards or lots.
Budget Build
Smaller size means a smaller budget.
Living Flex
Great as an ADU guest house or studio.
Easy Upkeep
Less space, less upkeep, more peace of mind.
How it Works
Steps to Build a
400
sq ft ADU
Building a tiny ADU home doesn’t have to be complicated. Here’s a quick look at how we usually build a 400 sq ft ADU:
01
Property Review & Zoning Check
We check your lot and local ADU rules.
02
Choose Your Floor Plan
Pick from compact ADU floor plan ideas or customize.
03
Submit Permits
We prepare and submit your permit application.
04
Construction Begins
We build on-site or install your prefab unit.
05
Interior Work & Final Touches
Finishings like flooring, paint, and fixtures go in.
06
Walkthrough & Move-In Ready
We review everything with you before the hand-off.
Cost Estimate
A 500 sq ft ADU costs between $100,000 and $200,000. It’s a cost-effective way to create extra living space without the expense of building a full-size ADU.
Get My Cost EstimateFAQ
Quick Answers
Can a 400 sq ft ADU include a bedroom?
Yes, many small house ADU layouts include one cozy bedroom.
Is a 400 sq ft unit good for renting?
Absolutely - many use it as a rental or Airbnb.
Do I need permits for this size?
Yes, but we’ll help manage the entire process.
Is 400 sq ft enough space?
With a smart layout, it can feel just right.
Ready to Unlock More Space?
Let’s design the perfect small-space ADU - we’re here to help.
More information
A 400 sq ft ADU is a great choice if you want to add extra space and boost your property’s value without taking on a huge project. These compact homes work well as ADU guest houses or mini ADU homes for aging parents, college-age kids, or renters.
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