ADU Floor Plans 400SF

1 room, 1 bathroom, loft for storage and more possible

ADU Floor Plans 400SF  are a good start for an independent rental or a combo of guest house and home office. It can be built wheelchair accessible for older parents. What is possible in 400 square feet? It is truly versatile: this ADU floor plan 400sf can be used as a guest house and home office, place for older parents or adult kids, or as a rare rental that can house a whole family. 

400 square feet - What can fit in?

Permit-ready ADU Floor Plan 400SF

400SF ADU floor plan
Modern. Durable. Low Emissions. Healthy. Comfortable. Money-saving. Carefree maintenance.

What Is Included in Our 400 Square Feet House Plans

Living Area
  • Open space living/dining/kitchen with natural lighting
  • Dual-pane glass windows for lower utility bills
  • Smart HVAC unit for comfort
  • Modern frameless cabinet doors
  • Pre-fab quartz countertops
  • All electric appliances
  • High efficiency fan for moisture control
  • Smooth wall finish for fast cleaning time
  • Window for natural light
  • Solar panels for lower energy costs
  • Composite low maintenance decking
  • Lifetime warranty shingles

Slide ADU floor plans 400SF

All In One Solution

Starting from $245,000 

Sq Feet

400 sq ft

Bed / Bath

1Bed / 1Bath

*30 year, 5.7% APR, 680+ credit score for primary residence cash-out refinance. Your Loan Estimate terms may differ.

Other ADU floor plans available

1 bedroom 1 bathroom units

There is a number of pre-designed floor plans in our library – we have I shaped ADU, L shaped ADU and more.

Most ADUs under 400 sf boast one bedroom and one bathroom, but we can adapt floor plans to your requirements if you need a bigger studio with a  bathroom.

Every thousand dollars matters when you look at an ADU as an investment into your property. This is why we try to save you money with pre-designed plans. We can customize any of our ADU floor plans 400SF to fit your property or to address your family needs.


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Why people build 400 sf ADUs? 

Most often it is because of space constraints. When you are building an accessory dwelling unit, you should try to build as big of a unit as possible. Why? Because of the economics of the price per square foot. A lot of costs goes into utilities and site work.  If you can spread this cost over more square feet, you gain more property appreciation.

There is additional side benefit: ADUs under 750 sf are not subject to impact fees saving you thousand of dollars.

Is there a way to squeeze in a home office?

Yes. You can opt for a loft. ADUs can be as high as 16 feet ( at least until the new legislation kick in and allows more). You can build a loft above the bedroom and bathroom, while still keeping higher ceilings in the living room for a more spacious feel.

Is 400 sf  enough space to accommodate  aging parents or in-laws ?

The pandemic has brought in a sense of insecurity in the minds of all. This is more so in the minds of the older people. You may have to accommodate your  parents or in-laws who want to have you near them. Believe it or not, smaller spaces are more comfortable for older people than sprawling mansions. This floor plan is just enough.

How much can ADU Floor Plans 400SF cost?

Buying an ADU floor plan is easy – you go online and find a plan that can cost from $1,000 to $3,000. But do you need just an ADU floor plan? You need the plan set for the city or county department to process your permit application, correct?
If you plan to build an ADU, your plan set should include site plan, floor plan, elevations, sections, roof and foundation details, engineering calculations and drawings, Will Serve letters from utilities, energy consultant report and some other documents required by your local jurisdiction (i.e. soil report, survey etc.). This set can cost anywhere from $9,000 to $30,000.
You cannot buy a new single family home or even a condo in most places for the price of an ADU.  ADUs are less expensive to build than new detached single-family homes. ADUs offer benefits of better environmental quality and less expensive utility connections. 
Builders use cost-effective wood frames for ADUs, less expensive than other construction types. When looking at the budget, make sure you include design and permit fees, site work, utility connections and solar.

What are main ADU Benefits?

ADUs means benefits for both renters and homeowners. Homeowners receive extra monthly rental income. At the same time they add housing for teachers and nurses in their own community.
ADUs also present the flexibility of independent living areas with other family members. This allows seniors to age in place, even if they need more care. Extended families stay together while maintaining privacy. This means a more peaceful multi-generation household.