HOOLIEHAUSHouse Plans & 2D CAD Blueprints
Browse Plans
108 Backyard ADU / Granny Flat Floor Plans • 300–1,200 Sq Ft

Backyard ADU / Granny Flat Floor Plans & 2D Blueprints

High-efficiency 1-to-2 bedroom layouts featuring consolidated plumbing wet walls, zero-step accessible entries, full kitchens, and private outdoorliving patios.

Backyard ADU / Granny Flat 3D House Exterior
108 Plans
Shell Est: $28,000
View Plan
Shell Est: $15,000
View Plan
Shell Est: $18,500
View Plan
Shell Est: $21,500
View Plan
Shell Est: $23,000
View Plan
Shell Est: $24,500
View Plan
Shell Est: $27,500
View Plan
Shell Est: $27,500
View Plan
Shell Est: $30,500
View Plan
Shell Est: $30,500
View Plan
Shell Est: $20,500
View Plan
Shell Est: $24,000
View Plan

Backyard ADU / Granny Flat Build Cost Guide & Frequently Asked Questions

Shell kit pricing (~$48/sq ft), framing specifications (2x6 Dimensional Lumber Framing / Panelized SIP Option) & common questions

Structural Framing, Roof Pitch & Foundation Specs

High-efficiency 1-to-2 bedroom layouts featuring consolidated plumbing wet walls, zero-step accessible entries, full kitchens, and private outdoorliving patios. Every backyard adu / granny flat layout in this 108-plan hub is drafted on a true structural bay module (6" exterior walls, 4.5" interior partitions) using 2x6 Dimensional Lumber Framing / Panelized SIP Option. Standard builds pair a Stem Wall or Monolithic Concrete Slab-on-Grade with a 3:12 Architectural Standing-Seam Shed / Low-Slope Gable, eliminating complex roof valleys and reducing framing labor by 18% to 25%.

Shell Kit vs. Turnkey Budgeting & Plumbing Optimization

With dried-in shell pricing averaging $48/sq ft and turnkey builds averaging $195/sq ft, the fastest way to lower construction costs on a backyard adu / granny flat is consolidating mechanical runs. Our compositional CAD engine groups kitchens, baths, and laundry rooms along shared plumbing wet walls and keeps clear 36-inch circulation paths around every doorway and kitchen island.

How much does a Backyard ADU / Granny Flat cost to build per square foot?

Across our 108 engineered backyard adu / granny flat floor plans, dried-in structural shell packages average $48 per sq ft ($14,400 to $57,600 depending on footprint size), while complete turnkey construction averages $195 per sq ft of heated living space. The average turnkey build cost across this collection is $167,912.

What structural framing and foundation system is best for a Backyard ADU / Granny Flat?

Our backyard adu / granny flat blueprints are engineered around 2x6 Dimensional Lumber Framing / Panelized SIP Option paired with a Stem Wall or Monolithic Concrete Slab-on-Grade and a 3:12 Architectural Standing-Seam Shed / Low-Slope Gable. All exterior walls are dimensioned at 6 inches with 4.5-inch interior partitions for straightforward permitting and local lumber or kit takeoff.

Are these Backyard ADU / Granny Flat floor plans compliant with IRC residential building codes?

Yes. Every backyard adu / granny flat blueprint in the HoolieHaus StructuraCAD catalog is programmatically verified against 2024 International Residential Code (IRC) spatial standards—including R304 minimum room areas (70+ sq ft bedrooms, 7'-0" minimum width), R310 emergency egress window placement in all sleeping quarters, 36-inch main entry doors, and consolidated wet-wall plumbing cores.