Plan HG-1207•Backyard ADU / Granny Flat•40' × 20' Footprint

800 Sq Ft (20x40) 1 Bed 1 Bath Backyard ADU / Granny Flat Floor Plan

800 sq ft heated living • 1 Bedroom, 1 Bath • Free 2D CAD Blueprint (.SVG)

Download Free CAD (.SVG)

Room Dimensions & Zones

40' × 20' Shell

PRIMARY BEDROOM

225 sq ft

25'-0" × 9'-0"

BATH & LAUNDRY

135 sq ft

15'-0" × 9'-0"

GREAT ROOM & DINING

275 sq ft

25'-0" × 11'-0"

KITCHEN & ISLAND

165 sq ft

15'-0" × 11'-0"

Build Cost Estimator

Estimated Cost to Build (40' × 20' Backyard ADU / Granny Flat)

Region:

Shell / Building Kit

$37,500 – $48,000

Framing package, roof trusses & exterior shell for 800 sq ft base.

Owner-Builder

$103,000 – $135,000

Saves ~$46,000 by managing local slab & interior trades.

Turnkey Builder

$149,000 – $181,000

Full general contractor finish including slab, HVAC, kitchen & baths.

Est. Monthly Payment

$856 / mo

$132,000 financed (30-Yr)

Down Payment:20%

Interest Rate:6.75%

Free Vector CAD Blueprint • Plan HG-1207

Download 40' × 20' Backyard ADU / Granny Flat Floor Plan (.SVG)

Scalable 2D architectural vector drawing with exterior and room dimensions, door swings, and fixture layout. Opens in AutoCAD, Illustrator, Inkscape, or any browser.

Material Takeoff & Framing Specifications

Concrete volume (17 yd³), roof surface (~924 sq ft), wall framing & architectural notes

Building Package	Specification	Quantity	Est. Range
Structural Shell & Trusses	40'×20' 2x6 Dimensional Lumber Framing / Panelized SIP Option	800 sq ft shell kit	$37,500 – $48,000
Concrete Slab & Grade Beams	Stem Wall or Monolithic Concrete Slab-on-Grade	17 Cubic Yards (4,000 PSI)	$8,000 – $10,250
Roofing & Underlayment	Architectural Standing-Seam Shed / Low-Slope Gable (3:12 Pitch)	12 Roofing Squares (1,200 sq ft)	$5,040 – $8,160
Closed-Cell Spray Foam / Insulation	3" Closed-Cell Wall & Roof Deck Thermal Envelope (R-21 to R-38)	6,180 Board Feet	$8,343 – $11,433
Windows & Exterior Doors	Low-E Argon Black Architectural Glazing + 36" Fiberglass Entry	6 Windows • 3 Doors	$5,100 – $7,980
HVAC & Multi-Zone Mini-Split	High-SEER2 Heat Pump / Ductless Mini-Split System	1.5 Ton (18,000 BTU/hr)	$3,900 – $6,150

Exterior Perimeter

120 Linear Ft

Interior Partitions

~86 Linear Ft

Est. Concrete Slab

17 Cubic Yards

Roof Deck Area

~924 Sq Ft

Plan HG-1207 (800 Sq Ft (20x40) 1 Bed 1 Bath Backyard ADU / Granny Flat Floor Plan) is an IRC R304/R310-vetted backyard adu / granny flat blueprint engineered around a 40'-0" × 20'-0" structural grid (800 sq ft base footprint, 0.5:1 Square-Bay Proportion). Configured on the Consolidated Wet-Wall + Open Great Room topology, this layout delivers 800 sq ft of conditioned residential living area and 150 sq ft of covered outdoor porch deck.

Inside the conditioned envelope, the floor plan is organized into 4 distinct architectural zones: PRIMARY BEDROOM (25'-0" × 9'-0", 225 sq ft), BATH & LAUNDRY (15'-0" × 9'-0", 135 sq ft), GREAT ROOM & DINING (25'-0" × 11'-0", 275 sq ft), KITCHEN & ISLAND (15'-0" × 11'-0", 165 sq ft). Plumbing rough-ins are consolidated across BATH & LAUNDRY, KITCHEN & ISLAND to minimize sub-slab trenching and manifold pipe runs. Sleeping quarters (PRIMARY BEDROOM at 225 sq ft) are acoustically buffered from the primary living core and positioned on exterior elevations for code-compliant egress glazing.

From a builder takeoff standpoint, the 40' clear-span width utilizes 2x6 dimensional lumber framing / panelized sip option bearing on 120 linear feet of 6" exterior wall framing (~138 framing studs/posts) and 86 linear feet of interior partitions. The 3:12 architectural standing-seam shed / low-slope gable requires approximately 924 sq ft of roofing material (12 roofing squares), while the stem wall or monolithic concrete slab-on-grade pours at an estimated 17 cubic yards of 4,000-PSI concrete.

Frequently Asked Questions • Plan HG-1207

Building costs, foundation specs, egress & CAD customization questions

How much does it cost to build the 40x20 800 Sq Ft (20x40) 1 Bed 1 Bath Backyard ADU / Granny Flat Floor Plan (HG-1207)?

Based on current national residential construction data for backyard adu / granny flat structures, the dried-in structural shell for Plan HG-1207 (800 sq ft base footprint) ranges from $37,500 to $48,000 ($48/sq ft baseline). A complete turnkey build—including the 17-yard concrete foundation, 86 linear feet of interior framing, MEP rough-ins for 1 bath(s), and interior finishes across 800 sq ft of heated space—ranges from $149,000 to $181,000. Use the interactive Regional Cost Multiplier on this page to adjust for your local labor market and owner-builder sweat equity.

What are the exact room dimensions inside this 800 sq ft 1-bedroom layout?

Plan HG-1207 features 4 architecturally solved spaces inside its 40' × 20' footprint: PRIMARY BEDROOM (25'-0" × 9'-0", 225 sq ft), BATH & LAUNDRY (15'-0" × 9'-0", 135 sq ft), GREAT ROOM & DINING (25'-0" × 11'-0", 275 sq ft), KITCHEN & ISLAND (15'-0" × 11'-0", 165 sq ft). Every habitable room meets or exceeds IRC R304 minimum area (70+ sq ft) and minimum horizontal dimension (7'-0"+) requirements.

Can this 40' × 20' floor plan be built with post-frame, red-iron steel, or 2x6 stick framing?

Yes. Because the outer envelope is engineered on an even 40'-0" × 20'-0" structural grid (120 LF perimeter) with clear-span 3:12 trusses, a local structural engineer or building kit supplier can adapt the blueprint for 2x6 Dimensional Lumber Framing / Panelized SIP Option, conventional 2x6 stick framing at 16" o.c., laminated post-frame columns at 8' o.c., or structural insulated panels (SIPs).

What files are included in the free CAD blueprint download for Plan HG-1207?

Downloading Plan HG-1207 provides the high-resolution scalable vector floor plan (.SVG) with crisp architectural lineweights, exterior dimension strings (40'-0" × 20'-0"), room-by-room callouts, door swing arcs, and window schedules, plus instant browser printing for contractor bidding and preliminary municipal zoning review.