Plan HG-1126•Backyard ADU / Granny Flat•36' × 18' Footprint

648 Sq Ft (18x36) 2 Bed 1 Bath Backyard ADU / Granny Flat Floor Plan

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

Download Free CAD (.SVG)

Room Dimensions & Zones

36' × 18' Shell

PRIMARY SUITE

148 sq ft

18'-6" × 8'-0"

BEDROOM 2

140 sq ft

17'-6" × 8'-0"

GREAT ROOM & DINING

225 sq ft

22'-6" × 10'-0"

BATH & LAUNDRY

61 sq ft

13'-6" × 4'-6"

KITCHEN & ISLAND

74 sq ft

13'-6" × 5'-6"

Build Cost Estimator

Estimated Cost to Build (36' × 18' Backyard ADU / Granny Flat)

Region:

Shell / Building Kit

$30,500 – $39,000

Framing package, roof trusses & exterior shell for 648 sq ft base.

Owner-Builder

$83,500 – $109,500

Saves ~$37,500 by managing local slab & interior trades.

Turnkey Builder

$121,000 – $147,000

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

Est. Monthly Payment

$695 / mo

$107,200 financed (30-Yr)

Down Payment:20%

Interest Rate:6.75%

Free Vector CAD Blueprint • Plan HG-1126

Download 36' × 18' 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 (14 yd³), roof surface (~748 sq ft), wall framing & architectural notes

Building Package	Specification	Quantity	Est. Range
Structural Shell & Trusses	36'×18' 2x6 Dimensional Lumber Framing / Panelized SIP Option	648 sq ft shell kit	$30,500 – $39,000
Concrete Slab & Grade Beams	Stem Wall or Monolithic Concrete Slab-on-Grade	14 Cubic Yards (4,000 PSI)	$6,500 – $8,500
Roofing & Underlayment	Architectural Standing-Seam Shed / Low-Slope Gable (3:12 Pitch)	10 Roofing Squares (1,000 sq ft)	$4,200 – $6,800
Closed-Cell Spray Foam / Insulation	3" Closed-Cell Wall & Roof Deck Thermal Envelope (R-21 to R-38)	5,314 Board Feet	$7,174 – $9,831
Windows & Exterior Doors	Low-E Argon Black Architectural Glazing + 36" Fiberglass Entry	5 Windows • 4 Doors	$4,450 – $7,000
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

108 Linear Ft

Interior Partitions

~87 Linear Ft

Est. Concrete Slab

14 Cubic Yards

Roof Deck Area

~748 Sq Ft

Plan HG-1126 (648 Sq Ft (18x36) 2 Bed 1 Bath Backyard ADU / Granny Flat Floor Plan) is an IRC R304/R310-vetted backyard adu / granny flat blueprint engineered around a 36'-0" × 18'-0" structural grid (648 sq ft base footprint, 0.5:1 Square-Bay Proportion). Configured on the Consolidated Wet-Wall + Open Great Room topology, this layout delivers 648 sq ft of conditioned residential living area and 135 sq ft of covered outdoor porch deck.

Inside the conditioned envelope, the floor plan is organized into 5 distinct architectural zones: PRIMARY SUITE (18'-6" × 8'-0", 148 sq ft), BEDROOM 2 (17'-6" × 8'-0", 140 sq ft), GREAT ROOM & DINING (22'-6" × 10'-0", 225 sq ft), BATH & LAUNDRY (13'-6" × 4'-6", 61 sq ft), KITCHEN & ISLAND (13'-6" × 5'-6", 74 sq ft). Plumbing rough-ins are consolidated across BATH & LAUNDRY, KITCHEN & ISLAND to minimize sub-slab trenching and manifold pipe runs. Sleeping quarters (PRIMARY SUITE at 148 sq ft; BEDROOM 2 at 140 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 36' clear-span width utilizes 2x6 dimensional lumber framing / panelized sip option bearing on 108 linear feet of 6" exterior wall framing (~128 framing studs/posts) and 87 linear feet of interior partitions. The 3:12 architectural standing-seam shed / low-slope gable requires approximately 748 sq ft of roofing material (10 roofing squares), while the stem wall or monolithic concrete slab-on-grade pours at an estimated 14 cubic yards of 4,000-PSI concrete.

Frequently Asked Questions • Plan HG-1126

Building costs, foundation specs, egress & CAD customization questions

How much does it cost to build the 36x18 648 Sq Ft (18x36) 2 Bed 1 Bath Backyard ADU / Granny Flat Floor Plan (HG-1126)?

Based on current national residential construction data for backyard adu / granny flat structures, the dried-in structural shell for Plan HG-1126 (648 sq ft base footprint) ranges from $30,500 to $39,000 ($48/sq ft baseline). A complete turnkey build—including the 14-yard concrete foundation, 87 linear feet of interior framing, MEP rough-ins for 1 bath(s), and interior finishes across 648 sq ft of heated space—ranges from $121,000 to $147,000. 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 648 sq ft 2-bedroom layout?

Plan HG-1126 features 5 architecturally solved spaces inside its 36' × 18' footprint: PRIMARY SUITE (18'-6" × 8'-0", 148 sq ft), BEDROOM 2 (17'-6" × 8'-0", 140 sq ft), GREAT ROOM & DINING (22'-6" × 10'-0", 225 sq ft), BATH & LAUNDRY (13'-6" × 4'-6", 61 sq ft), KITCHEN & ISLAND (13'-6" × 5'-6", 74 sq ft). Every habitable room meets or exceeds IRC R304 minimum area (70+ sq ft) and minimum horizontal dimension (7'-0"+) requirements.

Can this 36' × 18' floor plan be built with post-frame, red-iron steel, or 2x6 stick framing?

Yes. Because the outer envelope is engineered on an even 36'-0" × 18'-0" structural grid (108 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-1126?

Downloading Plan HG-1126 provides the high-resolution scalable vector floor plan (.SVG) with crisp architectural lineweights, exterior dimension strings (36'-0" × 18'-0"), room-by-room callouts, door swing arcs, and window schedules, plus instant browser printing for contractor bidding and preliminary municipal zoning review.