12 x 20 Garden Shed Plan

Introduction

This garden shed plan will give you 320 square feet of storage space or easily converted livable space. It's large enough for just about any purpose, from a woodshop to a media room where it's OK to turn up the volume.
This shed has two windows and fresh air vents to pull in the fresh air and bring in daylight. The windows are framed with shutters, as is the door, which increases its elevation appeal. The double doors open to 60 inches making loading and unloading fast with the smooth, sloped entry ramp.
The roof is strong enough to support solar panels and there's enough space to install storage batteries. There's plenty of room in the walls to run pipes and wires. The plan uses gutters to drain away the rain or snowmelt from the foundation of the building.

Materials you’ll need

  • Concrete
  • Bricks
  • Pressure-Treated Lumber
  • Pressure-Treated Board
  • Plywood
  • Building paper
  • Asphalt shingles
  • Wood siding boards
  • Door hinges
  • Door Pulls
  • Surface Bolts
  • Galvanized nails
  • Wood screws

Step 1 – Foundation Preparation

1.1 Clear the area where you want to build the shed and layout for the foundation. Use the below illustration as a guide.

1.2 For the foundation, dig the trenches at least 1 foot wide and 1 foot deep.

1.3 Fill the trenches to ground level with concrete and let cure, or harden. Since curing times vary between brands, read the packaging for recommended curing times.

1.4 Once the concrete has cured, use standard-sized bricks and lay them across the foundation. You will need roughly 230 bricks for this step.
12x20 garden shed foundation preparation

Step 2 – Framing The Floor

2.1 Assemble the frame using 1 1/2″ x 7 1/4″ pressure-treated lumber. You will need fifteen boards cut to 11′-9″ that will be the joist.

2.2 Secure the beams with 8×5″ wood screws.

2.3 Using a speed square or carpenter’s square, check the corners to make sure they are 90°.
12x20 garden shed floor framing

Step 3 – Assemble Front Wall Frame

3.1 Using 1 1/2″ x 3 1/2″ and 3 1/2″ x 3 1/2″ pressure-treated lumber, construct front wall frame using the drawing below as a reference. You will need three boards cut to 11″ that will be the cripple studs, one board cut to 5′-4″ that will be the door header, sixteen boards cut to 6′-11″ that will be the studs, two boards cut to 7′-4″ that will be the bottom plates and one board cut to 20′ that will be the top plate.

3.2 Connect the beams with 2×4″ wood screws.

3.3 Using a speed square or carpenter’s square, check the corners to make sure they are 90°.
12x20 garden shed front wall framing

Step 4 – Assemble Back Wall Frame

4.1 Using 1 1/2″ x 3 1/2″ and 3 1/2″ x 3 1/2″ pressure-treated lumber, construct back wall frame using the drawing below as a reference. You will need seventeen boards cut to 6′-11″ that will be the studs and two boards cut to 20′ that will be the top and bottom plates.

4.2 Connect the beams with 2×4″ wood screws.

4.3 Using a speed square or carpenter’s square, check the corners to make sure they are 90°.
12x20 garden shed back wall framing

Step 5 – Assemble Side Walls Frames

5.1 Using 1 1/2″ x 3 1/2″ pressure-treated lumber, construct side wall frames using the drawing below as a reference. You will need four boards cut to 5 1/2″ that will be the cripple studs, four boards cut to 2′-10 1/2″ that will be the studs, two boards cut to 3′-4″ that will be the window header and rough sill, ten boards cut to 6′-11″ that will be the studs and two boards cut to 11′-5″ that will be the top and bottom plates.

5.2 Connect the beams with 2×4″ wood screws.

5.3 Using a speed square or carpenter’s square, check the corners to make sure they are 90°.
12x20 diy garden shed side walls framing

Step 6 – Assemble the Roof Frame

6.1 Using 1 1/2″ x 5 1/2″ pressure-treated lumber, cut thirty-four rafters 7′-8 1/2″ long according to the dimensions.

6.2 Using 1 1/2″ x 3 1/2″ pressure-treated lumber, cut fifteen collar ties 5′-11 3/4″ long according to the dimensions.

6.3 Using 3/4″ x 7 1/4″ pressure-treated board, cut the ridge board 20′ long according to the illustration below.

6.4 Connect the beams with 2×3″ wood screws.
12x20 diy garden shed roof framing

Step 7 – Install Shed Doors

7.1 Build the door frames for the shed using 1 1/2″ x 3 1/2″ pressure-treated lumber and secure with 5″ wood screws. You will need two boards cut to 5′-11 3/4″ that will be the vertical girts and two boards cut to 2′-3/4″ that will be the horizontal girts.

7.2 Prepare the 9/16″ plywood sheet with dimensions 2′-7 3/4″ x 5′-11 3/4″ for the doors according to the drawing.

7.3 Use 2 1/2″ x 3/4″ pressure-treated lumber for the door trim and fasten with 2″ wood screws. You will need two boards cut to 2′-2 3/4″ and two boards cut to 5′-11 3/4″.

7.4 Using 1/4″ x 3/4″ pressure-treated lumber, cut and install a starter course 2′-2 3/4″ long.

7.5 For the exterior siding on the door, use 1/2″ x 6″ wood siding boards and the illustration below as a reference.

7.6 Assemble siding shields with 2″ galvanized nails.

7.7 Install three 3″ door hinges using 6×1″ wood screws. Finish the installation of the doors by attaching 4″ surface bolts and 6″ door pulls.
12x20 garden shed door

Step 8 – Roof Sheathing Installation

8.1 You will need 330 Sq Ft of asphalt shingle roofing.

8.2 Add the metal drip edge to the fascias.

8.3 Cover the plywood with building paper.

8.4 Install asphalt shingle roofing using an industrial stapler.
12x20 diy garden shed roof sheathing

Step 9 – Window Installation for Side Walls

It is necessary to prepare 2 windows.

9.1 Using 1 1/2″ x 2 1/2″ pressure-treated lumber, assemble the outer frame for the window as shown in the drawing below. You will need two boards cut to 3′-1″ that will be the vertical girts and two boards cut to 3′-4″ that will be the horizontal girts. Additionally, add vertical 2′-11 1/2″ long and horizontal 3′-1″ long supports using 3/4″ x 1″ lumber and cut the recesses for the window hinges.

9.2 Use 1 1/2″ x 1 1/2″ pressure-treated material to make the inner frame and secure with 3″ wood screws. You will need two boards cut to 2′-9 3/4″ that will be the vertical girts and two boards cut to 3′-3/4″ that will be the horizontal girts. Mill a recess for the glass panes and for the hinges.

9.3 Use 1 1/4″ x 1 1/2″ pressure-treated material to make the inner frame supports and secure with 3″ wood screws. You will need two boards cut to 2′-9 3/4″ and mill a recess for interconnection.

9.4 Prepare and install glass into inner frame groove and fasten it by window beading from four sides. Use 1/2″ galvanized nails.

9.5 Install two hinges (3″) with 6×1″ wood screws and assemble the window. Install a lock on the inner side of the window.
12x20 diy garden shed window

Step 10 – Assemble and Install Window Shutters

It is necessary to prepare 4 windows shutters.

10.1 Assemble frames using 3/4″ x 1 1/2″ pressure-treated lumber and secure with 3″ wood screws. You will need one board cut to 1′-4 3/4″ two boards cut to 3′-3/4″ that will be the vertical girts and two boards cut to 1′-7 3/4″ that will be the horizontal girts.

10.2 Mill a recess along the vertical girts for the jalousies.

10.3 Use 1/4″ x 1 1/2″ pressure-treated lumber for the jalousies. You will need twenty-two boards cut to 1′-5 3/4″.

10.4 Install two 3″ door hinges using 6×1″ wood screws.
12x20 diy garden shed window shutters

Step 11 – Assemble Decorative Door Shutter

It is necessary to prepare two decorative door shutter.

11.1 Assemble front frame using 1 1/2″ x 1 1/2″ pressure-treated lumber and secure with 3″ wood screws. You will need two boards cut to 6′-7″ that will be the vertical girts and two boards cut to 1′-5 1/2″ that will be the horizontal girts.

11.2 Assemble back frame using 3/4″ x 2 1/2″ pressure-treated lumber and secure with 5″ wood screws. You will need two boards cut to 6′-7″ that will be the vertical girts and two boards cut to 1′-3 1/2″ that will be the horizontal girts.

11.3 Use 3/4″ x 3/4″ pressure-treated lumber for the lattice. You will need thirty-six boards cut to 2′-3/4″. Assemble according to the drawing.
12x20 diy garden shed decorative door shutters

Step 12 – Install Roof Drainage System

12.1 Assemble roof drainage system on the front fascia board. You will need 5″ half round gutter 18′ long, two end pieces with the outlet, six 45° elbows, two 3″
pipes 6′ long, two joint connectors and two end caps.

12.2 Fasten the round gutter to the fascia with the round fits of hunger.

12.3 Fasten the vertical pipe section with the four wall fasteners.
12x20 diy garden shed drainage system

Step 13 – Assemble and Install Door Ramp

13.1 Assemble five door ramp frames from pressure-treated lumber and secure with 3 and 5″ wood screws. For each frame you will need one 1 1/2″ x 1 1/2″ board cut to 1′-8″; one 1 1/2″ x 2 1/2″ board cut to 3′-3/4″ and one 1 1/2″ x 3 1/2″ board cut to 6 1/4″.

13.2 Connect and secure all frames using one 1 1/2″ x 2 1/2″ board 5′-9″ long and 3″ wood screws.

13.3 Cut the 9/16″ plywood sheet with dimensions 3′-3/4″ x 5′-9″ for the top plane and two sheets with dimensions 9 1/4″ x 2′-9 1/2″ for the sides.

13.4 Assemble siding shields with 2″ galvanized nails.
12x20 diy garden shed door ramp

Step 14 – Decorate the Shed

Now that you’ve finished the shed, you are ready to paint it or finish with a wood stain or preservative.

12x20 garden shed

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12x20 diy garden shed plan