20×30 Gable Pole Barn Roof Plans

This step by step diy woodworking project is about free 20×30 gable shed roof plans. This is PART 2 of the large post frame shelter, where I show you how to build the roof and add the siding to the exterior of the framing. The instructions are basic, so you won’t have problems if you follow them step by step. Read the local building codes and consider buying engineered trusses. Make sure you take a look over the rest of plans to see alternatives and more projects for your garden.

When buying the lumber, you should select the planks with great care, making sure they are straight and without any visible flaws (cracks, knots, twists, decay). Investing in cedar or other weather resistant lumber is a good idea, as it will pay off on the long run. Use a spirit level to plumb and align the components, before inserting the galvanized screws, otherwise the project won’t have a symmetrical look. If you have all the materials and tools required for the project, you could get the job done in about a day. See all my Premium Plans HERE.



Projects made from these plans




20×30 Gable Pole Barn Roof Plans




[tabs tab1=”Materials” tab2=”Tools” tab3=”Time”]

[tab id=1]

  • H – 21 pieces of 1/2″ OSB – 4’x8′ long, 6 pieces – 48″x72″ long, 4 pieces – 8 1/2″x22 3/4″ long, 2 pieces – 48″x65 1/2″ long, 2 pieces – 24″x48″ long, 2 pieces – 48″x48″ long, 6 pieces – 16 1/2″x96″ long, 2 pieces – 16 1/2″x72″ long WALL SHEETS
  • G – 1 piece of 2×4 lumber – 240″ long, 2 pieces – 144″ long, 2 pieces – 28 3/8″ long, 2 pieces – 57 5/8″ long 16xTRUSS
  • I – 14 pieces of 2×4 lumber – 84″ long, 28 pieces – 96″ long, 14 pieces – 108″ long PURLINS
  • J – 14 pieces of 1/2″ plywood – 48″x96″ long, 4 pieces – 48″x48″ long, 8 pieces – 47″x96″ long ROOF SHEETS
  • K – 800 sq ft of tar paper, 800 sq ft of asphalt shingles ROOFING
  • L – 4 pieces of 1×6 lumber – 145 1/2″ long, 6 pieces – 120″ long TRIMS
  • M – 6 pieces of 2×4 lumber – 10 ft SUPPORTS

  • 16 pieces of 2×4 lumber – 20 ft
  • 32 pieces of 2×4 lumber – 12 ft
  • 74 pieces of 2×4 lumber – 8 ft
  • 20 pieces of 2×4 lumber – 10 ft
  • 35 pieces of 1/2″ OSB – 4’x8′
  • 24 pieces of 1/2″ plywood – 4’x8′
  • 2 1/2″ screws, 3 1/2″ screws
  • 1 5/8″ screws
  • Truss plate, Truss plate
  • Truss ties
  • truss plate nails
  • 8d nails

[tab id=2]

 Hammer, Tape measure, Framing square, Post hole digger, Level

 Miter saw, Drill machinery, Screwdriver, Sander

 Safety Gloves, Safety Glasses

[tab id=3]

 One week





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How to build a 20×30 pole barn roof



I recommend you buy engineered trusses, as they give you a good balance between costs and benefits. They will give you instructions on the span you need to leave between them and on the thickness of the truss carriers.

However, I will show you my take on building the trusses by yourself. Remember to read the local codes so you can make adjustments if needed. The first step is to build the rafters for the trusses. Use 2×4 lumber for the bottom rafters and 2x4s for the common rafters. Make a 20.5 degree cut to both ends of the rafters and lay them on a level surface.

Leave no gaps between the rafters. Set the miter saw at 69.5 degree before making the cuts to both ends of the bottom rafter.

W supports

Web supports

In order to enhance the strength of the trusses, I recommend you to fit the W shaped supports. Use a saw to make the cuts to the supports, as shown in the diagram. Use 2x4s for the supports.



Attach the supports to the trusses and leave no gaps between the components. Fit the metal plates to the joints of the components, as shown in the diagram. Align the edges with attention and insert 1 1/2″ nails into the rafters.



Fit the trusses to the top of the shed, every 24″ on center. Plumb the trusses and then lock them to the carrier beams, using ties.

Supports for the roof trusses

Supports for the roof trusses

Fit the 2×4 supports to the bottom chords. These supports will enhance the rigidity of the roof structure. Use 3 1/2″ screws to secure the supports to the bottom chords. Drill pilot holes at both ends of the supports, to prevent the wood from splitting.

How to build a post frame barn - 20x30

How to build a post frame barn – 20×30

This is basically the structure of the 20×30 pole barn. You can add more braces if you live in an area with strong winds. Read the local codes so you make the required modifications.

Front wall panels - 20x30 large pole barn

Front wall panels – 20×30 large pole barn

Use 1/2″ OSB for the exterior walls. Cut the sheets as shown in the plans and attach them to the framing with 8d nails.  Leave no gaps between the sheets.

Back wall sheets - large post frame building

Back wall sheets – large post frame building

Fit the OSB sheets to the back of the pole barn, using the pattern shown in the plans.

Side wall panels - 20x30 pole barn

Side wall panels – 20×30 pole barn

Fit the sheets to the sides of the large pole barn.

Fitting the siding to the pole barn

Fitting the siding to the pole barn

Cover the exterior of the pole barn with house wrap. Afterwards, install siding sheets to finish the job. You can choose from lots of siding options.

Fitting the purlins - 20x30 pole barn

Fitting the purlins – 20×30 pole barn

Fit 2×4 purlins to the gable roof of the large shed. Place the purlins every 24″ on center, starting from the bottom to the top of the roof. Use 3 1/2″ screws to secure the purlins to the trusses. Make sure the overhangs are equal to the front and back. You can adjust the size of the overhangs.

Roof sheets - 20x30 pole barn

Roof sheets – 20×30 pole barn

Use 1/2″ plywood for the roof of the large pole barn. Cut the plywood sheets as shown in the diagram and attach them to the top of the shed. Leave no gaps between the sheets and insert 1 5/8″ screws, every 8″ along the supports.

You can skip this step and add metal roof sheets directly to the girt boards. If you want to install shingles, you need to install the 1/2″ plywood sheets.

Front and back roof trims

Front and back roof trims

Use 1×6 lumber for the front and back roof trims. Secure them to the purlins with 3 1/2″ screws.

Side roof trims - 20x30 pole barn

Side roof trims – 20×30 pole barn

Fit the 1×6 trims to the sides of the roof. Use 6d nails to secure the trims to the trusses.

Fitting the roofing

Fitting the roofing

Cover the roof with tar paper and then install the asphalt shingles. Make sure you also install the appropriate drip edges, so you can seal the shed roof. Read the manufacturer’s instructions for a tight fit.

20x30 pole barn plans - front view

20×30 pole barn plans – front view

You can also take a look over this 16×32 pole barn plans. I have lots of options if you want to make a post frame structure.



Last but not least, you need to take care of the finishing touches. Apply a few coats of paint over the exterior of the shed, to protect the components from the elements and to enhance the look of the structure and make it match the design of your house.

Top Tip: Check out the rest of the shed projects for more inspiration for your backyard. Take a look over my other shed plans HERE.



This woodworking project was about 20×30 pole barn roof plans. If you want to see more outdoor plans, check out the rest of our step by step projects and follow the instructions to obtain a professional result.





  1. tariq faridi
  2. Regina ten Brinke
  3. Dan No

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