Lean to Sheds | Construction Algorithm

Lean to sheds are exactly what their name says they are; sheds that “lean” on another structure. These simple buildings have a number of advantages. A wall on the parent building serves for the primary wall on the shed. This makes for a much easier project because the main wall is already built and their is no need for posts or bracing for that end. This project requires only a limited amount of experience since a starting point is already established. They also require a lower amount of money per square foot than just about any kind of building you can think of.

Lean to Sheds – Check for Headroom

There are have some disadvantages you need to be aware of. The most important of these is the headroom issue. The overhead space is directly related to how tall the wall is on the parent building. The tallest part of the roof the shed is below the lowest part of the parent building. With a 4/12 roof pitch the rafters will fall 48″ if the shed is 12′ wide. For example, if the tallest part you can attach to is 10′, and the shed is 12′ wide with a 4/12 roof pitch, then to top of the roof at its lowest point is 6′. This means that the bottom of the roof at it s lowest point is about six inches less than that. A roof pitch of no lower than 2/12 should be used. The “rise” for any roof is proportional to its pitch. A 4/12 roof pitch rises four inches per foot.

Lean to Sheds Rafters

8′ x 16′ lean to shed with a 4/12 roof pitch. 2 x 6 rafters and 2 x 8 ridge and band.

Lean to Sheds – Step by Step Building Instructions

A perfect starting point is the ridge. The ridge is the physical attachment between the lean to shed and the parent building. Typically, the ridge is fastened with nails. Bolts or screws are optional. In a nut shell, you nail a treated pine 2 x 6 where the top of the roof is.

  • Find the highest point you can safely attach the ridge for the lean to shed on the wall of the parent building and mark it.
  • Check the distance from a reference point on the parent building and mark it on the other end. Chalk a line between the marks.
  • If the parent building has wooden sides, then simply nail on the ridge. If the parent building is made from any other material, then you will have have to fasten it accordingly.
  • Mark the post holes. Make sure they are parallel and square to the parent building.
  • Dig the post holes deep enough so that 20% of the post is below ground.
  • Stand the posts in their holes. Brace them with 2 x 4’s so they are plumb.
  • Establish the top of the posts by determining the fall rafters. You can use whatever roof pitch you want, just do not drop below a 2/12.
  • Mark the other posts and saw them off.
  • Nail on a 2 x 8 band from post to post flush with the top of the posts.
  • Nail on a 2 x 4 top plate flush with outside of the band.
  • Make a rafter pattern. If you are puzzled by the whole rafter laying out process, then simply fasten a 2 x 6 to the side of the edge of the ridge and band and mark it. Its that simple!
  • Put lay out marks on the ridge and top plate. 2 feet center is a good spacing for the rafters.
  • Saw the rafters and nail them on.
  • Roof Rafters has more detail.
  • Nail on 1 x 4’s or 2 x 4’s to the top of the rafters running perpendicular. Start at the bottom and space them no more than 2 feet in between. Make sure the rafters are fairly straight. If you want overhangs, then let the boards hang over “wild” and saw them last.
  • Now you are ready for the metal top. Use metal screws with rubber washers.
  • Start on the end away from the most visibility so the laps are less noticeable. Tack down 2 sheets of metal with a screw at the top and bottom. Note how they match at the bottom and how they fit at the top. Make your adjustments now.
  • Screw the metal on the flat next to rib that laps with a screw next to each rib and in each batten.
  • For more detail on this see How to Install Metal Roof.
  • Remove all braces and add any cosmetics you want.
Lean to Sheds

A lean to shed can be fully enclosed; accessible only from the parent building.

Closing Thoughts

For other options you can add to lean to sheds, see these pages:

  • Barn Loft | Floor Construction includes images of framing details from different perspectives. This approach works for any building.
  • Build a Shed Ramp if you find you will be rolling things in and out of your shed.
  • DIY Barn Door includes step by step instructions and images for building any size barn door from wood or metal. Information on hinges and latches.

Treated pine is the ideal building material for lean to sheds. However, just about any kind of lumber will work. Pole barn metal makes a good choice for the roof. This construction technique is simple, strong, and economical. It is by no means carved in stone. Adapting to the situation is key to the success of any construction project including lean to sheds! Thanks to readers like you we can fund this project.