16x20 Lean-To Storage Shed Plan

The full plan is $19.99: buy the 16×20 lean-to shed plan. To see the drawing style first, open the free 16×20 lean-to shed plan PDF.

16×20 lean to shed plans: the numbers for a site check

Square the stakes to matching 25′ 7 3/8″ diagonals before any digging. All 20 ft of roof drains to the back edge, so leave room to reach it and plan where the water runs.

How the 16×20 lean-to shed goes together

The plan has 28 numbered sections, 19 of them build steps. Steps 9 to 27 run from preparation and ground breaking to the ramp, and a printable checklist lists all 19. Section 8, “Key joints up close”, is a page of close-ups of the floor corner, door, window, wall corner, rafter seats and rake.

Building 20 ft long from 16 ft stock

The skids, rims and long-wall plates are all longer than a 16 ft board, so the plan splices or sections each one and tells you where:

• Skids. Each 20 ft skid is an 8 ft and a 12 ft piece butted on the gravel, the five skids sitting 3′ 11 1/8″ on center. The joint is centered under a floor joist, gets a 3 ft pressure-treated 2×4 scab on both sides with six nails each, and stays 4 ft or more from the joint in the next skid.
• Rims. Each rim is cut 9′ 4 3/4″ + 10′ 7 1/4″ and breaks over a doubled joist, so both rim ends get three nails into a full joist.
• Wall plates. The front and back walls are framed in 2 sections each, so each section has its own plates. The second top plate goes on once the walls stand and bridges every section joint.

The nailed floor frame weighs about 680 lb, so the plan has you build it in place on the skids and square it there. A framing angle goes at every place a joist crosses a skid, 85 in all.

How the walls go up

Each wall is framed flat on the deck and raised as a bare frame, and the siding goes on after all four stand. The two 20 ft walls go up in 2 sections each so that two people can raise each one.

• Stop blocks. Two 12″ 2×4 offcuts nailed to the outside of the rim, tops 2″ above the deck, keep a bottom plate from kicking out as the wall tips up.
• Join the sections. The front wall breaks 13′ 4 3/4″ from the left corner and the back wall 11′ 11 1/4″ from the right corner. The second top plate bridges each joint.
• Stop posts and low braces on the tall wall. Three 4 ft stop posts screwed to the rim stop the 9′ 10 1/8″ front wall at plumb, and its braces go on about 7 ft up, where you reach them from the deck.
• Side walls drop in. They stand tight against the inside of the front and back walls, so plumb those two first.
• Twist straps. A lean-to side wall has no level plate to lap, so a metal strap ties each of the four corners.
• Wind. The plan says to pick a calm day: a bare frame catches wind like a sail.

Each side wall has 13 studs from 5′ 8 3/8″ to 9′ 6 3/16″, with beveled tops under the sloped plate. Studs over 7′ 8 5/8″ must come from full 96 in boards, not the 92 5/8 in precuts many stores sell as “8 ft studs”.

What fits in a 16×20 lean-to shed

The plan’s “What fits inside” drawing shows the room seen from above and to scale. Inside, the shed is 19′ 5″ wide and 15′ 5″ deep.

• Riding mower. A 42 in deck is 4′ 7 3/16″ x 5′ 10″, nose in. The door clear width is about 5′ 11 1/2″ with both leaves open, so a 42 in deck clears each side by 8 1/8″. A 48 in deck fits with its deflector raised. A 54 in deck does not.
• Wheelbarrow. 2′ 2″ x 5′ 0″.
• Two bikes. Handlebars staggered, 2′ 6″ x 5′ 10″.
• Shelves. 24 in deep on the back wall, and 16 in deep along the back 6 ft of each side wall. Keep the back shelves below the window sill, which is 2′ 2 1/2″ above the deck.
• Aisle. There is a 7′ 6″ aisle behind the mower to the back shelves.
• Lining up. The plan says to keep 10′ 0″ clear and level, measured from the wall (the ramp and one mower length), to line a tractor up square.
• Door swing. The leaves swing out, so keep room in front of them.

Door, window and ramp: sizes and positions

• Door. The opening is 6′ 0″ wide, centered in the front wall. Each leaf is T1-11 cut from a new sheet and 6′ 5 1/4″ tall, with a 1×4 frame and two Z braces cut at 36 degrees on the miter saw. Three T-strap hinges per leaf are bolted through. The fixed leaf is held closed by two barrel bolts and a 1×2 astragal.
• Door details. An aluminum threshold cap covers the deck edge with no threshold board, and brush sweeps close the gap under the leaves. Two hook-and-eyes hold the open leaves in wind.
• Window. A prefabricated window in a 3′ 0″ x 3′ 0″ rough opening in the back wall, 8′ 6″ to 11′ 6″ from the right corner, with its sill 2′ 1″ above the bottom plate. Flashing tape goes around the opening first.
• Ramp. A detachable pressure-treated ramp, 6′ 9″ wide and 3′ 6″ out at 1:6, with 8 stringers 11 3/8″ on center under 8 2×6 boards. Its top sits about 13/16″ below the deck, and two hook-and-eyes hold it to the ledger so you can unhook it and lift it away. Set a mower deck to its highest cut before you roll it up.

What is on the 16×20 shed materials list

The shopping list is split by stage, in the stock lengths that waste the least:

• Foundation and floor: 12 ft and 8 ft pressure-treated 4×4 skid pieces, splice scabs, 2×6 rims and 17 joists, and 10 sheets of 3/4″ tongue and groove plywood.
• Pad: one 10 ft, two 12 ft and four 16 ft pressure-treated 4x6s for the frame, 36 rebar stakes, 16 timber spikes and 6.7 cu yd of crushed stone.
• Walls: studs and plates, a doubled 2×8 door header and a doubled 2×6 window header, plus 18 sheets of 5/8″ T1-11 in 4×8, 4×9 and 4×10 sizes.
• Roof: 18 2×10 x 20 ft boards for 16 rafters and 2 fly rafters, 2×10 blocking, 14 sheets of 7/16″ OSB, 3 rolls of 15 lb felt, 14 bundles of shingles and 10 pieces of drip edge.
• Door, window, ramp and trim: 2 new T1-11 sheets for the door leaves, 6 T-strap hinges, a handle and latch, 2 barrel bolts, the threshold cap, the prefabricated window, the ramp lumber, 1×12 fascia, 1×4 casing and corner trim.
• Hardware: nails by the pound, 28 hurricane ties, 85 floor framing angles, 4 end-rafter framing angles, 4 twist straps, 8 ground anchors with straps, adhesive, flashing tape, drip cap, insect screen and 6 gallons of paint.

The rafters and rake fascia come from 20 ft boards, the longest on the list, so check your delivery before you order.

How the 16×20 lean-to roof is framed

A single-slope roof has no ridge and pushes nothing outward, so no rafter ties cross the shed. Hurricane ties hold the rafters down in wind, with a framing angle at each of the 4 corners.

• Why 2×10. The plan sizes the rafters as 2×10 for a 15′ 5″ clear span at 16″ on center, in #2 spruce-pine-fir or Douglas fir-larch at about 30 psf of ground snow. Check the size with your local permit office before you buy.
• Two birdsmouths. Each rafter hooks over both walls with a 3 1/2″ level seat and a 7/8″ plumb heel. Never cut deeper than one third of the rafter.
• Pattern first. Cut one pattern rafter from a straight 20 ft 2×10 (board 18′ 4 13/16″), test it on both walls at each end of the 20 ft run, keep it as the first rafter, then cut 15 more and 2 fly rafters.
• Feed them through the door. Each board weighs about 60 lb and is longer than the room, so two people feed it in through the open door, low end first, and lift it onto the walls.
• Blocking. 2×10 blocks, ripped to 8 5/8″ tall, fill the bays over each wall and have vent holes.
• Low pitch, double felt. At 3/12 the shingle makers ask for two layers: a 19″ starter strip, then 36″ courses lapping 19″ (Asphalt Roofing Manufacturers Association). The shingles are 3-tab at 5″ exposure, 44 courses and about 342 shingles in all, which is 14 bundles with the starter.

Anchoring the shed

The plan says an empty 16×20 on loose skids slides at about 13 psf of wind (gusts near 60 mph) and tips at about 35 psf, so it has you anchor it once the roof is on, before you fill it. It uses 8 screw-in auger anchors, 30″ or longer, galvanized, each with a steel strap: 4 along each of the two outside skids. Each strap runs up the skid and onto the rim joist and is fastened with 1 1/2″ structural screws, 4 into the skid and 2 into the rim. Check your local permit office for what your area asks.

Free 16×20 lean-to plan PDF vs the full plan

The free PDF is an 8-page preview that shows the drawing style and the finished shed. The full plan adds all 19 build steps, the key joint close-ups, the splice lengths, the section splits, the stepped stud lengths for the sloped walls, the rafter marks, the decking, siding and sheathing piece maps, the door leaf with its brace cuts, the ramp, and the shopping, cut and cutting lists.

Before you build a 16×20 lean-to shed

• Permits. At 320 sq ft and 11′ 8 11/16″ at the high edge, this is a big shed for many towns, and the plan itself says most towns ask for a permit at this size. Size, height and setback rules vary by town and HOA. Check your local permit office before you buy lumber.
• Snow and wind. Snow sits longer on a 3/12 roof. Heavy snow areas or high-wind zones may need closer rafter spacing or larger rafters. Your local permit office knows the loads for your address.
• Skids. Use ground-contact rated pressure-treated 4x4s (UC4A or higher), set crown up, and raise a low skid with gravel or treated shims only.
• Keep it dry. Leave 6″ or more between the siding and the soil or mulch.
• Materials. Store lumber flat and covered, since wet wood decays faster (USDA Forest Products Laboratory Wood Handbook). Check the stamp on each OSB sheet for its span rating (APA: OSB).

Tools and ladders the plan lists

Beyond a circular saw, drill/driver and framing hammer, the list adds a miter saw for the door braces and trim, a reciprocating saw for flush cuts, a 3 lb sledge for the pad frame’s spikes and stakes, two 24″ bar clamps for marking the rims and a hand tamper for the pad. Two 8 ft step ladders cover the walls and rafters, since the front plates sit 9′ 10 1/8″ above the deck and a 6 ft ladder falls short; a rolling scaffold tower is the better choice for the front fascia and the high ends of the rakes. A 20 ft extension ladder handles roof work, set up at the low back eave once the roof is on.

Related plans

• 2 ft shallower: the 14×20 lean-to shed plan or 4 ft shallower, the 12×20 lean-to shed plan.
• Smaller and 2 ft narrower: the 14×18 lean-to shed plan.
• Same footprint with a gable roof: the 16×20 gable shed plan.
• Choosing a base first? Read the shed foundation guide.
• Every size on the lean-to shed plans page.