10x20 Lean-To Storage Shed Plan

You can buy the 10×20 lean-to shed plan now, or open the free 10×20 lean-to shed plan PDF first and see how the drawings look. The door is in the 20 ft front wall, so you open it facing the full width of the shed.

10×20 lean to shed plans: the numbers for a site check

The door is in the 20 ft front wall, and the roof falls to the back, so the low 6′ 8″ wall with the window is where the water runs off.

Laying out the pad

Check with your permit office first for size, height and setback rules. Then call 811, the free call-before-you-dig line, a few working days before any stake goes in so the buried power, gas and water lines get marked.

Stake the corners, 20′ 0″ along the front and 10′ 0″ along the sides, and move one stake until both diagonals read 22′ 4 5/16″. Then strip the sod and roots over a 22′ x 12′ patch, a foot past the shed on every side so rain runs away from it. Digging knocks stakes around, so reset them and check the diagonals again.

The stone goes down 4″ deep, tamped in two layers, then raked level and checked with a long straight board and a level in several directions. The plan wants the pad within 1/4″ over its length.

On a sloped yard you stretch a string with a line level from the highest stake to each of the others and measure down at each. A few inches of fall gets made up with more stone on the low side, tamped every 2″. Anything more and you either dig the high side down or set solid concrete blocks on compacted stone under the skids on the low side and shim them with pressure-treated shims. Check the finished pad with the string and the board before a skid goes down.

How the 10×20 lean-to shed goes together

Skids, floor frame and deck

A 20 ft skid is longer than a 16 ft board, so each one is built from an 8 ft piece and a 12 ft piece butted on the gravel. Skids 1 and 3 run 8 ft then 12 ft from the left end, and skids 2 and 4 run 12 ft then 8 ft, so no two joints sit side by side. Every joint is centered under a floor joist and at least 4 ft from the joint in the next skid. A 3 ft pressure-treated 2×4 scab goes on both sides of each joint, with six 3 1/2″ galvanized nails per scab. The skids sit 3′ 2 13/16″ on center, the outer two flush with the floor edges, and they need to be ground-contact lumber (UC4A or higher), laid crown up.

The rim joists get the same treatment, as a 9′ 4 3/4″ piece and a 10′ 7 1/4″ piece. Both rims break at 9′ 4 3/4″ from the left end, over a doubled joist, so each rim end gets three nails into a full joist. That is why the list has 17 floor joists, not 16.

Once it’s nailed, the floor frame weighs about 450 lb and racks out of square if you lift it, so you never carry it. You build it right on the skids: stand each rim on edge over an outer skid, stand the 9′ 9″ joists between them on the marks, nail through the rims with three 3 1/2″ nails per joist, and push the long corner along the skids until both diagonals read 22′ 4 5/16″. Only then do you toe-nail it down at every crossing. Clamp the two rims together and mark the joists on both at once so they line up.

Eight sheets of 3/4″ tongue and groove plywood cover the deck. A sheet only covers about 47 1/2″ once its tongue sits in the next groove, so two full rows come to 7′ 11″ and the last row is 2′ 1″ wide. Two strips that wide won’t come out of one sheet side by side, so you rip full 8 ft strips and cut the pieces end to end. That narrow row flexes at its joints, which is why flat 2×4 blocks go between the joists under the seam and both sheet edges get screwed down to them.

Raising the four walls

Every wall is framed flat on the deck, tipped up as a bare frame and braced plumb. Siding waits until all four stand and the corners are nailed. The front and back walls are too long for one lift, so each goes up in two sections, and every section is a two-person job.

The front wall goes first, while the whole deck is empty. You lay it with the bottom plate set back 3 1/2″ from the front edge (snap a chalk line), because the wall swings out to the edge as it tips up on the inside edge of that plate, and it lands flush. Before the lift you drive two or three nails part way through the bottom plate so it hinges instead of sliding, and nail two 12″ stop blocks to the outside of the rim, 2″ above the deck. Then the lifters take the top plate to waist height and walk their hands up the end studs.

Nobody stands on the ground in front of a wall going up, because a wall that passes plumb falls outward, off the deck. Pick a calm day too: a bare frame catches wind like a sail. The braces are 12 ft 2x4s running out from both ends to 2×4 stakes about 5 ft from the shed, so the deck stays clear for the next wall.

Section 2 goes up tight against section 1. You clamp the two joint studs flush and nail them together with 3 1/2″ nails every 12″, staggered. A second top plate comes later and bridges the joint, lapping it by at least 4 ft on each side, so no two joints line up.

The back wall goes up the same way, set back 3 1/2″ from the back edge. The two side walls are framed flat on the deck between the standing front and back walls. Their plates are 1/4″ shorter than the gap, so they drop in. Diagonal braces stay tacked across the front and back walls until just before each wall gets its siding. The plumb braces only stop a wall leaning in or out; the diagonal is what stops it racking.

Cutting the sloped side walls

The side walls follow the roof, so each of the nine studs in them is a different length, from 6′ 5 3/8″ at the back to 8′ 9 3/16″ at the front. Each top gets a 14 degree bevel through the 1 1/2″ thickness, square across the face, with the long point facing the tall front end. The sloped top plate is a long parallelogram, not a wedge: both ends get the same bevel and both edges measure 9′ 8 1/4″.

Mark the sloped plate from its own column in the stud table. The spacing stretches along a slope, and if you copy the bottom plate marks instead, the last stud ends up 3 7/16″ off plumb. A sloped wall has unequal diagonals too, so you square a rectangle instead: mark both end studs 6′ 0″ up and check that the two diagonals to the opposite bottom corners both read 11′ 1 3/4″.

The right wall’s 8 ft boards have to be full 96″ boards, since its 7′ 10 1/4″ stud is longer than the 92 5/8″ precut sold as an “8 ft stud”. The tallest studs on both side walls come from 10 footers.

What is on the 10×20 lean-to shed materials list

The shopping list is split by stage, and every lumber line names the board length that wastes the least. Nothing on it is longer than 14 ft. The plan suggests adding 2 or 3 spare studs for bad boards.

For the foundation and floor you buy four pressure-treated 4×4 x 12 ft and four 4×4 x 8 ft for the skids, two 2×4 x 14 ft for the scabs, nineteen 2×6 x 10 ft for joists and the short rim pieces, two 2×6 x 12 ft for the long rim pieces, and 8 sheets of 3/4″ tongue and groove plywood. The front wall takes seventeen 2×4 x 10 ft studs, 2×4 x 14 ft plates and a doubled 2×8 header over the door with 1/2″ plywood between the plies. The back wall’s 19 studs come out of ten 14 ft boards. Siding is T1-11 in 4×8, 4×9 and 4×10 sheets, 16 of them for the four walls, each wall with its own sheet map, plus two more for the door leaves. No 4×9 at your store? The list says buy 4×10 and cut it to the same marked height.

The roof is 21 boards of 2×6 x 12 ft, which covers the 16 rafters, the 2 fly rafters and most of the blocking, with one 2×6 x 8 ft for the rest. Add 9 sheets of 7/16″ OSB, 2 rolls of 15 lb felt, 9 bundles of shingles and 10 pieces of drip edge. Fascia is 1×8: two 10 footers and two 12 footers for the eaves, two 14 footers for the rakes.

Hardware: 30 lb of 16d galvanized framing nails, 28 hurricane ties, 4 framing angles for the end rafters, 4 twist straps for the wall corners, 18 temporary 2×4 braces to reuse, 10 tubes of construction adhesive and 5 gallons of exterior paint and primer in one for two coats. It also lists the 8 ground anchors and 48 structural screws that hold the shed down.

Buying the lumber in stages

The plan gives quantities only, no prices. The list is split by section so each stage has its parts.

Sheet goods: 8 sheets of tongue and groove plywood, 18 of T1-11 counting the door leaves, 9 of OSB and two of 1/2″ plywood. The 1/2″ plywood does two jobs, first as the header fillers and then as the soffit strips.

The double door and the window

The door opening is 5′ 0″ wide and 6′ 4 1/2″ tall, and it runs from 7′ 6″ to 12′ 6″ measured from the left corner, with a king stud and a trimmer on each side. The bottom plate runs straight through it while the wall goes up and gets cut out flush with the trimmers once the siding is on, which leaves 6′ 6″ of framed height.

You build two leaves, each 2′ 5 5/8″ wide and 6′ 5 1/4″ tall, from two new sheets of T1-11, because the piece cut out of the opening is too short. A 1×4 frame of two stiles and three rails goes on the outside of each, then two Z braces cut on the miter saw at 29 degrees. Both braces rise from the hinge side toward the latch so they carry the weight into the hinges. Each leaf hangs on three T-strap hinges against a 1×2 stop under the header, which leaves 6′ 5 1/4″ clear under that stop.

Only one leaf is the working door. The other is fixed with a barrel bolt at the top and one at the bottom, and a 1×2 astragal on its inside face gives the active leaf something to close against. The active leaf swings out, and the latch goes on it.

The window is a prefabricated unit made for a 36″ x 36″ rough opening (units usually run 1/2″ smaller). It sits in the back wall, from 8′ 6″ to 11′ 6″ measured from the right corner, with its sill 2′ 10″ above the bottom plate. Tape the opening before the window goes in, sill first, then the sides, then the head. Drip cap goes over the door and window casings.

What fits in a 10×20 lean-to shed

The front is the tall side, 9′ 1 1/8″ with plates. The back wall is 6′ 8″ and holds the window. Front to back the clear span inside is 9′ 5″.

The door opening is 5′ 0″ wide, the astragal on the fixed leaf stands 3/4″ past its edge, and the deck sits 9 3/4″ above the gravel. The plan has no ramp.

How the 10×20 lean-to roof is framed

A single-slope roof has no ridge, so it pushes nothing outward, and the hurricane ties hold it down in wind. Each rafter gets a hurricane tie on the inside face of both walls, and the two end rafters, where the side walls cover that spot, get framing angles instead. The end rafters also get nailed up through the sloped side plates every 16″.

For the 9′ 5″ clear span the plan uses 2×6 rafters at 16″ on center, in #2 spruce-pine-fir or Douglas fir-larch, assuming about 30 psf of ground snow. Snow loads and the span table differ from place to place, so the plan says to check the rafter size with your local permit office before you buy.

Each rafter hooks over both walls with a birdsmouth: a 3 1/2″ level seat and a 7/8″ heel, about 15% of the rafter’s depth (the plan says never cut deeper than a third). Before cutting all of them, measure from the inside face of the front plates to the outside face of the back plates at both ends and in the middle. It should read 9′ 8 1/2″ every time. If the middle is off, push or pull the wall there and hold it with a temporary 2×4 across the plates until the rafters are in.

Then cut one pattern rafter from a straight 2×6, try it at both ends of the shed and cut the rest to match. The front birdsmouth is the one that gets cut backwards, and it has its own drawing. The 2 fly rafters have no birdsmouth. They sit 2 1/2″ outside the end rafters on 2×4 lookout blocks and carry the 1×8 rake fascia.

Venting, felt and shingles

The blocking over both walls is ripped to 4 3/4″ tall and drilled with 1″ vent holes. Air comes in through a 1/4″ gap at the back soffit, rises up the rafter bays and leaves at the front. Staple the insect screen to the underside of the tails, working from outside, before the soffit strips go on.

At 3/12 the shingle makers ask for double felt: a 19″ starter strip, then 36″ courses each lapping 19″, with 4″ end laps. The drip edge goes under the felt at the low eave and over it on the rakes and the high front edge, where the water runs away. Then you lay 28 courses at 5″ exposure, about 221 shingles or 9 bundles including the starter, with the last course trimmed flush at the front and sealed with roofing cement.

Ground anchors

The plan works out that an empty 10×20 on loose skids slides at about 10 psf of wind (gusts near 55 mph) and tips at about 19 psf, so it has you anchor the shed once the roof is on, before you fill it. You use 8 screw-in auger anchors, 30″ or longer and galvanized, each with a galvanized steel strap: four along each outside skid, about 12″ in from each end and no more than 8 ft apart. The plan gives the positions from the left end, and each anchor sits 3″ or more clear of a splice scab.

Each one goes in tight against the outside face of the skid until its eye is about 1″ above the ground. The strap runs up the skid’s outer face and onto the rim joist, below the siding, and takes four structural screws into the skid and two into the rim. Firm, undisturbed soil holds best, and in sand or loose fill the plan says to use longer anchors.

Ladders and roof safety

With the high edge about 10′ 7″ off the ground, the tools list calls for a 20 ft extension ladder plus two 6 ft step ladders for the walls and rafters. Set the ladder 1 ft out for every 4 ft up, tie the top to a rafter or the fascia, and let it reach 3 ft or more past the edge. Look up before you raise a ladder or carry a sheet, and keep yourself, the ladder and the sheets at least 10 ft from any overhead power line.

On the roof, a 2×4 screwed down a foot above the eave gives you a foot stop, and nobody works up there alone. Don’t climb with a sheet in both hands: hand OSB up on its long edge to a helper on a step ladder. Shingle bundles weigh about 60 to 80 lb, so carry half a bundle at a time or ask the supplier if they’ll deliver them onto the roof.

Free 10×20 lean to shed plans PDF vs the full plan

The free PDF is 7 pages. It walks the five stages (site, floor, walls, roof, trim) with 3D views of the same model, so you can see the drawing style and the finished shed before you pay. The full 46-page plan adds the shopping list, the cut list, the cutting plan, every wall drawn stud by stud with a position table, the rafter marks, piece maps for the deck, siding and roof sheathing, and pro tips on most steps. It runs from ground prep in step 8 to paint in step 25, with a checklist page to tick off. Every number comes from one 3D model that passed 86 automatic checks, such as plates plus studs adding up to the wall height.

Before you build a 10×20 lean-to shed

Rules for sheds come from your town, and from your HOA if you have one. Size, height, distance to the property line and whether you need a permit at all vary, so check your local permit office before you spend money on lumber. Ask the same office about snow and wind, since heavy snow or high wind can call for closer rafters or bigger rafters. This is common small-shed framing, not an engineered design, and the disclaimer says so on page 2.

Raise a low skid with gravel or treated shims, never untreated wood. Keep 6″ or more between the siding and the soil or mulch, and keep the drip edges clear. Each spring, look for lifted shingles, re-caulk the trim, touch up the paint and check that the skids are still level and dry.

Tools the plan lists

The plan assumes a circular saw with a rip guide, a drill/driver and a framing hammer. On top of those come a miter saw for the door braces and trim, a reciprocating saw or oscillating tool for the flush cuts in the door and window openings, two bar clamps, 24″ or longer, for marking the rims together, a 3 lb sledge for the brace stakes, and a shovel, rake and hand tamper for the gravel.

Related plans

• Same 20 ft width, 4 ft deeper: the 14×20 lean-to shed plan.
• Same 10 ft depth, 4 ft narrower: the 10×16 lean-to shed plan.
• Same footprint with a two-sided gable roof: the 10×20 gable shed plan.
• Every size on the lean-to shed plans page.