How to Build a Lean-to Shed

Storage can be a problem for many people. The average house just doesn’t seem to have enough storage space for all the stuff we think we need. Some handle this by renting a storage space in one of the many self-store warehouses that dot our cities. But that’s not convenient for things that you might need to be able to get to on a regular basis. Better to have something that is on your own property, like a shed.

Of course, building a shed is a pretty hefty project for some people; beyond their budget and maybe even their skills. A simpler solution is to build a lean-to shed, attached to the back of the house or garage. While such a structure is smaller, it is also easier and less costly to build, yet still provides you with some very convenient storage space, which you can use for yard & garden, camping gear, or just about anything.

The name lean-to defines this sort of shed as being attached to a larger structure. This is part of what makes it cheaper to build, as it doesn’t have to be structurally strong, in and of itself. Rather, it gains strength and support from the common wall it shares with the larger structure.

The other thing that makes a lean-to easier to build than other shed designs, is that it has a shed-type roof. This means that it only pitches in one direction, rather than two. More than anything, this simplifies the process, as you don’t have to build roof trusses and you only have to lay shingles in one direction, rather than two.

Building a lean-to shed is a simple enough project, that someone with average skills and a few tools can do it in a weekend, following these simple step-by-step instructions.

Starting from the Bottom Up

As with any project, we must start this one from the bottom up. So the first decision you have to make is what sort of a floor you want. There are three basic options:

If you’re going to go with concrete, you’ll need to pour a slab before going any further. I won’t bother going into detail about that here, as I’ve dealt with how to pour concrete in other articles.

Wood Floor

To make a simple wood floor, you’re going to need to frame it and set it on the ground. I’d recommend starting out by setting some paving stones for the corners and leveling them. Ultimately, you’re better off leveling the paving stones, than having to shim the floor on top of them. the shims wouldn’t be all that strong and may crumble over time.

A wood floor should be framed and covered with pressure-treated lumber, to ensure that it doesn’t decompose, destroying your shed. Since we’re talking a small area, it can be framed out of 2”x 4” dimensional lumber, on 16” centers, rather than anything larger. You should use ¾” pressure-treated plywood for the floor, rather than anything thinner or using plywood that isn’t pressure treated.

Dirt Floor

The simplest solution is a dirt floor, if you don’t have any reason to need a cement or wood floor. If all you’re using your lean-to shed for is yard and garden, a floor really doesn’t gain you anything. Setting the shed directly on the ground saves you time, energy and money.

In this case, you should use pressure-treated lumber for the floor plate, rather than normal dimensional lumberyard. I would also recommend a double floor plate, so that you could attach the siding to just the upper one of those plates, leaving a gap between the bottom edge of the siding and the ground. That way, it won’t be wicking up moisture from the ground, destroying the siding.

Framing the Walls

You only have three walls to build, rather than the typical four, which is one of the benefits of this sort of shed. Not only that, but the outer wall, which is the long one, is going to be mostly taken up with the doors, reducing the amount of framing you have to do. Use the diagram below for reference.

framing, walls, sketch
Framing the walls

To make the outer wall, start out by determining the overall dimensions and the door width. Make a rectangle out of 2”x 4” lumber, using pressure treated lumber for the floor plate, if needed. Then add in double studs for the sides of the door frame. Double studs are used, so that you can attach the door hinges. Notice that these studs are not the same height in the diagram above. The inner one is shorter, to allow the door header to sit on top of it.

It is doubtful that you will need to use any additional studs between the door frame and the corners; but if you do, they should be spaced on 16” centers. While you could use 24” centers, there’s too much of a chance that the siding will warp with that much space between them.

You can make the header itself out of two 2”x 4” studs, with some scraps of ½” thick plywood between them, acting as a spacer. This creates a square cross-section. Even so, install it with the 4” dimension of the 2”x 4”s vertically, so as to gain the greatest strength from the header.

Notice that there are small blocks of 2”x 4” above the door header, in the diagram. Those are not there for structural strength, as much as they are there to provide something to nail the siding to. The header should be self-supporting, resting on the studs that form the door frame.

Finally, notice that the floor plate is intact, running across the doorway. This is normal when framing a wall. Once the wall is installed, and the siding is put on it, this 2”x 4” will be cut, removing the part that is in the doorway itself. But by leaving it in place until then, you are assured of keeping the door frame aligned and spaced correctly.

With the front wall framed, the side walls are much simpler, as they won’t have a door frame in them. All you need, is to use top and bottom plates, with as many studs as it takes to give you the width you need, at 16” centers. It is common to make a shed of this sort only four feet deep, as that is the size of a sheet of plywood, saving you from having to cut another piece to finish out the wall.

There is no need to double stud the corners, as there would be if you were framing inside your home. the double stud used in the corners is done so as to provide something to nail the drywall to. Since your shed won’t have any drywall inside it, this would be a waste.

Framing the Roof

To make the roof of your shed, pick a point on the wall, at which you are going to attach the header. This is going to be the peak of your roof. You want it high enough so as to provide good drainage for the roof of your shed. This header is a 2”x 4”, which should be nailed horizontal and level to the wall. The rafters for your shed will attach to it. You want to be sure to align it carefully with the shed, making it slightly wider than the dimensions of your shed, so that the roof can overhang slightly.

The easiest way to make your rafters is to place one bridging from the top of your outer shed wall to the end of the header you just nailed to the wall of your home. You can then mark the angle for the cut at the header and where you should be cutting the rafter off at. If your shed is dimensionally square, all of your rafters should be able to be cut the same.

Install the rafters on 16” centers, with the 2”x 4”s sitting vertically. Toe nail them to the header and the top plate of the front wall of your shed. Add another 2”x 4” across the front edge, forming a fascia.

Chances are that you will also need to add some gable studs to the ends of the roof, providing support for the siding that is to be attached to the gable ends of your shed. This should be spaced in alignment with the studs in your end walls. You may also need to scab some blocks of scrap 2”x 4” to the top of the top plates, on the end walls, to give yourself something to attach these pieces of siding to.

Skinning it Over

You could use any kind of siding you want to on your shed, and might want to consider using the same kind of siding that the house is covered with. If that is not possible, then the easiest way to skin the shed is with T-111 siding, which comes in 4’x 8’ sheets, like plywood. If you are going to cover your shed with aluminum or vinyl siding, you should still use T-111 siding or ½” CDX plywood underneath it as sheathing, as the siding itself won’t be strong enough to withstand damage from something inside falling against it.

The siding at the corners of the structure should be covered with 1”x 3” wood strips to cover up the joint where the siding comes together. Two pieces are used, with one laid on one side, then the other overlapping it from the other side, as shown in the diagram below. Notice that the siding and trim are laid with the overlap coming from different sides, so as to help seal the corner.

siding, sketch

With the walls sealed in, you are now ready to cover the roof with ½” CDX sheathing or plywood, being sure that all the joints fall on the studs. If your shed is four feet deep, you won’t be able to run these sheets of sheathing lengthwise across the roof, but rather will need to run them so that they are perpendicular to the wall of the house.

The roof sheathing is then covered with a layer of roofing felt, then shingles. Hopefully you can find shingles which match those already used on your home, so that the shed will look like it belongs as part of the home, rather than something you’ve added on.

Finish with the Doors

Hopefully, you’ll have enough of your siding left over to make the doors to your shed. That way, they’ll match nicely, giving the whole thing a good finish. There are a number of ways you can make your doors, but they all boil down to supporting the T-111 siding, so that it doesn’t warp.

Start by cutting two pieces of siding, the same size, which together fill the space for your doors. There should be a little bit of a gap (1/4”) all the way around, as well as about the same size gap between them, but you really don’t want much more.

We’re going to support this piece of wood, giving it more rigidity, by framing it with 1”x 4” pieces of lumber. This can be done on the inside or the outside, depending on the look you want to create. If you do it on the outside, you can give your doors a “barn door look” by using a similar pattern to what is typically used for barn doors.

It’s important to use 1”x 4”s which are straight and true for this. I find that they tend to be twisted, when I buy them at my local home improvement warehouse, so take the time to sort through their stock and find some good ones.

You want to assemble the doors on a flat surface, as attaching the trim pieces to the doors will make any twist permanent. Glue and nail or screw the trim onto the doors, framing them and running diagonals. It is these diagonals, more than anything, which will help to hold the door flat and prevent warping. Add one additional piece, on the backside of one of the doors, overlapping the edge, so that it can close the space between the two doors.

With the doors made, all you have to do is hang them and add some hardware.

Be sure to caulk all the seams between wood pieces, before applying the paint to your lean-to shed’s siding and trim. A contrasting color is usually used for the trim.

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