How to Build a Water Heater Shed

Carson Barrett

A water heater is a vital appliance in your home, but it's also an appliance that can require a lot of space. This can be an issue if your home is fairly small and you need to maximize the space you have available. You can work around this issue by moving the water heater outside your home.

Building a lean-to water heater shed against the exterior of your home can protect the water heater from the elements. Placing the shed on a concrete slab provides a stable base that protects the water heater and pipes from the shifting ground.


Wear safety goggles when sawing the wood.

Building the Foundation

  1. Spray paint the ground next to the house to mark the perimeter of the shed. In this example, we'll build a 4-foot by 6-foot shed. This will allow access around the entire water heater, as well as a little extra storage space. Make the markings slightly larger than the perimeter of the shed, so add 3 inches to the front edge and each side of the shed.

  2. Excavate the ground inside the spray-painted lines to a depth of 4 inches. Rake the soil in the bottom of the trench smooth.

  3. Place landscaping fabric over the dirt in the hole. This stabilizes the soil and prevents weeds from growing.

  4. Pour 2 inches of gravel into the hole, then rake the gravel smooth and tamp it.

  5. Lay rebar on top of the gravel to provide reinforcement for the concrete. Place the rebar in a grid, with the bars placed one foot apart from each other.

  6. Build a wooden frame around the edge of the hole by hammering wooden stakes into the ground every 3 feet around the hole and nailing two-by-fours to them along the inner edge.

  7. Place an expansion strip next to the house's foundation. This allows the foundation and slab for the lean-to to expand and contract.

  8. Mix concrete, following the manufacturer's instructions, and fill the hole.

  9. Smooth the surface of the concrete by dragging a two-by-four across the top of the wooden frame. Allow the concrete to cure for at least four to five days, then remove the wooden form.

Building the Shed

  1. Measure and cut four pressure-treated two-by-fours to be the sill plates. These boards connect the wall framing to the concrete slab. Cut the two side boards to a length of 41 inches, and the front and back boards to a length of 72 inches.

  2. Place the back sill plate onto the slab against the side of the house, centering it so that there are 3 inches of slab on each side of the sill plate. Drive masonry screws through the sill plate and into the slab every 6 inches with a hammer drill. Place the side plates onto the slab, aligning the outer edges with the outer edge of the back plate, and attach them with masonry screws. Install the front plate against the side plates, using the same process.

  3. Cut the top and bottom plates for the front wall of the shed from untreated lumber. The top plate is 6 feet long, and the two bottom plates are each 1 foot long.

  4. Cut four wall studs for the front wall that are 81-1/4 inches long, and two jack studs that are 71-1/2 inches long. Place the jack studs on the sides of the door frame to provide added strength to the frame.

  5. Nail a wall stud into each end of the bottom plates to form a frame that looks like the letter "U." Lay one of the frames flat on the ground, then line up the edge of the top plate with the outer stud, and drive two nails into each stud through the top plate. Repeat this on the other side.

  6. Cut the lumber for the back wall frame from two-by-fours. Cut a top and bottom plate that are each 6 feet long, and four wall studs that are 8 feet high. Make a miter cut along the top of the wall studs at an 18-degree angle to provide for the slope of the roof. Nail the studs into the bottom plate 18 inches on center, then nail the top plate to the tops of the studs. When you're nailing the studs into the bottom plate, use the straight, unmitered edge, and make sure the cuts on the top of the studs are all going in the same direction.

  7. Nail half-inch plywood or oriented-strand board to the back of the back wall frame. Cut the sheathing so that it's about 3-1/2 inches higher than the framing to accommodate the width of the roof rafters. Stagger the boards so there is no point where the corners of four boards come together.

  8. Cut top and bottom plates for the side walls that are 41 inches long, and three studs for each side of the shed that are 8 feet long. Nail the studs into the bottom plates, keeping them 16 inches apart. Do not nail the top plate to the side walls yet.

  9. Raise each wall frame onto its corresponding sill plate, and nail it to the sill plates every 6 inches in a zigzag pattern. When installing the back wall frame, position it so that the top plate slopes down toward the front wall. Nail the end studs of each adjoining wall together to strengthen the shed.

  10. Tack a string to the outer edge of the top plate on the back wall frame. Run the string down to the back corner of the top plate for the front wall, and tack it tautly to the top plate. Trace the string line onto the studs on the side walls. This shows you where to cut the studs so that the roof can slope down to the front of the shed. Repeat this step on the other side wall.

  11. Nail the jack studs to the end studs that make up the door frame.

  12. Cut two 4-foot long two-by-four boards, then stack them on top of each other and nail them together. This is the header for the door frame. Place it on top of the jack studs, and nail the header boards into the end studs along the door frame.

  13. Create a template board for the roof rafters. Cut a two-by-four board that is 51 inches long, then make a 72-degree miter cut on one edge of the board. Hold the board on the outer edge of one of the side walls, with the mitered edge lined up with the sheathing that rises above the back wall. Trace the edge of the front wall onto the rafter, then cut the board along the lines you traced.

  14. Cut five rafters for the roof, using the template as a guide. Nail the rafters to the top of the walls by driving the nails through the bottom edge of the top plates and into the rafters. Space the rafters evenly across the roof, keeping them no more than 16 inches apart.

  15. Cut a 6-foot long two-by-four board and nail it to the front edges of the rafters. This is the fascia board.

  16. Nail half-inch plywood sheathing or oriented-strand board to the outer frame of the shed, covering the walls and roof.

  17. Cover the sheathing on the walls and roof with 30-pound roofing felt. Start at the bottom of the walls and roof, and staple the felt to the sheathing every 6 inches with a hammer stapler. Overlap the edges of the paper by 1 inch.

  18. Finish the side and front walls of the shed with the material of your choice. Options include siding and wood. Prime and paint the fascia board.

  19. Install the shingles onto the roof. Begin at the bottom of the roof, and work toward the top. Stagger the shingles in each row so that the joints overlap.

  20. Cut strips of rolled fiberglass insulation to fit in between the wall studs and rafters. Place the insulation in position with the paper or foil facing inward, and staples the edge of the foil or paper to the wood. The insulation helps prevent the water heater from freezing.

  21. Install the doors onto the shed.