Flat roof storage sheds are the most common type of storage sheds. The construction is not difficult. Before you begin, you need to have a plan, whether you purchase a blueprint or design the shed yourself. Consider the items you will store in the structure, to ensure you build a shed that fits your needs. Before you start the project, become familiar with local building codes that apply to exterior structures. You may need to obtain a building permit before you start construction.
Carefully consider the site to place the shed. Do not locate the shed in a low-lying area. Position the shed away from frequent water runoff. Trees, brush and shrubbery should be no closer than 3 feet from the perimeter of the shed. Position the shed so it receives natural sunlight and wind, to facilitate natural drying and circulation.
Sheds of 200 square feet or more usually require a permanent foundation. While constructing the foundation, remove soil at least 4 inches deep and install gravel. Gravel will not only give you a level and solid service for the foundation, but will also ensure there is proper drainage. Use solid concrete blocks to form the foundation of the shed. Do not use hollow concrete blocks, so you reduce the likelihood that you will have to replace damaged blocks at some point. Treated timbers are also an option for the foundation, since the timbers are resistant to decay and rot.
Construct the shed floor with 2-by-6 pressure-treated boards or a sill around the perimeter of the foundation. Anchor the sill to the foundation with lag bolts. The sill should be at least six inches to protect against moisture penetration. When you install the band joist, use 2-by-8 decay-resistant lumber, and make sure the outer edge of the band joist is flush with the outside edges of the sill. The band joist is necessary for securing the floor joists. Typically, joists are placed 16 or 24 inches on centre. Check local building codes for guidance. Install 3/4-inch pressure-treated plywood for the flooring. If you desire a stronger floor, use tongue-in-groove plywood.
Walls, Windows and Doors
Frame the walls, constructing rough openings for the windows and doors. You can use 2-by-4 or 2-by-6 boards for the studs. Cover the exterior walls with one-half plywood sheathing. When positioning the door, make sure it will allow easy access to each part of the shed. Double check the measurements for the door to be sure you can get large objects through, such as a riding lawnmower, once the door is installed.
A flat shed roof has a slope of 0 to 10 per cent. This is the easiest type of roof construction, and is simply a matter of installing roof rafters with the proper slope. Once the roof rafters are in place, apply sheathing and then add the roofing materials.
The finishing materials you choose need to be selected with durability and low maintenance in mind. For example, vinyl or aluminium siding may not be the best choice for the exterior cladding, because it is more easily damaged or "dinged." Use a durable alternative, such as fibre-cement siding. Install fibreglass doors and aluminium or vinyl windows.