Things You'll Need
Large micro-lam beam sufficient for the span
4-inch by 6-inch posts
*opt. 4-inch-by-12-inch posts
2-inch-by-6-inch joist boards
*opt. 2-inch-by-4-inch stud boards
¾- to 1-inch heavy-duty plywood sheets
2- to 3-inch screws for brackets
2 to 4 ladders
Gloves, boots, eye protection
A garage loft is a shelf that runs the width or depth of a garage and is supported at the outside walls by in-the-wall support posts. This type of loft is used for long-term storage that is easy to access but is above head height. If properly designed, this type of shelf can carry the load of a floor in a two-story home, allowing for the storage of heavier pieces. To create a garage loft it is helpful to have a nonstandard-height garage ceiling; otherwise the lowered height of the loft may interfere with headroom in the garage. This is heavy work and can take several days. The result is a nice garage loft that will hold belongings comfortably without risk of sag or collapse.
Measure from the corner of the back wall (of the proposed loft area) 4 feet and mark the wall on both sides. This is the outside dimension of the sheet of plywood, and there is less waste if the sheet is used intact.
If the garage walls are finished, open the side wall cavities from the 4-foot mark toward the back wall. The opening should be at least 1 foot wide (or until a stud is exposed) and it should run from the floor to the ceiling. Inside the wall cavity, the support post and the micro-laminate beam will be positioned so that the wall (if it is Sheetrock) can be resurfaced after the project is complete.
Find a stud in the wall cavity that the new post material will mount against for additional support. It is unlikely that both outside walls will have studs in the same position, so add additional studs as necessary to match the same measurement from the back wall along each side wall. You want your spanning beam to be parallel with the back wall.
Measure from the garage floor up. There are two choices: headroom can be measured from the lowest point (the bottom of the beam) or from the joist hanger (approximately 6 inches from the top of the beam). Depending on the use under the loft, the lower beam measurement may be OK if the space below is used for a workbench where headroom is not an issue. Otherwise, opt for full headroom under the bottom of the beam. Mark the studs next to where the posts will be installed.
Measure the width of the garage, including the cavity space into each side wall. This is the length of micro-laminate beam that needs to be ordered. The beam should be approximately 1 inch narrower than the full width. This will allow for maneuvering of the beam into the cavities.
Order the micro-laminate beam from the local lumberyard by telling the lumberyard the width of the span being covered. Staff will calculate the size of the beam and will also cut it for you, so be certain of your width measurements, as these beams are expensive and heavy. The lumberyard can often deliver the beam to the garage for you.
Measure and mark the side wall studs the height of the micro-laminate beam. This top mark represents the top of the joists using joist hangers.
Use a stud finder (for finished walls) to find the studs in the back wall, and mount a 2-by-6 ledger board the full width of the garage with the top of the ledge, matching the measurement of the proposed top of the micro-laminate beam.
Cut the support posts and nail the posts to the adjacent studs in the side walls. These posts should be the correct height for the bottom of the micro-laminate beam so that when the beam is lifted into position it will rest on the support posts while it is blocked and nailed into place.
Lift and install the micro-laminate beam with the help of several friends and several ladders. These beams are very heavy and they will be lifted above your head height, so many helping hands are necessary. Rest the beam on the posts already in place. Immediately brace, block and nail the beam into position. You can accomplish this by installing a stud next to the post and beam so that the beam is sandwiched between two studs, or you can block the beam in using scrap pieces of 2-by-4 boards nailed into position.
Use joist hangers from the top of the micro-laminate beam to the top of the ledger on the back wall, and hang joists at 24 inches on center. Screw the joist hangers and joists into position.
Lay the sheet of plywood across the joists and screw or nail the plywood into position, trimming as necessary. The plywood can overhang the beam by several inches without any problem.
Have everything ready before the beam is lifted so that it can be immediately lowered onto the waiting posts.