During your home's construction, your contractor may have installed trusses to frame the roof. These roof trusses, which are custom-engineered to fit your house's design, do not allow you to vault a ceiling or finish out attic space. During a remodel, you may choose to replace some of the roof trusses with stick framing, opening up the space for a loft or additional living space. Because replacing roof trusses means you are altering the load-bearing structure of your house, a structural engineer must design the new plans.
Hire an engineer to re-design your roof's load-bearing structure before removing any trusses. A roof truss bears the weight of roof roof and transfers that weight to the sidewalls of your home. Before you can cut away any of the trusses, alternate load-bearing measures must be in place.
Run a support header beneath the ridge of your roof, spanning the length of your roof. Support headers may be steel I-beams or dimensional wood timbers. Your engineer will determine what type of header is necessary based upon the distance of your roof span and the configuration of your roof.
Plan to construct support walls or beams. Once you cut the roof trusses, the weight of the roof will shift to the new supports. Each end of the ridge header must rest upon a support that runs all the way down to the concrete footer beneath your foundation. You may need additional supports in the center of the house. You may disguise the new supports within walls.
Reinforce the roof rafters. This may involve running additional rafters from the new support header to the sidewalls. This step is important because the lumber used to support the roof decking and the shingles is part of each roof truss section. When parts of the trusses are gone, the truss rafters will lose some of their ability to support the sides of the roof.
Cut and remove the trusses after the new support system is in place. Now you may remove the original trusses and open up the attic space. If you're planning to use the attic for living space, install stronger floor joists than those used in the original roof trusses.