Chris is renovating a 120-year-old house and wanted to open up the floor plan. Chris hired PERCH to design a pair of beams that could replace the existing loadbearing walls, spanning the 18-foot room width and picking up the existing floor joists. Chris wanted to procure the beams inexpensively and install them easily, with little or no disruption to the ceiling height.
Right away, using a steel wide-flange or T shape was out. Steel beams are expensive and heavy, and connecting them to the stringers would have required either complex details or temporary removal of the stringers. Ordinary dimensional lumber wasn’t strong enough for such a long span within the confines of the ceiling height, so PERCH looked to laminated veneer lumber (LVLs) for more strength. A pair of 3.5-inch-wide, 9.5-inch-deep LVLs were strong enough to get the job done. Joist hangers allowed the LVLs to share depth with the 2×8 joists, so the lumber only protruded down an inch from the existing finish ceiling.
PERCH also investigated a hybrid solution called a flitch plate: a steel plate sandwiched by two pieces of lumber. In theory the steel increases the assembly’s overall elastic modulus while the lumber keeps the beam light and enables nailed connections. But in the final analysis a flitch plate was too complicated. The beam would need to be assembled first, with through bolts ensuring the wood and steel share loads, and then it would be prohibitively heavy to lift into place.
PERCH developed an installation procedure (which required temporary support of the floor joists) and checked that a column of dimensional lumber built into the existing exterior stud walls would provide sufficient support. Chris followed the procedure and reported that everything went up perfectly.