We are planing a roof opening to access our roof top deck.

We were advised to use 3 ply LVL 1 3/4 x 11 7/8 beams.

Can we replace this with something shorter and wider (like 4 ply LVL 7 1/4) in order to reduce the overall height ?

closed as off-topic by isherwood, The Evil Greebo, Machavity, ThreePhaseEel, Tyson Jun 6 '18 at 23:50

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  • 2
    Probably not unless you go with steel. Height is critical, and 7" is just too short for your span if it calls for a tripled 12". Cutting height by almost half would call for more than doubling width, and that's a very non-standard arrangement. That said, we're not the place to ask. You need an engineer's signature. VTC. – isherwood Jun 6 '18 at 14:03

Probably not. Height adds much more strength than width does. A beam that is 1 3/4 x 11 7/8 has an I of 975 [I = (b*h^3)/3]. A 7 1/4" tall beam would need to be ~7 3/4" wide to provide roughly the same capacity (as @isherwood said, WE ARE NOT PROFESSIONAL ENGINEERS). This seems that it would be more inconvenient to your design.

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