First, I’m using the 4″x12″x8′ lvl stringer in a set to run into a landing on a left hand timber staircase. does anyone think a flitch plate sistered to the stringer is a good idea? My experience includes removing the original cracked/sagging 2×12 stringers and I want something strong enough to pass time as well as code. Note: treads are 4×12 open rise.

Second, if the landing is 2×6 framed, is a second 2×6 below enough to support the weight or is sistering necessary.

thanks!

edit: my local Greenfield engineer said 1/2 in hardwood plywood between 2x 2x12s makes a full flitch. To finish, cladding it with finished hardwood it will be stronger and look better than timber.