How to Install a Flitch Plate by: Editor - Rich Bergman
A flitch plate is merely a flat piece of steel that runs the length of a beam and is sandwiched in between two or more wood beams.
You really should find some engineering tables which are available on the web to give you a good idea of the strength you can achieve by combining various thicknesses and widths and lengths of flitch plates with corresponding wood beams.
The flitch plate would allow you theoretically to take 2 2x10 beams and increase its strength equivalent to maybe 3 2x10s or even 4 2x10s. The engineering tables will tell you the exact strength of your chosen combination.
Now, you have 3 2x10s which is a bit problematic. Normally the flitch plate goes in the middle, between an equal number of wood beams on either side of the flitch plate. So with two or four beams you would install the plate in the middle.
With three beams you will either have to remove one beam, install the plate, then reinstall the other beam and perhaps add one more to balance it out.
But depending on the thickness of the plate you may only need to have 2 2x10s and the plate in the middle to span the distance you wish thus eliminating a middle supporting 6x6 column.
Its impossible for me to tell you the exact engineering because I am not an engineer, just a guy who has swung a hammer for many years. But I think this should give you the basic concept relative to your situation.
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