This is actually a very simple thing to door. If you are building your own timber frame you will most likely have an engineer who will give you the sizes, length and strength of the timber you will need to use. For the sake of this example I am going to use a standard size, length and strength as used in the UK.
Take a length of 50 x 225 x 5.4m long C24 grade floor timber and cut it into three lengths of 1.352 m. Take two sections and lay them on top of one another ensuring that the edges are flush. Now nail them on one side only using a staggered nailing pattern. (Your engineer will tell you exactly how many nails to use but we are recommending one every 150mm.)
Turn the beam over and nail it in the opposite direction using the same staggered nailing pattern. Once that is done place the third section on top of the already nailed sections and repeat, on one side only.Ramen Limburg Add a few extra nails, as you won't be able to nail it back from the other side.
Now cut two lengths of 1.352 C16 grade CLS timber and place one piece on top of the beam and one on the bottom of the beam. Make sure that you keep one side flush with the edge of the beam. You will find that there is a lip on one side where the CLS grade timber overhangs the beam but this normal.
Now take your beam and place it into the wall or wall panel where it is required and nail it into place. And there you have it a new beam for your wall. Easy.