Expert: Bruce E. Johnson - 3/1/2010

Question
I am building a coverd patio. It is  10' out and 19' across. I am using 0ne 6x6 post at each outer corner and 4x6 for the timberframe rafters, and beams.( half lapped and Lagged to gether 3 pieces total per rafter). I have put them at 30" OC and I have run a 19' 4x6 to tie the end posts together so they dont spread under the weight of the rafters. I have a 10' span from house to posts and the rafters will be sitting perpendicular to these 2 beams, and they are supported by the posts at each end and brackets off from the house onto an existing huse beam. There are 3 of the rafters sitting on the beam itself and the other 2 are at each end. I want to use only 1 4 x 6 beam for support to allow for head clearance.  Do I need more support than that? If so can I double up the 4x6? making it a 8x6 does that work or must I add a 2x8 or 10 to that 4x6 beam.

Answer
Hi marc, a 4x6 for a 19 foot span is a little puny.  You can, however add a knee brace at each end to cut the span of that 4x6 down. A 45 degree brace that sticks out four feet at the top and down 4 feet at the post will decrease the span of the 4x6 from 19 feet to 11 feet.  I am attaching a drawing.   I hope  this information helps please feel free to write again sincerely bruce e johnson..bejohnsonconsulting.com