This is incorrect, or at least conditional. If the built up elements are not connected to each other with a proper nailing schedule, they can warp independently of each other and one may take all the actual load.
A single 4x6 will rot from the outside, and can be painted and inspected from the outside. An assemblage of 2x lumber lets water run down between them, and cannot be painted or inspected. It can literally rot from the inside out. A 4x6 post can rot from the ends in, but that’s completely different.
What the American Wood Council has to say on this is:
Built-up Columns with Mechanical Fastenings
Arrangement of laminations joined by nails, bolts or other mechanical fastenings into a built-up column assembly will not make a column fully equal in strength to a one-piece member of comparable material and dimensions. The following provisions apply to nailed or bolted built-up columns with 2 to 5 laminations… The column stability factor, C, shall be modified (multiplied) by 0.60 for built-up columns nailed in accordance with NDS section 15.3.3 or by 0.75 for built-up columns bolted in accordance with NDS section 15.3.4
(Source Wood Structural Design Data - American Wood Council AWC Wood Structural Design Data WSDD, 1992 Revision.)
So @jjonas if you enjoy insulting and belittling on this forum, I suppose that’s your role. If not then please make a deposit in this bin:
And let others weigh in on the differences between built up and single columns in this application, and what the downsides may be. The deck was modern built – I was told the date but forgot – and clearly without permits. It is however solid and not immediately unsound.
It’s clear to me that some through lag bolts and a flashing would greatly improve this design. But that’s well beyond my role as an inspector, and specifying such a solution would shift liability. I wish to describe the situation instead.
The post is three 2x4’s, flanked by two 2x6’s with nails and no lag bolts. The built up members were not painted or glued prior to assembly, and there’s no flashing on top. The deck has many other differences from a code compliant view.
Likely no action will ever be taken to “fix” this, so I need to write appropriately to educate all parties involved, and protect myself.
Additional photos at [https://photos.app.goo.gl/caP1U4Q7xMacd9M68](Photo Album)