I'm in the process of levelling my deck. Top down diagram below, showing decking perimeter (black), beams (blue) and posts/footings (red).
Because of the irregular shape posts 1 and 3 are only 20" apart. I found in the process of levelling that beam 1-2 is nearly redundant under normal conditions. The joists above the beam can hold up beam 1-2 at post 1 if post 1 is removed without wincing.
The question is, how do I ensure that all of the posts are sharing the load evenly when I remove the temporary levelling supports, especially posts 1 and 3? It seems like it quite be easy to arrive in some position where one of these posts looks like it's doing something but actually just floating (since the deck can carry beam 1-2 without help). I will likely have to shim the posts because balancing this by cutting would need too much precision. I could shim the posts, but how do I ensure that the weight is roughly balanced as opposed to just tight enough to squeeze the shims a little?
Best Answer
The idea would be to just adjust all the posts so that they are tight and snug the same amount under the deck joists when the deck dead weight is resting on them. The carrying ability of the posts and beams will come into consideration when later you place a live load on the deck and the joists flex some in response. Keep in mind that just because it appears that beam 1-2 is redundant only gives testament to the fact that there is design margin at play.
Note that the beam 1-2 was clearly installed there because it was needed to deal with the joist span from the ledger to the 1-2 beam. If there had not been a 1-2 beam then the joists would have had to be engineered to carry the load for the longest span from the ledger to 1-3. That may have increased the joist height and cost a fair amount.