jar546 said:
This is a monetary issue for contractors which is not a code factor that we are allowed to consider.
I hate to do it...but...
"R101.3 Intent: The purpose of this code is to establish minimum reqirements to safeguard the public safety, health and general welfare through affordability, ...."
Both those terms speak to cost. "Affordability" even gets first billing in the list. Like Brad Pitt or Morgan Freeman would. The best damn code in the world is just ink on paper if no one is willing to follow it. Same goes for any laws of a democracy. They can only go as far as the people will accept.
I don't see the point of using old rotten decks with non-flashed ledgers nailed to cantilevered band joists as a basis for arguing this topic. If I were to judge the performance of a ledger attached according to today's code for ledger attachments (just the fastening table), I would look at a deck built to those standards, like what Dr.'s Bender and Woeste tested. Those code-installed deck ledgers held against loads 4X what humans can create. I would not look to a deck built decades ago to gauge performance of today's ledger connections.
I've also seen roof rafter's rot from poorly flashed chimney sidewalls. I don't use that point to argue that we should have additional rafters in case some rot. I would look at the issue causing such rot...the flashing. If the flashing were to be enhanced in the code (i.e. ledger table that enhanced the ledger connections from that of the past) I wouldn't diminish my opinion of new construction with the new flashing because poorly built jobs of the past rotted the rafters out. Essentially saying this. You shouldn't judge an IRC 09 ledger connection made according to the IRC table based on performance of decks built prior to that table. You should judge the connections in the table on the most current information of how connections according to that table are performing. That would be the research tests I am pointing you to. If you have a case study of a deck built since that new table, without hold downs, and it failed...I would love to learn of it. The current argument, however, would be like using home fire statistics from pre-sprinkler homes, to argue that current sprinkler provisions are not sufficient.
I don't know why you keep mention DP or freestanding. Here's the breakdown.
-The IRC requires all structures (even decks) to resist the loads applicable to them. No snow design in Florida.
-A "permitted" method to resist undefined lateral loads is to slap some metal up there (i.e. the hold down anchors). You should be "less" comfortable with this simply from the knowledge that indeed it's unfounded. Ignorance was bliss kind of thing.
-There is nothing in the IRC that tells you as a building official that the ledger fastening according to the table doesn't resist lateral loads. I hope everyone assumed at least "some" lateral restraint could be generated by the withdrawal resistance of lag screws into the band joist. Try to pull the ledger off laterally with your hands? You can't...because it resists lateral loads. No one questioned the ledger's ability to do that until this lateral detail was presented and the code development committee asked. We finally have the answer.
-Now you have a well-respected research report that tells you the lag screw connection of the ledger according to the IRC table can and does indeed resist lateral loads of 4X what humans can produce. It's a prescriptive connection, and testing shows it performs. What's the problem? As far as being a means to hold a deck to a rotten band joist/ledger, R301 directs us that structures must resist loads as applicable to the design. I know of no direction what-so-ever in the IRC that would allow us to require a structure to resist a "what if" situation where the structure has rotten ten years from now. Perhaps in the property maintenance code? If you want to stop those old, poorly-built decks from falling off homes from decades of rot, encourage a deck inspection and repair program. That would be great! Unnecessarily driving up the cost of a new deck definitely isn't going to help get those old ones replaced (not with a permit at least).
Don't punish new, properly built decks, based on performance of old, rotten, poorly built decks.
Man...careful saying "lateral loads" around me these days. I can't wait until I can summarize these test results and share them with you all. It is eye-opening.