Buelligan said:
I did address it on the plans. I asked for rail post blocking or support details! The response and correction I got was "he has been building decks for 20 years, he knows what they need". so she wrote the statement on the plans "rail posts will be blocked" and that's it. SO I said fine I will accept this but will fail it at inspection if it is not correct. I had that conversation with him when he came in after the second failure. He said it was up to me to tell him what "I wanted" and my response was that" you stated you would block posts to code and it is up to you to provide me with details of how you will accomplish that. I cannot design it for you. Next time provide me with actual detailed plans and I will let you know if it is acceptable. This is why I prefer not to accept just a statement." Didn't want to argue with 20 years of experience.
As always late to the party,
As pointed out by some, there is no defelection limit on guards, however the criteria mainly used is that the guards deflection is required to stop without the guards height descending down below the required minimum height, Model IRC code, 36".
The main thing everyone forgets is that guards are not required to have posts, nor their single attachment required to resist 500 or even 200 lb's, the top of the guard system at any point is required to resist a 200 lb point load.
The blocking, and all the bracket mumbo jumbo is not the correct way or only way, just a tested method. The testing done was limited to non-real life construction, you are missing the guard, and the full construction of the deck, ie flooring and therefore testing a single part and they come to the deduction, well this is the method we suggest.
As to lags vrs bolts, pretty much all the screw manufactures state and engineers concur, that a minimum of 3" of solid wood is required for a lag to hold loads, thus in order to use the lags, they would need a double rim board.
Also, if they installed a double rim board had every balusters 1.5" square, double lagged to the rim board, installed a 2x4 sub-rail and a 5/4 x 6 top board, all screwed together and then tested for the 200 lb point load at the top, the deflection would be very little and and the guard system would pass and there would be no posts.
The issue here was you felt the guard moved to much and therefore felt unsafe, you failed it and requested it be fixed or proof it met compliance, they had the options, from what I am reading you provided a direction by supplying DCA6, last time I checked DCA6 was not an ICC code, just an AWS pamphlet unless a local AHJ adoptedit, I venture a guess that you noted, well I am not sure how you built this one, but it does not feel safe, it seems to move more than I feel is safe without confirmation from an engineer, but if you follow these pages and diagrams, I know decks built like this in the past, don't seem to move like that.
They might have 20 years, but lots of things change as you noted, DCA6 is not 20 years old I believe, but back to design options, mounting guards to construction structure is and has always been a concern to many and then not to others, NYC is currently requiring all buildings with it's limits to complete facade inspections and bring all the exterior structure and guards up to code compliance, as they have found many of them in place don't comply and or are unsafe.
I guess I went off topic a bit, but I always get a bit of a hair raising when people talk about guard structure and loads and focus on a single post and not the entire system. I also get a bit off kilter with noting code requires blocking, as there is nothing in the IRC code prior to 2015, and in the new section 507 exterior decks, section 507 it just notes to stop lateral resistance in R507.5.1, it does not say you need to use blocking, only stop the rotation, and if blocking is used then.
However, deflection is measured with engineering testing standards and thus as an inspector, if you fail a guard for deflection, are you not moving this in to an engineers corner period?
For don't you need confirmation, your feel test does not verify it does or does not comply, just notes a flag, if an engineer can validate it complies or it does not comply the question becomes after all my ramblings, if as an inspector you fail a guard for deflection without preforming the proper testing method, how can you then approved your failure flag without a proper engineer sign off or engineers inspection report?
Your failure was a guess, as is your approval now?
Once you fail a project for a structure issue that can only be verified by an engineer, how does one approve and pass that item without an engineers report it complies?
That is my question?
Tom
