Placing fasteners in ledgers and the 2021 International Residential Code

hello and welcome to building codes for building decks ledgers and lateral loads in this session we're going to continue talking about ledger attachment but we're going to get specific to the ledger fastener locations we'll start by looking at this section here that outlines the requirements for the ledger to band joist connection and the first requirement is that the fasteners be either hot dipped galvanized or stainless steel that's easy and from here it's going to get a little bit messier it also references a table with fastener distance limitations and a figure depicting more different limitations and there's a second figure as well that shows it to us from the side just to help you realize how complicated this is now i'm not saying this lightly this is the most unusable and infeasible prescriptive design code ever published i'm going to do my best to explain this to you while also hoping you understand why i'm saying these ugly words let's start with the first table that it references and everything in these graphics that looks like wood that's going to be the house framing so we see a band joist here on a double top plate with a three-quarter inch subfloor i'm going to use this green square with an orange outline as the ledger and it's transparent so that we can combine the various placement limitations of the band joist with the ledger and the goal here is we want to see how far below the floor we can attach this ledger a lot of regions with snow it's common to design a step down and the step down also helps to properly flash a counter flash above the ledger and also be able to properly seal the door threshold so we'll do the easy stuff first for both the ledger and the band joist fasteners have to be at least two inches away from any end or from both sides of the end to end break it's going to get a little complicated as we carry on so i'm using solid orange for the areas you cannot place a fastener in the ledger and solid red where you can't place it and the band joist now there also must be a fastener within five inches of each end of a ledger or both sides of a break all right let's move on now to the top and bottom edges there are no fasteners permitted in the top three quarter inches of the band joist or the bottom two inches so i've got those marked out in red no fasteners now let's bring the ledger in and it's the same except it flips two inches at the top and three quarter at the bottom when you see the puke green color this is the area left where fasteners can be placed now the fasteners also have to be staggered they're staggered up and down across the ledger according to the minimum horizontal distance required from the design table i presented in the previous session but there are limits to the vertical height of this stagger the stagger between the lower and upper fastener can be no less than one and five-eighths inch vertical distance and no more than five inches between them all right that's it we're done with this table now we've got to add all of this to it so there's a minimum allowable distance from the bottom fastener to the top of the ledger and it's different for each of the three different ledger sizes recognized in the irc it's seven and a half inches on a two by twelve six and a half inches on a two by ten and five and a half inches on a two by eight though there's an exception for that one we're going to get to a little later so we're going to shade this in with orange because this means now that the lower fastener cannot be in these orange ledger areas and that's going to affect the vertical height of this ledger compared to the band joist now i've made this drawing as close to scale as i could and what it's showing is a 2x8 band joist let's get rid of the interior floor sheathing and will also not show any decking on the ledgers this just to make it easier and compare simply the ledger to the band joist now if we overlay those three ledgers like this we can see that we've reduced a bit of our of our puke green area but we'd also have to obviously lower them because they're higher than the floor but we can't do that yet because we've got to put in the previous area for no fasteners on the band joist and you can see here we have a problem our green area is getting rather small and we've lost it completely on the 2x8 and that's where the exception comes in the exception allows a minimum distance to be reduced from five and a half inches to four and a half inches but only when a two by eight ledger is on a two by eight band joist okay but we still need to now bring these ledgers down as much as we can and we can see that we don't have a lot of room to do so so what we're going to do is lower the ledger so that the lower fastener can't go any lower on the band joist because of the red but it also can't go any higher on the ledger because of the orange and what we're going to find is that a 2 by 12 and a 2 by 10 ledger over the top of a two by eight band joist well it's gonna be above the two by eight band joist and you may have a tough time with the door coming out of the house to that deck if we take this same math now and we comply it to apply it to a 2 by 10 band joist it's going to look like this and we see that that 2 by 12 ledger still is not going to work here and so much for talking about a step down at this point right finally if we look at a 2 by 12 band joist we actually get options for all three ledger sizes however the largest step down that we can come up with using the irc prescriptive design tables is a three and three quarter inch step which ironically is just a quarter inch less than the minimum height step still considered safe for the public in the international building code psi now we've got to dig into the last figure because it gets more complicated no i'm just kidding this figure is just an elevation view of the same things we've already talked about but i want you to imagine trying to figure out all these parameters between outside on the ledger and inside and the band joists and do this in the backyard of a real house and not on a computer then consider the few ledger to banjoy's combinations that would be even below the interior floor and i'm hoping you may understand now my previous bold comment just a little bit better my name is glenn mathewson thanks for learning with me this course has been provided to you by buildingcodecollege.com where we go beyond the words

Channel: Glenn Mathewson

Views: 676

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Id: 4P5sJUKH2L0

Length: 7min 41sec (461 seconds)

Published: Sat Feb 13 2021