NEW 2021 International Residential Codes for Guard Construction.

all right so here we go here's the section then brand new one for deck guards and there are four sub-sections to this but i want to start on the very last one because it's a pretty important one it makes it very clear that this section is not trying to demand that all americans live under one design of guard other gaza guards are absolutely welcome if they can prove that they do the job and that'd be by following the manufacturer's installation instructions part of the approval of the guard system or through following accepted engineering practices all right now we can also knock out the third subsection there because it just points us right back here to this section on plastic composites just like we talked about for decking guard and handrails made out of plastic composites astm d7032 and what installed per manufacturer's installation instructions all right so let's dig in now to the first subsection about supporting deck guards and it says that these need to be supported when they're connected to the side of the or to a deck supported in a way that it transfers the loads into the framing into the deck joists so let's look at this kind of typical guard post a load is placed here outward at the top and that load becomes a whole lot greater right here at the point of resistance because of this leverage but it can't just be resisted by one single member of the deck on the outside the loads got to be connected and transferred somehow back into the entire horizontal floor assembly now in recent years you will find all over the internet and for manufacturers plenty of great guidance for some awesome products for guard post installations that can resist a 500 pound load applied at the top of the guard and though these details and products and guidance definitely meet code when installed as directed a lot of folks wonder why the target load is 500 pounds when the code talks about 200 well guards have been evaluated for their strength and their ability to resist this load for pretty much all of time with with just a test at final inspection a little push on the guard but if you wanted a more formal path for verifying guard live load resistance you would go to ibc chapter 17 for testing and there's a section there that's quite applicable to this discussion we're having it says and i'll read it where there is a reasonable doubt as to the stability or load-bearing capacity of a completed building structure or portion thereof for the expected loads an engineering assessment shall be required now when you dig further into this section the chapter goes on to provide a method for in-situ testing of a guard once it's built on site and this is like what we've been doing for all of time but not according to this protocol and then you have another method of test procedures for approving an assembly and for proving its capability prior to real construction like a laboratory research and both of these reference a 2.5 times safety factor and that's how 200 pounds because becomes 500 pounds when you're legitimately testing a guard so the connection itself though is actually taking more than 500 pounds so if you just did some basic rounding for ease the leverage of this post height compared to the distance between the fasteners and the leverage and the resistance well a 500 pound load comes out to be more like a 2000 pound load at this connection wow but remember this is simulating a guard assembly that is comprised of nothing but unconnected 4x4 posts or posts each having to resist this 500 pound load completely on their own and that's a bit of an unusual guard assembly remember a guard is an assembly of components not just a post now compare that to this post on this card an outward load here is going to be pretty quickly resisted right in line with that load not down at the connection of the post and it's going to push these top caps outward now i built this deck 20 something years ago and happen to know that post is sitting on nothing but a basic post cap on that concrete slab and it was rock solid so what we the message there is that the rest of the guard system beyond the post and how it's built and designed is part of the load resistance even every turn and corner in the top cap of a guard when constructed well can provide resistance to this outward load a lot of guards are built maybe with a flat two by four two by six top cap that extends over the post so a concentrated low load that happened to land right on this post is actually distributed across this 2x6 to a few other connection points now that's different than when we look at these posts where they run through the top of the guard and these posts don't get much help at all from the guard assembly or the shape or turns in the guard i'd have some concerns and real careful look at how these are connected so with the variety of guards and variety of deck shape i personally don't think it's appropriate to assign a blanket 500 pound load expectation to every post again a guard's a system not a post the overall shape of the guard top cap and the strength of the shapes that it creates in its different angles remember it's not all about posts they might be six feet apart from each other this loads got to re-resist it all the way along the top cap so at first likely is going to hit the guard so how's that connected to those posts because that's pretty critical we can't just look at the post connection like i said how close are those posts how many of them are sharing this load with a continuous top cap does that make a difference or do the posts come up through the middle and we don't get this horizontal beam effect always pay close attention to these middle posts especially in long straight runs so this section addresses the common connection now of a post to the side of a joist or beam and it's trying to give some guidance on how to do this without giving a specific design and again it starts out by referring to this connection having to transfer the loads into other parts into the adjacent joists and then it goes on to talk about preventing rotation of the joist or beam that it's connected to so now we have a little bit of a performance described that we need to expect and this can help us in evaluating these guard connections now next it says that you can't rely only on an end grain connection of lumber so that's now we have an outright prohibition to work with all right so let's go back to looking at this guard and let's think about the forces and its resistance the force at the top of the post is translated right here into this connection and it becomes a lot more right now this is resisted directly in line with it via the connection and transmitting it back into the floor structure but this load at the top and that connection there in the midpoint at the top of the deck well that creates a rotation that now is going to be putting a load pushing in at the bottom of the deck down here so where's its resistance so let's look at this one here's a post mounted to a side joist the outward load on the guard creates an inward load on this bottom portion of the post and with nothing to resist that you'd get rotation which was a performance specifically prohibited to prohibit the rotation of the beam or joist is what the new code language tells us so here was an attempt to correct this now understand this was long before the 2021 provisions were talking about were published so what this builder did was they added a 2x4 to the bottom and this is an attempt to resist that inward rotation now the fasteners aren't in end grain here though i might have preferred blocking who's to say is this sufficient or not though we would probably want to be there to do that old-fashioned push on the guard i hate to say it now what about this top connection is there a continuous load path for the outward force here that translates or that connects back to the adjacent joists well i think we now see a problem the 2021 irc is specifically addressing so considering the guard design variables and this new section for support at the side of framing let's look at some pictures of some connections just to get us thinking now we don't have all the details of these guard assemblies as a whole in their entire load paths so i'm not necessarily endorsing or condemning any of these i just want to talk about them a bit so here's an interesting one the tension at the top fastener from the outward load well it's attempting to be addressed in this bolt and all thread rod tying it back to a block right further into the floor framing and we have compression along the bottom resisted by these two adjacent joists they're not directly behind the beam but i think they're probably doing pretty good to keep that beam from rotating however these this rod it would be pulling on this block which is only relying on fasteners wear in the end grain so we get these angle brackets installed on the side that the tension would be pulling towards and now i don't know what loads are here i don't know what's being resisted but i know that now it's not only fasteners and ingrained and this is what the 2021 irc is trying to get folks to do to think through this process and to do something better than we've been doing so let's look at this one we've got blocking all around the post that looks good it's a good way to tie the load back into the adjacent joists have we satisfied the not using only fasteners in to the end grain of a cut maybe not these are some other examples of blocking and blocking is incredibly useful at the side joist condition to stop that compression at the bottom and keep the rotation but we of course need the tension at the top so there's some bolts in the right side picture that's a good choice but does this satisfy all those things that we just talked about now this one's interesting they've blocked down this whole edge lots of blocks i love it that's probably there to support a picture frame design in the framing but do we have the status have we satisfied the only fasteners in ingrain requirement here we've got bolts right another stout connection all the way through the 4x4 but these bolts only connect that 4x4 to that one member and then beyond that we've got to get the load path to the other joists and is that just nails in the end grain now this one's a similar one but look at the difference the bolt catches the block and now ties the bolting with the block to the joists but still maybe some things to consider here's another one this is an interesting totally different hardware design it's not using the typical hold downs but the block provides compression at the bottom the two brackets the one wraps around the outside there's no in it fasteners and in joist this looks rather stout now this one is one mounted on the outside and that drastically changes the load distribution because you're no longer able to utilize that outer rim board to kind of spread that load around this one's also installed with very narrow head timber screws that have very little surface area like a washer to stop that post from pulling through i might have some questions here and this guys this post is notched and just screwed on with some typical gold coated gold colored looking screws not even corrosion resistant now i'll tell you this picture's over 20 years old and this is what we're trying to prohibit in the irc 2021 we're not trying to provide one exact way you build guards and you're guaranteed everything's great free america is not ready for that we're looking at trying to get people thinking about the load path into the structure and eliminate these notoriously insufficient connections like this one a hollow composite post with some random structural screws through with no connection to anything else or this example that i don't even know what to say we have been building some very scary guard post connections all across this country and that's really what the 2021 is after so just keep that perspective as you apply these new provisions now stairs stairs are incredibly difficult to create this stout guard post connection and in this example you can see they've used hold downs in the top fastener for that tension and they've tied it with the risers and blocking back to the center stringer again tying it into other framing in this case not joists in a deck but the structure of the stairs and then the blocks at the bottom are providing the compression resistance of that bottom part of the post pushing in the real concern here is just simply the lateral bracing of the whole stair and will this not just sway back and forth when the guards are loaded the bottom of stairs are also incredibly tricky because the riser height is limited the riser height down here limits the fasteners and how far apart they can be and often you will find guards at the bottom of stairs like this getting sunk into concrete foundations to help support those loads kind of like a fence so that's another effective way to resist this remember these design methods are not part of the code simply what the code is trying to achieve okay next we're going to talk about this section and this is about guards posts that are supported on top of the deck framing and it requires essentially all of the same fundamentals we discussed but this is also a heavily manufactured product you're not just connecting a 4x4 piece of wood down to some more wood without some product so these also have got to be installed according to the manufacturer's installation instructions but the important note the code is getting here is that you can't just connect to decking you need some other blocking and framing members in here that are going to transfer that load into the whole floor system you've got to understand a surface-mounted connection like this when you have a horizontal load at 36 inches high resisted in this tiny little distance between these fasteners you have an incredible uplift force that's created and finally we have this part about 4x4 posts for guards the long common but very questionable practice of notching four by fours at the connection point to the deck well research has shown that the majority of these notch posts the way they've been done with four by fours are generally going to be insufficient to handle these loads and so the 2021 does now outright prohibit it now as far as how you verify hand rail loads because i'm moving off of guards these have to require 200 pounds in any direction and we don't have a point in the irc where we've got guidance for this yet it's going to be up to you i mean unless of course that handrail is built into a guard right then all of those guard connections that we just talked about if that's the load path from the handrail to the earth well those are still going to apply now there's a lot more to talk about in overall guard discussion remember the code's just addressing the posts which might be six feet apart at this point but this is a strictly code based course so we're gonna go ahead and move on

Channel: Glenn Mathewson

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Length: 17min 18sec (1038 seconds)

Published: Tue Jul 13 2021