Add Horizontal Blocking for a Scissor Gable Truss

Video Transcript:

 In this video we are going to add horizontal blocking to our scissor gable to better support the fireplace mono trusses from Training Plan 3.

From Layout, let’s click our scissor gable truss, labeled B01-GBL. Using the 3D camera, we'll explore the layout to see what we're dealing with in this scenario.

Because these fireplace mono trusses are tying into the gable, we will add horizontal blocking to serve as nailers.

However, before we can add blocking, we need to identify a few important dimensions.

Click on the Dimensions Bearing Envelopes icon to display bearing dimensions. With the bearing dimensions visible, we can see that the fireplace ties in at 16 feet from the left end of the scissor gable.

The fireplace dimension is 5 feet, so we'll want to place horizontal blocking from 16 feet to 21 feet.

We also need to determine the height to place the blocking. Let’s take a look at one of the fireplace trusses (FO1) to determine the overall height. Double click it from the 3D view, and we can see that the height is a little over one foot - four (inches).

Let’s take a dimension to the bottom of the top chord by right clicking and selecting it from the menu or by clicking the icon for Dimension Mode.

That's at a little over one foot. We will place a two by six block at one foot and see if that does the trick.

Alright, let's get to work on our scissor gable. Expand the left sidebar and click to open our scissor gable truss named B01-GBL.

First thing we will do is click to analyze this truss. We need to identify any overcapacity plate pairs or members.

Looks like this gable stud at the ceiling peak needs adjusted. Let's click on the plate and delete it. We'll make adjustments to the bottom of W23.

Click on W23, and go over to the properties panel to see what is being used as our Bottom Cuts. Scroll down, and we will see the cuts used to trim the bottom.

If we hover over the B4 Port cut in the list, we see this is one of the cuts used to cut the bottom. Let’s delete this cut which should extend the gable block down to B3.

Let’s re-analyze this. By adjusting the end cut we have better grip for this joint. That all looks good.

Next, let's add the horizontal blocking for our fireplace trusses. So, zoom out and pan over to the left, so we can focus on the area between W11 and W14.

We know that our blocking will begin around 16 feet from the left end of the truss.

We can also see that a splice is here at 18 feet. So, we are going to create a member starting to the right side of W11, which should do the trick.

Let's add some blocking.

Right click in the scene, and select member from the list. We will reference the bottom edge of the truss, and then go up one foot, and click to place the member here.

We want this blocking to be above the line, so let's right click, select geometry, and then select above line.

We need to change the blocking to a two by six. To do so, right click, and select edit lumber, then select 2 by 6.

So, before we get too carried away with all of these, let's take a look at our 3D layout to make sure the blocking was placed in the correct spot. And sure enough, it looks good. This will provide ample blocking once we get the remainder of the members added.

Let's go back over to Design mode and we will add the remaining blocking.

Right click, and select member, then select the right side of W12, and then the left side of W13. Right click again select member, click on the right side of W13, and over to the left side of W14. And for the last block, right click select member, click the right of W14, and select the left side of W15. That should be all of the blocking here.

Next, let’s change the blocking to be 2 by sixes.

Press Control, and click to select the 3 members, then right click, and select edit lumber, from the dimensions option we will select 2 by 6.

Before we wrap up this truss design, let's verify that the fireplace mono trusses do not show up as Carried Components which would apply additional load on the gable.

From the right sidebar, access Carried Components.

Here you may see multiple connections for the F01 fireplace mono trusses. If so, right click on the Carried Components menu, and select Delete all Connections.

We can now click to re-analyze this truss to see that everything looks good, and the truss passes checks.

To wrap up this exercise, let's explore the analog by toggling on the Analog Model. The blocking members are defined as Webs, and are therefore included in the Analog model.

For this example, it would be acceptable to change the member types for these blocking members from Webs to Nonstructural Blocks, which removes them from the Analog model.

To demonstrate this, select one of the blocks, and from the Properties panel, change Member Type to Nonstructural Block.

Now, let's re-analyze this and note the change to the analog model in which the Nonstructural Block is no longer included in the analog.

And that's going to do it for this instructional video on adding horizontal blocking.

 Thanks for watching!