Wall Details


Insulation calculation in a wall isn't based on batts, which are optimized for stud frame applications. In the stud frame world, spaces between studs are the cavities that insulation is placed in. These are of course a nominal size. Note illustration below. Cavities are either natural (INS 1) or created (INS 4 and INS 5) as rectangular areas. The natural cavities are arbitrarily sized by definition (i.e. post/column spacing of 8' yields roughly 7.5' cavity width and 6' spacing yields around 5.5' cavity width.)

Staggered Girts

Note that the girts "stagger" course by course when possible. The purpose of the coloring is to help make it easier to see:

Misc Details

Note illustration below.

First, note the spacing (Note 1.) The outer spacing is from the outer edge of the column to the centerline of the next one. The nominal is 8', so how can we have only 7' 10 1/2"? We inset the post by the girt edge dimension (1 1/2") so that the building outside edges are the nominal size. This is normal.

Second (Note 2), the framing of the windows is added in red. This is usually done in a separate drawing (drawings can get busy, fast) but added here for instructional clarity. The normal practice is one window per bay with a member above and below and then one or more on each side. Hopefully you can now see the method by which the girts attach to the framing.

Third (Note 3) look at the girts going from the edge to the first window edge. These are not fully 8'. What is done by this system is to try to use leftover cut lengths from other girts depending on opening positions and odd bay sizes. If possible a leftover will be used for these two girts. At worst case a single 8' length is used to cut the lengths for these two.

What also ought to be apparent here is that micro-managing lumber lengths (e.g. picking only 8' and 16' for 8' nominal bay sizes) is a strategy that overall doesn't really work. As you can see there are a number of pieces of lumber that are of various lengths; picking only 2 lengths may seem like a good idea, but generally isn't. And this is just in reference to openings alone; any micro-management advantage possible is negated as soon as you create a wall length that is not a nominal bay multiple (e.g. a 42' wall but insisting on 8' bays.)

Interesting Stuff -- Oversize Doors

Note illustration below.

Yes. There it is. You can put a 9' high door into a 8' high endwall. Now, to do this, you want to change the end trusses to rafters and make sure to use girts all the way to the roof peak.

Note that the 8' Nominal Hgt line doesn't go all the way to the side. Surely this is in error? Nope. This building has a 5" truss heel; the siding goes to (Nominal Hgt + Heel) which in this case makes it 8' 5".

Interesting Stuff -- Extension Posts

Note illustration below.

Put an 19' or 20' wide door in a wall, and you're going to interrupt things like posts that carry trusses. And, how do you run a girt all the way across the space above the door? This is the function of above door extension posts.

Interesting Stuff -- Steel Siding Tricks

Note illustration below.

Note how the steel siding panels meet perfectly at the underside of the roof peak. This is called "Seam At Peak." There is another option called "Center At Peak" where underside of the roof peak centers on a panel. There doesn't appear to be an argument here regarding symmetricality (i.e. buying as many of the same sizes as possible) so much as using this option to control coverage (i.e. keep the parts count minimal) depending on the building width. In the illustrated case the 30' structure width and 3' panel width results in the least part count (no waste) by seaming at the peak.

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