Further Adventures in ISBU Barn Building

8 Aug

Boy, was you born in a barn?

Um…. nope. Actually, I was born in an airplane… 🙂

We’ve been talking about the prospect of building a big ISBU BARN-Style home.

Now, usually, when I’m talking about building an “ISBU BARN”… I’m talking about erecting a big metal building to BUILD ISBUs in.

But many of you have expressed a desire to build a rural house using ISBUs that fits in with the landscape and resembles “the old homestead” that a lot of us dream about… just like in the movies… 😉

Many of you will think this more “stable-like” than “barn-like”. Okay, we’ll take it. 😉

Let’s face it…

There are those among us that aren’t plagued by hurricanes or tornadoes. The ground doesn’t roll and  shake under your feet. That means you can do some things that we don’t normally do… like combining ISBUs with traditional “stick” builds to create “Corten Cool Homes” for “cheap-er”…

Yes, I said “CHEAP-ER”.

And just to prove it, we’re going to dissect one of these homes, in order to look at it under a magnifying glass.

One of the first things that you want to do when you start a build like this its to get it weathered in. That means you need a roof.

I know, I know…

I go on and on about SIPs (Structural Insulated Panels).

But (sigh!)  there ARE other ways to build a roof.

You CAN build a pretty cool roof using standard attic trusses as long as you UNDERSTAND how they are used and you don’t push them beyond their design specs.

Now, it won’t be as cool as a SIP roof, but… 😉

Attic trusses are the most economical (and most popular) method for building roofs that include attic space.

And before you ask, YES, you can put SIPS over Attic Trusses. Coming from “wind country” (I blame my wife…) I like low-profile roof systems with decreased soffit overhangs. It’s less roof to tear off when hurricanes prowl the neighborhood…

But we’re talking about attics;

These spaces can be used for many purposes –  attic storage space as well as useable and residential space.  Beyond the “regular old run of the mill gable” roof… this also makes them ideal for the gambrel roof and cool “woodsy” A-frame roof profiles.

A roof truss isn’t rocket science.

A roof truss is just a load-carrying, spanning member made of wood or steel components (usually 2x material when they use dimensional lumber), connected together with metal plates and shear connectors.

And, it’s pretty straight-forward. You design your roof trusses around the load capacity that you require.

Okay, Lesson One:

Attic trusses don’t just hold up the roof.

They function as 3 separate structural components in your structure system. An attic truss literally becomes your floor, walls and roof.

The bottom chord forms your floor joist. It’s often 2×4, however 2×8, 2×10 and 2×12 versions are available. Most common are 2×4 bottom and top chords.

But wait… there’s more,

When you use attic trusses, you don’t get “a typical floor” like the other floors in your home.

That 2x “Whatever” actually has your roof loading being transferred down through it right along with the floor loading. It will also include the storage loading beyond the knee walls and even the loading for the wall covering (dry wall/OSB/plywood/paneling) that you install on the knee walls.

  • Every once in a while you’ll come across a home with 2X6 lower chords.
  • Every once in a while you’ll find 2X6 top AND bottom chords.
  • And every so often you even see 2×8’s, 10’s, 12’s being used as part of the truss construction.

Now, we’re talking “beefy trusses”. If I was building out in “the wilds” you can bet that I’d sure consider using these “trusses on steroids”.

More wood equals more strength.

Here’s how it normally works:

When we specify a “conventional” roof, plans typically include a roof framing (layout) plan, a cross-section view and what I like to call a “glamour view”. 😉

This is just a guideline to (a) show you what you’re building and (b) it illustrates the recommended truss profile to anyone that asks.  In most cases, this “roof package” is what you’re going to give to your truss engineering firm or manufacturer, so they can build/ship the right trusses to your local supplier.

Okay, I love Hip Roofs… I just love them… 😉

You’ll get a similar package that contains your attic roof plan, based on your projects criteria and requirements.

But it doesn’t stop there:

While you are ordering your trusses through your materials supplier or setting up your project with your builder, you can request adjustments to the profile. This gets really important if you’re trying to match an adjacent building, conform to a local set of CC&R’s etc…

Roofing trusses are a big deal.

Remember, the roofing truss system is integrated into your home’s primary support system.

And now you know that Attic Trusses are indeed STRUCTURAL TRUSSES.

This means that you don’t let idiots cut or drill holes in them under any circumstances. Your plumber doesn’t get to modify them by drilling holes in them to pass PVC or PEX  thru  like he would other 2xX’s in your home!

Stop him/her, or at the very least, take them to task for it! 

They’re screwing with the STRUCTURE of your home.

Why? Because that’s that Attic Truss Floor is NOT just a floor.

Aren’t you paying attention? Huh? 🙂

Next time, we’re gonna start learning “ISBU Truss Design 101”.

Stay tuned.

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