Transferring different loads through many engineered lumber beams is central to remodel framing
RECAP: Recycling, demolition, and deconstruction
Last time on Building Resilience we were salvaging some windows from one part of the house…
…and chucking these windows in the dumpster.
But on resilient construction sites, the dumpsters are recycle bins. And so are the recycle bins like these PVC recycling bins from AZEK.
This time, we’re going to dig into the framing process, which is minor on this job because there are only a couple of walls and a small section of roof to frame,
… which the crew knocks out quickly.
So we’re going to look at some of the clumsy framing from the former remodeler, and explore the engineered products and hardware used for framing like you give a damn.
PLAN OF ATTACK: Tracing the load path and redirecting it
Alright, we are making really good progress here at the Gruda house. As you can see, we’ve demolished quite a bit of the structure, we’ve got the roof torn off, and we’ve gotten into structural framing.
We’ve got a couple of really beautiful LVLs—big beautiful beams up there that are picking up that roof load and transferring it to that lonely PSL column there…
That lonely PSL column, which is carrying about half of the roo has a 6-inch square footprint which is called a point load. That point load must be transferred to something solid—like the foundation—or the whole thing will come crashing down.
Because of physics.
The good news is that on the way to the foundation, the point load is transferred to a bigger post which is made from a lot of wood.
This is a lot of wood. It’s a bunch of sticks, and they’re carrying a LOT of weight.You know, to the untrained eye, it looks fine—to the previous builder it looked fine—but it’s not.
Let’s look at what it’s picking up. Up here, these two studs are picking up this triple LVL. That’s carrying this half of the house, this was a bearing wall of the house, and it’s been removed, so we’ve got a bunch of weight that way and a bunch of loads this way.
The next two and a quarter, two and a half studs are picking up this double LVL, carrying the floor and roof load going this direction and bringing it to this point.
And then we have this stud here, which is picking up the original rim joist—it’s a balloon-framed house, so the rim would have been let-in.
And then because we took out that bearing wall as well, we’ve added this 5-½ inch PSL column.
But it gets worse. If we go up, we’ll see there’s another PSL post that’s dropped on this and an additional triple LVL that’s picking up parts of the second floor and bringing them over here, as well as another beam from the attic that’s coming here.
So, is it carrying a skyscraper? Not quite, but let me tell you—there is A LOT of weight coming down on these sticks. But here is a BIG problem:
- This (PSL) is a post.
- This (6 2x6 studs) is a collection of sticks. This is not a post. Each of these sticks alone is able to withstand the compressive force, the load that is coming down on them. Where they are weak is in lateral force and in shear.
We have to make these guys into a team, so we can resist those additional forces.
We have three ways that we can do that (make a structural post from multiple studs).
- Option 1 to make a structural post from multiple studs: Remove all of the studs and replace them with a glulam or PSL column.
- Option 2 to make a structural post from multiple studs: Make a giant gusset plate with construction adhesive and nails.
- Option 3 to make a structural post from multiple studs: Drive 12-inch structural fasteners from Simpson Strong Drive through all of the studs and into the PSL post. Every eight inches staggered, we’re going to have one of these beauties, kind of like magic.
It is NOT kind of like magic, it is engineering, which is based on PHYSICS.
Speaking of physics, here’s some in real life. Stephen is demonstrating a lever in action to pull the old wall plumb, while a brace is screwed into that lonely PSL post.
With the outside wall where it wants to be, they can start stacking more LVL beams to load up that post because they know Michael is going to try to squeeze all the layers together in a few minutes, and they want to mess with him.
Speaking of layers, here’s a cool tip for flushing up layers of a built-up beam: a partially-driven screw and a prybar.
I know it seems obvious, but some people don’t know it.
When Sol is satisfied that the beam is level, David fills in studs below the end, but he will screw those studs together into a post instead of a collection of sticks.
JOBSITE KNOWHOW: Engineered lumber beam types
Speaking of posts and beams, there are a lot of engineered options for these structural members.
Because trees aren’t big enough anymore to make solid posts and beams, lumber companies have come up with ways to mash small trees into big beams.
So everyone's heard of OSB and Plywood, which are laminated sheets of wood or chips of wood that are squished and glued together.
But we also use engineered wood products in our structural work. We’ve got 2x4s and 2x6s, but then we’ve got the fun stuff, which is LVL, PSL, and GluLam… and this is a piece of steel because steel has a purpose and a modern carpenter has to work with steel.
PSLs are parallel strand lumber
They take these long strands and line them, up so they're going the same direction and then they glue them up. The moisture content is very low, so they are dimensionally stable. What makes PSLs particularly useful is that they are strong in multiple directions.
PSLs really great for columns, we use them a lot for posts. In fact, all of the major posts on this job are made from PSL. You can also use them horizontally in either direction.
Depending on what your engineer is looking for, PSL is a very flexible and dynamic material.
GluLams are really like a bunch of 2x material that’s been glued up
GluLam beams are laminated glued-up pieces of wood. GluLams are actually stronger when used as a post to resist the downward force; not as strong in some of the other dimensions.
Where GluLam beams are particularly useful is when we’re doing really large beams where the top of the beam has different requirements than the bottom of the beam.
When we engineer a GluLam, we can design it so there’s a top and a bottom, and they can achieve some pretty incredible spans.
LVL is Laminated Veneer Lumber
This is what we often use in header material, so LVLs are probably our most common beam material. So, the PSL was made from strands, LVL is made from veneer, this is like plywood, really.
Because it’s laminated veneer, we can manufacture really long lengths—kind of infinite lengths. Both PSLs and LVLs are manufactured into what are called billets—giant pieces that are then cut down into the sizes that they need.
LVLs are really strong horizontally in the upright direction, not so much laying flat.
When we have a lot of weight or a big span and we don’t want deflection, we use steel I-beams
Steel I-beams can achieve in seven or eight inches what an LVL or GluLam might need 12 or 14 inches.
If you don’t want a header to stick down from the ceiling, steel is a great option.
We’re also using steel in a lot of other places and a lot of it is a lot smaller. We’re using structural screws from Simpson, Post bases that resist lateral (sideways) movement as well as upward movement. These rafter hangers tie the bottom end of a rafter to the side of a beam.
Normally when we think about transferring loads, we think of a post holding up a beam, which then has joists or rafters on top of it.
Joists can also hang below beams with specialized joist hangers. This is useful, again, when you don’t want a beam that sticks down into the room. In this case, I’m going to put a beam in the attic and hang the floor joists below it, and the beam will drop down to a bearing wall and a post.
Previous remodelers often 'mess' up bearing walls without realizing it
Aw geez, look at this. I guess the former guy wasn’t happy rotting the walls and overstressing the pile of sticks on the first floor, look what he did to this wall.
This is a mess. We like to play a little game called find the load path. I have no idea where it is here. There’s half a stick back there and it’s connected to that, but that’s not connected to anything, and they doubled up that guy over there, but that’s over nothing, and this has been cut out. I mean, it’s just like… yeah.
BUT, here’s what we’ve figured out. This staircase is actually being held up by the first floor joist in the hallway, which is super-stressed out. We can see it from below, there’s one floor joist that’s pushing down with a lot of deflection on it.
So, shame on the previous remodelers who carved this up and we are going to do our best to fix it because—yes, we could slap drywall over it, but that would be unfair to that poor floor joist in the floor.
It would also be dishonest, devious, and probably illegal.
Something that’s not illegal, though, is sealing up leaky wet crawlspaces with sheets of rigid styrofoam and froth packs of spray polyurethane.
Because—again—the former guy messed it up.
I’m standing at the intersection between really old and a little bit old. This is 1910 and this is 2001. This is an addition that was put on by another builder, attached to the outside of the house.
And they built it with the best of intentions, but it’s a classic example of—to quote John Tooley:
- You can do the right thing the right way
- You can do the right thing the wrong way
- You can do the wrong thing the right way
- You can do the wrong thing the wrong way
But only one of them is right.
This would be an example of doing the wrong thing, the right way.
And we’ll dig into those crawlspaces next time on Building Resilience.
—Building Resilience is a production of the SGC Horizon media network. See all of season two here.