Engineered lumber does everything solid-sawn lumber does, except better. It's stronger, lighter, straighter, and more stable. But working with I-joists and laminated veneer lumber (LVL) is different than solid-sawn lumber, so check out these tips for getting better, faster results.
Beams and Rim Joists. When you hang joists off a built-up center-span LVL beam (or flush header), check the widths of the LVL components. I've seen these vary as much as 3/8 inch from one another, which is enough to throw a top-hung joist hanger out of line. When the hanger is off, it's difficult to set the joist properly. To compensate for this we assemble headers and beams and then power plane them flush to flatten the top edge, before installing hangers and joists.
OSB rim joists can vary in thickness. Moisture swells them quickly, which can affect your joist measurements and slow you down. The best strategy to avoid this is to schedule delivery of your rim joist material just in time to use it, and keep it as dry as possible until it's installed.
Storage. Manufacturers recommend storing I-joists on edge. If laid flat on uneven terrain, they can take on a wobble. Using layout marks on your floor sheathing helps you keep joists in line as you lay the sheathing.
Cutting. You don't have to, but we find it's easier to use guides for cutting I-joists. My crew makes Lexan plastic jigs that span the joist web and give the saw base a smooth surface to ride on without sacrificing much depth of cut. This makes it easy to get square cuts and the Lexan is tough enough to handle jobsite abuse.
Handling and Installing. Before we spread the joists, we make sure to measure for cuts from the same end so that the knockouts for plumbing and electrical lines will line up with each other when we're done framing the floor. Also, pay attention to the up/down orientation of the knockouts and install them all the same way.
I-joists are light?one person can handle a 40-footer -- but they're floppy. When we're sending them across the foundation to frame the floor, we hook the flange of the first joist over the rim board and slide it along until it's in position. Once in position, we nail it. We then skate each subsequent joist out over the one that precedes it, nailing them off as we go.
To avoid squeaks from joists hung off a flush header, leave a 1/4-inch gap between the end of your I-joist in the hanger and the LVL header. Nail through all the holes in the hanger only. The other source of squeaks I've found is sloppy nailing during the sheathing process. To catch squeaks, I walk the floor. If I hear a squeak, I circle it, then look for nails that may have missed the joist, pound them back out, and re-nail. We also apply glue to the tops of joists before setting each sheet of sheathing.
Blocking. Just like with solid-sawn lumber, blocking is required at mid-span in an I-joist floor. I cut these from the joist cut-offs with a radial arm saw. We stagger these blocks on either side of the span's centerline unless otherwise required. You may have to use fillers on the webs of the joists for fire-blocking where the blocking meets the joists.
Web Stiffeners. In certain applications, like where joists line up under a load-bearing partition, you have to install web stiffeners between the flanges of the I-joists. The ideal material for this is the LVL rim-joist stock. We clamp pieces of rim stock to each side of the joist web and shoot through all the pieces at the same time. A 2-3/8-inch framing nail is perfect for this. This technique saves you from having to bend over nails shot through from one side before putting blocking in on the other side of the web.
Specs and Plans. While you can spec engineered lumber yourself by reading manufacturers' span charts, you're better off working with your supplier who's been trained to do this. Stairwell headers, doubled joists, long spans (which could result in bouncy floors), and other framing complications call for some product-specific number crunching.
When I get a new set of plans, I review them with my framer to go over layout and details. We locate all the toilets, plumbing rough-ins, and anything else that deviates from uniform layout. If we see the need to change anything, I check with my supplier to make sure the deviations will work. And any time I see solid-sawn lumber combined with the engineered stuff, I call the architect and ask him to reconsider. Solid-sawn lumber shrinks and swells; engineered lumber doesn't?so the two are incompatible as far as I'm concerned.
Safety. Don't walk on un-braced joists?it's a surefire trip to the hospital. We brace unsheathed joists with 1x strapping every 6 to 8 feet and lay rim-joist material across the joists so we can move around on the unsheathed deck. Note: Rim-joist material spanning 14 inches between joists is safe to walk on. It is not safe to use as a staging plank and should never be used as one.
Scott Woelful is owner and president of Francis E. Woelful in Harwichport, Mass.