Framing with Pre-Cut Components Continued

Accurate cut lists.

Chris then works through the drawings to define logical areas or "units" that can be grouped into a package — such as apartments with identical floor plans. Wall plate and component cut lists are compiled, and three copies of every list are printed. The lists are precise. The item counts are cross-referenced. Quantities are confirmed and totals balanced in much the same way an accountant might tie in figures on a financial statement. When the field operation begins, everyone is provided with specific instructions on what is required to complete the work.

Splitting Up the Tasks

The operation is broken into two production "lines" — wall plates and components. On the plate side, lumber is dropped at the cutting station, and I receive the first of the three wall plate lists. I check the quality of each piece of lumber, and I use the premium lumber first for the longest lengths on our various cut lists. Material with defects, such as bows or excessively large knots, is trimmed and the defects removed. Shorter walls are then cut from the salvaged material. The smallest and least desirable materials are cut into blocks for channels and corners. Nothing goes to waste. By working from the longest to the shortest, we are able to use every section of lumber, even down to pieces as small as 6 inches.

Dimensional consistency.

Often a CCA-treated 2x6 will measure 5 3/4 inches wide, while the nontreated plate is 5 1/2 inches. If walls are framed with the bottom plates wider than the top plates, problems occur during plumb and line. If the bottom plate of an intersecting wall is 1/4 inch too wide, then the top of the wall will be 1/4 inch out of plumb. This is a progressive error that gets worse the more walls you tie together. By running every piece of treated plate through a table saw, we ensure that the top and bottom plates are the same size. This ensures that plumb and line goes faster and smoother and that the finished product is better. Organizing the plates. Once the plates have been cut to length, they are numbered. The wall designation is written on the top, bottom, and end of each plate as well. Experience has taught us that it is not always possible to view the bottom of the wall to read the number. By taking a few extra seconds per wall to write the designation on the end of each plate, we can save valuable time for those in the field. The plates are then joined together — one nail within 12 inches of the end of the plate and one nail every 6 feet along the length of the wall. The fastening of the plates plays an important role in getting a straight wall to the site. The guys on the tables complain a bit about how hard it is to split the plates, but at least when they are separated, they are straight. We are careful to nail through the top plate only. This way, once the wall is split and assembled, an 8d nail left sticking out will be hanging harmlessly from the top, as opposed to sticking up out of the bottom plate, waiting to impale an unsuspecting foot. Wall plates are sorted, and each set of plates is checked off of the computer printout. The wall plates, along with the verified list, are bundled into a package. This package then moves from the cutting/nailing station to the layout station.

Layout

When Chris receives a package, he checks the list again to verify that it was completed. He then discards the list from the cut station and begins checking the length, plate dimension, and quality of each set of plates using a second copy of the wall-plate list as he lays them out (Figure 3, previous page). Anything that doesn't meet Chris's high standards is recut. Chris lays out the wall plates and stacks them. He double-checks the second copy of the panel list to ensure that the package is accurate and complete. Then he sends the package to the top plate-prep station.

Figure 3. As wall plates are cut to length, they are labeled and nailed into sets (left). Pre-cut plates are then moved to the layout station, where stud and component placement, top plate length and positioning, anchor bolts, and "courtesy cuts" at doorways are laid out (right).

At this station, top plates are cut, labeled, and tacked to the wall plates. Also, in order to speed completion in the field, two 1/4-inch kerfs (or courtesy cuts) are made on the bottom plate to allow easy removal of door plates after erection. As plates and components are moved from one station to another in the yard, they are bundled, reusing the banding from the original lumber bunks. The project that we are fabricating now requires expansion anchors at 24 inches on-center at certain interior bearing walls. The bolt layout is included in our computer wall elevation. The bolt layout is done by Chris, and the holes are predrilled in the bottom plate. This eliminates the need for the field supervisor to determine which walls require bolting or to do a layout. He simply hands a carpenter's helper the box of expansion anchors that was included in the wall pack and instructs him to install an anchor in every pre-drilled hole.

Components

While the plates are traveling through the various stations, the component crews are hard at work assembling headers, trimmers, channels, and corners from lists that are cross-referenced to the wall panel elevations. The header team gets one copy of the list to check off timber and engineered-lumber headers and posts. Another copy of the list is provided to the crew that nails up all the stud-based components, such as king stud/trimmers, corners, and channels. Each piece of cut lumber is clearly marked and then checked off the list. Structural elements include dimensional lumber, Paralam and LVL headers, and king stud/trimmer assemblies ranging from single, double, triple, and quad trimmers, to Paralam trimmers and support columns. A wide range of rough openings and load-path considerations makes buildup a challenge. However, it is precisely this type of project that is best suited for our system. By placing all these various headers, trimmers, sills, and blocks together in one package, each piece clearly marked to match the layout, we make what would otherwise be a very difficult and confusing task a fairly simple "frame by number" assembly. We normally use solid timbers in lieu of built-up header assemblies. The cutoffs from the timbers are recycled into solid blocks for channels. We use 4x4, 4x6, and 6x6 blocks to form two-way corners and channels. This is one more way that we take the thinking out of wall assembly and save time in the field. These components are universal, so you can't put a tee or corner in backwards (Figure 4).

Figure 4. Perfectly uniform two-way channels make backwards installation impossible. Note the efficient use of lumber that might otherwise be scrap.

Cripples. We use these timber cut-offs to solve another common framing problem. If the header does not completely fill the space from the top of the opening to the bottom of the double top plate, cripples must be cut to fit in this space. Once dimensional lumber is cut to a length shorter than its width (for example, a 2x6 cripple cut shorter than 5 1/2 inches), it is likely to split when nailed. For example, to fill a 3 3/4-inch void between the top of a header and the bottom of the double plate in a 2x6 wall, we cut solid cripples from beam stock 5 1/2 inches wide (to match the 2x6 wall), 4 inches long, and 3 3/4 inches deep (Figure 5). These cripples can be toe-nailed to the top of the header with no danger of splitting.

Figure 5. These timber cutoffs have been salvaged from the scrap pile and ripped down to 2 3/4 inches for use as cripples. This eliminates splitting problems, reduces waste, expedites assembly, and improves quality.

The buildup crew is also responsible for holddown assemblies. Posts for holddowns are cut to length and marked with the bolt pattern for the scheduled hardware. The posts are then run through a two-step process on our drill press. First, we drill an oversized hole on the back side of the post to allow the nut and washer to be countersunk into the column, so as to not interfere with wall sheathing. Then the hole for the bolt is drilled through the post at 1/16 inch larger than the required fastener. Using a drill press ensures that the holes are straight and true. In many cases we will go ahead and bolt the holddown onto the column. This assembly can be installed in the wall once concrete-embedded bolt locations are verified.