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Installing Manufactured Stairs, continued After everything's fastened, the installer adds reinforcing glue blocks on the back sides of all the tread, riser, and stringer joints (Figure 5).

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Figure 5. Glue blocks are stapled and glued to every joint from the underside (left) to add solidity and prevent squeaks. Next, cove molding is finish nailed beneath each tread nosing (right).

The bullnose riser assembly is a good example of the blend of efficiency and quality. The process involves routing and kerfing out a strip of 1-inch finish plywood for the riser, bending it around a radius form, gluing and nailing the whole assembly in place, trimming the butt end to length, and attaching the finished riser to the staircase (Figure 6). It probably takes less time for a worker to do this in the shop than it would take a carpenter on site to set up his power tools.

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Figure 6. Kerfed plywood is bent around a pre-made form to make a bullnose riser.

On-Site Installation

You can figure on two people taking part of a morning just to install the stairs (Figure 7). Railings might take the whole afternoon. If you've got a bigger set of stairs, like a full 90-degree radius stair, you'll need some extra labor on hand to help with the lifting. And, of course, expect the fine work to take longer.

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Figure 7. Two men can easily carry and place a typical straight staircase (left). For large or complicated staircases, you may need more manpower. The installer pins the lower staircase section in place, using a scrap of landing tread to determine the correct height for the top edge of the riser (right). He places the first screw where cove molding will cover it later.

By the way, if the stairs are big, remember to leave a way into the building. I forgot that once, and we had to cut a large curved stair in two pieces just to fit it through the door. Before you place stairs, a last check of openings and of plumb and level is a good idea. On the job featured here, the installer was confused for a minute because someone had removed a post under the floor to pour the basement slab. Every time the installer tried to shim up the landing, the floor below dropped instead -- until it dawned on him that he needed a temporary post in the basement. But if the framing is on the money, as it should be, installing a staircase is like installing one cabinet: Get it in place, check all your dimensions and spacing, check level and plumb, fasten it, and you're done. With a two-piece assembly, as soon as the lower run is tacked and clamped in place, you can walk on it (carefully!) while you're putting in the upper section. The joint where the two sections meet has to be dead-on plumb and level, and shimmed flush as needed (Figure 8). This location is a good place to put fasteners, because the landing newel-post will cover them up later.

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Figure 8. The joint at the landing newel (left) serves as a focal point for aligning the entire stair assembly. The installer shims and plumbs this location carefully, then screws through the upper stair stringer into the lower stair riser to firmly lock the joint (right). Fasteners at this point will be covered later by the newel-post.

That center joint is the focus for the whole stairs -- you get it right and pin it, and then adjust at the top and bottom of the stairs if you have to. Most of the time in new construction, everything fits right in place, but if there's any planing or shimming needed in a remodel job, do it at the bottom or the top.