I’ve renovated lots of porches over the past twenty years, and have always found that one of the most time-consuming phases of this type of project is rebuilding the staircase. Finding the rise and run is easy, but framing stairs by installing one piece at a time is slow and labor-intensive. In order to speed up the job and improve accuracy, I’ve recently started building prefabricated stair stringer ‘kits’.
To get started, I determine the stair’s rise, run, and width, and lay out the first stringer. After cutting it out, I use it as a template to lay out and cut the remaining stringers. I drill pocket holes in the tops of each stringer, which I will later use to fasten the assembled stringer kit to the deck framing with heavy-duty pocket screws.
Next, I cut a 2x10 bottom cleat and a 2x6 sub riser equal to the width of the stairs, minus three inches. The stringers are fastened to these components, which are used to attach the staircase to the landing pad and also to help strengthen the stringer-to-guard post connection. Before assembly, I trim 1 ½-inches from the bases of the interior stringers and 1 ½-inches from their ends, and apply wood preservative to all cuts and holes.
The beauty of this approach is that I can assemble the components on a work table, rather than while kneeling in the dirt. First I lay out the interior stringer locations on the cleat (12-in. o.c. in this case), then fasten the outer stringers to the ends of the cleat and sub riser using 3-in. long structural screws. After installing the remaining stringers, I add a temporary 2x brace to the top of the assembly to lock everything in place.
I also install the guard post, reinforcing the connection with a pair of 4x4 blocks, but I make these connections with as few fasteners as possible for now. There is always some shimming that will be needed around the post and blocks after the stairs are installed to make it perfectly plumb. I finish up the prefabrication by installing 2x8 blocking between the stringers.
When the deck framing is ready and the new concrete landing has been poured, my helper and I can lift the stringer kit up and set it into place. After lining the stringers up with our layout marks on the landing and securing them with pocket screws, we fasten the bottom cleat to the landing with three concrete wedge anchors. Then we plumb up the guard post and install the remaining fasteners. To finish up, all that is needed is to install our pre-assembled PVC skirt and riser kit…but that’s another story.