Supporting a Staircase

Zach is a carpenter who partially gutted a house he bought. Before outfitting the house with a new hardwood floor and an oak staircase, he hired PERCH to analyze his framing and see if it was up to the task.


Top of the new stairs.

Zach was smart to hire a structural engineer in this situation, because as it turned out the framing needed several improvements. The additional weight from the staircase was too great for the existing first floor joists to carry, so PERCH specified an additional 2×10 joist to pick up each of the stair stringers. The next step was to follow the load path and note that the joists are all supported by a triple-wide beam running across the middle of the basement ceiling. With increased weight on the triple-wide beam, it needed an extra support post too.

What about the rest of the first floor, where Zach would install new flooring? A finish floor is typically ¾” thick and doesn’t add a ton of weight. But some of the existing joists were notched to accommodate utilities like air ducts, and this weakened them beyond the minimum code requirement. PERCH added sister joists across the notches to bring these joists back to full strength.

Now it gets weird. The house has a partial second floor with a balcony overhanging a central loadbearing wall. (That loadbearing wall is directly above, you guessed it, the triple-wide beam in the basement.) The staircase ends in two winder stairs supported by the overhang. Anticipating the increased cantilver load, Zach had already added an extra joist where the staircase was supported. Analysis confirmed this extra joist was adequate for the load, provided he fastened it to the original joist over the entire length.

But again we need to follow the load path, and in this case it leads past the central loadbearing wall to the back wall. If there’s a big weight on the end of the cantilever, and no weight anywhere else, then the joist actually pushes UP on the back wall. (If you sit on one end of a seesaw, the other end goes up.) That means there needs to be a stud ABOVE the joist to carry the load up through the back wall, where it gets balanced out by downward forces from the roof. In reality the weights on the joist will be evenly distributed most of the time, and uplift will rarely occur. Still, a situation that causes uplift is plausible (like a crowded party on the balcony with nobody in the other rooms), so PERCH designed for it.


Original second floor renovation plan in PERCH Engineering Report.

When Zach received the Engineering Report, he asked if there was any way to support the stairs without the last stud. Opening up the back wall would require a lot of extra labor on his part, refinishing a wall he had already completed. We pitched ideas together and settled on supporting the top half of the staircase with a post leading back down to the first floor. PERCH located and sized the post to leave room for a piano behind the stairs, and sent along the revised design. This exploration of options is called value engineering, and it always proves that good communication makes good projects.


Mockup of the staircase support post location.


After Hans and I removed the rotted old decking and built out the new shape of the deck, it was time to install new boards. The roofed portion abuts the back door, a critical spot for moisture protection. We’d managed to pry out the old decking board from the wall without destroying the metal flashing, and we used a flat bar to cram the first new board into the same space. The flashing directs water down the siding and onto the deck, where otherwise it could flow back and get trapped inside the wall.


The first course of new decking slides into the existing flashing.

Our new decking was 1¼-inch-thick untreated pine. We didn’t use pressure-treated lumber because the sawdust is a bit toxic and because this was a budget job; the homeowners will stain the wood later to seal it from the elements. Hans cut lengths to stagger the joints and did a nice job minimizing waste. I mostly stayed on deck and screwed ‘em down.

As we approached the step down and again as we approached the new joists, we started to measure the distance remaining. Our goal was to reach the edge with a full-width decking board, running straight. We tweaked the spaces between boards and finished perfectly on the upper deck. I’m bummed about the lower deck where we finished a hair short, but it looks OK.


Hans cuts new decking to vary the joint location and minimize waste.

The last day was a scramble to finish lots of decking accessories. We built railings from scratch – 18 feet for the new squared-off lower deck plus two 4-foot lengths to create some intimacy on the upper deck (and highlight the step down). We replaced the top rail on all existing railings, cutting rounded ends with a jigsaw to match the shape of the old pieces we scrapped. We leveled the stairs on both sides and screwed new treads on top for equal-height risers. We scribed and cut little pieces of decking to fit around posts where we’d skipped earlier. And we cleaned up as many nails, screws, and wood scraps as we could find.


New railing at the step-down.

A few finishing touches on Saturday morning and the job was done in one week, with plenty of time to spare before the bridal shower.


Isn’t she lovely!

Get Rail

The Vermont Fire and Building Safety Code requires that all stairs have a fully graspable rail – that is, one you can wrap your hand around all the way, if your hand is big enough. Laura needed to upgrade her basement stair rail in order to meet the Code and sell her house.


From the Code.

I measured and determined Laura needed a 12-foot rail. A 12-foot-long piece of wood is not an easy thing to maneuver, but eventually I brought a circular rail to her house (at one point driving with my rear hatch open and taping an orange cone to the end) and navigated it into her stairwell. I brought three brackets as well, aiming for roughly a four-foot spacing to prevent excessive deflection.

Laura’s existing rail was basically a 2×4 spaced out from the wall. All I needed to do was attach the new rail to the old one. I installed the upper bracket first, screwing it upright into the 2×6, and then the lower bracket. Next I held the rail in place and marked where it would meet the upper bracket. Taking the rail down, I measured the width of the flat bottom (1 inch wide), centered my marks, and pre-drilled holes. I put the rail back in place and screwed it to the bracket connector. Now that the upper bracket held the rail in place, it was easy to connect the lower bracket, and finally position and connect the middle bracket.


Centering bracket attachment points on the underside of the rail.

The whole affair took maybe 20 minutes, and I could have done it even faster with a second drill. I must have swapped the 7/64” drill bit with the Phillips head a dozen times. An easy and functional fix to comply with the law.


All done.