Custom Stairs - The Design and Decision Process

The interior stairs have been the topic of many discussion between the architect, the builder, and the two of us. The drawings show open riser stairs with exposed stringers on each side, but there are numerous ways to construct this. Additionally, we had to consider the costs of the railing and how that impacted the total costs for the stairs.

We discussed numerous construction techniques, many of which were labor intensive with high materials costs. One of the challenges with open riser stairs is how to meet the code requirement that a 4" sphere cannot fit through the riser. There is some debate about whether or not the 4" sphere requirement even applies to the riser. Typically, the 4" requirement is for railing, but inspectors in Atlanta seem to apply that rule to all parts of the stairs. Personally, I think the requirement is 6" (see the section below on codes and my interpretation). But, I will not digress and just say that we decided to keep the open riser to 4" to avoid debate with the inspectors.

An open riser of 4" means having a really thick tread, a partially closed riser, or some other material preventing more than a 4" open space. The partially closed riser didn't work for us because we ran into the challenge of how to have a tread with enough structural integrity so that it wouldn't flex or break since the initial plan was to have treads that were sandwiched by two stringers on each side. But as we discussed this option, this wasn't looking like a cost effective option for us. The stringer construction would be expensive and we weren't finding a good railing option that was affordable. Back to the drawing board.

Paul, our architect, had the idea of putting a single stringer, quite thick, in the middle and having the treads somehow sit atop the stringer. This idea was great so we started talking about our options there. One idea was to sandwich two-bys together creating a large stringer that could be notched out for each stair tread. There was concern that getting this to look good and clean would be a challenge and add more materials and labor. Rather than notching the stringer for the treads we then discussed having some sort of bracket to hold each tread. This was starting to become more appealing. It would make the treads "float" somewhat and it would give the ability to either attach railing posts to the end of the tread (on the side face) or have it screw/bolt directly onto the top of the tread.

We were really starting to like this idea. Paul pretty much sealed the deal on this design when he had us meet him at a local specialty wood supplier. Why specialty wood? Well, that was the allure of Paul's design. Rather than using new lumber, Paul wanted to use old (really old) reclaimed timbers for the stringers. What a great idea! Rustic meets modern. We were hooked and started pricing out all the pieces to make this happen.

We had to get special treads made that were almost 4" thick so we got that priced from a local stair component supplier. The brackets would be one of a kind, but Paul designed these to be used with stock steel so little welding would be done. The brackets would be made from 4" x 4" x 1/2" angle steel pieces with holes drilled for mounting. Four of the brackets, the ones at the top of each flight, would have to be welded to create the "L" bracket for the top. Last, but not least, we had to convince the trim guy to accept the job. He thought we we're crazy at first, but after a couple of meetings he finally agreed.

Here's what we were setting out to build:

Stay tuned for the construction details and pics of how these turned out!

Building Codes Regarding Stairs

I was forced into learning a lot more about the residential building code than I ever wanted. The codes are not always straight forward and it seems that inspectors have simplified versions in their head so don't always take what they say at face value. Don't hesitate to pull out a printed copy of a code section and ask them for clarification if they claiming something doesn't meet code.

If you decide to build customer stairs, the code is going to come into play. The codes are getting more and more strict which will put constraints on your design. The "code" as it is often referred to is the International Residential Code for One- and Two-Family Dwellings. You can find it here: http://publicecodes.cyberregs.com/icod/irc/index.htm During our construction, the City of Atlanta was using the 2006 Edition, but has since started using 2009. I'll refer to the 2009 edition here.

You'll notice that there is no chapter on stairs. That would be too simple! Here are the relevant chapters and sections you'll want to reference for the stairs:
1. Chapter 3 - Building Planning, Section R311 Means of Egress - R311.7 outlines the required width, headroom, walkline, landings, handrails, and illumination. It does NOT have anything about the railing in this section.
2. Chapter 3 - Building Planning, Section R312 Guards - "Guards" are the railings that are required when you stairs or landing do not have a wall or other barrier to prevent people from going over the side. This is the section that has outlines the 4" sphere rule.
3. Chapter 3 - Building Planning, Section R301.5 Live Load - This section deals with how much load or force a building component must be able to withstand. You many need this when using alternative materials that inspectors haven't encounter on stairs before. We had to use this discuss our exterior railing with an inspector who didn't want to pass us.

As I stated at the beginning of this post, I don't agree that open riser needs to be less than 4" to adhere to the code. Here is the code section:

R312.3 Opening limitations. Required guards shall not have openings from the walking surface to the required guard height which allow passage of a sphere 4 inches (102 mm) in diameter.

Exceptions:

1. The triangular openings at the open side of a stair, formed by the riser, tread and bottom rail of a guard, shall not allow passage of a sphere 6 inches (153 mm) in diameter.

2. Guards on the open sides of stairs shall not have openings which allow passage of a sphere 4³/₈ inches (111 mm) in diameter.

The first exception while specific to the "triangular openings at the open side of a stair" is for all practical purposes the same as the opening created by an open riser. Perhaps the only argument against that is the fact that the riser is much wider (the width of the stair) than the triangular opening. However, I can't find any specifics in the code about the open risers so this seems to be one of those areas where inspectors are left to fill in the blanks. If you want an open riser more than 4" be prepared to go to the head inspector to argue you case. Hopefully, the above information will help you with that. I think there's a strong case for allowing a 6" open riser.