Typically, stair stringers are fastened to the end joist or rim joist of a deck without taking into consideration the additional weight that the stairway places on the structure of the deck. The deck joists, beams, and footings are only meant to support the weight of the deck itself; they do not take into account the stair connection. As a result, the structure is susceptible to being overloaded. To prevent an overload on the deck frame caused by the stairway, we have two different choices available to us. Either the frame of the deck can be designed to be able to sustain the weight of the stairs leading up to the deck, or the stairs themselves can be equipped with their independent support structure.
Treat the Staircase like a Separate Structure
Because I employ an independent support system, I don't have to hire an engineer to design the framing, and it's not difficult to put together either. A header for the stairs is supported by independent structural posts that each have their footings. The stringers of the stairs are attached to the header. In most cases, there will be a requirement for guard posts to be installed to provide support for the guardrail system at the top of the stairs. Those posts can continue down to the footings rather than simply terminating at the bottom of the joists. The size of the header is determined by how it will support the top cuts of the stringers; in most cases, a 2x8 will do the trick, unless the width of the stairs is greater than 4 feet. Either the header can be attached to the posts in the same way that a ledger is screwed to the house, or additional support can be supplied by putting jack studs on the face of the posts down to the footing.
Read more: Stair Stringer Attachment
If the length of your stringers is greater than 10 feet, you should consider adding a stiff beam at the midpoint of the span to further strengthen the structure. The incisions that are performed to produce the stair surfaces have the effect of significantly weakening the strength of the stair stringers. However, staircases need to be strong enough to resist heavy foot traffic and particularly stressful situations. Long stair runs should preferably be broken up with intermediate landings. Doing so is preferable from both an aesthetic and a structural standpoint. In some circumstances, on the other hand, you could be required to employ a single long run.
A brace will alleviate the shear stress that, if left unchecked, might cause the stringers in the middle of the steps to lose their structural integrity. The majority of deck stairs are poorly constructed, and as a result, they have a bouncy feel to them and are at risk of collapsing. This is especially the case after weathering can develop cracks in the stringers. To further improve the stability of your stairs, you could also try nailing two 2x12s together to create the appearance of a beam and then tripling the number of stringers that you use. The overall stair structure can be strengthened further by the addition of blocking in the spaces between the stringers.
Special Hardware makes Framing Connections Easy
Stringer connector hardware is used to make the connection between the stringers and the header. These have just been available for purchase for the past several years and are a straightforward method for establishing a safe connection between the stringers and the header. Connector nails can be used to install the connectors, but I find that using screws provides greater resistance to withdrawal and works better for me. Because the connections can be installed in either direction, you can conceal them by attaching them to the inside of the stringers that run around the perimeter of the deck. Put filler into all of the holes in the hardware that is installed into the header and the side of the stringer. On the bottom of the stringer, there is only one hole that requires a nail or screw.
2-Ways to Support the Bottom of the Stairs
There is no specialized fastening gear available to attach the underside of the stringers to the footing or landing. Conventional ways include notching in a 2x to the bottom of the stringers and utilizing guardrail posts as the link. Another method is to use a cleat. After the stringers have been positioned, adhesive anchor bolts or wedge anchor bolts can be drilled and placed to secure the 2x that has been notched, nailed, or screwed into the bottom of the stringers. This will allow the 2x to be securely attached to the footing or landing. When post bases are affixed to the bottom of the posts and then held down using adhesive or wedge anchors, the stairs can be secured to the footing or landing using the 4x4 guard posts that are bolted to the bottom step of the stringers.
Guardrails can Connect to the Ground or the Framing
There are a few different approaches that can be taken to ensure that the guardrail posts at the bottom of the steps are stable. The procedure of embedding 4x4 posts in frost-depth concrete footings and then fastening them to the outside stringers of the structure results in a sturdy connection at the base of the staircase as well as posts that are sturdy. A further method, which is demonstrated in the movie, involves inserting two rows of blocks in between the bottom steps of the stringers and screwing them in place. Install tension tie connectors to the blocks, and then screw through to the exterior of the posts. It is possible to produce a similar effect by threading a long threaded rod from the outside of the posts on the outside of the stairway and passing it through all of the stringers.