If you are getting ready to add or repair stairs and/or railings in your home, you will find that the most common denominator for any exterior stairway is the two, 2x6s or one 2x12 piece of lumber. The following information will help you as you work on this project, making it a success.
For the unit run and rise, you would generally leave a one-half inch gap between the two 2x6s with a tread depth of 11 1/2-inches. For the overhand, you would need to subtract 1/2-inch, which would leave you with a standard 11-inch stair, which is called a �unit run.� Then for the vertical distance between the steps, this is called a �unit rise�, typically 7 1/2-inches. The 11 x 7 1/2-inch combination is known as interior stairs, which complies with most building codes.
Risers are the boards that fill in the space between treads but they also work to provide support. Just keep in mind that this support is not the primary one, which is actually the middle stringer needed when stairs are wider than 36 inches. The front of the tread rests on the risers while the backside of the tread is just supported by a screw or nail that has been secured through the bottom of the next riser. If you have a stairway made where the screw or nail is the only thing keeping the tread firm, you might have a problem with the riser cracking close to that screw or nail, a common challenge in under built stairs.
When it comes to design of the stingers, you will find that there are three primary types to include housed, notched, and housed with a notched middle. Regardless, all three designs are cut using 2x12s. The following will give you a better understanding of the housed and notching stringers:
Housed � You can create a strong stringer by attaching it to the tread cleats, which are also called angles, by using a 2x12. You will need to remember that installing cleats does take time but in this case, any measurement mistakes can be corrected easily. Since there is no notching sticking out, you also have a lesser chance of the stringer breaking or cracking.
You do need to know that attaching these stringers does come with problems. For example, you might think all you need to do is drive screws going from the outside into the riser. You could do this but the result is that you will not have a strong riser. One wrong kick and it would easily crack. Instead, attach the risers to a 2x2 vertical cleat going from the inside of the housed stringer.
Notched � These stringers are cut so each tread can rest on the top of the notch. Although making a notched stringer is not difficult, you need to double check your measurements before cutting since this is a common problem. Additionally, notched singers do crack, which can happen during the construction process or as the home ages.
The good aspect of notched stringers is that they produce a very clean and classic look. Remember that if you have stairs wider than 36 inches, you would need to have a middle notched stringer regardless. Your best bet is to buy these stringers precut at your local lumberyard.