Replacing basement stairs may not be your first choice of a DIY task, but sometimes it's a necessary home repair project. If you're willing to rise to the challenge you can save yourself some money, if not, there are plenty of professionals who would be happy to do the work for you. With the right tools, careful planning and a little know-how you'll have a new flight of stairs you can be proud of! The Basic Rule of Replacing Basement Stairs There are a few basic rules of thumb when it comes to replacing basement stairs. However, these rules are somewhat adjustable to make the stair assembly fit into the stair opening. height of stair riser + tread width = 17" to 18"A stair riser is the vertical part of the stair and it should rise between 7 inches and 7-3/4 inches.A stair tread is the horizontal part of the stair that people step upon. It should be 10 inches.The stringers are on each side of the staircase. The rises and treads are attached to the stringers, which should be at a 35 degree angle. Here's a great website that covers all the components of stairs. Step-by-Step Guide:Replacing Basement Stairs Step One: MeasurementsUsing a tape measure determine the rise by measuring from the basement floor to the landing, where the top of the stairs will be.Divide the rise measurement by 7 or 7.5. This will be the number of individual risers (steps) your stringer will need to take you to the top floor.Round the number off to the nearest whole number.Re-divide the total rise by the whole number. Step Two: Mark and Cut the WoodThe most accurate way to measure your stringer is to attach brass stair gauges to a framing square at the points of your riser and tread measurements. Check the lumber to make sure it's straight. Lay the framing square on to the uncut stringer and mark the riser height and tread run with a pencil.Move the framing square next to the previous mark and with your pencil, mark another rise and tread.Repeat the process until all the stairs have been marked.On the last mark, remove the brass stair gauges. This will allow you to mark across the entire board. Use a circular saw to cut the majority of the stringer. Then switch to a hand saw to finish the cuts.Once you have cut one Stringer, clamp it to another piece of lumber. Trace the Rise and Tread lines with a pencil. Use care when cutting. The saw blade should be on the same side of your penciled line with each cut. The bottom riser should be cut one tread thickness shorter than the others. Step Three: Attaching the StairsPlace plywood where your landing will be. This will become the connection point for your stringers.Position the stringers on your layout marks and fasten them to the riser from behind. Each riser must be cut exactly the same as the others. This will ensure that the stair does not vary in width.Securely attach the risers to the stringers. We recommend using glue and screws to make a permanent bond and eliminate squeaks.Fasten the treads to the stringers with screws and glue. Place the screws from behind the riser into the edge of the tread. This will provide more stability because everything will be bound together as a unit. As you will see in this video, you can keep things simple or make them very fancy. Step Four: Attaching the HandleAll stair cases should have a sturdy rail. This is an important safety feature and it needs to be built properly and meet your local building codes. Handrails can be fancy or they can be no-nonsense. It really just depends on the look you are trying to achieve.