When building outdoor stairs, the simplest way is the best way. This means that you can use two 2 X 10's or 2 X 12's as stringers and then attach the stair tread by means of a metal bracket. This saves the need for notching the stringer, a process that can bring on rapid rot in the great outdoors. Instead build a simple pair of stringers and nail the treads from the side and then add metal support brackets underneath each tread to insure a strong set of stairs that is not as likely to develop a quick case of the fungus or mould.
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Things you need
- 2 X 10 or 2 x 12 framing timbers
- Circular saw
- Saw horses
- Safety glasses
- Framing Nails
- metal stair brackets
- Framing square
- Short galvanised box nails (1 1/2 inches )
Measure the overall height of the stairs (this is called the rise) so that you can also calculate the run as well. For example if you have a four foot height, your run will be about 70 inches or just about six feet. How is this done? By using the ratio of 7 to 10 for all calculations. This means that all your treads will be 10 inches wide and 7 inches apart in height. So for a height of 48 inches we get approximately seven steps that are located seven inches apart. (Actually 7 steps would need 49 inches of height but that is close enough.) So seven risers need seven treads and since the treads are 10-inches wide that adds up to 70 inches. That means we will be landing our stairs 70 inches away from the edge of the deck.
Prepare the surface of the ground at the 70 inch mark. Prepare a large enough area to insure a level spot. A gravel base can be added if you live in a wet climate and drainage is a problem.
Place two ten foot long boards on a pair of saw horses. And cut each end close to one end using a framing and a 7 to 10 ratio. Use the framing square by placing the outside corner on the bottom side of the board. Tilt and move the square until there is a seven inch and a ten inch gap between the inside corner of the square and the bottom of the board. The seven inch gap will be towards the top of the stairs and the ten inch gap will be towards the bottom. Mark this line and cut along the line with the circular saw. Do the same for the other stringer.
Mark the first stair. It will be a line that is 8 1/2 inches below the top point. Why 8 1/2 inches? Because you have to add the thickness of one tread to the first measurement. This is because the two stair stringers will attach to the frame of the deck just below the deck planking. That is why you add the 1 1/2 inches. (If your deck is thicker then that number will change slightly.) So come down 8 1/2 inches following the cut that you just made from the top point and make a mark. Put your square on that mark and extend it exactly ten inches along a perpendicular line. This is the location of the bottom of your first tread. Now continue down the board by going down 7 inches and across 10 inches. Do this for all seven stairs. If all lines are perpendicular and your rise is always seven and run or width of the tread is always 10, you can stop at the end of the seventh step and admire your handiwork. It should vaguely resemble an Aztec line. Don't stop now, for we got an eighth step to mark. The final tread will be only six inches because it begins at the bottom of the tread and goes to the ground. So make a right angle turn and head down 6 inches and make another right hand turn and continue this line all the way across the board. This will be the bottom. Repeat this layout for the second stringer.
Build the stairs separate from the deck. First attach the metal corner brackets (these can be purchased at most hardware stores). Use 1 1/2 inch nails to secure the bracket to the stringer to the bottom of each line. For seven stairs you will need 14 metal brackets. Then choose a length for each tread. From 2 X 10 stock, cut seven treads with square corners. The 1/2 inch difference won't matter; 3 or 4 feet is a good length for outdoor treads.
Nail the treads in place. Use #16 Common nails to drive the stringer into the end of each tread. Next, drive 1 1/2 inch nails upwards through the metal bracket and into the tread. Attach all seven treads to the two stringers before you install the set of stairs against the frame.
Nail the two stringers into the frame of the deck with 8 to 10 framing nails. Be certain the top of the stringer comes right up to the point where the deck boards meet the frame.
Adjust the gravel pad where the bottom of the stairs meets the ground to insure that both stringers share the weight of the stairs.
Tips and warnings
- Paint your stairs with latex primer before construction.
- Make sure all lumber is in excellent condition.
- If you use redwood or any other rot resistant wood, you might need thicker timbers.