How many steps would I need for my deck?

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Old 08-29-14, 04:42 PM
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How many steps would I need for my deck?

I just put on a new deck, I want to buy pre made stringers for my steps. The deck measures 37" from the ground to the top of the deck. How long of a stringer or how many steps would I need?
 
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Old 08-29-14, 04:56 PM
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37" / 5 steps = roughly 7 3/8" rise each. So 5 steps is the minimum number of steps you could have. Steps 1, 2, 3, 4 are on your stringer and the 5th step will be the one where you step up onto the deck surface (not part of your stringer). So if your treads are 10" each, the stringer would have a run of 40"... so a 48" piece "should" be long enough. You might get a 16' piece if you're making 3 stringers, though, and have them cut it into 3 equal pieces that you can fit inside your car.
 
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Old 08-29-14, 05:16 PM
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Actually, the stringer run will be longer than both 40" and 48". The sum of the 4 treads is 40", in a horizontal plane. Stringers will be inclined, at an angle whose tangent equals 37 divided by 40: Arctan 37/40 = arctan 0.925 = 42.8 degrees. Stringer run = 40/cos 42.8 = 54.5". A quick check using the Pythagoras theorem: 37 (squared) + 40 (squared) = 2969; square root of 2969 = 54.5".
 
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Old 08-30-14, 03:38 PM
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The stringer could be drawn as 4 triangles placed point to point in a stairstepped manner. 3 of them will have a rise of 7.375, and a tread of 10, so their hypotenuse is 12.42. The 4th triangle will not have a rise of 7.375 since the tread height is deducted from that run. So that 4th triangle would be, let's say 6.375, assuming he uses 1" thick decking as the treads. The hypotenuse of that triangle would be 11.86. The length of the stringer is the total length of the hypotenuses added together.

So, 12.42 + 12.42 + 12.42 + 11.86 = 49.12". That's how long the stringer would be. I really didn't want to figure out "exactly" how long it would be, but you forced me to do the math, bridgeman. LOL! I hated showing my work in school.

I dunno why we have different numbers but I do know that stairs as mentioned above are usually around 34-37, not 42. So maybe your rise is wrong. I didn't calculate that stringer would go to the top edge of the deck. It starts 7.375" below the top edge of the deck framing.

Either way, a 16' piece cut in thirds will be plenty long.
 
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Old 08-30-14, 04:07 PM
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I made the mistake of using a total rise of 40", but instead should have only used 4 risers at 7.4" each, making the total rise for the 4 steps just 29.6". Arctan 29.6/40 = 0.74, or an angle of 36.5 degrees. Stringer length will be 40/cos 36.5 = 49.76", plus some "meat" for anchoring into the deck framing (inside of platform).

It's easier for me to use geometry instead of keeping track of and counting little triangles. I sometimes even forget what I go to the refrigerator for.
 
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