Fine Woodworking Ideas - Building Outdoor Stairs . part3

Fine Woodworking Ideas - Building Outdoor Stairs 

Part 3 DESIGNING YOUR STAIRS 

• To design the stairway, first find the total rise. Divide that number by 7

(the ideal riser height) to find the number of steps. You'll probably have  a fractional remainder, so round your result up or down to the nearest whole number.

Fig 4

Common tread-to-riser ratios. From the Sunset book, Decks, © Sunset Publishing Corporation.

• Then divide the total rise by that number to find the exact height of each riser. For example:

1) Total rise = 40-1/2"

2) 40-1/2" divided by 7" per riser = 5.78 risers

3) Round 5.78 up to 6 risers, then 40-1/2" divided by 6 = 6.75" or 6-3/4" per riser

This document assumes that the total run is not limited, so you can make the assembly as long as you want. Use the following table to determine the width of the treads, depending on your riser height.

Riser Height          Run Width

6"                              14"

6-1/4"                     13-1/2"

6-1/2"                        13"

6-3/4"                     12-1/2"

7"                               12"

7-1/4"                      11-1/2"

7-1/2"                         11"

• To find the amount of material needed for risers, simply multiply the number of risers by the passage width. To find the amount of tread material, subtract 1 from the number of risers (you'll need one fewer tread than risers) and multiply by the passage width. Remember to double up if you'll be using two boards for each tread.

• To find the length of the stringers, you'll need a calculator with a square root function. First, find the total run (number of treads multiplied by the width of each tread).

• Then find the square of the total run (total run multiplied by itself) and the square of the total rise and add them together.

• The square root of the result gives you the exact stringer length; round up to the nearest standard lumber length, then multiply by the number of stringers you'll need.

Fine Woodworking Ideas - Building Outdor Stairs PART 1  --- PART 2 --- PART 4

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