In this tutorial we show you an example of how to make lumber exterior steps 900mm (36") wide, coming
off a deck 900mm (36") high.
Practical Safety Rules for Lumber Steps :
1 Treads must be at least 280mm (11 1/2") deep.
2 Rises must be a maximum of 185mm (7 3/8") high.
3 Front of tread must overlap the back of tread below by between 15mm (5/8") to 25mm (1").
4 There should be no gap more than 100mm (4") between the vertical distance of treads, therefore
riser boards will be needed to close any gaps. see Fig1 below
Getting Started:
To start off find the overall height from the top to the bottom of the steps.
We know the height of the deck is 900mm (36") above ground, but the ground coming away from the deck might not
necessarily be level and the slope of the ground will affect the overall height of
the steps.
To find the true overall height of the steps first measure the height of the deck
from the ground where the steps are to fit. We know that measurement is 900mm (36").
Then measure out from the deck (in the direction the steps are to go) in a
level line, one and a half times the deck height measurement (approximately).
In this case, 1350mm. (54")
See Fig 2
(A) Height of deck off ground. 900mm (36")
(B) Distance out from deck where steps will finish. This measurement is 1.5x
measurement A. 900 (36")x1.5 = 1350mm (54")
(C) Level line from top of deck.
(D) This height is the overall height of steps. 900mm (36") + 150mm (6") ground slope = 1050mm (42").
Now we know the overall height of our steps which is 1050mm (42"). Next work out
the height of each rise. This is the vertical distance from the top of one tread,
to the top of the tread above it. We know the maximum height of each rise
can be 185mm (7 3/8") max. Knowing this we need to divide into 1050mm (42") which is the overall height of the steps, to get an even
measurement of 185mm (7 3/8") or less. In this case, the even measurement is 175mm (7"), as 175 (7")
divides into 1050mm (42") 6 times. This means that
there will be six rises, each 175mm (7"), which gives us a total height of 1050mm. (42")
We have now established the dimensions of out steps.
Six Rises at 175mm (7") and five treads at 280mm (11 1/2") deep. Always make the treads 280mm (11 1/2")
regardless of the rise measurements.
The Lumber to Use:
Stringers  Surfaced/dressed treated Pine, 250x50 (2x10) finishes approximately 240x46 (1 1/2x 9 1/2)
Treads  Surfaced/dressed treated Pine, 150x50 (2x6), two per tread. Finishes approximately 145x46 (1 1/2x 5 1/2).
Riser boards  Surfaced/dressed treated Pine, 150x19 (3/4x 5 1/2).
Quantities:
Stringers  250x50 (2x10), two at 2.1m (7ft)
Treads  150x50 (2x6), ten at 0.9m (36")
Riser Boards  150x19 (3/4x 5 1/2), three at 1.8m (72")
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