Landing height versus riser height

[atgcpaul]

I built an extension off my porch that consists of 4 steps. The tread to tread
height is 7". The problem is I put in the stairs before I finished off the
flagstone landing. The bottom step is about 5" above grade. If I put the
flagstone at 7" below the bottom step, 2" of the surrounding soil has to be
removed for a decent sized area. It made sense when I built the porch last
October but not 6 months later when I'm putting in the landing.

I realize code varies by region, but does the height of the bottom step to the
landing have to match the tread to tread height of the stairs? I could see it
being a trip hazard if the landing was significantly further away, but closer?

Thanks, Paul

[pelligrini]

Most codes call for no greather than a 3/8" variance in riser height. The 2003 IRC calls for 3/8". You could be expanding your lialibility if you kept it at a 2" difference.

Closer or further, the trip hazard is more a function of repititon. The body and mind will be expecting a similar height and depth when moving up or down stairs. I would assume it is not as big as a problem with 5 risers.

[HarmsWay]

I'm guessing if you leave it at a two inch difference, it will bug you every time you use it.

[master53yoda]

unless removing the soil drops the landing below grade I would remove the soil. 2" short on the bottom step will cause a thump on anyone coming down those stairs that are not conscious of the bottom step. 2" is enough to cause a fall due to buckling the persons knee.

just my 2 cents worth

[jabe]

Stair/step math

To build stairs correctly you must adhere to these rules;
1. All individual treads & risers will have uniform rise & run in any one flight of stairs.
2. The best average ht. for individual risers is 7"
3. The height of the individual risers must be proportional to the width of the tread.
4. Except in special cases, there is one more riser than treads, as the top floor acts as a tread. This means the stairs start and end with a riser.

There are 3 formulas, to calculate if your stairs are proportioned correctly:
1. The 1 tread + 2 risers = 24" to 25"
2. The 1 tread + 1 riser = 17" to 18"
3. Tread X rise = 70" to 75" total run

If your calculation conforms to the above rules you have a good tread /rise ratio that would pass any building code.

You must know the total rise, which is the top of your porch to the top of your finish landing. This is the verticle measurement from the top of your porch deck to the top of your flagstone landing.
For ease of calculation lets say the total rise is 42".

A. 42" divided by 7" = 6" Take the closest whole number which is 6, so you will have 6 risers.

B. Now divide the no of rise (6) into the total rise (42").
44" divided by 6 = 7", this means each rise will be 7"

C. Since there is no definite location where the porch steps will end, the formulas given in deteriming the width of each tread can be strickly followed.
Since there are 6 rise there will be 5 treads (one fewer tread than riser, this is cause you're using the porch deck as a tread).
11" tread + 7 " rise = 18"
* Now you must add 1" to 1 1/2" to the tread so your tread will overhang/nosiing on each step. I usually add 1 1/2" so it'll cover my 3/4" thick riser board giving me a 3/4" overhang.

I always taught my students in stairs/step math the magic numbers are 7/11.
so if your calculation comes close to these numbers you're OK.

Check calculation:
Rule 1. tread 11" + 2 risers 14" = 25 "

Rule 2. tread 11" + 7" riser = 18"

Rule 3. tread 11" X rise 7" = 77"
*2" over from the rule, you have 2 choices, leave it as is cause it's an outdoor step and the total run is not a problem. Or if the total run is limited, you can change the tread to 10 7/16" so the calculation will fall within the rule parameter in this example 73 1/16".

To calculate the total run so u will know approximately how long your stringer should be is:
No. of treads is 1 less than risers, in this case it'll be 5 treads.
no of treads 5 X 11" = 55" total run
The total run measurement gives U the approximate location of your landing from the porch deck.

** I would use a 2 x 12 X 6' to make the stringer.
*** when laying out the stairs you must subtract the thickness of 1 tread from the bottom step rise. So if you're using 2 X material for your tread, subtract 1 1/2" from the bottom step rise so it'll be 5 1/2" rise. All other rise on your layout will remain at 7".

I would recommend buying a Construction Master calculater and borrow a carpentry book like "Modern Carpentry" from your library so you can see all the sample diagrams on stairs construction. This is long but it'll meet code if done correctly, I hope this helps.