Monday, July 12, 2010

Troubles in Stair Land

Went down to the city today to check if they allow open risers on exterior, secondary stairs...nope not allowed exactly. They can be semi-open but they have to pass the 4" sphere rule. Which means that a 4" sphere can not pass thru the opening.

While I was there I browsed through the selection of hand outs and picked up their stair guidelines sheet. It looks different than the one I have.....I started reading the copy and....and....
They changed their fricken stair requirements!!!
The new minimum tread depth is 10" and the new maximum riser height is 7 3/4"!!!
Dang, I'm screwed, I thought.

To Review: A total rise of 81" and a total run of 99 1/4" is the sorta captive conditions I am trying to fit. That gave me 11 risers-stairs with individual run of 9" and a individual rise of 7 4/11". The rise is still within spec but the run is not....dang I'm going to have to go to 12 risers-steps.

I asked my question on the breaktime classic forum about the one less tread than riser thing and a nice guy produced these drawings for me. This one shows the last step being the deck. He gets a run of 9 15/16" and a rise of 7 3/8".

This is what it would look like if the last step is part of the stairs. Using this method he gets a rise of 7 3/8" still and a run of 9 1/32".

So to squeeze the most individual run in the smallest total run I did to do the top case and make the deck the top step.

Stair Math Part 2
Now its a little different. I still have a total rise of 81" but the run will be whatever it will be.
I will need to increase the riser count to 12 and then I get a individual rise of (total rise)/(# of risers)=81"/12= 6 3/4" of rise. To get the new total run I'll use the new smallest run allowed of 10" and I get. Total run= (individual run)(# of treads)= (10")(12)= 120".
Dang my new total run is 20 3/4" longer!

Referring back to the top picture that means that the new stairway will have intrude into the side yard by almost 2'!! And I'll have to pour a new concrete bottom step for the stair to land on....bummer...

But Wait All Is Not Lost

I just remembered that this is not a normal stair job, this is a normalization!
This deck and stairs where built before we owned the house without permits so we have to get them normalized. As part of that process I had to have my immediate neighbors sign papers saying that the deck had been there at least 10yrs.

Then, a city inspector came out and agreed with that number and he called out a couple of things that needed to be fixed to meet code, the stairs being one of them.

But here's the rub, officially the stairs only need to meet the code in force at the time they where built!!! That means that I should be able to use the earlier allowed rise/run and have my stairs land on the concrete retaining wall as planned.

Of course when I asked which codes where in force 10yrs ago they looked at me like I just asked them to explain Einsteins Theory of General, I think I'll have to work on that aspect....

I guess now the question I have to answer is, if the steeper stairs will be walkable enough or if they will be so bad that it will be worth the extra effort of pouring a new bottom step and the intrusion into the side yard to get a more comfortable walkable stairway?



Anonymous said...

I think the new code requirements for rise and run are there for a reason. You'd probably be happier if you built the stairs to current codes.

Do it right the first time?

Luke said...

OK, I have watched your "stair math" since the original post, with some consternation.

Suppose you go for the top option (last riser is the deck itself - I am assuming this is within code). Now the top of the deck is 81 inches above the ground, correct? The minimum number of risers you can have if you stay within code is 11 (10 gives you too high a rise, but 81/11 is less than 7 3/4). You then need 10 treads, right, one less than the number of risers? The easy way to think about it is that when you step on the first tread you are one riser height up, the second you are two, and so on, so at the tenth tread you are ten risers high, and only have to step up one riser height to reach the deck. Now 10 treads at 10 inches per tread is 100 inches, which is what you want, pretty much. So where is the problem?

Kitt said...

There's a lot to be said for stairs that are comfortable to use. Having the super-steep shallow ones in my house has been a literal pain on occasion. If you plan to use those stairs a lot, especially while carrying things (a tray of drinks, for example), you may well be happier to cede a couple of feet.

The MadScientist said...

Anon, ya they are.
Kitt our last house had a stair that was 10 and 7 and it took a couple times up and down but then it felt natural.

The MadScientist said...

I'm not sure why I have such a mental block about this....

If you look at the two CAD drawings I don't have to change the # of risers.

I just need to add 1/16 to each 9 15/16 tread to get the code minimum. Which I think adds 5/8 to the total run.