New Basement Staircase build advice

[branimal]

I'm in the process of building a new staircase from the 1st floor to the basement. The opening in both directions is somewhat limited. From the landing to the headroom obstruction I have 98 3/4". Staircase width from foundation wall to staircase header I have 30 1/2".

Headroom obstruction heaight is 87 5/16".
Total Rise is 98 5/16".

Based on the math I believe I can get:
unit rise: 7 9/16"
unit run 8 9/16" with 1 1/4" overhang.
Treads : 1 1/16" pine from lowes

Headroom clearance = 78 3/4". Short of the 80" requirement.

I think I'm going to leave the foundation wall exposed in the staircase area. I will also leave the staircase header exposed. Wall and header will both be cleaned up and painted white with a grace spray gun.

While this is not ideal, nor code compliant, this is the best I can get. FYI - I am not getting inspected. This is a 100 year old brooklyn rowhouse. The staircase I removed was more like a ladder than a staircase. And the width was 25-26".

The pipe in the picture will run thru a riser. There will be a toilet under the staircase. See toilet pvc stubout. String will sit on PT lumber. 1st floor landing and basement floor will be LVP 1/4".

I've never built a staircase before. Looking for some advice and tips.

Thanks.

 

[duneslider]

In old houses, sometimes it is what it is and you can't do anything about it. If you can't make any adjustments to the opening size you don't have much choice.

That said, when I was a kid we flipped our stairs and due to how the framing was with the flip the opening was essentially smaller in reguards to the headroom. In our case we got city/code approval to bend the rules and 8x9 RR were approved. It did make for steep stairs. I wouldn't recommend it for the older folks but at the time my parents were pretty young so it wasn't an issue. Make sure your hand rail is good and sturdy.

 

[larry4406]

Where are you hitting your head?

At the bottom of the proposed stairs? If so, it appears that the 1st deck has 2 sets of headed off joists with mini (short joists) in between. Perhaps you can encroach in this space by reducing the vertical depth of the head knocker and the mini-joists.




I had a similar head height issue at my basement stair. I shifted the joist (mines under a cabinet above) to net the needed head height. I moved my header to above the subfloor (its the one with the orange foam) and glued and screwed the subfloor up from below. If you have same, this should pocket under the stair tread from above.

 

[branimal]

Where are you hitting your head?

At the bottom of the proposed stairs? If so, it appears that the 1st deck has 2 sets of headed off joists with mini (short joists) in between. Perhaps you can encroach in this space by reducing the vertical depth of the head knocker and the mini-joists.




I had a similar head height issue at my basement stair. I shifted the joist (mines under a cabinet above) to net the needed head height. I moved my header to above the subfloor (its the one with the orange foam) and glued and screwed the subfloor up from below. If you have same, this should pocket under the stair tread from above.

As you noted - The headknocker joist is the supporting the staircase stringer above it. One side of it is resting on the foundation wall. The joist behind it is a full joist.

I'm not sure how I could move it and still provide support for the stringer. I'll go down there and poke around.


FYI - I put those "mini-joists" in a year ago thinking I was firming things up. It probably doesn't do anything.

 

[LopezBart]

Would an alternating tread stair help meet your space constraints?

Alternating Tread Stair Dimensions

The correct stair dimensions for alternating tread stairs include a 50-70 degree incline, 8-11 inch step depth, and 8-10 inch riser height. Learn more inside.

oakvalleydesigns.com

 

[larry4406]

What is the net horizontal distance from the beginning of the framed opening to the head knocker? This is an important piece of the puzzle.

Google says max allowable rise for Brooklyn NY is 8.25" and minimum residential treads are 9"+ nosing.

Some basics of stairs:

• Number of risers is always a whole number
• The number of treads is always one less than the number of risers.
• When head height is a concern, you want the tallest riser allowable to minimize the number of treads
• When head height is a concern, you want the shortest allowable tread to minimize the total run.
• Risers are numbered sequentially upward from the bottom.

So lets play with some math in Excel. From this we learn that a 12R stair with 11 treads is the max riser that does not exceed 8.25". Red is bad, green is good. The bottom chart shows the elevation after stepping sequentially down from the upper deck to the concrete floor below. It also shows the total run and the net vertical head height from that elevation relative to the head knocker. So, we need a run of at least 108" to avoid the head knocker.

What is the horizontal distance from the beginning of the framed opening to the head knocker? If it is less than 108", then you accept it as is, or try to pocket it upwards. If the framed opening is 108" or longer, then a 12R stair at 8.193" riser height with 9" treads plus nose works.

Note that a tall riser height coupled with a short tread, makes it uncomfortable. For comparison at the day job, we target a Rise of 7.5-7.75" with a 10.5" tread+ nose.

 

[branimal]

Thanks for the detailed response.

The headknocker (HK) is 98 3/4" (horizontally) from the staircase opening.


Scenario 1:
8 1/4" rise and 9" run certainly works. A plumb line from front edge of the 2nd step would be 8" horizontally from the HK. I'm using that as a feel of what a person might perceive when walking down the staircase. Headroom clearance would be 79 1/16" from 1st step. Angle would be 42.125*


Scenario 2:
7 9/16" rise and 8 1/2". Not code compliant on the run. But the staircase isn't code compliant b/c minimum tread width is 36". A plumb line from front edge of the 2nd step would be 4 1/2" horizontally from the HK. Headroom clearance would be 79 3/4". Angle would be 41.5*

Both scenarios would have 1 1/4" overhang treads.

Scenario 1 is code complaint on run minimum. But a bit steeper.
Scenario 2 might feel more comfortable walking. But not code compliant.


The other staircases (1st floor - 2nd, 2nd to 3rd) have runs of 8 5/8". I don't plan on rebuilding those staircases. Not enough available run to make a meaningful impact.

 

[larry4406]

Your riser is 8-3/16 not 8-1/4. May seem like splitting hairs, but the error will cascade and you end up with either a stair out of level or an unequal riser. 98-5/16 divided by 12 = 8.1927 which is nearly 8-3/16.

Within a stair flight, the max allowable difference between the minimum and maximum riser is 3/8".

79" of head height while standing on the first tread from the bottom is 6'-7" while Code wants 6'-8". I would be inclined to proceed as-is at 12R, R=8-3/16", and a tread length of 9" + nose. You could change the head knocker to a reduced size joist to pick up the 1".

I think if you shorten the tread, it will be very uncomfortable to walk on.

 

[CraigStu]

I'd build it how you want and add corner guards.

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