Basic stairway 'adjustment'


Hi all,
I've got 7 steps in my concrete-floor basement leading to a landing. Now I'm adding a subfloor with a height of 1.25". Stair stringers will now rest on top of the subfloor. Which is the best option?
1) Do nothing, (top step height reduced by 1.25") 2) Cut 1.25" off the bottom of the stringers (bottom step height reduced by 1.25") 3) Cut 0.75" off the bottom of the stringers (0.75" reduction on top/ bottom step) 4) Build new stringers, adjusting each by 3/16" 5) ??
I'm slightly loathe to do #4, given my construction skills and the relatively easy 'fixes' proposed in #1-3. Thoughts?
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General consensus is that if a step needs to be different it should be the top or bottom one. Many, myself included feel that it is safer for the bottom step to be the oddball. That way if use misstep there is less distance to fall.
I would shorten the bottom riser and call the job done.
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Colbyt
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Borrall Wonnell wrote the following:

5. Build a small landing at the bottom that is as level as the bottom step. This will break the rhythm of the previous stair riser heights. It doesn't have to be large, but just enough to take another flat footstep The brain will then discard the previous rhythm and prepare for the new rhythm, i.e. the one step that is 1.25" less in riser height.
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Bill
In Hamptonburgh, NY
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I'd build new stringers while the option is easy. I presume it's all going to be finished later.
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Nice one...I see you've got your thinking cap on!
A landing was my preferred option, because it allows extra width for the hallway at the bottom of the stairs. It would also simplify one of my partition walls due to an obstruction at the other end of basement.
However, there will be a door opposite the stairs, 36" away. Door location is due to rough plumbing (bathroom)...only way to move the door away from the stairs would be to move the rough plumbing. Might get expensive!
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I believe 3/8" is the max allowable variance. Rebuild the stairs.
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Build the stairs properly the first time...
Fabricate new stringers that have equal spacing so that your stairs are safe and will not have to be rebuilt at a later time...
Why are you building a 1.25" sub-floor on top of an existing concrete slab floor in the basement ? That sounds very odd unless it is some sort of over-pour to allow for the installation of underfloor heating...
~~ Evan
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Stairs with one odd riser are dangerous. That riser is known as a "tripper" for very good reasons. My BIL built a log house in Canada back when and due to logs shrinking as they dry, the second floor kept lowering. He had a 'tripper' in the stairs and even knowing it was there I would stumble on it.
Best to redo the stringers. The math and layout involved are not that bad - check out a carpentry book and read up on it.
Harry K
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Agreed, I'm convinced. By the time the finished flooring is installed, it'll be more like 1.5" difference. A definite 'tripper'. I'm still thinking about that landing idea though...in which case I've got a lot more to worry about than building a couple of stringers.

The math isn't my concern...it's my skill with a saw! :)
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Heh I learned from a respected engineer this that applies to cutting two stringers:
"It is a simple project to make one thing alike. The problem is making two things alike" :). I lay out one, cut it and then use that as a pattern for the second. The sawing is not a "millimeter accuracy" thing - close will do.
Harry K
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WHy so thick a subfloor? 1/2" is closer to what most of us would have expected.
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wrote:

Thick subfloor? Most 'standard' subfloors around here consist of 2x4 sleepers laid flat + 5/8 plywood. The subfloor is 1/2" extruded (high-density) styrofoam + 5/8 OSB. Sold in 2'x2' T&G pieces here in Canada.
The basement measures 92" from concrete floor to ceiling joists, so I'm trying to reduce my height loss while simultaneously insulating the area.
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On Fri, 9 Jul 2010 08:43:35 -0700 (PDT), Borrall Wonnell

Why not skip the subfloor at the base of the stairs. Then you'll have a 1.5 step up once you get to the bottom. Would that be a tripper?

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As others have mentioned, having one riser off by 1.25" is definitely a safety hazard and not a reasonable solution. If you don't want to rebuild the stringers, then I suggest you progressively shim the tops of the existing stringers:
First triple check that after the finish floor and finish treads the discrepancy will still be 1.25". Then cut 1.25" off the bottom of the existing stringers, so all the error is accumulated at the bottom.
Now prepare a series of shims (rounding to the nearest 1/32 of an inch): 3/16", 11/32", 17/32", 23/32", 29/32", 1 1/16", 1 1/4". Depending on your skills and available tools, you could rip each of these out of solid lumber. Or you can approximate each shim by a couple thicknesses of plywood: e.g. nominal 1/4" (actual 7/32"), 3/8" (11/32"), 1/4" + 3/8" (18/32"), 3/4" (23/32"), 3/4" + 1/4" (30/32"), 3/4" + 3/8" (34/32"), and 1/4" + 3/8" + 3/4" (41/32").
Then just apply the shims to the tops of the stringers progressing down from the top.
Wayne
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Whoops, you won't need the 1 1/4" shims, since you have already raised the basement floor by 1 1/4".
Cheers, Wayne
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