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/
4) Build new stringers, adjusting each by 3/16"
I'm slightly loathe to do #4, given my construction skills and the
relatively easy 'fixes' proposed in #1-3. Thoughts?
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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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.
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
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
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
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
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.
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! :)
Heh I learned from a respected engineer this that applies to cutting
"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.
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
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.
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