Saw this today. Apparently when the home was built 13 years ago, the carpenters weren’t paying attention and cut the stringers, and sistered in some 2x4’s. What say you? Would you report it, if so what would you say?
I don’t think its a problem. The stair stringers are not going anywhere.
I did note the crack a the one cut out. I would have nailed the stringers into the wall joists as well.
This is a simple fix for reinforcing the stringer. If the stairs were solid when you put your body weight on them, they’re fine. Simply note on the report “to monitor reinforcements under basement stairs, for worsening”.
Thanks guys, that’s what I was thinking too. I appreciate the re-enforcement.
In your second picture it looks like the 2 x ? lumber for the stringers were to short and they pieced the stringer together using a 2 x 4. This is very poor/sloppy craftsmanship. Are the stairs solid, do the stringers or treads have give; move and squeak? If they are solid, I would write it up as non standard construction/poor craftsmanship. If not solid; recommend a qualified contractor should evaluate and make repairs as necessary.
Gary
They were solid…I’m 250, and didn’t notice a thing going down them shortly before seeing this underneath.
There were several 2x4’s that were 3 to 4 ft in length.
Hi. Mark;
Looking at your pictures a few things caught my eye and that would be, why add a 2 x 4 to a stringer that is nailed to the wall?
In the first picture, you can see three members, the first one is a 2 x 4 nailed to the wall studs and this provides room for the drywall and the 3/4" skirt board above the stairs.
I also noticed that the standard of not providing a pressure treated shoe on the concrete floor to support the stair stringers was not installed and some evidence of moisture absorbtion by the concrete and wood contact is evident. Should be repaired, the riser closure at the bottom is also wicking moisture and rot is possible.
The other point is why add an addittional 2x4 when their is no splice in the 2x12 stringer.
Then I noticed that the stringers were being worked on by the carpenter on his horses and drove the skil saw blade through the surface in a few locations. That can be seen in two pictures.
Where this would in fact weaken the stringer, he added a scab.
The stair is not going anywhere, but would note what I saw in this scenario.
Hope this helps.
Marcel 
Thanks Marcel,
There’s been some “finishing” going on in the basement, and this wall has been added sometime after the stairs were built. So the fact that we can’t see the stringer nailed to the walls doesn’t bother me.
As to the moisture staining on the wood/floor, what you are actually seeing is dirt and cobwebs (not clear in the reduced res image.). It was dry, and there was no wicking. (It’s obvious in person :D)
I always add 2X4s to my interior stair stringers to add strength.
I always add an extra stringer to all of mine. ha. ha.
And I never use them as a workbench while cutting. :mrgreen:
Marcel 
Marcel Are those nail s in the 2x4.?
Should they be into the studs?
Hey Bob,
The only nails I see in the picture are for the scab to the stringer.
The sequence of installation, I think was described in the other posts. I was told that the wall was installed after the fact, but usually it is not, when you see a two member stringer from underneath.
Marcel
Never saw the other posts so I was confused.
Never mind.
It looks like nails in the 2x4 to me.
Robert you are correct. Those are nails securing 2x4 sections (<4ft) to the stringer. Stringer not (visibly) attached to walls. It appears wall was installed after initial construction (but of course there is no way to know for sure). I say that because the basement has lots of open 2 x 4 walls, and “naked” drywall. And it’s a 13 yr old home. Looks like half way handy man basement finishing.