Replies

1. 
   calvin | Dec 21, 2021 10:37pm | #1

   Have you thrown down a long straightedge to gauge the waves in the subfloor?

1. 
   dan_ya | Dec 22, 2021 06:02am | #4

   Hi Calvin, Yes I did quite a bit of flatness checking of subfloor. I have/had some local sags. Worst was over about a 4' by 2' area with max dip of about 5/8". I glued and screwed plywood over the dip and feathered with multiple plywood thicknesses. That sag is about 3 feet from the subject end wall. Along the end wall, the subfloor seems pretty flat, less than 1/8" gaps in the area of my pictures. See attached file. I will also reply to CT Yankee's comments and double check near the end wall.

   
2. 
   ct_yankee | Dec 21, 2021 11:08pm | #2

   Calvin offers good advice. Better still, pull a string line along the entire length of the gable end wall. Set the string 3/4" or 1" above the subfloor at each end. Pull the string as tight as possible. Measure the gap between the string and the subfloor at regular intervals.
   The goal is to determine if the floor is actually flat and not sagging.
   Are the floor joists parallel to the gable end wall or perpendicular to it?
   It may also be helpful to understand how the floor is supported in the garage space below.
   [CT, MA, RI structural engineer here]

1. 
   dan_ya | Dec 22, 2021 07:14am | #6

   Hi CT, See attached document and pic. I used my laser level. Measurements are in Red.
   Joists are shown on Floor Flatness info document, numbered 1 thru 18 and running perpendicular to the gable end wall. In garage, there is an dropped beam in center running front to back and supported by two steel lally columns in addition to the end walls. The joists sit on top of that beam (about a 12 ft span on each side of beam). Did not see any visible damage in garage (no cracked plaster, no water stains)
   Thank you for any info regarding cause and remedy.
   Dan

   
3. 
   unclemike42 | Dec 22, 2021 06:02am | #3

   It seems to me the most likely story is that this gap was there when the wall was installed.

   second story, likely the wall was framed and sheathed laying on the deck, with the sheathing running long so it would meet sheathing on the exterior wall which was installed short to leave a gap below the floor line. So now, in addition to wherever the wall frame sets on something to hold it up, the sheathing is holding up the wall. Not ideal, but as a gable end, the roof and ceiling loads should be on the adjacent walls, so not as much of a concern.

   the floor framing and subfloor had some defect. could be the rim joist was high and deck installed around it, it is also possible that an extra piece of wood was on the deck that should have been removed before the wall went up. say some strapping to hold a tarp or plastic in place.

   But it is what it is now. how long has the house been standing?

   With the gap, can you determine where (or if) the wall bottom plate is nailed to the floor?

   I defer to the structural engineer, but it seems to me like shims to fill the gap close to the wall stud locations would be a fine idea, as would filling the rest of the gap with expanding foam to improve the air sealing and insulation while you have this open.

1. 
   dan_ya | Dec 22, 2021 07:36am | #7

   Thanks for reply, The house was build in 1987 and I am the original owner. Yes, I can see/feel nails in the gap, one nail near every joist.

   Wow, extra piece of wood! It very well could be, because in some places that wood is only an inch behind the sole plate.

   Regards,
   Dan

4. 
   andy_engel | Dec 22, 2021 06:28am | #5

   I see things like this all the time, particularly on walls that aren't particularly weight bearing like gable walls. The sheathing keeps the exterior wall the same dimension, while solid-sawn floor joist shrink and pull away from the plate.

5. 
   andy_engel | Dec 22, 2021 08:15am | #8

   I don't think this is a structural issue. The joists shrink in the winter and pull away. In the summer the gap probably disappears. Fill the gap with acoustical sealant for air sealing and carpet away.

6. 
   ct_yankee | Dec 22, 2021 11:55am | #9

   I think you've got your answers. True craftsmanship in framing is rare.

7. 
   dan_ya | Dec 22, 2021 03:20pm | #10

   Thank you all for the feedback and advice. I will go with sealing gaps with adhesive and / or spray foam and maybe a couple shims in the big gaps. I'm pretty sure the gap was there in the summer, so filling it makes sense to me. Glad to hear it is not a structural concern.
   Dan

1. 
   Simi19 | Feb 13, 2022 10:08pm | #11

   Any news on this fix? I have the same issue and i was curious if it worked

1. 
   dan_ya | Feb 14, 2022 04:52pm | #12

   Well, I did squeeze some construction adhesive in the gaps and put a couple wooden shims where the gap was biggest. As far as determining if it "worked"....I guess I will never know. Perhaps even if I did nothing, it would have been fine. Maybe someone else would know the consequences of leaving such a gap? This was only one room, if this is a construction related issue, I imagine I probably have more gaps that are hidden....
   Good Luck ,
   Dan

1. 
   Simi19 | Feb 14, 2022 05:05pm | #13

   I think i have the same issue, only one wall. I changed the flooring for the entire second floor and saw the issue at a non-bearing wall.