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Floor level survey for cracks


ThomasE's Avatar
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01-13-09, 02:24 PM   #1  
Floor level survey for cracks

The short story:
I have some cracks in my wallboard and, in an attempt to figure out what is causing them, I did a floor level survey. My question is:

If I were to repeat the same survey in a few months or a few years, what magnitude of changes in elevation would be acceptable / unacceptable?

The much longer story:
- Our house is a tract home from the late 50’s (cheap construction - but good quality lumber).

- I did the floor level survey using a water level and made an attempt to account for different floor thicknesses in some of the rooms (carpet vs. new/old hardwood vs. linoleum).

- There is currently a maximum 1.5 inch difference in level between one side of the house and the other but no significant abrupt changes over small distances. I imagine there is no sure way to determine whether these level differences existed since the house was built or occurred later on?

There are no cracks in the foundation. (We have perimeter foundation with crawlspace and additional foundation walls below weight bearing inner walls, no posts).

I do though have one somewhat large crack in my kitchen ceiling 1/8” to 3/16” wide and 5 ft long between wallboard sheets. I had put pencil marks on the crack 10 years ago and there seems to be almost no active movement. I checked the foundation below that area more carefully and I can see no cracks or dislocations. Also, the floor level survey did not reveal any abrupt changes in floor level in the vicinity of this crack.

I also have some smaller (less than 1/16” wide) cracks in a few places between wallboard sheets and a few narrow but short (4” to 12”) diagonal cracks around two doors. These smaller cracks seem to have grown a little over the past 10 years.

So far, I suspect that the cracks are caused either by house settling/seasonal ground movement/gradual ground movement OR by some insufficient bracing on the roof corners/ceilings (I will not get into that because it would be hard to explain without a diagram). For the large crack on the ceiling, I also suspect some sort of failure in one or more of the adjacent bathroom joists. I am planning to rip the floor in that bathroom to remodel anyway, so I will get the chance to take a better look at it.

In any case, the main purpose of my floor level survey is to determine (over time perhaps) whether it is ground shifting or roof bracing that caused (still causes?) the cracks and, of course, I’m interested in taking the appropriate remedial action.

 
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01-14-09, 04:00 AM   #2  
You are making a big production out of this. You have a 50 year old development house. You don't say how long you have lived there (at least 10 years) and if you have done any work on your interior yet. If you had repaired all the sheetrock, repainted the interior 6 months ago and had all these cracks I would be worried. Go ahead and fix your sheetrock and see what happens down the road, maybe use mesh tape instead of paper. Houses settle over time. Your foundation appears to be solid.
In all likelihood, your floors and ceilings are underframed, 2x8 instead of 2x10, etc. so the floors flex slightly. Not much you can do about this.
As far as your house being an inch and a half out of level end to end, I'd be surprised if it wasn't.

 
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01-15-09, 10:16 PM   #3  
I have lived in the house 18 years and I had originally patched the cracks when I moved in, but they started reappearing after 2-4? Years. Now the cracks have regressed to a little worse than when I bought the house.

I would like to find out whether it is shifting, missing bracing or something else that is causing the cracks before I patch/replace the wallboard. For example, if it is shifting that causes the cracks, I immagine, it may make sense to first take a stab at improving the drainage (not much rain though here in San Jose California - but clay soil).

Yes, my floor joists are indeed 2x8 ,16” OC, but all spans are 12’. Would that be underframed by today’s standards?

I think though that there is a joist overload problem where the two tiolets were installed, where 2 joists were cut to install the toilet without reinforcing the adjacent joists and that is something I plan to correct once I remodel the bathrooms.

 
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01-17-09, 12:13 AM   #4  
Here are some pictures:


This is the main (largest) crack in the house, on the kitchen ceiling. It is approx 1/8” wide and runs across the ceiling, starts diagonal for about 4” at a corner and then moves along between wallboard sheets across the room (about 8 ft).


This is the second most significant crack, adjacent to the previous ceiling crack (about 3 ft away). Here you can see clearly from the marks that there is a relative shear movement beween the wallboard sheets. The marks show past alignment from about 10 years ago on 11/1998 and 1/1999. As you can see an additional 1/16” of movement has occurred since. However, I have watched this crack over the years and it seems to move about 1/16” up and down, perhaps with the change of the seasons. The peculiar thing about this crack is that it is most prominent at the ceiling and almost vanishes as you move closer to the floor.

I have checked the foundation (perimeter foundation) in the crawlspace below these cracks and I can see no cracks/displacements in the concrete. I do though need to mention that on the ceiling of the bathroom immediately on the other side of these cracks there is evidence of water damage on the ceiling, I believe an old roof leak (previous owners) must have caused this water damage since there was still a small roof leak when I moved in the house (I replaced the roof shortly after I moved in) and the old roof has signs of having been patched many times.


And finally, this is what I would consider the 3rd most prominent crack in the living room ceiling.

There are a few other cracks throughout the house but they are minor normal, I thought, cracks that one may see in many older homes.

 
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01-24-09, 02:59 PM   #5  
Those are some impressive cracks in your drywall. The last one, in your living room ceiling definitely appears to be water damage as the tape is lifting. Not quite sure what to say about the other two. If it was me, I would repair the damage and use mesh tape. The mesh has more give to it than paper tape and will hopefully hold up better. Don't know what else to tell you but I would try the mesh repair first.

 
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02-01-09, 11:39 PM   #6  
Thanks for the replies.

Craig 845: I know that the third crack looks like water damage but I think it is more a matter of incorrect patching. See, I did the pathcing myself and that was my first attempt at any house work 18 something years ago (I’ve improved some since…). But there is not any water leaking up there, I replaced the roof before patching that crack and there have been no signs of water leackage. The crack reappeared gradually over the span of a few years - what you see is now 18 years later. But I think there is some movement up there that is causing the cracks.

In any case, since I cannot see any fault with the foundation, I do have another possible theory, about insufficient bracing of roof forces in this particular house I live in, a theory I would like to get an opinion on – on a different thread perhaps – as soon as I complete the diagram I have in mind to present my theory…

…also note that my house has no sheathing on the walls, so, as I understand, all shear forces are borne by the drywall and the exterior stucco which is just stucco on some sort of compressed paper board backing (perhaps something that was used in the late 50’s?

Thanks again. For those of you who are not bored yet, I will post soon another thread with my “deficient roof bracing theory”…

ThomasE

 
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