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Floor level survey for cracks

Posted by orourke (My Page) on
Fri, Jan 16, 09 at 13:10

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 50s (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, Im interested in taking the appropriate remedial action.

Follow-Up Postings:

RE: Floor level survey for cracks

Not being a structural engineer, just a homeowner that used to own a house from the 40's and have expeienced some of the same problems, here is my 2 cents worth.

The crack on the ceiling between 2 sheets of wallboard- I had a similarcrack that when patched would open up again in a couple of years. My house was plaster with plasterboard as the base. I attributed the crack not to settling but the heat and cooling of the attic and the roof rafters causiing the problem. the crack would always be the same when it reopened. I finally filled it in with latex caulk and painted over it. end of problem. The diagonal cracks are probably from settling. The cracks between wallboard sheets could be caused by changing seasonal humidity levels affecting the lumber. If you had major house settling you would notice it in binding doors and windows

I always figured the framing in a house subtley moved season to season.

RE: Floor level survey for cracks

"Our house is a tract home from the late 50s (cheap construction - but good quality lumber)."

It would be very interesting if you would elaborate on what you mean by cheap construction. Considering the house is now over 50 years old and the problems you mentioned seem to be minor.

RE: Floor level survey for cracks

One thing I did in my house when remodeling and all the drywall was down, was to apply lots of Simpson hardware, various plates and angles, to all doorway framing. I'd had drywall cracks in these areas so it seemed like a good idea and 4 years later, no new cracks. I recessed the wood a bit with a router, say 1/8" or so, so the hardware wouldn't cause any bulge in the new drywall. For any built up headers, I either replaced them or bolted/lagged together the component pieces, which had just been nailed.


RE: Floor level survey for cracks

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 had 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.

RE: Floor level survey for cracks

Thanks for the replies.
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. But I will post that on a different thread 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 commonly used in the late 50s? so it may have a name )

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

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