Josh wrote:
I'm getting ready to set some ceramic tiles on my kitchen wall for a
backsplash. A few days ago I screwed a couple of very straight 5'
steel bars end to end horizontally along the wall studs, to serve as a
ledge to mount the first row of tiles on. I was very careful to get
the two bars' ends completely flush with each other and level, using a
good accurate 48" Johnson level. I checked their level later that
night, and again the next day. Both bars were dead-on level.
Yesterday I checked their level one more time prior to beginning the
tiling and guess what: they're both off somewhere between an eight and
a quarter of an inch.

I set the level at the same place on the bars each time, and used the
same side of the level. The bars can't slip....they're still securely
screwed to the studs behind the drywall. And their ends are still
flush with each other, so I have a good 10' straight edge along the
wall. But what's up with the changing level?

This house is a 50 year old single story brick veneer, built on a
concrete slab in West Texas. Is it normal for houses or individual
walls to shift that much from day to day? Maybe due to temperature
variations?

I'd be more inclined to suspect the different expansion rates of the
steel bars and wall structure during temperature swings. Most people use
an eyeball-straight 1x4 for what you are doing. Not like you are lining
up laser optics or anything, here. Lay a marble on the bar, and see
which way it wants to roll.

Having said that, this is Texas, and the laws of physics on your
infamous clay soil are different at times. Had any rain or big temp
swings outside?

I'd not lose a lot of sleep over it. Most people set the counter and
upper cabinets before they set the backsplash, and fudge as needed so it
looks right. Eyes looking at it will key off the back edge of counter
and bottom edge of upper cabinets. Tile is seldom gauge-block uniform in
size and square anyway.

--
aem sends...