Replies

1. 
   Guest_ | Dec 13, 1999 12:27am | #1

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   Another explanation for this (and quite often occurs in my region of Southeast Texas) is that the expansion and contraction of the engineered joists, or the trusses, is on a different scale than the wall framing (top plates included).

   What happens is the joists (whether engineered or truss) expand, and bow slightly upward (toward the roof), or contract, and bow slightly back toward the room. This bow is very slight, but it lifts the ceiling drywall with it. This opens up the joints at the ceiling/walls.

   Install crown molding at the seam (wall to ceiling) but attach the crown to the ceiling joists ONLY. Do not attach the crown molding to the wall or top plate. Also, do not caulk the bottom of the crown molding. When this is done, and the joists expand or contract, the drywall on the ceiling, as well as the crown molding attached to it, will move ever so slightly upward or downward, but the crown molding will cover the open seam, and you will never know it is there.

   I have seen this happen on homes that had excellent ventilation (both home and attic), and have seen it happen often. I see a lot of new custom homes now where the builder already anticipates this as a potential problem, and installs the crown molding before the homeowner ever moves in. The homeowner never knows this expansion and contraction is taking place.

   The use of engineered lumber has its drawbacks (very small, and very few) but the advantages far outweigh those drawbacks. This is just one of those drawbacks, and isn't happening everywhere. The most common areas (according to some manufacturers) are wet, humid regions, and very cold regions (lots of snow).

   Just my humble opinion...

   James DuHamel

1. 
   Guest_ | Dec 13, 1999 02:51am | #2

   *Another thought is that perhaps the ceiling drywall was screwed too close to the walls, eliminating any flex as the ceiling joists move as described above. This is a common problem with "truss lift" over non-bearing interior walls. If this is the case, you might be able to pop the ceiling sheet rock loose a foot or so back from the walls, working carefully from the attic above with a 5-in one or a flat bar. Since the perimeter of the ceiling sheetrock is supported by the wall sheetrock, the ceiling won't come crashing down, your taped joints should hold, and the crown moulding wouldn't be needed.Good luck, Steve

1. 
   Guest_ | Dec 17, 1999 08:25am | #3

   *I built an addition on my house a few years ago, The first winter (3 mos) after completion, There was a crack that formed all the way around the room at the DW joint at wall/ceiling. I tried to patch it, it came back less than a month later. I figured the foundation settled, or moved with the frost heaving. Then I remembered it poured rain after I had all the rough framing/sheathing done, and thus the studs were swollen with moisture when they were insulated and DW`d only to shrink in thickness and in length as they dried out. Then I remembered I used that wonderful DW mesh tape, yep that must be the cause of it? I still dont know why this happens for certain, but my professor at the U said it usually happens with lower sloped roofs, since the rafter lies close to the ceiling joist, there is much more expansion/contraction going on, due to the shingles fluctuating in temp, thus causing the c. joist which is very nearby, to constantly change. I guess his point is, the steeper the roof, the more distance you have between these two, causing a more stable environment. I also didnt use hurricane ties, which as of ever since, I will never set a truss/rafter without one. So its real hard to say what exactly caused mine to do it, probably a little of each, I guess? The gap I had got as big as 1/8" at its worst, and nearly disappeared in the warmer months. The gap is now caulked shut behind some nice crownmoulding, and looks good as new. Hope this helps-

2. 
   Chris_Briley | Jan 06, 2000 09:15am | #4

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   Is your bedroom an attic space? With rafters above and joists below, as in the room exists in a space that is basicly a triangle?

3. 
   SP | Jan 06, 2000 09:15am | #5

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   I added a third floor BR to my home in Chicago. The roof is TJI spanning the full room. The non-bearing walls inside run perpendicular to the joists and create a bathroom and closet. For the second winter in a row, the ceiling drywall (which is screwed directly to the joists) is seperating from the wall drywall. The ceiling insulation is stapled to the face of the joists. What did I do wrong and is there any way to fix this problem now? Any help will be greatly appreciated.