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RE: Finishing a curved ceiling - need some advice

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< 1. Remove and replace the ceiling to allow the radius to be formed from
two 
layers of 1/4" gypsum board which is intended to allow the layers some room 
for movement. I believe that the USG book covers special conditions where 
curved surfaces are covered. >
We just finished several interior jobs with curved walls/ceilings.  The
contractor was very familiar with the techniques required for this
construction using gypsum board.  They were very adamant about using the
layered system.  For walls, two layers of 1/4" were used.  For ceilings, two
to three layers were used depending on the radius.
< 2. Remove and replace using metal "Hat" channels between the joists and
beams 
and the Gypsum to allow for flexibility in the ceiling without transference 
of cracks in the gypsum. >
In my opinion, flexible gypsum board anchors would be more appropriate.
These anchors are usually specified for acoustical control between
rooms/floors.  Make sure the contractor installs them properly because we
inspected a wall that had all of the anchors flattened which defeated the
whole purpose of putting them in.
< 3. I also suggested that the owner might consider finishing the ceiling in
an 
elastomeric finish which would stretch with the movement in the roof. >
The elastomeric finish would conceal the cracks; however it will conceal
other tell-tale signs of structural cracking and/or water infiltration.  We
inspected a masonry structure with an elastomeric finish.  It looked great
on the outside but water had no way to get out and this caused extensive
corrosion of the structural steel frame and deteriorated the masonry.
< 4. I have heard that the ceiling should have been finished in lath and 
plaster which would have been more forgiving for movement and creep as the 
lath would allow some play in between the materials. >
Installing a lath and plaster ceiling on black iron channels with hangers is
the system I would recommend for this application to allow for the greatest
flexibility between the ceiling system and the roof framing system.

Does anybody who inspected the construction know if the contractor taped the
joints?  I know this sounds stupid but I've seen this happen in houses and
it usually occurs at 3 p.m. on a Friday and nobody remembers to finish the
job on Monday morning.

William J. Keil, P.E.