BobAtVandy wrote:

The ceiling in my outdoor lanai in Florida is drywall with papered and
compounded seams. The paper is coming up in places and there are signs this
has been repaird in the past so I want to eliminate the problem. The
ceiling is exposed to outdoor humidity, but completely protected from rain.

I've investigated various solutions, including vinyl beadboard sheets, wood
planking (v-joint or beadboard), and hardipanel. By far the least
expensive, is hardipanel, but the problem is how to handle the seams. An
easy solution is to cover the seams with a batten and try to make it look
decorative, but I'd prefer a completely flat ceiling as I have at present.

Hardie Products recommends caulking seams, but caulk shrinks, can't be
sanded smooth, etc. So, my thought is to leave, say 1/8" (or less) crevices
between panels and using plaster (no joint paper) to fill them, and sand it
smooth. (Hardipanel is very little thermal expansion/contraction.) The
Hardipanel comes in a smooth finish, but it's pre-primed, including the
edges. My questions therefore are primarily as to whether the plaster would
do the job.

1. Will the plaster adhere adequately to the pre-primed hardipanel?

2. If not, if I simply roughed the edges with a coarse file, would that
solve it sufficiently?

3. If you think the plaster will work, and assuming it gets a good coat of
paint, will there be any other long-term issues using plaster?

4. If, instead of intentionally leaving gaps into which plaster could fill
(and hopefully adhere), I butt the seams and just use plaster to fill the
fine remaining crack, does that make the solution better or worse?

5. Do you have any alternative solutions that will give me a ceiling that
has very low long-term maintenance?

Many thanks in advance.





We have similar ceilings in our condo atrium .. under roof but not
enclosed. AFAIK, it is ordinary wallboard (old) with no taped seams.
Seams are caulked but not filled up and the edge of the wallboard shows.

Our patio, with concrete balcony above, has 1x4 wood boards as the
ceiling (painted). I would be concerned about bugs getting behind the
panels if the seams and edges aren't filled. Ordinary wallboard should
work fine if the seams and edges are sealed up well and all painted.

I don't know how Hardie compares to ordinary wallboard for
shrinkage/expansion, but flexible caulk allows for it much better than a
rigid compound. You can order the seams so that they are evenly placed
and leave them visible, with just a little caulk to seal the seam but
not fill it up.