I am finishing out the ceiling of a study with stained white oak. The
ceiling has four beams laid out like a tic-tac-toe pattern. I am going
to cover the beams with 3/4" plywood. I will put 1/4 ply on the
ceiling inside each of 9 squares of the tic-tac-toe pattern (I will
attach the 1/4' sheeting with brad nails and construction adhesive). I
am then going to put crown inside each of the nine squares. Since I
have 3/4" ply on the beams, I will have a good nailing surface for the
bottom edge of the crown. If I shoot a finish nail through the crown
into the ceiling it will only have sheetrock and 1/4" ply to hold it.
Will that be sufficient to hold the crown or will I need to install a
backer strip or go into the attic and install blocking? Note that the
maximum length of any one piece of crown is 48", so the mitered ends
will somewhat lock things in place.
1/4 ply and sheetrock will be enough to hold since the top of the crown will
be relatively undisturbed. Don't shoot your nails straight in, shoot them at
different angles. This will help hold the crown tight against the ceiling
and will help prevent it from popping out if you have to stress it any.
One thing to think about... I have had crown molding warp away from
the ceiling when I have not secured it. If your molding is any kind
of hardwood, you will also face this, especially as the wood "seasons"
ion the room and dries completely over the next several months.
Remember you are finishing only the face, and the back of the unsealed
molding may cause it to misbehave.
If it is a smaller crown, the bottom only solution of nailing to he
plywood will be great as you may actually go as much as half way up
the molding. But if is the larger stuff (4" and 6") now favored for
that type of detail you will definitely have trouble with the upper
parts, sometimes just getting the original fit to be acceptable.
However, your solution is easy and you are prepared for the big
molding. Shoot the bottom of the molding into the plywood, then take
your 18ga. brad nailer and shoot a brad at an acute angle into the
1/4" plywood ceiling/sheetrock on 8" centers. The plywood/sheetrock
will hold these brads fine, and thus the molding. Then you will have
no problems as it is now secured top and bottom, and these 18ga. nail
holes are so small they are a breeze to fill and will not be visible
on the ceiling from the floor.
On 22 Jan 2004 08:07:35 -0800, firstname.lastname@example.org (Kent) wrote:
I've done a number of coffered ceilings, one of which is shown at:
That one only has wallboard in the fields, rather than ply. I'd
caution you to be careful when using 1/4" ply and
construction/pannelling adhesive. If you don't squeeze the lines of
the adhesive out they will read through as ridges in the 1/4" ply and
the ply will look wavy over time. When I've done it I've use 1/2",
which doesn't show the ridges and provides more substantial nailing
for the upper edge of the crown. If you are committed to the 1/4",
I'd think about running over the adhesive with a notched trowel and
putting a dead man or two against the panel face while it sets up
Except in the cheapest work, I've always ripped out triangular
blocking to go behind the crown molding as a nailer. You should be
able to get a good bite on the 3/4" ply by using construction adhesive
and common/box nails into the ply (or screws). Crown can twist and
the good nailing afforded by the blocking/nailer is well worth the
minimal time and expense, as you will not be able to caulk the joint
line at the ceiling and have things look nice. It doesn't have to be
ripped to the exact inside face of the crown. It just has to provide
something solid to nail into ( I prefer finish screws). You'll like
having that blocking to nail to when you get a cope that doesn't want
to lay down just right and needs a bit of persuasion.
Thomas J. Watson-Cabinetmaker (ret)
Real Email is: tjwatson1ATcomcastDOTnet
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