On Apr 17, 9:07 pm, Italian Mason wrote:
On Apr 17, 5:26 pm, "Steve W." sjwNOSPAMatripnet.com wrote:

Hello, I am screwing down some plywood before I begin a tile job. I am
uinable to locate the floor joists, as the basement ceiling has been
drywalled covering the joists. How am i to screw the sub floor down into the
joists if I can't locate them. Is it imperative that I screw into the
subfloor?
regards
Steve

I think what you mean to ask is "is it imperative that I hit the
joists?" the answer to that is NO
If you are putting down plywood for tile I'm assuming it is on the
floor and not the ceiling. I am also assuming that this is not a NEW
sub floor otherwise the joist would be exposed. So that tells me you
have a wood floor that you are putting plywood over to do tile on.
first of all why plywood and not something like hardibacker? second if
you have a sub floor weither you use plywood or hardi you should put
coated screws in 12" on center and closer on the joints.http://palmisanoconcrete.com

Procedure for screwing them down? In other words, do holes need to be
predrilled & countersunk to prevent that "bump" from forming as you
drive a countersink screw into a non-countersunk hole? Or do you sand
the 100's of bumps? OP didn't specify what type tile he is setting,
but if CVT it will show every irregularity in the plywood,