Replies

1. 
   Gabe | May 02, 2003 02:51am | #1

   How long have you been screwing plywood with glue? It works better with screws.

   Assuming that you're screwing down plywood as a subfloor over concrete slab, the screw spacing would be every foot. More if it's uneven.

   Gabe

1. 
   EdJW | May 02, 2003 05:15pm | #2

   Gabe, I guess that is the way it sounded.  I was going to go with 3/16"x2-1/4" tapcons. -Ed

2. 
   Piccioni | May 02, 2003 09:16pm | #3

   Just curious - why are you screwing it down? A bit of PL and you will have to chisle it off. I think tapcons are supposed to penetrate a minimum of 3/4 into the concrete (so you need to drill a 1" hole). I would probably only use a few screws unless the floor is very uneven, but then again it depends on why you are so keen to have it screwed down. 1' on center is a lot of drilling.

1. 
   EdJW | May 02, 2003 09:38pm | #4

   Piccioni, I just figured that I would use the tapcons to secure the ply while the glue was setting up.  The less holes I have to drill the better.  -Ed

1. 
   Piccioni | May 02, 2003 09:48pm | #5

   In that case you may consider just a couple to stop the ply from shifting around and borrow some bricks or something to weight down the ply. PL sets up pretty quickly. Maybe a few 5 gallon pails of water would do. Of course, if the concrete is uneven, thats a different story. But boy, does PL hold like heck.

2. 
   Gabe | May 02, 2003 11:43pm | #6

   Don't worry about using screws to simply hold down the plywood while the glue sets, worry about the bottom veneer delaminating because you didn't screw the plywood down properly.

   But hey, don't worry, do a half asssed job and save a few bucks, you can always repost later for advice on the expensive fix for your failed floor.

   Gabe

1. 
   EdJW | May 03, 2003 12:03am | #7

   Gabe, are you recommending every foot around the edges as well as the field?  I don't want to do a half assed job that's why I'm asking the question before I do the job.  I don't mind spending the time or money to do the job right.  Thanks for reposting.  -Ed

1. 
   Gabe | May 03, 2003 12:46am | #8

   It all has to do with the slab. If the slab is perfectly level, you can probably only do it every 2 ft but most slabs have all kinds of dips and bumps. The bottom line is that the plywood can't have too many voids along the seams or walking on it over time will cause it to move or delaminate.

   Start by screwing down every 2 ft and if you can feel give as you walk on it, double up in those locations. screwing down every foot is a fairly safe bet over slab because of the rigidity of concrete versus the spring found in joists.

   The size of tapcon you mentioned is fine, in most applications, 1 inch of embedment does the job.

   Check your floor for level and if you do have a lot of dips and bumps more than 3/8 inch on a 4 ft level, you may want to fill or chip before you install the plywood.

   Never make the mistake of using one product to cover the mistakes of another. Fix the mistakes first and the end product will show quality for life.

   Gabe

2. 
   EdJW | May 04, 2003 03:13pm | #13

   Gabe and the rest of the guys that have posted, Thanks for the advice.   I'm going to start with a self leveler first to fill in the voids.  As far as the hex-head over philips, I agree that the philips do cam out so I'm going to try the square drive from McFeely's.  Guys, thanks again.  -Ed

3. 
   butch | May 03, 2003 01:58am | #9

   before using the 2 1/4" I'd try the 1 3/4", you'll probably have a hard time flushing up the 2 1/4" and  if possible use the hex head and countersink because the phillips screws can be hard to set before they cam out. Just my two cents.

1. 
   MisterT | May 03, 2003 02:26am | #10

   Tapcons are only meant to thread into the concrete 1". anything over that will not give much additional holding power and will greatly increase breakage and spinout.

   Unless your concrete is fairly green (less than 1 year old) you will probably have better results with 1/4" tapcons. 3/16 always seem too break just before you get it  flush.Mr T

   Do not try this at home!

   I am an Experienced Professional!

4. 
   Wet_Head | May 03, 2003 05:08am | #11

   What are YOU worrying about the size of women's sanitary products for here on BT?

   oh, you said TAPCONS, not TAMPONS... sorry....

1. 
   Qtrmeg | May 03, 2003 04:42pm | #12

   You've been hanging around with our dyslexic friend too much. ;-)