Tiling over plywood. Can I just use red guard floor membrane?

5 Responses to Tiling over plywood. Can I just use red guard floor membrane?

1. cajuntracker says:

   March 22, 2010 at 6:30 am

   If you want the floor to last, you need to check the subfloor thickness, joist spacing, size, and spans. The deflection is sometimes more than L/360, which is the maximum tile will tolerate. The subfloor needs to be 1 and 1/8" thick, typically by applying plywood underlayment (not CDX or sheathing grade ply) over the existing subfloor to reach the thickness. If this is in a bath or kitchen, I wouldn’t recommend tiling directly to the ply, as the moisture that gets to the ply will cause it to swell and pop off tiles.
   If thickness is an issue, and you can’t add 3/8" to 5/8" of underlayment to get your desired floor height, look into Shluter "Ditra" underlayment, which adds only 1/8", is waterproof, and crack isolating. It does not require 1 1/8" subfloor thickness on most joist spacings.
   References :
2. rob s says:

   March 22, 2010 at 7:05 am

   You don t say were your doing the tile, but the MINIMUM thickness of a flooring substrate for tile is 1 1/4. This is going by the ATC and TCA ( American Tile council and the Tile Council of America)..
   In using plywood it must also be a 3 ply fir..So in most cases its a 1/2" 3 ply fir. The use on either ,Red guard or Blue seal ( sry I ve never heard of that one) won t hurt you either way.. If doing a "wet area" such as a bathroom then use a waterproofing seal like Red Guard but its much safer and better off using a 1/2" cement board , thin setted and nailed down properly..
   Any questions you can e mail me through my avatar and check my qualifications there.. GL
   References :
   20 years in flooring as a store owner/installer
3. domedweller2 says:

   March 22, 2010 at 7:17 am

   Tiling over plywood is a big no-no.
   Take from someone that did it and regret it.
   There are 2′x4′panels that are made from cement and can be screwed on the plywood and then you can tile on top of that.
   One caution,they are very heavy,so make sure that the joists under the plywood are strong enough to support the wheigh.
   References :
4. John L says:

   March 22, 2010 at 7:40 am

   Yes you could but you will have problems later down the road. The secret for keeping your tiles and grout from not cracking is a good sub-floor installation. If you have 1/2" plywood, you should add at least 1/2" cement or rock board over it. Install with screw that are made for this type of installation. Then your ready for your tile installation. Make sure you use thinset mortar.
   References :
   http://tile-repair.net/how-to-install-and-choose-floor-tiles/
5. Tedruski says:

   March 22, 2010 at 7:57 am

   Simply screw down 1/4" hardi board or 5/16" durock(cement board). Screw it down using the proper screws, drywall screws will corrode, use a ceramic coated screw made for durock.
   Plywood sucks the moisture out of the adhesive. What You can do is to seal the plywood with a 50% mix of denatured alcohol and shellac, let dry and then install ceramic tile.
   3 PLY-plywood is not much good for anything. Anytime you buy plywood, always buy it with at least 5 plys if you can afford it. The center ply is always the base ply. To keep it from pulling and twisting within itself you always need the same number of plies on both sides of the base ply. Thus an odd number of plies is the best performing plywood. 5 ply is a base center ply with 2 additional plies on each side of the base ply. This creates a uniform pull or warp factor which keeps the plywood flat and without buckling,warping or twisting.
   Back to the floor prep. Good installers will apply a bed of thinset mortar to the floor and set the cement board down in this wet bed of thinset and also screw it down.
   References :
   General Contractor 30yrs and counting