Subfloor advice


Old 08-02-11, 12:45 PM
Thread Starter
Join Date: May 2010
Location: USA
Posts: 40
Subfloor advice

I have a split level townhome built in 1979. Due to moisture damage in a few areas (sliding glass door, kitchen, and shower surround) I need to replace some subflooring.

In the living room and bedrooms, there's 5/8" (I think)particle board on top of 1/2" plywood. In these areas, I plan to replace damaged areas only and in the end, will install some engineered hardwood and some carpet.

In the kitchen & bath, the existing subfloor consists of two layers of plywood - 5/8" (I think) on top of 1/2". In these areas, I'm replacing the 5/8" top layer (due to existing vynil that won't peel up) and any damaged areas of the bottom layer. In the end, these areas will have ceramic tile with radiant heat.

I know that current practice for tiled areas is to have 3/4" plywood subfloor with a 1/4" cement backer underlay.

My question is this... From a tile perspecive, Is 5/8" on top of 1/2" equal (or superior) to 3/4"? Obviously, the total thickness is more, but does the extra layer introduce any problems?
Sponsored Links
Old 08-02-11, 12:57 PM
Group Moderator
Join Date: Oct 2004
Location: WI/MN
Posts: 18,648
Your plywood is fine, what size are the joists and what length do they span?
Old 08-02-11, 02:02 PM
Forum Topic Moderator
Join Date: Mar 2005
Location: USA
Posts: 43,782
.... and hopefully the plywood joints are staggered.
Old 08-05-11, 06:13 AM
Join Date: Jan 2006
Location: USA
Posts: 3,487
1/2" is unusual for a subfloor. Additionally, particle board (if thats what you really have) cannot be used anywhere in a ceramic tile installation, even if you cover it up with another layer of plywood. Partcle board swells to much with moisture changes creating vertical movement in the floor and will cause grout joints to crack and sometimes tile to crack as well. Are you sure you have particle board, and not OSB? Is the subfloor really only 1/2" thick, and not 5/8"?

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes