Ceramic Tile Advice Forums - John Bridge Ceramic Tile

Welcome to John Bridge / Tile Your World, the friendliest DIY Forum on the Internet


Advertiser Directory
JohnBridge.com Home
Buy John Bridge's Books

Go Back   Ceramic Tile Advice Forums - John Bridge Ceramic Tile > Tile & Stone Forums > Tile Forum/Advice Board

Sponsors


Reply
Thread Tools Search this Thread
Unread 03-08-2008, 11:16 AM   #1
vernon933
Registered User
 
Join Date: Mar 2008
Posts: 4
Seeking advise on tiling foyer

Hello to all
First time posting and new to tiling

This is my situation: I am tiling a 4'x8' foyer area at the front door using 2'x2'x1/2" (8) granite tiles which is surrounded by solid oak hardwood flooring on 2 sides and solid oak border on the other 2 sides (door and staircase). I have exactly 1" from sub floor to hardwood floor.
The sub floor is 3/4" OSB, joist are 2x10 16" OC, and span is 12' from foundation to I-beam.

My plan is to use 1/4" hardibacker with modified thinset underneath and unmodified thinset above along with 1/2" tile and hopefully keep tile flush or 1/16" above hardwood floor.

My questions are:

1. Will I meet L720 or do i need to reinforce joist structure since I cant add plywood because of 1" restriction.

2. I believe I am correct on modified thinset under hardibacker. What brand or types of thinset and aditives should I use on the OSB?

3. As for the thinset above, should I use modified or unmodified to bond the granite? Which brands or types should I use? Will 1/4" trowel and butter the tiles be sufficient? Can I tile immediately tile after installing the hardibacker?

4. Is it ok to seal the tiles after grouting or should I seal them beforehand?

5. Is my calculation correct: thinset+hardibacker+thinset+tile=1"-1 1/16"

I researched all this, but looking for peace of mind with some feedback.
vernon933 is offline   Reply With Quote
Sponsored Links
Unread 03-08-2008, 11:55 AM   #2
bbcamp
Registered User
 
Join Date: Jul 2002
Posts: 30,274
Welcome, Vernon!

1) No, your joists are rated L/580. Good for ceramic tile, but not for stone. Also, you have only one layer of subfloor. Stone installations need 2 for a total of 1-1/4".

2) The thinset under the backerboard is to fill any voids, not to adhere the backerboard to the OSB. Any thinset except premixed or $5 a bag junk is fine.

3) Use a modified medium set mortar, such as Custom's Granite and Marble mortar. It helps support the weight of the tile without it sinking into the mortar. If the tile backs are smooth and the floor is very flat, you might make a 1/4" square notch trowel work. However, I'd have a bigger trowel on hand, just in case. You can always backbutter the tile to increase the amount of mortar. Your goal is near 100% coverage on the tile backs. Pull a few as you go to check.

4) Granite may not need sealing. Do a water and olive oil test. Pour a bit of water on one spot of the tile and oil on another, wait 5 or so minutes, then wipe up. If no discoloration is seen, no sealer is needed. If you do seal first, keep the sealer off the edges of the tile so the grout will bond properly.

5) I think you'll be closer to 1-1/8" due to the size of your tile and the likelyhood that you'll need a bigger notch. If you can make the 1/4" trowel work, then your calc seems good.

Gotta do something about those joists and the subfloor, though...
bbcamp is offline   Reply With Quote
Unread 03-08-2008, 01:13 PM   #3
vernon933
Registered User
 
Join Date: Mar 2008
Posts: 4
Thanks for feedback bbcamp

If I change my strategy by:
1. gluing and screwing sister boards to the joists
2. glue and screw 3/8 plywood to 3/4 OSB for total 1-1/8"
3. use ditra instead of hardibacker

Would this be an acceptable alternative

And if so
CDX plywood or OSB?
considering #1 above, do I need to go beyond where the tile will be layed (not span, but width wise) ?
3/8 plywood + ditra & thinset + 1/2 tile should hopefully not exceed 1-1/8" ?
vernon933 is offline   Reply With Quote
Unread 03-08-2008, 01:40 PM   #4
bbcamp
Registered User
 
Join Date: Jul 2002
Posts: 30,274
Your joists need to be sistered in the middle 2/3s of their span, not just under the tiled area. CDX plywood is not acceptable. Look for AC or BC grade, Exterior or Exposure 1 rated. You'll probably need to go to a real building supply store, instead of a big box.

Ditra is 1/8" installed, so your new foyer will be about 1-1/8" or so thick.
bbcamp is offline   Reply With Quote
Unread 03-08-2008, 02:17 PM   #5
vernon933
Registered User
 
Join Date: Mar 2008
Posts: 4
Thanks again bbcamp

I may not have worded the sistering part right

I plan on sistering all the joist (4) the full 12' span from I-beam to foundation ledge (I'll call this east-west; the tiles will be 8' E-W hugging the west side) for the 4' north-south tiles (joists line up almost perfect with tile edges running E-W or in other words; joist=tile edge-joist-joist-joist=tile edge)

Do I need to beyond the tiles N-S when sistering the joist?

I believe were both on the same page, but just want to confirm
vernon933 is offline   Reply With Quote
Unread 03-08-2008, 02:32 PM   #6
bbcamp
Registered User
 
Join Date: Jul 2002
Posts: 30,274
I'm not sure I follow your last post, so I'll try to shed some more darkness: The joists under the tiled ares should be sistered. If the tiled area stops between joists, then sister the next joist, too.
bbcamp is offline   Reply With Quote
Unread 03-08-2008, 04:07 PM   #7
vernon933
Registered User
 
Join Date: Mar 2008
Posts: 4
OK, I am clear on everything now except which thinsets to use with ditra

Is prolastic part B mortar ok to use?
mixing it with latex additive for underneath and water for above the ditra?

Or should i use something different?
vernon933 is offline   Reply With Quote
Unread 03-08-2008, 05:31 PM   #8
bbcamp
Registered User
 
Join Date: Jul 2002
Posts: 30,274
I'm not familiar with that brand, but it does sound correct. Mixed only with water, it's un-modified. Mixed with latex, it's modified. Mix it a little stiff to set the tiles, and be alert for any settling.
bbcamp is offline   Reply With Quote
Reply

Stonetooling.com   Tile-Assn.com   National Gypsum Permabase


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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
Forum Jump


All times are GMT -6. The time now is 02:11 AM.


Sponsors

Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Copyright 2018 John Bridge & Associates, LLC