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 06-17-2021, 01:49 PM   #1
humpbeez
Registered User
 
Join Date: Jun 2021
Posts: 3
installation of slate tile on hallway

I would like to install slate tile on the hallway and foyer (blue rectangles in attached image) of my house. However, the framing in the hallway does not meet the L/720 deflection necessary for natural stone. So I was hoping I could get some advice and opinion on fixes and feasibility of such a project.

The joists are douglas fir 2x8, 16" on center with a length of 13.5 ft (yellow dimension). The supporting beam runs along the center wall (red line). With these specs, I get an L/221 deflection. Unfortunately, I have a finished basement, so sistering the joists is not feasible. Additionally, I would like to match the height of the hardwood floor installed in my living room, which gives me 3/4" total height on top of the existing 3/4" plywood (the stone tile has a thickness of 3/8"). 1/8" or even a 1/4" above the hardwood would be ok, but undesirable.

Given that the hallway is adjacent to the support beam, I expect the deflection to be significantly less than that calculated by the deflectometer, which gives the maximum deflection over the entire span of the joists. This is typically not considered by deflection calculators. Would this help at all? Does it make a difference?

I've also read about products like blanke permat that may mitigate deflection, but it seems this only minimizes the deflection of the subfloor, not the joists themselves, correct?

Any comment or advice would be greatly appreciated.
Attached Images
 
__________________
Humphrey
humpbeez is offline   Reply With Quote
Sponsored Links
Unread 06-17-2021, 04:03 PM   #2
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 93,629
Welcome, Humphrey.

Couple problems there. First would be your joist deflection, of course, but I'd like you to verify that there is no other support under that joist structure. As described, your floor would not even meet the most basic building code even if your joists are of high quality material and of a very good grade. Our Deflectometer is a more conservative tool, so designed because our visitors are nearly always dealing with remodel work rather than new construction. But even using other, more traditional, span calculators that joist structure is far, far below good construction standards.

The fact that the area to be tiled is closer to the support beam is, technically, of no help. The load applied to the joists in other areas of the house over the same unsupported span of the joists can still cause deflection in the area to be tiled. Enough to make it fail? I dunno. It's your floor, though, and you can tile over whatever you feel comfortable with.

Second problem would be your subflooring. Even were you willing to install natural stone over the joist structure you have, the stone tile industry requires a double layer of subflooring regardless the joist spacing. That doesn't preclude your using natural stone, it only makes it impossible to match the height of your adjacent flooring.

Yeah, yeah, everybody wants their new tile to match the height of their adjacent flooring, but the time to plan for that is during the design of the house. Rarely an option is any remodel project.

As for the Blanke Permat, I find this in their advertising:
Quote:
Originally Posted by Blanke
BLANKE PERMAT is an expertly engineered underlayment that utilizes layers of fiberglass mesh that bond with thinset, preventing deflection, stiffening wood substrates,..
I'm afraid I find that a bit difficult to buy, but that, again, is up to you. I don't know what they're calling the product, but I'm reasonably certain there is no ceramic tile industry standard for it, just as there is no standard for the competing uncoupling membranes. Their claim of a "Heavy Industrial" rating in a "Robinson Floor Test" tells us nothing without knowledge of the entire floor package that was tested. And I'm not familiar with "heavy industrial" as a result category, although it may exist.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 06-17-2021, 04:37 PM   #3
humpbeez
Registered User
 
Join Date: Jun 2021
Posts: 3
Hi, cx. Thanks for your comments.

I am not sure if this is a complete representation of the structural components of the house, but someone with framing expertise has the following guess from looking at the floor plan. Red lines represent load bearing walls and blue lines represent beams. Not sure about the orange boxes.

Regarding the subfloor, what would be the thickness of the second layer of plywood? Does it require a second 3/4" or could a thinner layer be used? Because a 1/2" plywood would result in a 1/4" step (1/2" plywood + 1/8" thinset + 3/8" tile), which is not catastrophic.

Would it be possible to somehow reinforce the joists from the top? I could access them by removing the subfloor in the hallway completely, but it would be hard to sister them because I would not be able to fit the long joists in through the small access in the hallway.
Attached Images
 
__________________
Humphrey
humpbeez is offline   Reply With Quote
Unread 06-17-2021, 08:43 PM   #4
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 93,629
The minimum second layer of subflooring I would use is nominal 1/2" exterior glue plywood with no face of grade lower than C.

If you use a Schluter membrane (Ditra or Ditra XL) the manufacturer recommends a second layer of a minimum nominal 3/8th" thickness. I don't favor ever using material that thin simply because it's difficult to find any that's sufficiently flat and even then it's difficult to install it flat enough over the first layer. But that's the manufacturer's recommendation.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 06-18-2021, 01:31 PM   #5
john619
Registered User
 
Join Date: Oct 2014
Location: San Diego, CA
Posts: 205
use a porcelain look alike. slate is not a terrific choice
__________________
john
john619 is offline   Reply With Quote
Unread 06-18-2021, 03:31 PM   #6
humpbeez
Registered User
 
Join Date: Jun 2021
Posts: 3
Hi, John. Thanks for your comment.

Is the suggestion based on looks or performance?

The porcelain tile would be less likely to crack, but the look of the ones we saw was definitely not as nice as the natural stone.
__________________
Humphrey
humpbeez 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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Slate Tile Installation Laurine Tile Forum/Advice Board 2 10-08-2012 09:22 PM
slate tile installation pops8 Tile Forum/Advice Board 2 10-30-2006 07:53 AM
Slate Tile Installation Unregistered Cleaning, Restoration and Sealing 4 11-07-2004 10:57 AM
tile over slate installation vic b Tile Forum/Advice Board 1 06-26-2004 02:32 PM
Slate Tile Installation villenej Tile Forum/Advice Board 8 03-31-2004 07:20 PM


All times are GMT -6. The time now is 01:20 AM.


Sponsors

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