Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Flooring

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 04-10-2012, 09:22 PM   #1
Newbie
 
Join Date: Apr 2012
Posts: 4
Rewards Points: 10
Default

Assistance in determining concrete slab flatness


Hello all. First post here but I'm sure it won't be my last since I've just gotten started with the spring to-do list. Let me first say thank you in advance for any and all advice.

I am about to undertake a kitchen tiling project with 12x12 ceramic mixed with 6x6 ceramic. Should nice once done, but I'm OCD when it comes to work I do myself so i want to ensure things are done right. Already got the linoleum removed and adhesive scraped all up. Now comes time for checking 'flattness'. This is where I'm a bit unsure. I see the general rule is for 10' straightedge, no more than 1/4" deviation. Now does this mean no more than 1/4" deviation at any one point along that 10' or aggregate? I tried using a straightedge, but decided to go with a stringline for better accuracy (hopefully). So I've got a 10' section of taught stringline which just so happens to fit nicelely from wall-to-cabinets. It sits 1/2" off the ground at each end, supported by tile pieces at each end. I make 2ft passes across one end of the room, then go across again perpendicular to cover both directions. Does this sound like a solid plan? So from a few passes so far, I'm getting a drstring-to-ground height of 3/8" where there's a 'high spot' almost in the center of the room with the rest still close to 1/2" string-to-ground. This difference is under the 1/4" so I should be ok right? A goofy paint sketch outlines the method..



I'm hoping not to have to use SLC but haven't finished the measurements yet. I'm sure I'll be back with more questions after I get this part knocked out. Thx

usafdrew is offline   Reply With Quote
Old 04-11-2012, 05:35 AM   #2
DIY staff
 
Join Date: Sep 2009
Location: Kane county,Illinois
Posts: 21,850
Rewards Points: 2,348
Default

Assistance in determining concrete slab flatness


That's the hard way---I use a straight edge---nice to be able to spin the straight edge to check in all directions.

I think you may be okay---get the straigt edge out again--stack coins in the deepest low spots--see what you really have---

__________________
New members: Adding your location to your profile helps in many ways.--M--
oh'mike is offline   Reply With Quote
Old 04-11-2012, 11:45 AM   #3
Tileguy
 
JazMan's Avatar
 
Join Date: Feb 2007
Location: Troy, Michigan
Posts: 4,071
Rewards Points: 2,000
Default

Assistance in determining concrete slab flatness


I agree the straight edge is the best way. Make sure it's really straight with no flex. If it's wood, I think a 1x4 is the best. The floor need to be "within 1/4" in 10 ft. and 1/16" in 12" of the required plane. for standard ceramic tiles. It needs to be flatter if the tiles are large and/or smooth and shiny.

Jaz
__________________
Tile 4 You LLC Troy, MI

DITRA Installs - KERDI Watertight-Mold-Free Showers. I have NEVER made a mistake, I thought I did ONCE, but, I was WRONG! A+ BBB rating - est. 1987 - over 50 yrs. exp.
JazMan is offline   Reply With Quote
Old 04-11-2012, 01:21 PM   #4
Newbie
 
Join Date: Apr 2012
Posts: 4
Rewards Points: 10
Default

Assistance in determining concrete slab flatness


I tried using a straightedge with most straight I could find 1x4x8, but even then it had a 1/8" bow at the end. The 1x4x10s were firewood. I gave up when nothing measured was consistent and went with the string. I've finished checking the room with it and it's been spot on. A little more difficult to move around, but I got 10ft readings every 2 ft from both sides of the room.

There are a few high spots that hit 1/4" deviation in 10ft. No more than 1/4" though, so instead of sanding down, could I just be a little more generous with a mallet there when setting the tiles?
usafdrew is offline   Reply With Quote
Old 04-11-2012, 02:20 PM   #5
Tileguy
 
JazMan's Avatar
 
Join Date: Feb 2007
Location: Troy, Michigan
Posts: 4,071
Rewards Points: 2,000
Default

Assistance in determining concrete slab flatness


Quote:
could I just be a little more generous with a mallet there when setting the tiles?
Well sure, that, along with a beating block are part of the procedure, but the cured thickness of the thinset should be at least 3/32" or so.

Are these high quality tiles, are they regular edges or rectified? How wide a grout joint or do you have a choice with the pattern?

Jaz
__________________
Tile 4 You LLC Troy, MI

DITRA Installs - KERDI Watertight-Mold-Free Showers. I have NEVER made a mistake, I thought I did ONCE, but, I was WRONG! A+ BBB rating - est. 1987 - over 50 yrs. exp.
JazMan is offline   Reply With Quote
Old 04-11-2012, 03:02 PM   #6
Newbie
 
Join Date: Apr 2012
Posts: 4
Rewards Points: 10
Default

Assistance in determining concrete slab flatness


Quote:
Originally Posted by JazMan View Post
Well sure, that, along with a beating block are part of the procedure, but the cured thickness of the thinset should be at least 3/32" or so.

Are these high quality tiles, are they regular edges or rectified? How wide a grout joint or do you have a choice with the pattern?

Jaz
The tiles are 12x12 Del Conca Roman Stone porcelain. Edges are slight rounded and has a PEI rating of 5 (heavy traffic). They'll be mixed with 6x6 Eliane Mt Everest Verde porcelain which also has slight rounded edges but don't know the quality. I was planning on 1/4" grout lines.

Another couple questions come to mind now that I'm moving forward. With the linoleum adhesive scraped off, there are large areas of the slab that seem almost polished and when water is poured on it, it takes a real long time to absorb. The rest of the slab is fine and water absorbs at a steady rate. Should I be worried about this before applying the tile adhesive? I asked the Lowes guy. He seemed pretty knowledgable and said not to worry, just as long as all the old adhesive is removed. Also, there is one crack that can be handled with Redgard that I have. Originally I was going to membrane the entire slab, but the Lowes guy talked me out of it since the slab is 15 yrs old and won't be cracking anymore. Does this sound right? Thx.
usafdrew is offline   Reply With Quote
Old 04-11-2012, 08:15 PM   #7
Tileguy
 
JazMan's Avatar
 
Join Date: Feb 2007
Location: Troy, Michigan
Posts: 4,071
Rewards Points: 2,000
Default

Assistance in determining concrete slab flatness


You should be concerned about those areas in question. Moisture has to be able to soak into the slab to achieve a bond. Most sheet vinyl adhesives are water soluble, so I think it matters.

I'd be soaking the area with hot water as a first step. Even adhesive that has been removed will leave a residue in the pores of the concrete.
Quote:
just as long as all the old adhesive is removed.
That's the point, it has not been removed. That is why water won't readily soak now. I would test and not have continue on faith alone.

Jaz
__________________
Tile 4 You LLC Troy, MI

DITRA Installs - KERDI Watertight-Mold-Free Showers. I have NEVER made a mistake, I thought I did ONCE, but, I was WRONG! A+ BBB rating - est. 1987 - over 50 yrs. exp.
JazMan is offline   Reply With Quote
Old 04-24-2012, 12:46 PM   #8
Newbie
 
Join Date: Apr 2012
Posts: 4
Rewards Points: 10
Default

Assistance in determining concrete slab flatness


Quote:
Originally Posted by JazMan View Post
You should be concerned about those areas in question. Moisture has to be able to soak into the slab to achieve a bond. Most sheet vinyl adhesives are water soluble, so I think it matters.

I'd be soaking the area with hot water as a first step. Even adhesive that has been removed will leave a residue in the pores of the concrete. That's the point, it has not been removed. That is why water won't readily soak now. I would test and not have continue on faith alone.

Jaz
Thanks for the advice. I went at the floor with a grinder to take off what must have been a sealant and now the water will absorb and all adhesive is gone. I've also now finished mapping out the floor and there is just one high hump that doesn't quite hit 1/4" deviation anywhere in that area from floor to string line. Does this mean I'm probably good to start laying tile?
usafdrew is offline   Reply With Quote
Old 04-24-2012, 03:24 PM   #9
Tileguy
 
JazMan's Avatar
 
Join Date: Feb 2007
Location: Troy, Michigan
Posts: 4,071
Rewards Points: 2,000
Default

Assistance in determining concrete slab flatness


Quote:
there is just one high hump that doesn't quite hit 1/4" deviation anywhere in that area
If that hump falls within the specs as I wrote in post #3, then you would be OK. Better check again.

Jaz

__________________
Tile 4 You LLC Troy, MI

DITRA Installs - KERDI Watertight-Mold-Free Showers. I have NEVER made a mistake, I thought I did ONCE, but, I was WRONG! A+ BBB rating - est. 1987 - over 50 yrs. exp.
JazMan is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fix or Replace Porch Concrete Slab Majoram Building & Construction 10 06-25-2011 02:45 PM
Help stone over concrete slab Johnnyquest Flooring 0 05-20-2011 03:36 PM
PVC underneath the floor (concrete slab) massimo Building & Construction 6 11-19-2008 10:37 AM
pouring a level concrete slab over sloped concrete Jayne Building & Construction 4 05-11-2008 08:55 AM
Concrete slab weeps moisture dale h Flooring 2 04-30-2005 10:29 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.