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Discussion Starter #1
I'm sure a lot of you have seen my previous posts on subflooring before installing 12x24 porcelain tile. I have finally finished installing the hardie backer and just checked my floor flatness before I start tiling. I used a 2 ft grid and laser level to find my high spot/spots and have figured out the flatness of the floor relative to said high spots. Unfortunately the floor is a little less flat than I had hoped. I have included a diagram showing the high spots on my floor (marked with an H) and then the measurement for how much lower the floor is every 2 ft. All the measurements are in inches. All measurements next to the wall are 1 ft from the wall. I have also inclued a diagram showing the overall dimensions of the kitchen.





So my lowest spot on the floor is 1 1/8" inches below my high spots (right at the threshold of course). Now i know that the floor doesn't need to be "level" it just needs to be relatively flat for the large tiles. My question is do I need to use enough slc to get everything even with my high spots and make the floor completely level/flat or is there something else I can do to make the floor suitable for installation of large porcelain tile?

If i do need to get the floor up to the highspot's level do I just need to buy 15 bags of SLC (about $30 a bag) or is there a more cost efficient way? I was thinking maybe using thinset for like 3/4-1 inch then finishing off with slc not sure if that is a valid option.

Also should i be worried about the weight that this much filler will add to my floor since it is over 2x6 joists covered by plank flooring covered by 3/4 inch osb t&g which is then coverred with thinset and 1/4 hardie backer? Just worried about the added weight. I'll include a diagram of my joists as well (Sorry it is flipped. I dont have time to redo anything.)



Lastly, (sorry i know this is a wordy post) if i have to add 1 1/8 inch to the floor then install the tile over that this will add a good 1.5 inches to 2 inches to my floor at the threshold. How do i deal with this to not make it look out of place?

Thank you guys in advance for any input.
 

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What is the span of these 2x6 floor joist, I hate to tell you this but I dont think they will support this floor without flexing to much
 

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Discussion Starter #3
Thanks for your input. I have already looked into the flexing. Just wondering about the issues I brought up on this post.
 

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Tileguy
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2x6" joists are very unusual for homes. Was this area a deck or porch at one time? Let us know how it's framed. Size, spacing and span of the joists. Not the size of the room. If you know the species and grade include that info.

That floor is way out of plane, yicks. The easiest way to make the floor flat is to continue as you planned with the SLC. Yes you're going to step up into the room. Or......you could use a floor patch instead of SLC and keep the slope. But that will be very tricky to do and get the floor flat.

Jaz
 
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Tileguy
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Sorry, the joists are 2x8 not 2x6.
So you're saying the deflection spec is good for ceramic tiles? Care to share the span/species/grade of the joists and/or the "L" rating?

Jaz
 

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Tileguy
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Thanks for your input. I have already looked into the flexing. Just wondering about the issues I brought up on this post.
Ridiculous!
You haven't looked into the flexing very well because if you had you wouldn't be barging ahead with ceramic tile on a structure that won't support the project.
 

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Discussion Starter #9
In terms of not supporting the project does that just mean there is a danger of cracked tile or would I have to worry about the structural integrity of the floor for adding so much weight? I can take a chance on a cracked tile but I don't want to break my house. Thanks.
 

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Pro Flooring Installer
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You did put thinset under the Hardie, right? You don't mention that.
 

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Ridiculous!
You haven't looked into the flexing very well because if you had you wouldn't be barging ahead with ceramic tile on a structure that won't support the project.
+1 the time to level the floor and check for deflection is before you lay the backer.You just wasted a lot of time and money in my book.
 

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Discussion Starter #12
1. Yes I installed the Hardie with thinset.
2. I was told on a previous post that it is fine to lay the backer board then use the SLC.
3. Everyone that I talk to in real life says not to worry too much about the deflection. (They could obviously be wrong. If I knew I wouldn't be here)

I'm starting to just think I should scrap the tile and put down pergo. any *constructive* input on this? If I went with pergo laminate I could just lay right on top of the Hardie right?
 

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Tileguy
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Whyjune1st,

BTW, do you have a name we can use?

Bud posted 6-7 minutes after you corrected yourself by saying the joists are 8" and not 6". I'll bet he started the post before he saw your correction.

Whyjune said:
2. I was told on a previous post that it is fine to lay the backer board then use the SLC.
That's the right way to tweak the floor, yes.

Whyjune said:
3. Everyone that I talk to in real life says not to worry too much about the deflection. (They could obviously be wrong. If I knew I wouldn't be here
2x8" @ 11' should be kinda marginal for ceramic if they're in good condition. But you never mentioned the species and grade.

Whyjune said:
I'm starting to just think I should scrap the tile and put down pergo.
I don't get that. That's a pretty extreme change.

Jaz
 
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In terms of not supporting the project does that just mean there is a danger of cracked tile or would I have to worry about the structural integrity of the floor for adding so much weight? I can take a chance on a cracked tile but I don't want to break my house. Thanks.

It's not that you need to worry about falling through the floor after job is done. what I think these guys are trying to say is you don't want too much or any up and down movement for tile or it will cause grout to crack tile to pop ect.

You can cross brace between joists and or add more plywood although you need to state the spacing between joists what ever too minimize movement. SLC will be the 1st to crack if your subfloor is not sound and sturdy.

In the real world it takes engineers too determine true deflection so don't be scared about L rating these guys ask for lol
 

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Discussion Starter #15
The true dimension of the joists are 7 3/8" x 1 5/8". The house was built in 1940 and I have no clue as to what wood the joists are. There is cross bridging between most of the joists over the long span and they are marked by the red x's on the diagram. Also two of the joists are sistered as marked in the diagram as "double".



I know I'm not much help w/the wood type but the joists seem to be in good condition and I will include photos so you can see what i'm working with. Thanks for all the helpful input I appreciate it and really just want to get this floor in so i can finish my kitchen.









I'm just getting fed up with this floor and was thinking that going Pergo I could just snap it in and be done with it so I can start putting in cabinets. I dont want to put a floor in thats just going to crack and create more a problem after its done.

Thanks for all your input. I do appreciate it.
 

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Tileguy
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The cabinets go in first, especially if you do go with anything other than ceramic tiles.

Modern 2x8's are 1.5 x 7.25", so what you've got is right for that period. The joists are obviously some species of pine, but not sure which. They usually have a grade seal stamped on each, but maybe yours don't.

We normally see #2 grade used in joists. Most species should be fine up to 11' 6" to meet 50/20 live/dead load rating of L360 for ceramic. This deflection (joists) is a little forgiving, the between the joists deflection is more important. In other words the subfloor sheathing. ¾" t&g OSB is the min. and is good enough if installed correctly and the joists are 16" oc.

Is the longest span 11' 0", or are you ball parking it? We need to know to the inch not approx. Either way I think you're very close, but now is the time to improve the stiffness if you wanna make the floor as sturdy as possible.

Jaz
 
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Discussion Starter #17
I am installing the ceramic first b/c the floor cabs I am putting in have a toe kick but are hollow underneath (hence the need for the floor to go wall to wall so no moisture gets to the subfloor).

The measurements on the diagram are to the inch. There are 3 joists that are 12 foot span (one of which is sistered) and the other only has a 14 oc gap between the next joist and is surrounded by 10 ft span and 11 ft span sections.

I will look for a grade stamp tomorrow and see if I can find any more info.

Thanks for the sound advice.
 

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Tileguy
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Installing ceramic before the cabinets is fine, done ala time. I said it because you threatened to cheap out and go with a laminate or perhaps other type of flooring.

All cabinets are hollow underneath, you wouldn't want it any other way.

Jaz
 

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Discussion Starter #19
Haha. I really was not threatening to use Pergo i just want to get this floor done. I'll update the type of wood later if I can find a stamp. My name is Ben by the way. Thanks.
 

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Discussion Starter #20
So I looked all over down stairs and cannot find a stamp anywhere. Is there any quick way to stiffen the floor just to be sure? I heard sistering joists and perhaps adding more bracing. I didn't really want to get into sistering so I was wondering if adding bracing would significantly help the floor's stiffness.

Also what is the best way to apply the slc? I know that I first have to apply the primer. But since I am going to be using probably close to 15 bags should I apply one bag at a time then immediately apply the next bag after mixing or do I need to wait between bags or somehow figure out how to mix a lot at once?

Thanks for the input.
 
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