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Old 04-06-2011, 07:31 PM   #16
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how do you figure floor flex?


Keep in mind that Lowe's and all of the big box stores are all about "sales".

Sales, sales, sales. If they were to train their people on standards that have existed for forty years or more they would lose sales to the diligent and wise.

Let's Build Something Together, You Can Do It, We Can Help. Screw the consequences! You'll be back to buy more when the first job fails and they point the finger at YOU.

Not all floor structures are suitable for ceramic tile.

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Old 04-06-2011, 09:41 PM   #17
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how do you figure floor flex?


Jaz,
that "Hydroment" stuff looks great. you know the coverage of that 50# bag? I'd use that for the kitchen, but it sure ain't cheap! would I have to use smaller tiles? (I assume big tiles would be more prone to cracking in my case)
is the thinset Lowes and HD sells any good? if it's decent I'd use that everywhere else.

tnx,
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Old 04-06-2011, 10:28 PM   #18
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how do you figure floor flex?


Quote:
that "Hydroment" stuff looks great. you know the coverage of that 50# bag? I'd use that for the kitchen, but it sure ain't cheap!
How much is it out there? Coverage is normal. From about 80-100 ft. per bag. With 1/4x3/8" trowel I'd figure about 80 ft., the basic trowel for 12-13" tiles. I'd stick to tiles in the under 14" size. Large tiles are more challenging to set too.

Quote:
is the thinset Lowes and HD sells any good?
All companies make good materials for their type and price point. The only negative comment about a product is the unmodified thin set the orange place sells. We think it's really bad. They think you want cheap stuff...I guess? You probably will not be using unmodified though. (unless you go with Ditra membrane instead of a concrete backer board.)

Jaz
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Old 04-07-2011, 08:25 AM   #19
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how do you figure floor flex?


If you can verify the following info, I will check that your joists can support code minimum loading:

Dead loads:
2x10 at 16" = 2.5 psf
3/4" subfloor= 3 psf
1/4 underlayment= 1 psf???
Vinyl flooring = 1 psf
Misc mech, plumbing, electric= 2 psf
1/2 gyps ceiling with wood furring= 3 psf??
Grout bed = 50#/100 sqft = 5 psf
Ceramic tile = 10 psf???
Total = 27.5 psf
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Old 04-07-2011, 09:43 AM   #20
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how do you figure floor flex?


Quote:
Originally Posted by Talbot3 View Post
If you can verify the following info, I will check that your joists can support code minimum loading:

Dead loads:
2x10 at 16" = 2.5 psf
3/4" subfloor= 3 psf
1/4 underlayment= 1 psf???
Vinyl flooring = 1 psf
Misc mech, plumbing, electric= 2 psf
1/2 gyps ceiling with wood furring= 3 psf??
Grout bed = 50#/100 sqft = 5 psf
Ceramic tile = 10 psf???
Total = 27.5 psf

thanks talbot3 but I've already decided to put ceramic tile down even though I'm a bit out of spec.

tnx,
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Old 04-07-2011, 11:31 AM   #21
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how do you figure floor flex?


Quote:
If you can verify the following info, I will check that your joists can support code minimum loading:
I'll take your word for some of those weights, but I know q few that are wrong.

Quote:
1/4 underlayment= 1 psf???
Vinyl flooring = 1 psf
These two items will be at the curb, although you need to add the new plywood underlayment. Also add tile backer or membrane. .3 to 4 lbs sq. ft.

Quote:
Grout bed = 50#/100 sqft = 5 psf
I guess you meant the thin set adhesive. About .5 lbs.

Quote:
Ceramic tile = 10 psf???
Tile is no way near 10. Figure 4 lbs.

So the total can be in the 15-20 lbs per sq. ft range. That's why I like to figure 50 live @ 20 dead. If the installation was a true "mud-job" of 1 1/4" thickness, that alone would be about 16 plus everything else.

Jaz
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Old 04-07-2011, 12:42 PM   #22
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how do you figure floor flex?


Thanks Jaz. Going with Jaz's adjustments, the strength of the joist ( doug fir larch # 2) is not an issue. So it seems you are going in the right direction with selecting products to allow for some flexibly. Good luck and let us know how it turns out.

Last edited by Talbot3; 04-07-2011 at 01:58 PM.
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Old 04-08-2011, 02:53 AM   #23
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how do you figure floor flex?


I am not a tile installer , I am a Hardwood installer . SOOOO Here goes my answer ...
I also use to frame houses , the general rule is 1 foot of span for every inch . a X10 will span 10 feet . and doug fir is stronger ,A 2X10 at 15 feet sounds a little long to me , Have you layed your head on the floor and had a large person walk across ? I have seen tile floors crack up .I could feel the floor flex if I bounced a little . I would not be so concerned with complex math , If you just figure what the joist is and the span . The rule of thumb I use is what the national wood flooring association says , I have read stuff about tile in their magazines .So instead of trying so hard to reinvent the math , I know i have read some where ,Where some one has these tables all figured allready .
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Old 04-08-2011, 05:59 AM   #24
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how do you figure floor flex?


Quote:
Span

I am not a tile installer , I am a Hardwood installer . SOOOO Here goes my answer ...
I also use to frame houses , the general rule is 1 foot of span for every inch . a X10 will span 10 feet . and doug fir is stronger ,A 2X10 at 15 feet sounds a little long to me , Have you layed your head on the floor and had a large person walk across ? I have seen tile floors crack up .I could feel the floor flex if I bounced a little . I would not be so concerned with complex math , If you just figure what the joist is and the span . The rule of thumb I use is what the national wood flooring association says , I have read stuff about tile in their magazines .So instead of trying so hard to reinvent the math , I know i have read some where ,Where some one has these tables all figured allready .
tacomahardwoodfloor


There ya go!

Without going to my span tables I am recalling that generally speaking a 2X10 can span only about 11 feet to maintain the 1/360 deflection required for a rigid tile installation. Although the use of flexible thinsets is always a good idea I wouldn't bet the farm on their use when floor joists are over-spanned. Flexible thinset and flexible ceramic tile are two different things. Wishin' and hopin' and prayin' appears to be the practice being brought into play here.
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Old 04-08-2011, 11:37 AM   #25
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how do you figure floor flex?


In the end this is more of an art and not science even though all these numbers and terms like Modulus of Elasticity, Bending Strength, Bearing Strength, Shear Strength are involved. All we can do is consult the charts. If I'm on the job I can add the "feel", but from behind my keyboard I'm limited.

I will list a few max spans that meet L360 at 50/20 (live/dead) for the most common species. I will give these spans for several grades too. Keep in mind most joists are #2 grade. I will also give the 40/10 max span which is what most builders shoot for. The 40/10 numbers is also what residential building codes call for. In other words, the worst standard you can build too and still pass.

2x10' Joists @ 16" o.c.

Species -------------Grade ------------ Max span L360@50/20 --------- Max span L360@40/10

Southern Pine ------- 2 --------- ---------- 13' 7" ---------------------------------- 16' 1"
Southern Pine -----Select Structural ------15' 10" -------- ------------------------ 17' 0"
Doug. Fir Larch ------2 -------------------- 13' 2" ---------------------------------- 15' 7"
Doug. Fir ----- Select Structural ---------- 16' 1" ---------------------------------- 17' 4"
Spruce-Pine-Fir ------ 2 ------------------- 13' 0" ---------------------------------- 15' 5"
Spruce-Pine-Fir--Select Structural ------- 14' 11" --------------------------------- 16' 0"
Hem-Fir -------------- 2 ------------------- 13' 11" --------------------------------- 16' 5"
E. Hem-Balsam-Fir -- 2 ------------------- 10' 7" ---------------------------------- 12' 6"

As you can see we have good reason when we ask for the species and grade of the joists. I think maybe 5% are able to tell us the species and I don't recall anyone also knowing the grade. They just guessed, and that's all we can do in that case.

Jaz
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Last edited by JazMan; 04-08-2011 at 11:40 AM.
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Old 04-08-2011, 09:49 PM   #26
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how do you figure floor flex?


just a note in passing: this house has only been owned by 2 people,the guy who built it and me. I'm quite sure that the reason why the span of those 2x10's is 15' is because the room directly under the kitchen is a "pool room" which as you know,has to provide plenty of room for "pool cue's". (I know it was meant to be a "pool room" because I bought the pool table which is still in the same spot) I can only hope and pray that the builder took that long span into account and used higher strength 2x10's. (but,I certainly wouldn't bet on it)

tnx,
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Old 04-08-2011, 09:58 PM   #27
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It is unlikely he used anything better than #2's. I showed the better grade just to illustrate the difference in grade and species.

I think you'll be ok. What did you find out about the Reflex thin set?

Jaz
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Old 04-08-2011, 11:22 PM   #28
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how do you figure floor flex?


Quote:
Originally Posted by JazMan View Post
It is unlikely he used anything better than #2's. I showed the better grade just to illustrate the difference in grade and species.

I think you'll be ok. What did you find out about the Reflex thin set?

Jaz

there is a "building supply" place a few miles from me that carries it. haven't called yet.

tnx,
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Old 04-09-2011, 08:23 AM   #29
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What about......forget reinforcement and just go with floating porcelain interlock? I'm not sure if you can or not, but I"m asking for my own needs as well. Just trying to read all that info about span and deflection ect. makes my head spin. I know my floor is probably not suitable for ceramic, but when I factor in the cost and labour of making it right, it makes that expensive inter lock look kind of tempting. I'm just not sure if it is suitable for the original poster or myself.
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Old 04-14-2011, 05:46 PM   #30
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Quote:
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Call and go to Bedrosians, see if they have and will sell you Hydroment's Reflex mortar. Hydroment says it'll work even at L240. (that's what they say).

Bedrosians is located on N. Citadel Dr. South of Galley Rd. bet. North Academy Blvd. & North Chelton Rd. in Colorado Springs. (719) 591-7770

Jaz
ok Jaz, went to "Bedrosians" and they've got the Reflex mortar.(and they've got some good looking tile too) I'll buy some along with the stuff I need to tile my spare bathroom floor.
just a few questions about tiling that floor: (ok,lots)
1) how much tile should I get for a floor that's 42 sq. ft. I know you should get some extra.
2) is "Hydroment" good thinset? I'm thinking of getting some of the less expensive stuff for the bath and save the "Reflex" for the kitchen.
3) how thick should the thinset be?
4) is the "backer board" at HD ok? 1/4"?
5) don't have to seal the joints in the backer,right?
6) how long does regular thinset remain workable? a couple hours in the bucket you mix it in?

tnx,

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