[freelabor4me]

Hi All,
Looking to do some 12x24 porcelain tiles in my bathrooms house is about 13 years old and sub floors are such:

Above Grade:

• Engineered Joists around 12" tall, 3.5x1.5 blocks top and bottom, varied centering with largest measured 19.5 OC 16in between adjacent blocks, span estimated 19-20' (Finished basement)
• 5/8 OSB decking
• 3/8 particle board sub-floor
• Nasty roll out vinyl that needs to go

Below Grade (Basement):

• Concrete slab
• Dricore R+ (Blue foam over OSB) currently floating
• Floating Vinyl tile

Looking for some advice on sub-floor and thin-set this project as this is a first time:

• I do not know how to calculate the deflection above grade since I have engineered joists I understand I need L360:
• The main floor is already tiled with 3/8 OSB or PB over the 5/8 house was built that way so 1" sub-floor with 3/8 tile + thick mortar bed

1) Since I do not want to go broke on the sub-floor or end up 5/8 transition my options for sub-floor (replacing PB 3/8): 3/8 Ply, 1/4 CBU, 7/16 CBU (Wonderboard)


2) Since I am new there is a wide world of mortar out there to choose from I will use cheap unmodified under cement board but above for polymer added my options are versabond ($19/bag), MAPEI LTF/medbed ($27/bag), Flexbond 1/16 deflection ($33/bag ), Flexbond LTF/medbed ($36/bag)


Basement:
I understand this is VERY unpopular from reading posts here but lets just entertain the idea of not ripping up this Dricore subfloor that is already there and I would assume build up with mud bed or SLC.


Dricore says to tarpon the flooring to the concrete and tile some people have done this. My floor has a high ridge down the center and slopes down about 1/4" towards each wall, if I tried this should I:


1) SLC under the Dricore, screw it through as Dricore suggests (Breaking up the SLC?) and add 1/4" mortar CBU, mortar tile


2) Screw Dricore down, SCL on top, tile on top of SLC ( cheaper, save height, no risk of busting up SLC with screws)

 

[JazMan]

Hi Free, how about you put a name in your profile to call you by?

I don't think I understand what you're trying to say here;

varied centering with largest measured 19.5 OC 16in between adjacent blocks,

The ⅝" OSB is the subfloor, the ⅜" is the underlayment. If the ⅜" is particle board, it needs to be taken to the curb.

Generally I-joists are engineered to meet L480. But you'll have to call the manufacturer and ask them.

What does the following mean? The bold part.

The main floor is already tiled with 3/8 OSB or PB over the 5/8 house was built that way so 1" sub-floor with 3/8 tile + thick mortar bed

I'd be leery of a subfloor that was just ⅝" OSB. I don't know of any approved method where that is allowed. The min. is ¾" OSB subfloor that is t&g, glued and in perfect condition. I also suspect your joists are 19.2" oc. You need another layer of ply, then the ¼" cbu set in thinset/fastened etc. or a membrane such as Ditra.

You're not going to go broke with this project. If you thought there was a chance of it, you wouldn't be doing it. Don't expect the floors to be at the same level. If you need them all the same level, best to do is to install the same floors in all the rooms.

For the basement, I see Dricore now says they don't mind if you use it under ceramic tiles. That seems ridiculous to me. Did you read this? NOTE: DRIcore must lay perfectly stable. How are you gonna do that? And when the grout and/or tiles start to crack, what will be the reason? Right, they will say you messed up.

Jaz

 

[freelabor4me]

Hi Jaz, my name is Marc.
I did match up the dimensions of the I-beams on a manufacture website and they do seem to be designed to be L480 or better as you expected.
I thought I would be able to add 1/2" CB on top of the decking but sounds like the ply is a must, the CB or Ditra is then up to me. Can you use 3/8 Plywood to keep down the thickness?
Also I am curious about the install on my main floor I did not know anything about tile before I bought but now wonder if I may have issues with it down the road (Seems fine so far 13 years old). Looks like 5/8 OSB -> 3/8 PB -> 3/8 Tile...
Wish I could put in pictures but they do not seem to work.
As for the Dricore... might just leave it alone. The site said fasten it down using 5 Tapcon screws per panel,1 each corner and center plus more if you find any give in an area.... This seemed iffy to begin with but with a sloping floor I would still need to level it also, was a nice thought I guess but nothing more.

 

[JazMan]

Yes Marc, I noticed your name somewhere else.

⅜" ply would do some good, I recommend min. ½". ⅜" is kinda flexible as you know. Why not go with Ditra upstairs which is ⅛" installed. ¼" cbu will be at least 5/16" installed. Are the joists 19.2 oc?

In the basement I would tile direct to the slab or SLC.

Jaz

 

[freelabor4me]

Yes the joists are 19.2 OC, but now that I think of it I do have a washer and dryer in the one bathroom and a spa tub in the other so ply + CBU is likely necessary anyways. I was thinking I should go with the flexbond LFT also just to make sure.

 

[JazMan]

Are you positive and have double checked that your subfloor is really ⅝", and it's t&g? If so, give my regards to the cheap-ass builder and building department for letting that slide. (You're located where?) ⅝" is bad enough at 16" oc, at 19.2" it's ridiculous.

Ok, you already know you need more ply, but how much? I think if you add a true ⅜", you'll be up to a ¾" rating +-. So I said to go with ½" and compensate with Ditra instead of ¼" cbu so the end results will be the same height. However the Ditra will give you a premium system.

There's lots of good mortars for large tiles. Main decision for you now is whether to go with Ditra or a similar membrane or stay with ¼" cbu. and therefore ⅜" or ½" underlayment.

Jaz

 

[freelabor4me]

I am thinking 3/8 plywood 1/4 cement backer might be the way to go in this case, do you think this is acceptable? The 1/2 would just go to high and the ditra would be really expressive since it is $320 150 sqft/roll and I would possibly need 200 sqft...

When I was at the tile shops the other day they all said they just install over plywood and not one suggested the cement. Is that the "old school" way of doing it or just a way of cutting corners to get down their quotes to beat competitors?

 

[JazMan]

Where do you live? I might be able to help you with Ditra.

Your ⅝" OSB + ⅜" ply + ¼" cbu is no match for ⅝" OSB + ½" ply + Ditra. Even over the same ply, going Ditra gives you a better system. As for is method #1 ok? It may work, but darn if I can find any cbu manufacturer that says it's fine with 19.2 oc. Over 16" oc, fine.

When I was at the tile shops the other day they all said they just install over plywood and not one suggested the cement. Is that the "old school" way of doing it or just a way of cutting corners to get down their quotes to beat competitors?

Over double plywood I presume. It's definitely not "old time", unless you mean old-time-hack. The good old method would be a "mud-job" which is 1 ¼" of mud or more. You're correct in your assessment, skipping a few steps is always cheaper.

Jaz

 

[freelabor4me]

Where do you live? I might be able to help you with Ditra.

Alberta Canada.

 

[JazMan]

Aha....I see. Is that where 400k homes go for 1.3 mil?

I can send you some for about 1.60 usd plus s&h.

Also, what brands of thinset can you get and where?

Jaz

 

[freelabor4me]

When I was down in texas doing training I figured the houses were aprox. 1/2 the price from here (2000SQFT Above grade=500K) so pretty much. I think our dollar is worth .74US right now and I would have to pay customs import fee so I figure I would not see much savings by the time it got here. I appreciate the offer though.

I will just stick with the CBU and have to decide if I want to stay with 3/8ply or add a little more height for 1/2.

 

[freelabor4me]

Actually I was shopping around for thin set, was going to go with mapei LFT Ultra flex 1 $27 a bag or Flexbond LFT $36/bag...

Came across a place here that carries a Canadian manufactured brand with similar stats ( 250 psi wood to quarry 450 psi quarry to quarry shear ) and they will give me the 40% contractor rate so like $20/bag. Called Profix Optiflex. They also make a sanded grout Poly 500 and additive Octane so I do not have to reseal, figure that would be the way to go.

 

[freelabor4me]

One last option that was suggested I am unsure about, is it acceptable to use ditra xl rather than adding plywood?

 

[JazMan]

No, not with ⅝" OSB. If it was ¾" I'd say ok and hope for the best.

Jaz

 

[freelabor4me]

So far the only thing they did not cheap out on is the staples and glue they used to cement the PB to the OSB

Another quick question, do you fill in your expansion gaps between plywood sheets with caulk or mortar ? I have read here some people cover it with tape to insure there is nothing in there at all to hinder the expansion...

 

[JazMan]

That's a question for the thinset manufacturer, could be either way.

Jaz