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Unread 01-03-2020, 10:53 AM   #1
Turridu
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How Long does a mud floor need to dry before tile, Do you "Cure" it?

Pardon if this is repetitive, I searched and didn't get a good answer. I am embedding 1/2" pex, hydronic tubing, in a 1.5 inch mud slab, thus a little more than the 3/4" minimum (7/8") over the top of the tubing per TCNA.
My questions:
Do people hydrate their mud slabs? Curing the slab by hydrating it (keep it wet) will increase the strength of the slab by up to 50%. I have been hydrating it for 1 week, wetting it each day, before letting it dry. I don't think this happens on most job as it time consuming and slows the job. So THEORETICALLY, should it be cured for 7 days?
When is it best to install tile over the slab? I have read some recommend on day 3, without hydrating it. Google says 28 days later when the slab is dry (assuming concrete slab). My buddy and tile guys says stop watering it and once the surface appears dry tile it. Whats the real answer?

I understand the best practice is not always what happens on the job. Most contractors are dogmatic, they do it the way they were taught, regardless of the latest building science or best practice guidelines.
Thanks for constructive input!
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Unread 01-03-2020, 11:09 AM   #2
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Welcome to the forum.

Very skilled installers can work over fresh mud right away. Most of us wait until the next day.

You're in good shape as far as the watering goes
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Unread 01-03-2020, 11:30 AM   #3
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Welcome, Turridu.
Quote:
Originally Posted by Turridu
I am embedding 1/2" pex, hydronic tubing, in a 1.5 inch mud slab, thus a little more than the 3/4" minimum (7/8") over the top of the tubing per TCNA.
Which TCNA Method are you referring to in your application?

When you speak of a "mud slab," are you talking about poured concrete or placed deck mud or mortar as commonly used in ceramic tile installations?

Over what substrate are you installing this hydronic heating and tile?

If this is a common deck mud (5:1 sand/cement mix with minimal water) placement, you do not want to add any water at all after the mud is placed. You can, and usually should, cover the fresh mud with polyethylene sheeting to promote proper curing, but no additional water should be put onto the surface of the mortar bed. That would be an appropriate treatment for poured concrete after it reaches about 500 psi, but not for a deck mud installation.

Let's be sure what kind of "mud slab" we're talking about before we go further.

My opinion; worth price charged.
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Unread 01-03-2020, 11:40 AM   #4
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To further clarify, watering the deck mud after it has set for a day or so isn't going to hurt it.
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Unread 01-03-2020, 11:59 AM   #5
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Details

It is a suspended slab. first floor subfloor is 3/4" tongue and groove plywood, glued and screwed. The Tyvek, then 2.5 lb/yd diamond mesh lath. 1/2" Pex (outer diameter is 5/8" TCNA dictates a min of 3/4" above the tube to the top of the slab, I got 7/8"), stapled down, then 1.5" of Sand-portland in a 3:1 ratio, minimal water just enough to allow packing. It tamped down, then leveled.
I treated it like a concrete slab, albeit no aggregate, and have been wetting it daily to increase the slab strength. Per what I read, can increase slab strength by 50% by curing it with water. I've done this for up to a week, then let it dry. Did the entire second floor this way, then had an experienced tile guy lay the tile. So far so good. I am now doing the first floor and was wondering details how others treat their mud slabs, timing of hydration/curing process and when to lay tile .

THANKS TO THE ABOVE HELPFUL COMMENTS!
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Unread 01-03-2020, 12:43 PM   #6
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Quote:
Originally Posted by Turridu
It is a suspended slab. first floor subfloor is 3/4" tongue and groove plywood, glued and screwed.
Confusing me further. A "suspended slab" would normally be an above grade pre-cast concrete floor. I'm guessing that is not what you have, right? Your hydronic heat and mud bed are over a wood framed subfloor, yes?

In either case, what you have is not one of the recognized methods published in the TCNA Handbook. Or at least not in mine. For Hydronic heat over a wood framed subfloor, you'd need to have bedded your hydronic tubes in deck mud, then install a cleavage membrane, then place a minimum 1 1/4" unbonded mortar bed with welded wire mesh in the vertical center of the mortar, then your tile. That would comply with the TCNA published method RH141.

I think you might be relying upon method RH110A, which is not what you're dealing with.

The ANSI standards require a minimum 20 hour cure for a "cured mortar bed," but "longer mortar bed cures up to 10 days are desirable." A108.01, 4.2.2.1.

Not saying what you've done can't work, Just pointing out what the industry standards recommend and where the smart money will be betting.

You have evaluated your floor joist structure with an eye toward the very substantial additional dead weight you'll be putting on it?

My opinion; worth price charged.
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Unread 01-03-2020, 02:21 PM   #7
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I understand "suspended slab" refers to embedded tubing on a floor supported by joists. Can be embedded in concrete, light weight concrete, in my case mortar.

Thanks for the reference number, method RH110A, now if I only had the actual TCNA manual, I'd love to read about it.

Does the Tyvek act as a slip sheet? Keeping the mortar from bonding to the substrate? In the event of this need to keep the mortar bed from bonding to the subfloor (sounds like a floating floor), why do the tile guys nail or staple the bejeesus out of the lath to the subfloor?

Floor was engineered and stamped, the I-joist were bumped up for the weight load.

Thanks!
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