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Unread 09-06-2021, 01:21 PM   #16
Skivvt
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Dan,
I actually have 2 stacks both are 3” Copper, this one services the shower, toilet only. Copper looks good on the upper 24” or so so I will replace it with 3” pvc to the good bits.

Phil, the 56sqft kit has like 38sqft coverage, I did a quick check and the cable won’t be too long.

Dan, I always run 12/2 unless the application calls for more I only mentioned the 15a breaker if i was to make it a dedicated circuit, it’s only pulling 4ish amps would the 15 even protect it or does the tstat hav built in protection?

So i planning on running a new line for the ditra regardless and was thinking of branching off for the lights only, should probably call Schluter on this. They do mention somewhere (at least I thought i saw it in there literature) that if there is a circuit near buy under load that it could be used.

Also I can’t imagine that a few lights and the Ditra heat only pulling 4 amps on a 20a or even 15a circuit would make the lights fliccer but i could be wrong (it happens…) Assuming 4 100w bulbs each about 0.83a so thats 3.3a.

You do make a good point if there is an issue with the floor, no lights…suppose if the floor ever failed where it couldn’t be repaired you could just bypass it.
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Unread 09-06-2021, 02:55 PM   #17
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Quote:
Originally Posted by Mark
Dan, I always run 12/2 unless the application calls for more I only mentioned the 15a breaker if i was to make it a dedicated circuit, it’s only pulling 4ish amps would the 15 even protect it or does the tstat hav built in protection?
Mark, the circuit breaker is meant to protect the wiring, not the connected appliance. You would connect your #12 wire to a 20 amp breaker.

My opinion; worth price charged.
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Unread 09-07-2021, 06:58 AM   #18
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Mark, the DH controller does have built in GFCI protection, and a diagnostic routine to test it. Well, the touch screen, but non-wifi, unit I use does.

I'd be, um, shocked if the only thing on that existing 15A circuit are the lights for only that bath. But stranger things have happened.

I get your reasoning. The dice are yours to roll.
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Unread 09-07-2021, 07:28 AM   #19
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Dan,
I will be running a new 20a circuit for the ditra and 3 lights so there will not be a problem.
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Unread 09-07-2021, 09:02 PM   #20
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Starting to make plans for the demo of the existing tub/shower and prep for new walk in shower. Original plan was to cut existing ply 6” or so past the vent pipe and in front of tub to the joists and replace with 3/4”. However after further investigation there is more going on here that may require a different approach.

(Refer to photo1]
1. The joist furthest from the front of the tub is about 2.5” past the wall.
So i was planning on adding 2”x6” between the center joist and the one 2.5” beyond, however i was able to sneak a camera in the bay and found that there are electrical wires running in the bay and whoever installed this used 2”x4” blocking so the wires could pass below. So i am not sure if the 2x4 blocking is enough to support the wall side of the shower.

2. The floor is a double layer of 1/2” ply except under the toilet area, there is 5/8” on top of 1/2” and under the tub it is just one layer of 1/2”.

(Refer to photo2]
1. I am thinking i should remove the 5/8” in the toilet area, cut back the top layer of 1/2” ply to about 6” in front of the joist which is the blue line and the whole width of the bathroom.
2. Then fill in the tub area with 1/2” then another 1/2” spanning the tub and toilet area (the full width of the bathroom)

The floor is not level in the tub area, maybe a 1/4” downhill from the wall to the front of the tub
a). It could be that they just did a crap job and it’s an easy fix (doubting it is an easy fix) but thinking of just sistering new joist to make it level - would this be the best approach? Since a Schluter pan will be used I am assuming it need to be dead level or close to it.

I just realized while typing this, That if i sister the joists in the tub area the plan to use one piece of 1/2” ply extending the ply forward of the tub and over the toilet area won’t work because of a height discrepancy.

So now I am thinking:
I would still sister the joists in the shower footprint add 1/2” to make up the diff from the joist to the first 1/2” layer then 3/4” ply being sure the area is fully supported on the right, left and rear (the front will be directly over a joist).
Remove the 5/8” under the toilet area from side id shower to wall and 6” past the joist and replace with 1/2” ply.

I am sure I will need to clarify some more but any input would be appreciated
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Unread 09-08-2021, 06:11 PM   #21
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Ok, let me try again.

Here is what I have
Joists are 16” on center, 1.5” x 9” with a span of 11’ 4” and appear to be spruce. That gives me an L/579.

The subfloor is 1/2” running perpendicular to the joists with another 1/2” running perpendicular to the one below.

The top 1/2” seems to not be screwed down enough and when you wack on it with your fist or hammer you can tell its loose. And of course as y’all know screwing 1/2” to 1/2” doesn’t work so I can’t tighten it up

I currently have about 1”-1/8” from the top of the two 1/2” pieces to the top of the hardwood floor in the hallway.

1. Could i just put 5/8 or 3/4 on top of the double 1/2” and screw to the joists and call it good? I will be using the ditra heat.

Thanks for your help
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Unread 09-08-2021, 07:34 PM   #22
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Mark, that first layer of nominal half-inch plywood does not have T&G edges and almost certainly does not have blocking under those seams. That subfloor does not even meet the most minimal of residential building codes.

The second layer has the same limitations and is not even correctly oriented with the strength axis perpendicular to the joists, making it virtually useless as a second layer of subflooring.

I would recommend you remove at least the top layer so your not having so many spacers under your proposed new subfloor, spacers that are prone to permitting slight vertical movement of the topmost layer.

Installing a layer of nominal three-quarter-inch plywood over the unwanted single layer of half-inch plywood would at least give you the minimum required subfloor for a ceramic tile installation. You must be sure to use fasteners long enough to penetrate at least three-quarters of an inch into the joists.

Poor situation, but that might give you a usable subfloor. Removing all the existing subflooring and starting fresh at the joist tops would, of course, be better.

My opinion; worth price charged.
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Unread 09-08-2021, 08:13 PM   #23
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Thanks cx, so sounds like I should just bite the bullet and strip it to the joists. If i do that is the 3/4” sufficient or do i need to add 1/2” or 5/8 on top of that as well?

I might get a quote for that part, what should I specify for them to quote to make sure it is done correctly? Adhesive on the joists, 3/4” t&g, 1/4” gap around the perimeter and what would the screw schedule look like? Every 6”?

I just want to be specific with the quote so I don’t find that they didn’t glue it and only used 6 screws…

Thanks!
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Unread 09-09-2021, 07:50 AM   #24
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I thought the same thing when I saw and read your post yesterday, Mark, remove it all. Doing so might also give you an opportunity to level the floor if needed and relocate that 3" drain.

That one joist set back 2.5" is a little problematic but not a show stopper. If you do elect to hire this out you'll want someone who knows framing. Even if you can find such a specialist I think you'll have to police the work. Basically, each edge of the new plywood, 3/4" should be fine, must be supported.
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Unread 09-09-2021, 10:02 AM   #25
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Thanks for the response Dan, after letting it all sink in ripping it all up to the joists and replacing it will be best in the long run.

I will probably be doing this myself, I will probably leave the drain and stack where it is. My current plan is to rebuild that wall with 2x6's so it fits better.

The floors appear to be level which I suppose could change once the old ply is stripped, I did say earlier the floor under the tub was not level but it is (at least in the spot I could check.

As far as the 2.5" setback - thinking I will use joist hangers to install blocking and will notch the top of them (I gots a real fancy sliding table saw to take care of this) at the wall side to accept a 2x4 so there will be full perimeter contact with the ply



Question on the 3/4" ply, the area to be covered is approximately 7'-4" by 9'-6". the joists are running the 9'-6" direction so I will run the 8' of the ply perpendicular, so basically I will have 2-4'x 9'-5.5" and one 4' x 18" (minus gaps).

Would it be better to place the narrow strip at the back wall by the toilet or could it be placed at the door opening or does it even matter, I ask because it would seem to me to place it were there is less foot traffic BUT work flow wise I plan on leaving the tub/shower in place as long as I can (the tile guy is scheduled for Oct 18th)

So for now I would demo all the ceramic tile then take out 4' of the bad ply in the toilet area and replace with the new 3/4" do all the other work I can and on Oct 14 or 15 do the rest.

Toilet is on the 46.75" wall
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Unread 09-10-2021, 09:41 AM   #26
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Suppose my post are to long-winded, will try to keep them shorter…

Also just a note, although I don’t mention it I do search the site for the info needed before posting…

1. So sounds like 3/4” is sufficient for a successful subfloor for ditra and 12x24 porcelain tile - true or false? (Assume joists/framing are in spec)
a). The plywood should be - t&g 3/4” type1, no voids (BCX?) correct?
b). The ply should be glued to the joists with something like PL400, correct?
c). Screw every 6” with min 3/4” penetration
d). 1/4” gap at walls, t&g and any butted joints.
e). I have come across applying 5/8” (without t&g) glued with T1 or T2 and screw ed (avoiding joists) to the 3/4” - does this gain me anything over just using the 3/4”?

Thanks for your feedback in advanced!
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Unread 09-10-2021, 10:09 AM   #27
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1. It exceeds the Ditra manufacturer's minimum requirement.

a. It must be an exterior glue plywood with no face of grade lower than C.

b. PL400 is a good choice.

c. Won't hurt, but a bit excessive. 6" spacing on the short edges and 8" in the field should be more than adequate.

d. Don't see where you would have any butt joints, but they would be gapped at 1/8th" normally. The 1/4" at the perimeter is good.

e. Adding a second layer of nominal half-inch plywood subfloor, screwed to the first layer, makes a much stiffer subfloor. Here is a good article from our Liberry on the method I think best for installing the second layer. It must be of the same grade and type as the first layer. I do not recommend you bother trying to glue the layers.

My opinion; worth price charged.
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Unread 09-11-2021, 07:57 AM   #28
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Mark, when determining the length of your screws I think you'll find that a minimum of 3/4" into the joist is just not enough. I did. The 1st 1/8" or so of the screw tip is tapered, so with only 5/8" ish of full diameter shank they won't get enough bite into the joists and will likely just spin. If they don't spin, they'll just barely hold. IMO, the min should be 1".

2" inch construction screws to fasten 3/4" ply would be prefect.
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Unread 09-11-2021, 08:39 AM   #29
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Thanks cx,

I will do the 3/4” and 1/2”, it doesn’t really cost and take much more time and will result in a better end result.

The only reason I mentioned butt joints is that I may not be able to a 4’ x7’ish piece up the stairs and in the bath. I think i have a piece of foam board that i can cut to size to check.

Dan, i was thinking the same thing, i got bunches of 2” construction screws so thats what I will use for the 3/4”
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Unread 09-11-2021, 08:52 AM   #30
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If you need to cut one of your second layer panels in order to get it into place, Mark, it's still best to make the cut fall at the quarter-span area between your joists.

First layer cut would need to fall on a joist, of course, and you want all your pieces to span at least three joists.

My opinion; worth price charged.
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