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Unread 10-07-2020, 08:33 AM   #16
Kman
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With their proprietary sealant, you do the nail penetrations and seams, plus the joint between the bottom of the Densshield and the mud.
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Unread 10-08-2020, 12:44 PM   #17
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So I found out I dont have densheild. I have CertainTeed diamondback backer board. Which is also a waterproof tile backer.

Can I use the blue mapei hpg on the walls and joints?

Also is it possible to do the kerdi membrane on the drypac shower pan?
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Unread 10-08-2020, 01:19 PM   #18
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https://www.certainteed.com/resource..._Guide_Eng.pdf
If you want to use Kerdi, you would need their drain on the shower pan. There are restrictions on how low you can run this board on the walls similar to that of a fiber-cement board, but the specifics are a bit different which is why you need to read, understand, and follow the manufacturer's instructions. This panel is still a gypsum based product. Water resistant or not, it is not waterproof. If you want a waterproof shower, you don't want

Kerdi is a 'system', meant to be used as a system, which includes their drain and the membrane on the entire shower enclosure at least up to the height of the shower head.
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Unread 10-09-2020, 12:10 PM   #19
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So i decided i will with a roll on waterproof membrane. Im just wondering now does the tiler contractor put mesh and thin set on joints and screws first then i roll on the waterproof membrane or do i go in first and waterproof the joints and screws first?
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Unread 10-09-2020, 12:31 PM   #20
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you want to waterproof over the fasteners and joints. If you did it the other way your back to putting holes in it!
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Unread 10-09-2020, 02:02 PM   #21
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PIck up a wet film thickness gauge, probably from a paint store...they're cheap, and learn how to use it properly. When using a liquid applied waterproofing, it is critical that your wet coats are between the stated min/max, and even if you use the recommended roller, that is far from a certainty depending on how you load it up and how much your press, and how many times you go over it. Too thick is as bad as too thin, and more coats are not good, either. You need two proper coats, applied as recommended.
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Unread 10-09-2020, 05:03 PM   #22
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Another thread about your backer board.
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Unread 10-10-2020, 09:14 AM   #23
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ok again question not answered hahah.

1.Do i put the waterproof roll on membrane before my tiler does his thin set over joints or after?
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Unread 10-10-2020, 09:48 AM   #24
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For a roll on membrane, you would tape and mortar the joints before applying the membrane. But this still does nothing to alleviate the problems of your cobbled-together system. I think members are reluctant to continue answering your questions, when you show little interest in following their advice.
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Unread 10-10-2020, 12:59 PM   #25
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Here's the only thing about Diamond Board. Maybe someone who's actually used it can verify this.

The TDS says it's "water resistant", not waterproof. And we know it has a gypsum core. In the thread I linked to, Craig says to treat it like cement board.

So wouldn't a person want to waterproof the entire surface, if that's the case? I'm bringing this up because I don't want the OP to mistakenly think it's okay to just hit the seams and fasteners, if that's not the case.
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Unread 10-10-2020, 02:57 PM   #26
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I have taken into consideration the other posts. I'm not ignoring the advice.

I'm taking out the bottom half of the backerboard redoing the liner with a preslope, and this time not screwing into the curb and keeping all screws about 7 inchs above the floor when I screw the bottom boards back in.

I will then wait for tiler to do his thinset and morter and drypack floor then I will go over everything boards and joints and floor with mapei HPG waterproofing liquid.

Does that sound about right?

Also what should I fill in the gaps with on the backerboard between some joints I have some gaps.
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Unread 10-10-2020, 04:08 PM   #27
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It would somewhat depend on how large those gaps between boards are. The whole idea of taping and thinsetting the joints between the sheets is to tie them together like a monolithic wall that was mudded (old school, but still used and great if you have the skill). The big danger when using a liquid waterproofing is that those seams and penetrations need to be covered first before you add it. The tendency is to end up with a speed bump over the seams which you do NOT want! It's not like a drywall seam. When using a sheet membrane, the sheet becomes the seam reinforcement so you don't prefill and tape them, and there's no danger of speed bumps there. With liquid applied ones, you need to be particularly careful not to get a buildup or it can become a pain getting the tile to lay flat over it.
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Unread 10-10-2020, 06:00 PM   #28
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Quote:
Originally Posted by V
...and keeping all screws about 7 inchs above the floor when I screw the bottom boards back in.
Does that equate to at least two inches above the top of your rough shower curb?

Have you read the installation instructions for the Mapelastic MPG? Have you ever applied such a product at 40 mils thickness?

Folks commonly want to use the liquid applied direct bonded waterproofing membranes because they think it will be easy, like painting the bedroom. It's not. Read the instructions for that product.

And You do not want to apply that liquid membrane over the floor of a shower receptor that has a traditional liner installed. You want to use one waterproofing system for your receptor and depend upon it working properly if it's been properly installed. Adding that second waterproofing membrane is not overkill, it's just kill.

My opinion; worth price charged.
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Unread 10-11-2020, 04:32 AM   #29
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Quote:
Does that equate to at least two inches above the top of your rough shower curb?
Yes it does.

Quote:
Have you read the installation instructions for the Mapelastic MPG? Have you ever applied such a product at 40 mils thickness?
I have never applied such product. What waterproofing system do you recommend doing with the certainteed diamondback backerboard?

Quote:
And You do not want to apply that liquid membrane over the floor of a shower receptor that has a traditional liner installed. You want to use one waterproofing system for your receptor and depend upon it working properly if it's been properly installed. Adding that second waterproofing membrane is not overkill, it's just kill.
So your saying if i do a preslope pan-liner-drypac shower floor, i do NOT need to waterproof the shower floor?

Also if i do a metal and lath shower curb do i NOT need to waterproof that also?


Quote:
It would somewhat depend on how large those gaps between boards are. The whole idea of taping and thinsetting the joints between the sheets is to tie them together like a monolithic wall that was mudded (old school, but still used and great if you have the skill). The big danger when using a liquid waterproofing is that those seams and penetrations need to be covered first before you add it. The tendency is to end up with a speed bump over the seams which you do NOT want! It's not like a drywall seam. When using a sheet membrane, the sheet becomes the seam reinforcement so you don't prefill and tape them, and there's no danger of speed bumps there. With liquid applied ones, you need to be particularly careful not to get a buildup or it can become a pain getting the tile to lay flat over it.
How would i tie in a sheet membrane into my shower pan? Which one would i use? Kerdi membrane? I thought you guys said not to use a that because i do not have the whole system.

Also how high should i leave my diamondback backer board off the floor when reinstalling? I cannot find it the PDF. I want to leave enough room for the mudpan to go under then fill the gap with sealant and mortar.
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Unread 10-11-2020, 04:36 PM   #30
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A properly installed liner IS the waterproofing of a conventionally built shower...the top surface is not then later waterproofed. Tile is the decorative, wear surface, and some moisture is expected to get beneath it. In a conventional shower, that's into the setting mud bed on top of the liner. If you use a sheet membrane, that is the liner and where the tile is attached, so there's much less that can get damp. That top mud layer is expected to get wet, is porous by design, and the liner must be sloped so that it can drain into the weep holes of the drain.

That liner MUST go over the curb and up the walls at least 3" above the top of the curb...well, further, since you need some length to attach it to the walls so you can keep the holes high enough. YOu need to use the preformed corners to seal around the edges of the curb.

You cannot screw anything into the curb after you've attached the liner, so typically, you'd bend some metal lath over it, attaching only on the outside, then use a different cement mix to form over it that can then be tiled.

This is all explained in the 'liberry' in the blue bar above. You also need to read the instructions on the materials you choose, so that you don't have problems.
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