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Unread 06-23-2008, 12:26 PM   #1
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Well intentioned newbie building a wheelchair accessible shower and bathroom

My Dad was recently paralyzed from an unexpected complication following surgery. He may or may not ever walk again, but my bet is that even if he does, he'll use a walker for the rest of his life. He's 81. Right now, he's using a wheelchair and is due to come home in a week. To accommodate him, my brother and I are converting my parents' dining room into a bedroom and enlarging a first floor half bath into a full bath. I plan on building an accessible shower with a bench just like the one John shows on this forum under the accessible shower link. It will be about 60" by 48". The main shower is 60" by 32" with a 60" by 16" ramp leading into the shower area. The bench will sit on one end and be 20" x 28". The drain will be centered at 30" directly underneath the shower.

I'm flying to my parents' house to do this so I'm trying to coordinate materials etc. long distance. I've tiled a slate and marble floor before but have never built a shower stall. I know many of you say doing the cement mud pan is easy, but it makes me nervous. Instead, I would like to use the Kerdi prefab shower floor, drain, Kerdi material etc. to build this. Here are my questions:

1. I can build the bench outside of the Kerdi prefab pan (I can just cut into the pan to do this so the pan fits around it on two sides). If I do this, I'm not sure how to ensure that no water leaks under the bench. I could wrap the bench in Kerdi membrane, but I don't know if that will work well enough. I was also going to cover the bench in hardiboard.
2. I planned on putting hardiboard on the walls (before I decided to use Kerdi). Since it's already in my parents' garage waiting for me, can I use it for the walls? Will the Kerdi and thinset stick to it well enough? So I still need to tape and mud the hardiboard seams? Or, should I return the hardiboard and get drywall instead. Part of my problem is not having a car big enough to haul the larger drywall boards.
3. If I use the Kerdi prefab floor tray, does anyone have a recommendation for how thick my subfloor needs to be. If you can believe it, it's currently only 3/8" plywood. The original builder really cut some corners. The rest of the bathroom floor isn't going to be tile. Instead, it will be a peel and stick tile that matches my parents kitchen since one of the bathroom doors opens into their kitchen. The total height of the subfloor and tile will be 1 1/4 inches.

I thought about finding a contractor to build the mud floor base for me instead of using the Kerdi prefab floor pan, but the tray is only $80, so it seems easier and economical to me to use that.

Thanks loads, Heather.
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Unread 06-23-2008, 01:05 PM   #2
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Hi Heather,
sorry to hear about your troubles.

let's see if we can help you here.

to do a Roll in /Handicapped shower you will need to have the shower area depressed a few inches to make the finish floor lower for the water to drain.

if not you will still need a curb in the shower area to retain the water.

you can use the Hardibacker with the Kerdi. it just needs to be dampened with a sponge when you install the Kerdi & thinset.

you can build the bench, cut and put in the Kerdi pan and Kerdi everything to make it waterproofed.

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Unread 06-23-2008, 01:06 PM   #3
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Welcome to the JB Forums.

Before you can go any further you must find out about your floor structure.
The size of the joists, how they are centered and the span of the joists.

Click on "Deflecto" in the dark blue banner above and fill in the information.

The builder may have cut some corners in the floor systems as well.

No curb, walk-in shower.

Last edited by chuck stevenson; 06-23-2008 at 01:42 PM.
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Unread 06-23-2008, 04:39 PM   #4
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Brian - Thanks for your reply. It gives me confidence!

Chuck - Great info regarding the floor joists. I'll use the calculator. I bet we'll need to do some reinforcing. Don't want the floor to sag or anything.

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Unread 06-23-2008, 05:02 PM   #5
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Heather, welcome to the forum.

Sorry to hear about your Dad, hope he does well.

The folks here are happy do what we can to assist you in your project, so please feel free to ask whenever you need some help.
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Unread 06-25-2008, 11:46 AM   #6
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I am planning on going ahead with the Kerdi prefab floor, but I lack the skills to lower my existing floor. Using their ramp instead of the shower curb, I feel like I could slope the shower just like John Bridge shows in the accessible shower you can view through the Tile and Marble page.

If I do as he suggests and hang the shower curtain inside the slope going down toward the drain, I feel like it will contain the water. Am I nuts? I don't think I want to tackle a mud floor right now even though all of you say it's easy. My other option is to have a contractor build the mud floor, but it's still going to end up being just like the shower in the link which I could do myself with the Kerdi and prefab tray.

Thanks, Heather.
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Unread 06-25-2008, 12:25 PM   #7
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Welcome Heather. Sorry you are having to do this project under such difficult circumstances. Unless I missed something you still haven't run the deflecto. You will need to do this in order to make sure that your floor will support the extra weight you will be adding.

Denise Gunnels, Realtor

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Unread 06-25-2008, 02:01 PM   #8
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Neesie - No I haven't run the deflecto. I'm in Kansas and my parents' place is in NY, so I'm trying to get my brother in NY to make the measurements I need. I know I'm ignorant here, but if I "fail" the deflecto test, can't we reinforce the floor joist?

Thanks, Heather.
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Unread 06-25-2008, 02:45 PM   #9
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Yes, if there is a basement it should be fairly easy to do with an open ceiling but this too will take time.
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Unread 06-25-2008, 08:35 PM   #10
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My brother will measure the basement joists and run the deflecto measurements tomorrow. He thinks we're ok, but we need to run the numbers. Luckily, we can access the basement underneath the new shower.


The Schluter folks told me that a 3/4" subfloor would be fine underneath the prefab pan. I called to see what thickness the floor needed to be since I couldn't find it anywhere. It may be in John's Kerdi book which I plan to download onto my laptop. I just haven't gotten to that yet.

Currently, the place where we are building the shower is in the middle of the old living room. When we pulled up the carpet, we found a tongue and groove hardwood floor that as far as we can tell, has always had carpet on it. The house is about 50 years old. I can rip out the hardwood floor under the shower and put down 3/4" plywood, or I can just build the shower on top of the hardwood floor (mucho easier!).

Any thoughts?

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Unread 07-05-2008, 07:18 AM   #11
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Hi all! I'm back in NY and we're making progress on the bathroom. I decided to go with the Kerdi system, including the prefab tray and slope. After reading John's e-book, watching the Schluter installation videos and reading lots of posts, especially Chuck's documented new mater bath, I feel like we can do this. I would have done a mud bed, but time is short and I'd prefer to do that first in my house versus in my parent's.

Thus far, we've framed, sheetrocked and I cut the trays to fit. We also hired a plumber and the plumbing is in. He'll build the p-trap from below once I insall the Kerdi drain. Our space is open to the basement. Lucky us.

Today, we will cut the drain hole and then I will thinset and screw hardiboard to the floor. We are installing this on top of a plywood subfloor and tongue and groove hardwood floor, so Schluter recommended adding hardiboard to minimize movement.

We built a bench out of 2 x 4's with a plywood top and hardiboard on the vertical surfaces.

1. Is the hardi ok for the vertical surfaces? I assumed Kerdi would stick to hardiboard.
2. Should I add sheetrock or hardi on top of the plywood? I don't want my bench to get too much taller, but I read a post that Kerdi didn't like plywood.
3. The store we bought the Kerdi from recommended a unmodified Tec thinset for the hardi and the Kerdi and a stronger Tec 3N1 for the tiles (which are big and heavy). I'm nervous about the tiles staying put on the walls, so I'll put up a ledger board to hold them. Do you think the Tec 3N1 is strong enough? I know I need to patch the ledger holes. Is there a different way to do the wall tiles without a ledger?

Thanks tons. Heather.
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Unread 07-05-2008, 08:10 AM   #12
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Hardi is OK for use under Kerdi and that would be true for both vertical and horizontal surfaces. Be advised, however, that drywall is much easier to work with in a Kerdi setting. Hardi is very thirsty and sucks the moisture out of motar very quickly. Work fast and pre-dampen first, that is a must.

Schluter advises not to lay Kerdi directly over plywood so adding some Sheetrock on top of the bench would be a good thing.

TEC 3N1 is a good mortar but not for use when setting tile to Kerdi. It's highly modified. You really should use an unmodified mortar over Kerdi, like TEC Full Set.

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Unread 07-05-2008, 09:27 PM   #13
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Hah! I paid more for the Tec at the fancy tile store rather than going to Lowe's or HD and it sounds like they sold me the wrong thing. They also gave me the wrong floor tile, but that's another story. Of course, I've lost count of the number of times a certain big box store has given me wrong advice about buiilding a ramped shower.

** Any suggestions on a good unmodified thinset from Lowes or HD? My tiles are 12 inch squares and they are HEAVY so I need something that will really hold. I also think I'm going to run out of Tec to adhere my Kerdi. I'm doing that tomorrow and the tile store is closed until Monday.

I couldn't get an internet connection all day today and couldn't read this forum, so I decided to add hardi onto my plywood bench. I really learned how much it sucks up moisture first hand. Funny, I'd read people's posts about that but completely forgot until I experienced it myself. Duh!

I also laid hardi over the hardwood floor (with thinset underneath) and put in a gazillion screws. I also screwed the hardwood into the subfloor. I put the prefab tray on top of the hardi after I cut it out around the bench. It worked nicely. I was a bit gun shy so I lifted it up not once, but twice to check it and add more thinset in some low areas. Of course I ran out of thinset twice and had to run out to the garage to mix more while the hardi made great big sucking noises as it sucked the moisture out of the thinset on top of it. I made a big mess lifting it and was afraid it would break in half. Between the floor and the two ramps, I paid about $150 for what my brother calls really good styrofoam. However, it really was easy to work with for a newbie and I'm super glad I used it. Next time, I'll be confident enough to do a mud bed.

I'm just going to stress out until I get the drain done.

The only bad part about today is that I had to break for 4 1/2 hours to take my kids to the airport so to make up for lost time, I worked late - until 10 pm. By then, I was too tired to drink that glass of Malbec waiting for me. Instead, I ate a bowl of cereal. What a sacrifice!

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Unread 07-05-2008, 09:51 PM   #14
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Originally Posted by Heather
Any suggestions on a good unmodified thinset from Lowes or HD? My tiles are 12 inch squares and they are HEAVY so I need something that will really hold.
Don't get hung up on thinking the weight of your tiles is gonna be a problem, heather. Those 12-inch tiles are no heavier than a gross of some one-inch tiles. Even the unmodified thinset, if it meets ANSI standards, will have a minimum shear bond strength of at least 50 pounds per square inch. That limits your 12x12 tiles to something over 7,000 pounds each. I think you'll be under that, eh?

At Home Depot there are no longer any good quality unmodified thinset mortars available.

At Lowe's you may find Mapei's KeraBond, an excellent choice. May also find Laticrete's 317 or their Mega Bond.

My opinion; worth price charged.

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Unread 07-05-2008, 10:01 PM   #15
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heather where abouts in ny are you?
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