Help needed - non standard size tile shower install

[bobinmadison]

Hi, I am new to the forum and could use some expert advice. I would like to install a curbless shower with linear drain in our new master bath. The bath is part of a new addition to our house (recently framed). I am an experienced DIY'er and have installed floor tile before, but never a shower system. The planned size of this double shower is rather large (4' x 8' rectangle) and I am thinking of running the drain along one of the 8’ walls. The floor is framed with I-joists and ¾” sheathing (I-joists run parallel to 8' shower dimension). I would like to keep the entry to the shower the same elevation as the rest of the bath (no curb) for ADA (wheelchair) access. Because I need pitch for the drain and I can’t notch the I-joists, I am thinking of removing the existing sheathing in the shower area and nailing some ledgers on both sides of the I-joists. I would then lay down sheathing between the I-joists such that the sheathing bears on the ledgers and is flush with the top of the I-joists. This would lower the shower area by ¾”.


My questions are these:

1) Does this scheme seem feasible and is lowering the shower area by ¾” going to allow enough pitch to drain over the 4’ run across the shower?

2) Because this is a non standard size shower, what would be the best way to create the pitch and waterproof the shower? I would like to use a prefab shower system (Kerdi, Laticrete, etc) to save time, but all seem to assume a standard sized area (32x60, 42x42, etc). Any suggestions on the best shower system for a non standard size? Or, do I have to go with a mortar bed for this shower? Any advice and suggestions on how to construct this shower would be appreciated.



Thanks in advance. Cheers, bob

 

[bobinmadison]

Hi, I am new to the forum and could use some expert advice. I would like to install a curbless shower with linear drain in our new master bath. The bath is part of a new addition to our house (recently framed). I am an experienced DIY'er and have installed floor tile before, but never a shower system. The planned size of this double shower is rather large (4' x 8' rectangle) and I am thinking of running the drain along one of the 8’ walls. The floor is framed with I-joists and ¾” sheathing (I-joists run parallel to 8' shower dimension). I would like to keep the entry to the shower the same elevation as the rest of the bath (no curb) for ADA (wheelchair) access. Because I need pitch for the drain and I can’t notch the I-joists, I am thinking of removing the existing sheathing in the shower area and nailing some ledgers on both sides of the I-joists. I would then lay down sheathing between the I-joists such that the sheathing bears on the ledgers and is flush with the top of the I-joists. This would lower the shower area by ¾”.


My questions are these:

1) Does this scheme seem feasible and is lowering the shower area by ¾” going to allow enough pitch to drain over the 4’ run across the shower?

2) Because this is a non standard size shower, what would be the best way to create the pitch and waterproof the shower? I would like to use a prefab shower system (Kerdi, Laticrete, etc) to save time, but all seem to assume a standard sized area (32x60, 42x42, etc). Any suggestions on the best shower system for a non standard size? Or, do I have to go with a mortar bed for this shower? Any advice and suggestions on how to construct this shower would be appreciated.



Thanks in advance. Cheers, bob

 

[Sponsor]

 

[bobinmadison]

sorry, posted in wrong forum. Will repost in bath forum. My apologies.

 

[Jadnashua]

Your plumbing inspector would not allow 3/4" in 4'...the minimum slope is 1/4"/foot. Now, if you could live with a buildup of the rest of the room, you could do it. To gain a little extra, check with the I-joist manufacturer to see if they would allow (probably won't, but doesn't hurt to ask) if you could apply some cleats to the sides of them at the low end, and put in some subflooring between them at the level of the tops of the I-joists. That would gain you enough vertical space to consider that.

The other issue you'll have is with 'normal' deck mud, over a subfloor, you cannot taper it to zero - more like a minimum of 1.25" thickness, so you've lost all of your gains. But, you might be able to use a reinforced mudbed. Mudbeds in general have great compressive strength, but little bending strength which is why they need some minimum thickness in order to stay together.

Running the slope the long way would make entry messier, and require even more drop to the drain.

SOme have build a 'hump' on the input to the shower - still allows wheelchair to roll over it (think sort of a speed bump), but tiling that, unless you use a small tile can be an issue for lippage.

You're going to have some issues, and maybe the best place to start would be with the I-joist manufacturer's help line. Depending on how much you really want this and what you're willing to pay, they may have a few solutions for you.

The preformed pans are fast, but tend to be expensive and somewhat limited in sizes. While they can be cut, if you need to add onto them, you'd often end up using deckmud, and then, you might as well save money and do the whole thing out of it and compensate for any (often small, but not always!) imperfections in the floor that foam doesn't like. Wedi will make custom pans with their material, but it's not inexpensive. Depends on whether you're doing this yourself verses paying someone.

The other thing you'll find is that really long linear drains get very pricy. There's another thread similar to this that's current, and a few options were discussed in it you might like to read.

 

[bobinmadison]

Thanks for the quick reply. I doubt I will be able to modify the joists (I am a structural engineer and know that the joists can't be cut....lowered perhaps, but that would require a major structural modification to more than the bath, which is not feasible)....I could raise the floor of the rest of the bath, but perhaps only 1/4" as then I have to deal with a transition out of the bath into the bedroom. That could get me the 1/4" per foot I need to satisfy the building inspector. However, I still don't have room for the mortar as you noted. Is it possible to lay down a tapered piece of plywood (do such products exist?) and then use the Kerdi membrane directly over the plywood and tile over that? Thanks, bob

 

[Jadnashua]

Kerdi cannot be installed directly on plywood. Most similar products have similar issues. Noble makes some designed to waterproof an outdoor deck that might work on ply for you as well as some from Mapei. TO bond to plywood, you'd need to probably use one of their adhesives, and not mortar. Both have good tech support lines - see what they have to say about it. The hassle will be maintaining good vertical support for whatever subfloor you install on that slope. SOme of the reinforced mudbed products MIGHT allow you to feather it over ply - you'd have to read their spec sheets carefully. A standard mudbed, even with wire mesh over ply cannot go that thin. The reinforced stuff tends to use fibers like Kevlar to help provide flexural strength but there are limits with that, too.

Note, there are some cement based floor products that don't 'flow', and you could build a ramp out of them that might work, then you could use nearly any membrane on top of them. I know Mapei makes at least one - I was in a class where they demonstrated it but don't remember the exact product name - they can tell you if you describe your application. It only 'flows' when vibrated, but once you stop, it stays, thus, its ability to make a slope and be shaped.

 

[bobinmadison]

Kerdi cannot be installed directly on plywood. Most similar products have similar issues. Noble makes some designed to waterproof an outdoor deck that might work on ply for you as well as some from Mapei. TO bond to plywood, you'd need to probably use one of their adhesives, and not mortar. Both have good tech support lines - see what they have to say about it. The hassle will be maintaining good vertical support for whatever subfloor you install on that slope. SOme of the reinforced mudbed products MIGHT allow you to feather it over ply - you'd have to read their spec sheets carefully. A standard mudbed, even with wire mesh over ply cannot go that thin. The reinforced stuff tends to use fibers like Kevlar to help provide flexural strength but there are limits with that, too.

Note, there are some cement based floor products that don't 'flow', and you could build a ramp out of them that might work, then you could use nearly any membrane on top of them. I know Mapei makes at least one - I was in a class where they demonstrated it but don't remember the exact product name - they can tell you if you describe your application. It only 'flows' when vibrated, but once you stop, it stays, thus, its ability to make a slope and be shaped.

Thanks so much for the info....I will make some calls.....didn't think this would be so complicated. I did notice that Noble makes a tapered panel (1/8" to 1-1/4" over 5'), which would seem to work but it says its for under a mud bed.....what I don't understand is that you can apply the membrane directly over the floor pans but not over the presloped panels....perhaps made of different materials.....will have to call and see. thanks! bob

 

[Jadnashua]

Schluter's presloped foam panels now come with Kerdi already attached. Most of the Noble products tend to use either an epoxy or special adhesive to bond the membrane to things and if not the whole sheet, at least on the seams. Nearly 30-years of experience with Kerdi, Schluter has proven that thinset provides a seam that is waterproof with their product and does not recommend an epoxy, or other adhesive to do it. THey do have KerdiFix for special situations, but like some of the other manufacturer's products, they are a LOT more expensive than using just thinset. It depends on the type and thickness of the foam whether thinset would hold things to it or not. The extruded polystyrene Schluter uses works just fine to bond Kerdi to it using an unmodified thinset (as long as it's a premium version and not the economy loss-leader version). A premium unmodified tends to have significantly more cement in it than the economy versions and finer aggregate (mostly sand) that is often cleaner. IOW, on thinsets, you tend to get what you pay for.

 

[bobinmadison]

Schluter's presloped foam panels now come with Kerdi already attached. Most of the Noble products tend to use either an epoxy or special adhesive to bond the membrane to things and if not the whole sheet, at least on the seams. Nearly 30-years of experience with Kerdi, Schluter has proven that thinset provides a seam that is waterproof with their product and does not recommend an epoxy, or other adhesive to do it. THey do have KerdiFix for special situations, but like some of the other manufacturer's products, they are a LOT more expensive than using just thinset. It depends on the type and thickness of the foam whether thinset would hold things to it or not. The extruded polystyrene Schluter uses works just fine to bond Kerdi to it using an unmodified thinset (as long as it's a premium version and not the economy loss-leader version). A premium unmodified tends to have significantly more cement in it than the economy versions and finer aggregate (mostly sand) that is often cleaner. IOW, on thinsets, you tend to get what you pay for.

I do like what I see in the Schluter system, however unless I am missing something, their preformed panels are too thick for my application...the Noble tapers down to 1/8", which may make it workable with the limited depth I have. cheers, bob

 

[Jadnashua]

Kerdi works just fine installed over a mortar bed - IOW, you don't have to use the foam by any means - only if it works for your situation. Laticrete's fortified mudbed can go (according to a tech I asked today) down to 1/8". But, while it would be more expensive, one of their self-levelers (an industry misnomer if there ever was one!) can be placed and make a ramp and can go to a feather edge - NXT Plus (NXT would flow more, and not make a ramp). I know Mapei has a floor patching cement product that can do the same thing. You could use that to make your ramp, and if the I-joist company says there's a way to recess the subfloor to the top of the joists, you'd have your drop once you added underlayment and tile on the rest of the bathroom. Ditra installed is about 1/8", and can be tied into the Kerdi to provide a waterproof interface into the room giving you a little more leaway, or DitraXL, even a bit more (but you may have to build a ramp at the doorway). You could use Kerdiband around the walls and on the Ditra seams, but you'd still have the room's doorway where a flood could get out, but protect the floor in the room, at least!?

Call the respective tech support companies and explain what you're hoping, and they will probably offer you some choices that they'd warrant - Schluter, Laticrete, Mapei all have free tech support lines, along with most others as well.

 

[bobinmadison]

Kerdi works just fine installed over a mortar bed - IOW, you don't have to use the foam by any means - only if it works for your situation. Laticrete's fortified mudbed can go (according to a tech I asked today) down to 1/8". But, while it would be more expensive, one of their self-levelers (an industry misnomer if there ever was one!) can be placed and make a ramp and can go to a feather edge - NXT Plus (NXT would flow more, and not make a ramp). I know Mapei has a floor patching cement product that can do the same thing. You could use that to make your ramp, and if the I-joist company says there's a way to recess the subfloor to the top of the joists, you'd have your drop once you added underlayment and tile on the rest of the bathroom. Ditra installed is about 1/8", and can be tied into the Kerdi to provide a waterproof interface into the room giving you a little more leaway, or DitraXL, even a bit more (but you may have to build a ramp at the doorway). You could use Kerdiband around the walls and on the Ditra seams, but you'd still have the room's doorway where a flood could get out, but protect the floor in the room, at least!?

Call the respective tech support companies and explain what you're hoping, and they will probably offer you some choices that they'd warrant - Schluter, Laticrete, Mapei all have free tech support lines, along with most others as well.

Jadnashua, you have been most helpful and obviously understand my dilemma....I do appreciate your patience with my ignorance I called Shuluter Kerdi today and they were very helpful. I think I am going to go with a mortar bed with Kerdi over the top. They said I could lay the mortar right over the wood sheathing, which seems to make sense, though I will probably put down some roofing felt first...if Kerdi is truly waterproof and you do a good job on all the seams, it seems logical there is no reason to have multiple layers of mortar, waterproofing, weep holes in drains, and the like. I am intrigued by the Goof Proof system to get the pitch correct, but it gets costly! I'm thinking I will buy a piece of Trex decking and rip it on my table saw into tapered strips to mimic the Goof Proof system. Should save me some bucks.

I will use Ditra in the rest of the bathroom as you suggest and will likely put a drain in as well. I think some kind of marble or tile threshold at the bathroom door would help in case of a flood also.

Thanks again, Bob

 

[Jadnashua]

Well, almost. Typically, over wood, you tend to use a decoupling layer when doing a mudbed over plywood. This helps to ensure you don't suck too much moisture out of the mix before it hydrates (cures). This is often a layer of plastic or roofing felt. Using something like the NXT Plus, that requires a primer put down first (no decoupling, since you're bonding it to the ply with the help of the primer), which does two things: prevents moisture from being sucked out, and makes a good surface for the NXT Plus to adhere to (essentially, any SLC and many, but not all cement based floor patching materials require a primer). A conventional mudbed really needs to be at least 1.5" or so thick minimum over wood, and wouldn't work for your application. Laticrete's reinforced mudbed product can go thinner, and over wood, about 1/8" is the minimum per their tech guy (call and verify). It very much depends on the product you choose, but Kerdi and thinset will bond to any cement based material. The trick is getting it the shape and slope you want without birdbaths or flat spots. Deck mud is sort of like working with wet beach sand, but you need to pack it in place.