Fabricating 1 a KERDI-BOARD shower niche

[Cheese]

I've been involved in demoing a bathroom down to the studs for a while now. As it's the only bathroom in the house, it has to be done in a very methodical manner.  [eek]
At no time can the bath be out of service for longer than about 6-8 hours...it's challenging to say the least. So far, the new wall mounted vanity & sink/plumbing, the in-wall tank toilet/plumbing and the Robern in-wall storage cabinet have been installed along with some recessed lighting. Time to now focus on the shower area.

I'll be pulling out the cast iron tub and turning it into a curb-less walk-in shower and putting in 2 shower niches to hold the sundry items that need to be part of any shower.  I purchased 2 Schluter KERDI shower niches, a 12" x 12" and a 12" x 20" niche, however, after some sleuthing, I realized neither would fit in the available spaces without completely reframing the wall.

At that instant, I realized it'd be easier and faster just to make my own custom sized shower niches from 1/2" KERDI-BOARD. I decided to make 2 each 10" x 22" shower niches.

I used a Festool OF 1010 router with a MicroFence interface on a Festool FS rail to route the grooves. I also used a Bosch 90º groove cutter that I had on hand. Because the niche would be routed in a flat form and then folded up into a box, it was mandatory that the routed grooves were absolutely parallel to each other.

Photo 1: The first 2 grooves are cut in the KERDI.  The FS rail is always positioned at a specified distance off of the light red lines marked on the KERDI.   

Photo 2: The FS rail is located for the 3rd cut using 2 pieces of maple flooring that I cut to the same length (within .003") and then added a 45º bevel on one end to allow me to see the red layout lines easier.

Photo 3: Closeup of the spacer block. Using this block and a thin line (.30mm) permanent marker, I was able to keep any variation of the positions of the routed grooves within about .010".

Photo 4: Closeup of the Micron 02 marker that was used.

Photo 5: This shows the FS rail in place and the MicroFence interface. Ready to route the 3rd groove.

Photo 6: Third groove routed, just one more left.

Photo 7: The 4th groove routed and the flat form is ready to be removed from the KERDI.

Photo 8: The flat form has been cut from the KERDI and the excess material in the corners removed.

Photo 9: The flat form has now been folded into a box. A mounting flange will still have to be fabricated along with a couple of shelves.

 

[Cheese]

This part will detail the fabrication of the mounting flange for the shower niche. The mounting flange provides a surface to allow the niche to be mounted to the stud wall and it also has a 1/2" rebate on the back that holds the folded-up box. The mounting flange along with some KERDI-FIX sealant will secure the niche assembly and maintain its waterproofness.

I again used the OF 1010, a Whiteside 1/2"ø router bit and the MFS 700 & 1000 rails.

Photo 1: The flange was previously cut to size from the KERDI-BOARD. Here the MFS is placed properly on the flange and the rebate will be routed in the rear side of the flange.

Photo 2: The 1/2"ø rebate has been routed into the back of the flange. The rebate is about 12mm deep.

Photo 3: The MFS is removed to reveal the flange with the center piece still attached.

Photo 4: The center of the flange has been carefully cutout leaving the 1/2" rebate.

Photo 5: Close-up of the rebate.

Photo 6: The folded box has been joined to the flange. This is just a press fit for now. When the KERDI-FIX finally arrives, every joint and intersection will be bonded and sealed with the KERDI sealant.

Photo 7: A close-up of the intersection of the folded box wall and the flange.

Photo 8: Two custom sized, 10" x 22" KERDI shower niches completed minus sealant.

The 2 piece folded shelf is next.

 

[cpw]

I presume you're going to have to tape the corners seams, since the router hogged out the top level fabric for the inner corners.  Why not just cut something to size for the back, sides, and then use butt joints?  They make inside/outside corners for that, but of course 8 of them add up.

 

[Cheese]

Here's an interesting comparison.

[attachimg=1]

The niche on the left is a standard sized Schluter, 12" x 20".  The niche on the right is the home made custom sized version, 10" x 22".

 

[Svar]

Why not just cut something to size for the back, sides, and then use butt joints?

Because then you don't get to show off your very cool MFS template!  [big grin] [poke]

 

[RKA]

How much for the one on the left and what do you charge for the one on the right?  [wink]

 

[Peter_C]

Cheese, do you plan to use Kerdi corners, and Kerdi strips to seal your niche up? Very nice work, too bad it will be covered in tile.

I can not imagine how long it would take me to build like you did vs putting 1/4" Hardi in the back glued to the drywall on the backside, and building with 2x4"s pre-sloped and then laying the Kerdi membrane in. Kerdi corners are expensive, but super easy to install. I've seen the posts on the John Bridge forum where guys make their own corners though. 1/4" Hardi is my goto for the backs as it is thinner, and hopefully will slow down a nail or screw being driven from the backside...

 

[Cheese]

I presume you're going to have to tape the corners seams, since the router hogged out the top level fabric for the inner corners. 

Why not just cut something to size for the back, sides, and then use butt joints? 

That's where KERDI-FIX comes in.

I followed the same methodology that Schluter used...I figured they'd likely know what works and what doesn't.  [smile]

 

[Cheese]

How much for the one on the left and what do you charge for the one on the right?  [wink]

The Schluter niche cost around $100. The one I made cost 1 sheet of  32" x 48" x1/2" KERDI-BOARD or about $34.

However, cost wasn't the issue, the real problem was that I needed a specific size, and I needed 2 of them. I thought about modifying the Schluter niche, but after some thought, I realized that was a half-baked idea at best. I then figured I could replicate what Schluter makes with the tools I had on hand.  [big grin]

 

[RKA]

You didn't answer the second question!  [wink]  Does the $34 include shipping?  Hee hee.  Nice job!

 

[Cheese]

You didn't answer the second question!  [wink]  Does the $34 include shipping?  Hee hee.  Nice job!

Ya I thought I danced around your original query rather well.  [big grin]

Once set up, the process is incredibly easy to do. Accuracy is the key to the final product.

 

[Cheese]

Cheese, do you plan to use Kerdi corners, and Kerdi strips to seal your niche up? Very nice work, too bad it will be covered in tile.

Thanks for the complement Peter...After closely examining the Schluter factory niche, it appears to be held together with a low heat hot melt glue. I tried normal hot melt and it destroyed the foam. I then looked at a 3M low heat hot melt (being an ex-employee and all) adhesive, and in typical Mother Mining fashion, they sell the low temp glue sticks in minimum quantities of 12# each, that’s around 150 sticks. Glad to see their marketing strategy hasn’t changed much over almost 40 years.  [popcorn]

So with the low temp hot melt not being a very viable alternative, I turned to KERDI-FIX. It’s expensive at $25 per cartridge but they promote it as both an adhesive and a sealer/caulk.

So Peter, the plan is to use KERDI-FIX on all corners and joints as a bonding agent while also utilizing its sealant properties in the same areas. It occurred to me that if Schluter can get by with using hot melt on the corners and joints, then my solution may be the suspenders and belt approach.  [cool]

 

[ear3]

When do we get to see the completed shower [tongue]?

 

[Peter_C]

I will agree Kerdi-Fix is good stuff! Never thought to use it in the corners as glue/sealer as you plan to do, but it is often used on Kerdi board. Looking forward to seeing the finished job.

 

[Cheese]

When do we get to see the completed shower [tongue]?

Hey Edward...my wife’s hoping it’s sooner rather than later.  [tongue]

Up here in the tundra, it’s the beginning of gardening time.  [sad]

 

[Cheese]

The reason I decided to post this KERDI operation is because the same cut-and-fold techniques could be used with HDPE, polypro and PVC. If a heat gun was used during the folding process, I'm sure it'd work with plexiglass & acrylics.  You just need to experiment.  [big grin]

It may also be interesting to try this on wood, steaming or wetting the joint before folding.

Well, the last part of this thread is the construction of the shelf for the niche. It's a really straight forward process and so simple to do. The idea is the first strip of KERDI is folded in half, and the second strip of KERDI is folded around the first strip. Everything is again held in place with KERDI-FIX.

My KERDI-FIX has arrived and I will pick it up today.  [thumbs up]

Photo 1: This is the first strip, or the inner part of the shelf.

Photo 2: A closeup end view of the first strip. You can see how it will fold up like a book onto itself.

Photo 3: This shows both the inside (RH) and the outside (LH) skins of the shelf. You'll notice on the RH skin how uniform the brown strip down the middle of the KERDI is. The router on a rail allows this to happen and for it to be repeatable.

 

[Peter_C]

The V groove bit looks/works great for drywall too, which I want to try out.

I have been buying from DalTile for years. They are a wholesale operation and sell only to professionals, so their pricing is excellent. I looked and there are a couple in the Twin Cities area. They stock Schluter Systems, and Laticrete as I like using their epoxy grout and thinset. Epoxy is awesome as long as you break it down with a kitchen scale. Ask if you want more info.

 

[Cheese]

I have been buying from DalTile for years. They are a wholesale operation and sell only to professionals, so their pricing is excellent. I looked and there are a couple in the Twin Cities area. They stock Schluter Systems, and Laticrete as I like using their epoxy grout and thinset. Epoxy is awesome as long as you break it down with a kitchen scale. Ask if you want more info.

That's interesting... [scratch chin]...I've purchased from DalTile before and I'm certainly not a pro. Maybe it's just a local "Don't ask, don't tell" thing. [unsure]

I've used Bostik glass filled urethane grout on the kitchen stainless tiles. It's fantastic, you never have to seal the grout.  [thumbs up]    A PITA to apply but well worth the effort.
The glass filled grout also adds just a tiny bit of sparkle to the grout lines. Makes them seem to have a little more depth, hard to explain but others always seem to notice the difference.

How is epoxy grout to work with? Does it need to be sealed?

I'll be installing concrete colored porcelain tile.

 

[Peter_C]

Epoxy uses a different float. I buy the "Full" container, then break it down into 1/4's. Even then it is a fast paced workout. Work it into the grout lines at a good pace. Once finished start cleaning immediately with vinegar and water. The kits do come with a mix for cleaning too. Epoxy will leave a haze, so after the sponging, a good scrubbing pass with a scuffy pad, followed by a sponge wipe, followed by a final wipe with a micro-fiber cloth will finish it.https://troxellusa.com/cleanup/sponges/scrub-bug-epoxy-grout-sponge-white-soft/

The paint tubs from Home Depot that are about 2 quarts work great for mixing in. I have one of those small red paddles that fits my cordless drill. Latex gloves or the like are a must. A $15 kitchen scale is a must for breaking the mix down, or put some plastic wrap over your own kitchen scale. Throw tub on scale and zero. Squeeze/pour Part A into tub. Zero scale and put Part B into tub. Mix together. Zero scale and add sand/colorant. Get ready to grout! I can give you the numbers for mixing if you want them. I just cut a corner off the bags, and roll them back with a quick clamp. Harding is not an issue since they are two part. You can also put the mixed Epoxy into the freezer to slow it's hardening down. There have been many times I would only mix a small portion of grout for a repair, or if I came up short.

Once the Epoxy is installed it will be the easiest part to clean in the future. It has enough flex to not crack out like old school grout. Also waterproof so the Schluter products do not have to work as hard. The grout will never need maintenance.
https://laticrete.com/en/our-produc...ts/epoxy-grouts/spectralock-pro-premium-grout

Never used the urethane grouts but have read many people rave about them...but many of those people hate Epoxy grout as they don't break it down, and therefore it hardens before they can get the job done.

You can spend hours on the John Bridge forum reading all about grouts...

How large is that largest tile? You should probably be using a tile leveling system and I might just be able to help you out there

 

[Cheese]

So in the 4th fabrication post I showed the routed flat form of the shelf and how it would fold up and then around itself. This 5th post will show the KERDI shelf after it's been assembled with KERDI-FIX.

Photo 1: End view of the shelf showing some of the squeezed-out KERDI-FIX

Photo 2: Another view of the shelf and the amount of squeeze-out.

Photo 3: This is a photo of the original Schluter shelf. I'm assuming the squeeze-out you can see is some form of low temp hot melt glue.