1 yr. ago • 88%

Using a router on construction board (e.g. “Wedi”) to make a beveled corner

First of all, is my terminology correct? These are brands of synthetic wood alternatives:

Is “construction board” the generic name for this stuff? I think some people call them “building panels”. I ask because my search for Invidious (Youtube) vids came up short. I would rather not have a brand-dependent search query because I have to try many queries as it is to try to get this answer.

Qboard offers a factory made corner piece (called Qorner; attached to this post). I was trying to work out how I could do that myself. I’ve never worked with #constructionBoard, nor have I used a router, but I suspect they use a router to cut a “V” in the board without competely bottoming out (but nearly), so the outer skin does not get cut. Has anyone done this?

15 comments

Does the shutoff valve have to be in the shower? Could it be moved to the other side of a wall outside of the shower? The seems like the best long term solution, especially since you have to deconstruct the concrete block it's embedded in anyway.

From what I know of all of the "wet area" products you mentioned, you can cut the materials quite easily and put pieces together to build whatever you want. Once you have the walls and other structures put together, you have to tape and seal all of the joints to prevent water leaks. All of these products have tape/sealant specific to the product line.

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- Does the shutoff valve have to be in the shower? Could it be moved to the other side of a wall outside of the shower?
  
  The valve joins a steel pipe to PEX. Both pipes are still bedded in concrete even though I cleared away the concrete that the valve was embedded in. The valve could be moved but the pipe joints remain in place because it would be too big of a project to unbury all of it, cut the steel pipe & thread it, etc. So if I move the valve the box would still need to be accessible in case the joints fail.
  
  I need to update that other thread. I’ve already drilled a 14mm hole in the wall and ran a shaft through it which is now attached to a right angle gearbox mounted on the new valve, which has a replaceable cartridge. So what’s left to do is getting a custom handle on the shaft that goes through the wall and I need to build the box.
  
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I actually have used Wedi in a couple projects. I am not an expert or professional but will share what I know.

The stuff is essentially sturdy foamboard and can be cut with a razor knife, no power tools needed. It is critical that the entire system be fully sealed and waterproofed, with all joints sealed with the provided wedi sealant. (I used the stuff provided in caulk tubes) While you could cut a V and bend the board, I would not trust it to be waterproof and you would need to seal it with the sealant anyway , so it would probably be stronger to just do a butt joint with sealant.

While I would generally never recommend on planning on anything being accessed from inside the wet area, wedi sealant might work to your advantage because you could probably cut out the box along a sealant joint, replace the part, and then re-seal the box to the location with new sealant.

I’d check the wedi documentation for the correct joint details. I’m not sure exactly where your box will be and if it will have standing water against it, but if so the details might be different or even not at all recommended.

Hope that’s helpful.

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- Thanks for the feedback.
  
  While you could cut a V and bend the board, I would not trust it to be waterproof and you would need to seal it with the sealant anyway
  
  I think this is where the different kinds of boards differ. Some tests¹ demonstrate Wedi is not waterproof but Schluter KERDI and another brand is. This guy says KERDI board can be scored and snapped to fit into a car, and unfolded at installation and it maintains its waterproof properties.
  
  If I opt for foam board then it would probably be Wedi so indeed it would theoretically need a waterproofing system on top. I say theoretically because I don’t think the shower is waterproof to begin with (it’s apparently tile directly on concrete rendered over brick). But I should still probably practice doing it right.
  
  it would probably be stronger to just do a butt joint with sealant.
  
  I’ve noticed construction board is fastened using a big washer of sorts and a screw through it. If the board is 10—15mm thick and I use those washers on a corner, they would overhang. I suppose I could cut the overhung portions off with an angle grinder. I’m also unclear on how strong the joint is if a screw is driven just into the foam to fasten the butt joint. Wouldn’t the screw pull out without much force? Perhaps I’ll use a 2×3cm piece of wood on the inside corner and screw both boards to that since I have that wood on hand.
  
  Or when you say “with sealant”, do you mean no screws and sealant alone?
  
  not sure I linked the right video.. I can’t access videos right now to verify.
  
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  You wouldn’t use fasteners in the joint itself, and you’re exactly right that they would pull right out. The screws are used to fasten through the face of the wedi board to wooden studs behind it to provide strength, and then the penetrations and joints are all sealed with the wedi sealant. The board itself is waterproof, you’re only sealing the joints/penetrations. I believe that small shower niches with 1/2” board are sturdy enough that they don’t even need wooden framing and just rely on the board+sealant, but am not sure on that.
  
  I’m not sure if this is the latest version, but this technical document has a ton of information: https://www.masterwholesale.com/media/wedi_Technical_Handbook_January_2021_Digital.pdf
  
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If you're gonna buy and use power tools, just use regular construction materials. MDF is pressed wood fibers, cheap, reliable. It's what all the Ikea stuff is made of.

If it's just mockups, you could use something like "rigid pink foam" from a vendor like Owens Corning. If you can detail what you're trying to do I might be able to be more helpful.

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- I’m building a small box in the shower which I will tile over. The box will cover a valve and must be semi-accessible. The valve will actually be controlled from the other side of the wall, so the box need not be opened routinely -- only if the fitting leaks or goes bad will access be needed.
  
  I have an unlimited free supply of Ikea pressboard because neighbors throw it away daily. But I would not use it in a shower. Ikea pressboard is like a sponge with water. It’s also too thick. I have rigid space constraints. No limit on the box height, but the walls of the box must be thin (e.g. 10—15mm thick is what I have in mind). The construction board seems well suited for wet areas.
  
  This is the old box, which was previously a solid block of concrete:
  
  https://fedia.io/m/plumbing/t/58279/Advice-needed-exposed-water-valve-in-shower
  
  My building style is to make everything accessible and servicable. So in that pic you see a floor tile around the box. That tile is actually removable. I went to great lengths to give a solid mating subfloor but without gluing it down. So if needed I can just remove the caulking around that tile and get under the showerpan. This is why the box walls must be thin. If the box is big enough to overlap the floor tile, then it would ruin the accessibility of the floor tile. Unless I somehow figure out how to make the entire box easily removable.. then it wouldn’t matter if it rested on the floor tile.
  
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  If it's going to be in the shower, I can't recommend MDF or even plywood. Probably better to go with solid wood if you can, or even better if you can access a 3D printer, use that.
  
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  I don't have a lot of experience working in the wet part or a bathroom. I believe I saw a friend frame out a shower and then cover it with cement board once and then tile over it, so that may be an option, but take that advice with a grain of salt.
  
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