Foam Niches

Discussion in 'Shower & bathtub Forum & Blog' started by johnfrwhipple, Apr 13, 2013.

  1. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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  2. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Site Review of a twin Kerdi Board Shower Niche Installation

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  3. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    How to fix a Kerdi Board Niche - Adding the missing pre-slope to the niche's bottom

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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Two things: you should use the washers for the screws, and I do not know if the Ardex product works as well as Kerdiband, but any penetration is supposed to be covered with Kerdiband with the nominal 2" overlap.

    A reminder, it is the foam that is the waterproofing layer on Kerdiboard...the top layer is only for protection and thinset compatibility. So, any edge or penetration needs to be waterproofed per the standard installation of any Kerdi (banded).
  5. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Is it the foam waterproof in a kerdi board niche?

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  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The point on the washers is to not damage the surface so the waterproofing (Kerdiband, or whatever) can do its job. Any penetration is a potential weak point, and the washers spread the load on the fastener and hold things much better.
  7. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Kerdi Board Washers have spikes in them.

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  8. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Spray Foam as a brace on the back side of a Kerdi Board Niche

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  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The difference is, the screw goes all the way through, and with the head recessed, it's harder to get a good seal and the strength of the attachment is compromised (it wouldn't take much to pull through the rest of the foam; not a big deal if you've glued it in place from behind, but not a good 'sample' of how to do it!). The teeth on the washers spread the load, help prevent overdriving the screw, and do not penetrate. Then, adding the Kerdiband, you have both the strength, and the single penetration that actually holds the thing, rather than relying on the small area of the head to hold in the foam.
  10. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Think of it sort of like screwing drywall up...if you drive it in too far and get the head past the paper, it is MUCH weaker than if it is just recessed and the paper around the head is still intact. Same idea on the covering of the KerdiBoard and the screw fasteners - the washer spreads the load and really holds things tight. It gives you enough area to recess it so when you add the Kerdiband, it is still flat without the head sticking up. It IS a system and works best when used that way.
  12. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Kerdi Board System of Niches - Rules to follow

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  13. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Fixing the missing slope on a Kerdi Board Shower Niche - and divider shelf

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  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Since the foam is waterproof, and the shelf does not penetrate behind what is already waterproof, the only thing required is to anchor it to the recess well. You can do what you want, but that is all that is needed.
  15. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    In one of the classes, they specifically said that if the covering on Kerdiboard was penetrated, unless it went all the way through, there was no need to do anything to it...the foam is waterproof and unless you mechanically break the bond of the material to the foam, it getting wet isn't an issue.
  17. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Kerdi Board Shelf Niche

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  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The covering on Kerdiboard (for the umpteenth time) is NOT the waterproofing layer! The fact it can wick is irrelevant IF the penetrations are waterproofed at the edges and any through holes. The covering on the Kerdiboard is for THINSET compatibility and to provide some protection to the foam waterproofing layer. It doesn't matter that it wicks IF you've waterproofed the seams and penetrations...same exact idea as cbu - it wicks lots, too, but if there is some sort of waterproofing preventing it from getting to areas that can't handle it, it doesn't matter! But, in this case, the covering on Kerdiboard is MUCH thinner and will absorb LOTS LESS moisture than a cbu board, thus likely drying out faster (should it get wet in the first place!).

    So, in your niche, that is already waterproof, since there's likely to be no standing water pressure on the tile, it really doesn't matter on a shelf as long as when anchoring it, you have not penetrated the layer that IS the waterproofing (the foam of the actual niche body).

    Maybe YOU should go take a Schluter class before you trash it and gain some understanding on how it actually works! Even if you've been, you always pick up some new ideas and possibilities, plus, they add new products and evolve the methods. There's decades of knowledge and hundreds of thousands of installations of experience in the product's use. Everyone can learn, and what you learn is that you were not right or there is a better way to do things.

    Again, it is the FOAM THAT IS THE WATERPROOFING LAYER on Kerdiboard, NOT THE COVERING! Seal the foam edges and penetrations, and it is waterproof even without the orange covering.
  19. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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  20. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Kerdi Time - Tying in a Kerdi Board Shower Niche to the rest of the shower

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