Membrane on bathroom floor? [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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02-11-2013, 03:01 PM
I am about to set tile in my 2nd floor bathroom and wonder if a liquid membrane is necessary on the floor.
I have 3/4" OSB glued and nailed down to 1" thick tongue and groove pine. On top of the OSB I have used Versatile polymer modified thinset and backerboard screws to secure 1/4" Wonderboard to the OSB. I also plan on having someone grout with Spectraloc epoxy grout after I set the tile.

I wouldn't be too concerned about adding a liquid membrane ( I was thinking of using Merkrete Hydroguard) if the contractor had put down plywood instead of OSB, but there it is and I'm trying to make sure I'm not going to regret the extra step and expense.

With the shower, I'll have 130 square feet to cover, so I figure on 3 gallons. It costs $100 per gallon at the local tile shop and they and the contractor think its unnecessary (on both shower and floor for that matter).

Also, I was wondering if anyone knows of the difference between Hydroguard 1 and Hydroguard SP-1. I'd prefer to use the green SP-1, but I'd have to order it on line and wait a couple weeks for delivery and don't know if its essentially the same thing except for the color.

Thanks for any advice.


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02-11-2013, 03:50 PM
I have use redguard and Laticrete Hydroban over cement board a lot with out problems so imo if the recomendations state over cement board you should good with any 3 of those products.

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02-11-2013, 10:43 PM
I think it depends on the OSB. I have used Edgegold OSB subfloor from Weyerhauser, and it is superior in weather contact (usually during construction). We have CBU'd over this product in bathrooms and have then tiled and have never had callbacks. This is how my own kid's and master bathrooms are constructed, and they are 6 years old and look brand new (glass tile on 1/2 Hardi over EdgeGold 3/4 OSB subfloor over BCI floor joists 16" OC).

02-12-2013, 09:57 PM
Thanks Scott,

I do have the same OSB, but all the same I think I'll try to give the floor a single coat of Hydroguard if I have any left over from doing the shower. Not sure why it's more expensive than Redguard, but it seems that its what the pros prefer, from what I've heard.