Double slopes on a shower floor?

[Derek Sutherland]

I am getting ready to build a mortar base for a shower. I'm pretty sure I know how to do it correctly except for one part I'm confused about - the slope. Most videos show a two layer mortar system and it seems that each layer is sloped 1/4 inch per foot. After the second layer of mortar is added you now essentially have 1/2 slope per foot if you add each sloped layer together. Is that the final goal? 1/2 slope? Or should the second layer of mortar be even in thickness since the first layer is already sloped 1/4 inch per foot?

Also seems like the rule is 1/4 inch slope per foot yet if this was followed all the way around the drain the mortar would not be even along the walls. It seems that the correct way is to make sure your longest runs are sloped at 1/4 inch THEN you keep the mortar even along the walls which essentially will make the shorter runs sloped more than 1/4 inch per foot. Can anyone clarify this?

 

[Jadnashua]

You need a MINIMUM of 1/4"/foot. So, you'd take the longest distance from the drain, figure the 1/4"/foot, then draw a level line all around the shower. This means that the shorter walls will have a steeper slope. The top layer (on top of the liner) is parallel...i.e., even thickness, but because it is on a sloped bed, it will retain the same slope as what's underneath it.

Personally, while a conventional shower works when done right, I much prefer to use a surface applied membrane and make the entire shower including the walls, waterproof. In that case, you only need a single, sloped layer, then you install the waterproofing to it, and tile to the waterproofing. Schluter has a system they've been using in the USA for over 20-years. There are others that have copied it since the patent ran out. If you go to www.schluter.com you can watch a video on how this is accomplished. Laticrete has a similar product (about 3-years old now) that some like as well.

For help building your shower, check out www.johnbridge.com...lots of tiling pros over there.

Building a shower isn't rocket science, but is VERY detail oriented...get one bit wrong, and you may end up with a mess. Lots of different ways to do it depending on the materials selected, but you must follow the instructions (and comprehend them!) to get a successful result.

 

[Sponsor]

 

[Derek Sutherland]

You need a MINIMUM of 1/4"/foot. So, you'd take the longest distance from the drain, figure the 1/4"/foot, then draw a level line all around the shower. This means that the shorter walls will have a steeper slope. The top layer (on top of the liner) is parallel...i.e., even thickness, but because it is on a sloped bed, it will retain the same slope as what's underneath it.

Personally, while a conventional shower works when done right, I much prefer to use a surface applied membrane and make the entire shower including the walls, waterproof. In that case, you only need a single, sloped layer, then you install the waterproofing to it, and tile to the waterproofing. Schluter has a system they've been using in the USA for over 20-years. There are others that have copied it since the patent ran out. If you go to www.schluter.com you can watch a video on how this is accomplished. Laticrete has a similar product (about 3-years old now) that some like as well.

For help building your shower, check out www.johnbridge.com...lots of tiling pros over there.

Building a shower isn't rocket science, but is VERY detail oriented...get one bit wrong, and you may end up with a mess. Lots of different ways to do it depending on the materials selected, but you must follow the instructions (and comprehend them!) to get a successful result.

Excellent thank you - exactly what I thought had to happen but many of these videos leave out some details and leave you guessing. I agree with you that you have one shot at this - get something wrong and it could be very bad news for you.

I looked at Schluter and not mentioning the exorbitant retail prices ($60 for a small roll of seam tape?) I have my concerns about that system including a shifting floor that I feel could crack the grout over time. However, similar to this system I will still apply some water proofing coating on top of my cement board for an insurance policy and keep it off the bottom, slightly higher than the curb so that it never can touch water coming from the bottom. I just don't trust that water proofing method over time as the primary defense - secondary OK.

I striped my old shower to the frame and found leaks that got past the water proofing thinset (or some type of water proofing product) applied thickly to the bottom foot of the walls - and as a result soaked the cement board and framing. I think over time (29 years) it failed and if that stuff failed I can only wonder what will happen with these new products with very thin coats.

There are many different methods to approach this but I'm choosing my own sort of hybrid "best practices" approach that includes the membrane between two layers of mortar. Thank you again!

 

[Jadnashua]

Schluter's Kerdi has been in use now for almost 30-years...it is not new and hundreds of thousands of showers are built every year (they sell about 1/2-million drains a year last I heard). Topically applied liquid waterproofing can work, but it's not as easy as they imply. You really need the material applied between the min/max, and too much is as bad as too little. It's not hard to get runs or pinholes, and that can be problematic. Done properly, yes, it works, but personally, a sheet membrane is waterproof and you only have to really worry about doing the seam properly (which isn't really very hard, but you have to understand and perform per the instructions).

It can be dangerous mixing various waterproofing methods...you're best to follow one method and not try to reinvent the world.

There are lots of ways to mess up a liner install. I'll list a few:
- flat on the floor
- no blocking in the walls to hold it up
- nails/screws lower than 2" above the top of the curb - this makes it hard to hold the bottom of the cement board in place, depending on the actual type selected (some can be embedded, some cannot, they take different methods)
- failure to use the dam corners for the curb
- buildup in the corners making the wall covering bulge out
- penetrations in the curb (you CANNOT use cement board screwed to the curb through the liner!)
- failure to place the moisture barrier in the walls over the liner to the inside
- failure to seal the liner to the base of the drain
- failure to keep the weep holes of the drain clear

As I said, it's not hard, but it is very detail oriented. I personally think a sheet membrane is more reliable. FWIW, retail pricing verses what you can buy it for are not always the same!