Zero entry linear drain shower in a hydronic slab

[Kevn]

I am solo building an ICF house in Oregon with a hydronic (PEX) slab floor over 2 inches of foam (R-10) over 2-4 feet of compacted crushed concrete fill.
The hydronic concrete floors will be 5" thick with a troweled cream hardener finish (not polished, not slippery). The two zero entry showers have linear drains installed along the back wall.

The only wood in the structure is roof framing which is at least 10' above the shower floors.

Floors are supposed to pour in one week, only 6 weeks after originally scheduled. Finished slabs are one of the two trades/skillsets I do not do myself and the other one is not relevant to this project.

This project is being built in a small jurisdiction with only a couple inspectors, one old and coasting to retirement without the benefit of new knowledge and one young and new and unsure about anything that is not conventional wood framed residential construction over a crawlspace.

My concrete guy wants to do a mono-pour and simply slope the shower floor back to the linear drain which he has done in the past in other jurisdictions. This was also my design strategy.

Two code problems/challenges that I just became aware of during the under slab inspections:

1. The older inspector does not think that a concrete slab is legal as shower floor and that I must tile the shower floor. He cannot cite code.

2. Both think that I must install a shower pan liner which then divides the 4 inch thick slab (remember we lose one inch to the slope) into two thin slabs which will not be thick enough to be stable and will crack per the the concrete slab contractor.

I have spent some hours trying to find relevant codes for this application without success.
Any help appreciated.

[PC7060]

Hi Kevn, see you made it over here from the Heating Help site. Welcome!

Couple issues come to mind with the concrete shower floor. First is how you will waterproof the floor to keep the water from migrating throughout the slab and causing a moisture problem. Will the surface coating you describe prevent moisture absorption?

Second is how you will texture the floor to create a non slip surface but you seem to have a good handle on that.


Regarding the code, there is nothing requiring a specific type of material, just needs to pass 24” flood test. I can’t recall the code sections but I’m sure someone will post it shortly. Very smart bunch here!

[Tool Guy - Kg]

Welcome to the forum, Kevn!

We need to know which codes have been adopted in your area to get you to your answer. Can you tell us this? Otherwise, we can start looking it up ourselves if you tell us what city/town/village this structure is in.

At the heart of the matter, moisture management (in multiple areas) may be an issue. And lack of an impervious material for the floor may be an issue.

[ss3964spd]

If a typical stainless steel linear drain assembly will be used how will the perimeter of the drain body be sealed to the concrete so that water does not seep in between it and the concrete, thereby filling the concrete trough the drain sits in?

What is the plan to seal the joint between the slab and the walls?

[Kevn]

2021 State of Oregon Plumbing Specialty Code based on UPC

So same code throughout the state.

[Kevn]

Presumably the portland cement concrete floor would be treated with an applied liquid sealant just as would have to be done with pervious stone tiles and portland cement based tile grout.

The seal of stainless drainway to the concrete could be improved with a flexible sealant, but again, how would this differ from the seal between the stainless and a portland cement based tile grout?

[madmantrapper]

I not understanding exactly what you have there. I think you do not have a good understanding of sealing. Grout and deck mud does not seal a shower. A pan liner does which is mechanically sealed to the drain. It is also lapped by the wall waterproofing.

[PC7060]

Shower drains utilized either a clamping drain that connects to a pvc liner under a mud base or bonds to a surface applied membrane. The PVC liner and surface applied membrane both serve to water proof the floor and the floor to wall connections.

Re the UPC, it’s pretty specific about allowable shower construction methods.

P2709.2 Lining Required

The adjoining walls and floor framing enclosing on-site built-up shower receptors shall be lined with one of the following materials:
- Sheet lead.
- Sheet copper.
- Plastic liner material that complies with ASTM D4068 or ASTM D4551.
- Hot mopping in accordance with Section P2709.2.3.
- Sheet-applied load-bearing, bonded waterproof membranes that comply with ANSI A118.10.

The lining material shall extend not less than 2 inches (51 mm) beyond or around the rough jambs and not less than 2 inches (51 mm) above finished thresholds. Sheet-applied load bearing, bonded waterproof membranes shall be applied in accordance with the manufacturer's instructions

[John Bridge]

Local codes rule. Sweet talk an inspector and good things can happen.

[Davy]

Pour the slab leaving it about 3 inches lower in the shower area than the finish floor. Then you can mud the floor up and use a surface applied membrane over your dry pack. I wouldn't use a traditional pan liner in this case.