To build a raised bathroom to avoid running shower and toilet drainage under the concrete slab, you'll need to consider the minimum required height for plumbing drainage pipes and the slope necessary for proper drainage. Here are some general guidelines:
Plumbing Code Requirements: The height at which you need to elevate the bathroom depends on local building codes and plumbing regulations. These codes specify the minimum slope and diameter requirements for drain pipes. Generally, the standard slope for drainage pipes is 1/4 inch per foot (2% slope). However, specific requirements may vary by location, so it's crucial to check with your local building department for the exact guidelines.
Minimum Height for Shower Drain: To avoid running the shower drain under the concrete slab, you'll need to elevate the shower floor to provide enough space for the drain pipe. Typically, a shower drain requires about 2 to 3 inches of vertical space, including the pipe and the trap.
Toilet Drain: For the toilet, the height depends on the type of drainage system you're using (standard gravity-fed system or pressure-assisted system) and the distance between the toilet and the main sewer line. Usually, a standard toilet drain pipe diameter is 3 or 4 inches. You'll need to elevate the bathroom floor enough to accommodate the necessary slope and connect to the main sewer line.
Additional Considerations: Remember that raising the bathroom floor will affect the overall height of the room and may require adjustments to doors, fixtures, and other elements in the space.
Given the complexity of plumbing and building codes, it's essential to consult with a professional plumber and a licensed contractor or architect to plan and execute the raised bathroom project properly. They can ensure that your design meets all necessary codes and requirements while maintaining proper drainage and functionality. Additionally, a local building inspector can help review your plans to ensure compliance with the local building codes and regulations.