Bathroom Remodeling Guide: How to Plan a Code-Compliant Bathroom Remodel in Illinois (2026 Trends Included)

Bathroom remodeling remains one of the most requested residential construction projects in the United States. A well-planned bathroom renovation can improve daily comfort, increase property value, and prevent costly structural issues related to moisture or plumbing failures.

However, a professional bathroom remodel must go far beyond aesthetics. Contractors must evaluate structural conditions, plumbing systems, ventilation, waterproofing, and building codes applicable in Illinois. For this reason, we wrote this Bathroom Remodeling Guide for our clients.

This technical guide explains the most important considerations homeowners should understand before starting a bathroom renovation.

Click here to download the complete PDF guide

1. Structural Assessment Before Any Bathroom Remodel

Before demolition begins, contractors should inspect the existing structural components supporting the bathroom.

Key elements to evaluate include:

Subfloor condition

Many homes built between the 1950s and early 1990s often have subfloors that show:

• moisture damage

• insufficient plywood thickness

• structural deflection beneath tile floors

For modern tile installations, contractors typically recommend:

• ¾-inch plywood subfloor minimum

• cement board or uncoupling membrane underlayment

Without proper structural support, tile installations may crack due to floor deflection over time.

2. Ventilation Requirements Under Illinois Building Codes

Bathroom ventilation is one of the most critical elements for preventing mold, moisture damage, and poor indoor air quality.

Many municipalities in Illinois follow mechanical ventilation rules requiring bathrooms to be ventilated directly outdoors.

Local codes specify that:

• bathrooms must have mechanical ventilation exhausting directly to the exterior

• exhaust ducts in unconditioned spaces must be properly insulated.

Mechanical ventilation systems should also meet airflow requirements. Building guidelines typically require at least 50 cubic feet per minute (CFM) of exhaust airflow for intermittent bathroom fans.

A common rule used by contractors is:

• 1 CFM per square foot of bathroom area for rooms under 100 sq ft.

3. Plumbing Design Requirements (Illinois Plumbing Code)

Bathroom plumbing systems must comply with the Illinois Plumbing Code (77 Ill. Adm. Code Part 890), which regulates the installation and alteration of plumbing systems in remodeling projects.

One key concept in bathroom plumbing layout is wet venting, which allows multiple fixtures to share a vent under certain conditions.

According to the Illinois code:

• wet vent systems can be used for fixtures located on the same floor level

• the wet vent must be one pipe diameter larger than the trap size of the upper fixture.

Improper venting can lead to:

• slow drainage

• sewer gas odors

• pressure imbalance inside plumbing systems

4. Waterproofing Systems in Modern Bathroom Construction

One of the most frequent causes of bathroom failure is inadequate waterproofing behind tile installations.

Professional shower systems typically include:

1. Cement board or foam board substrate

2. Waterproof membrane

3. Properly sloped shower pan

4. Drain assembly

5. Tile installation with grout or epoxy grout

Industry best practices require a shower floor slope of approximately:

¼ inch per foot toward the drain

This prevents standing water and structural moisture damage.

5. Permits and Inspections in Illinois

Bathroom remodel permits are typically required when the project includes:

• plumbing modifications

• electrical changes

• structural alterations

• layout changes

Inspections often verify:

• licensed plumbing work

• proper venting installation

• final fixture installation

Homeowners should verify requirements with their municipality.

Bathroom Remodeling Guide: Design Trend for 2026

Bathroom design in 2026 is evolving toward spaces that combine comfort, minimal maintenance, and architectural aesthetics.

Below are some of the strongest trends shaping modern bathrooms.

Trend 1: Large-Format Tile and Seamless Surfaces

Large-format tiles and full porcelain slabs are becoming increasingly popular in bathroom design.

Design experts report that modern bathrooms are moving away from small tile patterns toward large surfaces that minimize grout lines.

Advantages include:

• easier cleaning

• reduced mold growth

• visually seamless walls and floors

Trend 2: Spa-Inspired Bathrooms

Bathrooms are increasingly designed as wellness spaces rather than purely functional rooms.

Many homeowners are incorporating features such as:

• walk-in showers

• soaking tubs

• heated floors

• calming lighting

Designers describe the modern bathroom as a personal retreat designed for relaxation and recovery.

Trend 3: Natural Materials and Warm Color Palettes

Bathroom palettes are shifting away from cold whites and grays toward natural colors and organic materials.

Trending materials include:

• limestone

• travertine

• wood-accent vanities

• textured porcelain tiles

Design experts say warm, nature-inspired palettes create calmer and more comfortable environments.

Final Thoughts

A successful bathroom remodel combines aesthetics with technical precision.

Key factors that determine long-term performance include:

• proper structural support

• code-compliant plumbing

• adequate ventilation

• professional waterproofing systems

• durable material selection

When these elements are properly implemented, a bathroom remodel not only improves daily comfort but also increases the overall value of a home.

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