Chapter 31 Exercises: Bathrooms — Waterproofing, Tile, Ventilation, and What Goes Wrong

Exercise 1: Exhaust Fan Performance Audit

Conduct a complete assessment of every bathroom exhaust fan in your home:

  1. Turn each fan on. Does it turn on at all? Does it produce audible airflow, or just a sound with minimal air movement?
  2. Hold a single sheet of toilet paper near the grille. Is it drawn firmly against the grille? If it barely flutters, the fan is underperforming.
  3. Locate the fan's manufacturer label (often visible through the grille or with grille removed) and note the model number. Look it up online to find the listed CFM rating and sone rating.
  4. Measure the bathroom square footage. Apply the 1 CFM/square foot rule from Section 31.1. Does the fan meet the minimum?
  5. Turn the fan off. Does the damper close? (You can check from the attic, or feel whether outdoor air comes through the grille on a windy day.)

Deliverable: For each bathroom fan in your home, rate it: adequate, marginal, or inadequate. Identify which fans you would prioritize replacing.

Exercise 2: Exhaust Fan Duct Trace

For at least one bathroom fan in your home (preferably the one you suspect of underperformance):

  1. Access the attic or crawlspace above the bathroom.
  2. Locate the exhaust fan duct — it should be a round duct connected to the fan housing above the ceiling.
  3. Follow the duct to its termination point. Does it exit through the roof? Through the soffit? Through an exterior wall? Or does it simply end in the attic, venting into the insulation?
  4. If the duct terminates in the attic, measure the approximate run length to the nearest exterior wall or roof exit point.
  5. Check the duct condition: is it insulated where it passes through cold attic space? Is it rigid metal or flexible? Are there any disconnections, sags, or pinches in the duct?

Deliverable: A written duct assessment with a proposed correction if the duct is improperly terminated. Include estimated materials and time for the fix.

Exercise 3: Shower Waterproofing Assessment

This exercise helps you understand what waterproofing situation your shower is in without demolition:

  1. Tap test: With a knuckle, systematically tap every tile in your shower, starting at the floor and working up each wall. Mark (mentally or with painter's tape) any tiles that sound hollow rather than solid. A solid tile sounds like a dull thud; a hollow tile sounds like a drum.
  2. Grout inspection: Look at every grout joint, particularly at inside corners (floor-to-wall, wall-to-wall) and at the transition between tile and tub or shower pan. Are there visible cracks? Gaps? Areas where the grout has receded below the tile surface?
  3. Caulk inspection: Look specifically at the inside corners and the tile-to-tub/pan joint. Is there caulk (flexible) or grout (rigid)? If it's grout, note it as an area needing correction.
  4. Behind-wall moisture check: If there is a wall below the shower (in a two-story home) or an accessible wall cavity, look for any water staining or discoloration on the ceiling below.
  5. Smell test: With the bathroom closed for several hours, do you notice any musty smell that isn't present when the bathroom is well-ventilated? This can indicate moisture in the wall cavities.

Deliverable: A written assessment of your shower's apparent waterproofing condition. Rate it: no visible concerns, minor concerns (grout/caulk maintenance needed), or significant concerns (hollow tiles, visible cracking, suspected moisture penetration).

Exercise 4: Caulk Replacement Practice

This exercise walks you through replacing caulk in at least one bathroom joint:

  1. Choose one inside corner of the shower tub surround where the caulk is visibly cracked, mildewed, or failing.
  2. Remove all old caulk from the joint using a utility knife and/or caulk remover tool. Be thorough — new caulk will not adhere over old caulk.
  3. Clean both surfaces with isopropyl alcohol. Allow to dry completely (minimum 30 minutes).
  4. Apply masking tape to both surfaces of the joint, about 1/8" back from the joint edge.
  5. Apply a bead of color-matched silicone caulk in one continuous motion.
  6. Smooth with a wet finger.
  7. Remove the tape immediately.
  8. Allow to cure for 24 hours before using the shower.

Deliverable: Before-and-after photographs of the joint. Note any challenges you encountered and how you resolved them.

Exercise 5: Exhaust Fan Replacement (Full Tutorial)

Using the step-by-step process from Section 31.6, replace one bathroom exhaust fan:

  1. Select a replacement fan rated for at least 110 CFM with a sone rating below 1.5.
  2. Follow the complete replacement process: power off, remove old unit, assess wiring, assess duct, install new housing, connect wiring, connect duct, install motor and grille, restore power, test.
  3. After installation, verify airflow with the toilet-paper test and confirm the exterior damper opens and closes.
  4. Replace the switch with a 20-minute timer switch ($15–$30).

Deliverable: A written log of the replacement process, including the old unit's CFM and sone rating, the new unit's specifications, and time required.

Exercise 6: Bathroom Humidity Measurement

Purchase a hygrometer (humidity/temperature monitor, available for $8–$20 online or at hardware stores):

  1. Place the hygrometer in your most-used bathroom.
  2. Record the humidity level before a shower.
  3. Record the humidity level during the shower.
  4. Record the humidity level every 5 minutes after the shower with the fan running.
  5. Note how long it takes to return to the pre-shower humidity level.
  6. Repeat the test with the fan NOT running (if safe to do for a single test) and note how long the humidity elevation persists.

Deliverable: A table of humidity readings with timestamps. Does your fan return the bathroom to baseline humidity within 20 minutes? If not, is it an undersized fan, inadequate run time, or improper duct termination?

Exercise 7: Grout Line Inspection and Sealing

For a bathroom floor or wall tile installation that is 3+ years old:

  1. Look closely at the grout joints. Do they appear to be the same color throughout, or are there staining patterns (typically darker near the drain or in corner areas)?
  2. Perform the "drop test": place a single drop of water on the grout joint. If it beads up, the sealer is still intact. If it absorbs immediately, the sealer has failed and the grout is unsealed.
  3. If sealer has failed, clean the grout thoroughly with a grout cleaner or diluted hydrogen peroxide.
  4. Apply a penetrating grout sealer, following manufacturer directions.
  5. Perform the drop test again after the sealer cures.

Deliverable: Document the condition of the grout before sealing and the results of the drop test before and after. How often should this maintenance be repeated?

Exercise 8: Toilet Rough-In Measurement

This exercise is useful before any toilet replacement:

  1. Remove the toilet tank lid and flush the toilet to empty it mostly.
  2. Measure from the finished wall behind the toilet to the center of the floor bolt caps (the plastic caps covering the bolts at the toilet base). This is the rough-in dimension.
  3. Is it 10", 12", or 14"? (12" is most common in homes built after 1960.)
  4. Look up two replacement toilet options in the same rough-in dimension — one in the $150–$250 range and one in the $350–$500 range — and compare their features, GPF (gallons per flush), and MaP (Maximum Performance) score.

Deliverable: Documentation of your toilet's rough-in dimension and a comparison of two replacement options at different price points.

Exercise 9: Bathroom Ventilation Code Compliance Check

Research the building code requirements for bathroom ventilation in your jurisdiction:

  1. Look up your local jurisdiction's adoption of the IRC (International Residential Code) or your state's equivalent. Most local building departments have this information online.
  2. Find the minimum bathroom exhaust fan requirements — CFM, sone rating if specified, duct requirements.
  3. Compare your bathrooms' current fans against the requirements.
  4. Check whether your jurisdiction requires GFCI protection for all bathroom outlets, what distance from water is specified, and whether that includes the outlet in the light fixture if present.

Deliverable: A one-page summary of your jurisdiction's bathroom ventilation requirements and whether your home meets them.

Exercise 10: Bathroom Renovation Sequencing Exercise

Using the renovation sequence from Section 31.7, create a hypothetical project plan for a full bathroom renovation:

  1. Assume you're renovating a 7×9 bathroom: new tile throughout, new vanity, new toilet, new shower with custom tile (no tub), and a properly installed exhaust fan.
  2. Create a sequenced task list in the correct order, noting which tasks require professional contractors.
  3. Estimate materials cost for each major item (tile, vanity, toilet, exhaust fan, waterproofing membrane, cement board).
  4. Estimate labor cost for the professional tasks (plumbing rough-in, electrical rough-in).
  5. Identify which tasks you would DIY and which you would hire out.

Deliverable: A complete renovation scope document with sequence, cost estimate, and DIY/pro assignments.