JADU Efficiency Bathroom.
Full-bath function in 30 square feet of well-planned space.
JADUs require a full bathroom — toilet, sink, and either tub or shower — but the entire JADU is capped at 500 sqft, so the bath usually has to fit in 30–45 sqft. We design these to feel like real bathrooms (full-height shower glass, decent vanity, code-compliant ventilation) rather than dorm-room half-baths.
Typical range
$8K – $24K complete
Per unit
$220 – $500 / sqft of bath
Timeline
2–3 weeks once plumbing rough is complete.
The short version.
The minimum JADU bathroom is roughly 30 sqft: a 30 in x 30 in shower (or 36 in x 36 in for comfort), a wall-hung toilet to save floor space, and a 24 in vanity. Fitting a tub-shower combo requires about 45 sqft minimum (60 in tub + 24 in vanity + toilet). Most JADU baths we build land at 36–40 sqft with a shower-only design — owners and renters consistently prefer the shower for usability.
The plumbing tie-in is usually straightforward — tap the existing main-house drain and supply lines wherever they're closest to the bath wall. The added load on the existing system is minimal (one toilet, one shower, one sink), but we verify the existing vent and drain capacity in the feasibility phase. Tankless or point-of-use water heaters are common to avoid running long hot-water lines.
Ventilation is non-negotiable. Bathrooms need 50 CFM continuous or 50 CFM on a humidity-sensing switch (CMC §403.7). For a JADU bath that gets daily use, we recommend humidity-sensing — turns on with shower steam, runs until the air dries, automatic. Skipping bath ventilation in California's humid coastal zones (SF, the Peninsula, Westside LA) leads to mildew within months.
What you can actually pick.
Shower-only with wall-hung toilet (30–36 sqft)
Pros — Most efficient use of space, modern aesthetic, easy to clean.
Cons — No tub for renters who want one.
$8K–$18K complete25+ yearsTub-shower combo with floor toilet (45 sqft+)
Pros — Maximum function in larger JADU, broader renter appeal.
Cons — Requires more space, longer plumbing rough.
$10K–$22K complete25+ yearsCurbless shower + wall-hung toilet (aging-in-place)
Pros — Accessible, modern, no threshold to step over.
Cons — Requires recessed subfloor and linear drain, higher cost.
$11K–$24K complete30+ years
What we deliver.
- Floor plan — minimum 30 sqft, layout optimized for the JADU's main entry
- Plumbing rough — tap existing main-house supply and drain
- Electrical rough — GFCI receptacle, lighting circuit, ventilation fan circuit
- Ventilation fan — 50 CFM continuous or humidity-sensing
- Shower waterproofing — Schluter Kerdi or hot-mopped pan
- Tile install — wall, floor, niche if included
- Toilet install — wall-hung or floor-mount per layout
- Vanity install — 24 in or 30 in with integral counter
- Glass enclosure or curtain (curtain saves $1.5K–$3K)
- Final fixture install and test
The code parts most owners miss.
- Bathroom requires either a window or 50 CFM ventilation (CMC §403.7).
- GFCI required at all receptacles in bathroom (NEC 210.8).
- Shower minimum interior dimension 30 in x 30 in (UPC §411.7).
- Toilet clearance: minimum 21 in front clearance, 15 in side clearance from any fixture or wall.
- Tankless water heater serving JADU bath: gas units need combustion air per CMC §701; electric units need a dedicated 40A circuit.
Why getting this right pays off.
The bathroom is the make-or-break room in a JADU. A well-designed 35 sqft shower-only bath with full-height glass, good tile, and silent ventilation feels modern and usable. A poorly designed bath of the same size feels cramped and pushes renters or family members away from the unit.
Ventilation specifically determines whether the JADU stays mildew-free over years of use. The $250–$500 cost difference between a basic 50 CFM fan and a quality humidity-sensing fan (Panasonic WhisperGreen, Broan-NuTone) returns 10× in avoided mildew remediation.
What goes wrong — and how to avoid it.
- Skipping bath ventilation — mildew within months in coastal climate
- Putting the toilet across from the door — opens to bad sightline from JADU entry
- Cheap fan with rated 1.5 sone — too loud to want to use, defeats the purpose
- No GFCI at the vanity receptacle — fails final inspection
- Floor-mount toilet in 30 sqft bath — wall-hung saves 8 in of floor
After we hand you the keys.
- Clean fan grille every 6 months to maintain CFM rating
- Re-caulk silicone at shower change-of-plane joints every 3–5 years
- Inspect under-sink for any leaks monthly
- Treat any grout discoloration as a moisture issue until proven otherwise
JADU bathrooms — compact fixtures, full performance.
A JADU bathroom typically fits in 30-45 sf — and on the smallest CA lots, that constraint forces every fixture choice. Knowing which brands make true compact + commercial-grade product is the difference between a bath that lasts and one that leaks.
US market size
US bathroom fixture market: ~$12B / year. Compact / wall-mount segment growing 14% with ADU + condo trends.
California reality
California Plumbing Code requires 1.28 GPF max toilet flush + 1.5 GPM max showerhead + 1.2 GPM max bath faucet. Most major brands have CA-compliant SKUs.
The manufacturers behind the spec sheet.
- Our default
Toto
Kitakyushu, Japan / Atlanta, GA.
Market — Largest toilet maker in the world; #1 in California.
Product — Drake II 1.28 GPF, Carlyle II wall-hung, Aquia IV dual-flush.
In California — WaterSense + EPAct compliant across full line. Drake II is the contractor default.
Most reliable flush in the industry. 1.28 GPF + 4" trapway = no clogs.
- Our default
Kohler
Kohler, WI — privately held.
Market — Largest US plumbing fixture maker.
Product — Cimarron toilet, Memoirs faucets, Veil wall-hung.
In California — Strong CA dealer network — Ferguson + Pacific Sales statewide.
Solid mid-range across toilets + faucets + sinks. Lifetime faucet warranty.
- Spec on request
Duravit
Hornberg, Germany.
Market — European premium ceramic + bath leader.
Product — Vero Air, Starck, ME by Starck wall-hung toilets + vanities.
In California — Spec on modern Bay Area + LA premium remodels; long lead (8-12 weeks).
Best European wall-hung toilet pair with Geberit in-wall carrier for floating look.
- Spec on request
Geberit
Jona, Switzerland.
Market — Largest in-wall carrier system maker globally.
Product — Sigma in-wall toilet carriers, Sigma actuator plates.
In California — Required behind any Duravit/Kohler Veil wall-hung toilet.
Universal carrier — accepts Toto, Duravit, Kohler, American Standard wall-hung bowls.
- Spec on request
Grohe
Düsseldorf, Germany — LIXIL subsidiary.
Market — Major European faucet + showerhead leader.
Product — Eurosmart, Concetto, Atrio thermostatic shower.
In California — Wide CA distribution; quality consistent across price tiers.
When client wants European brand without Hansgrohe price.
- Spec on request
Hansgrohe
Schiltach, Germany.
Market — Premium European faucet + shower system leader.
Product — Logis, Talis, Axor (Starck, Citterio).
In California — Premium spec for modern bathrooms; 10-year warranty.
When budget supports — best thermostatic shower valve in market (iBox + Ecostat).
- Our default
Delta + Moen
Carmel, IN / North Olmsted, OH.
Market — Top 2 US faucet makers by volume.
Product — Trinsic, Lahara (Delta); Brantford, Genta (Moen).
In California — Lifetime warranties + widespread parts availability. Wide CA distribution.
Default faucet spec for ADU + JADU; mid-range American option.
Tier-by-tier — what you actually get.
Budget JADU bath
$1,400–$2,400 total fixtures
e.g. Toto Drake II + Delta Trinsic + Sterling stall shower
Rental, compliance, fast install.
Mid JADU bath
$2,400–$4,800 total fixtures
e.g. Toto Aquia + Hansgrohe Logis + custom tile shower
Owner-occupied, premium rental.
Premium JADU bath
$4,800–$9,500 total fixtures
e.g. Duravit wall-hung + Geberit carrier + Hansgrohe Axor + Kerdi shower
Architect-led, modern minimal.
California distributors.
Ferguson Bath, Kitchen & Lighting
20+ CA showrooms.
Toto, Kohler, Duravit, Hansgrohe, Geberit, Delta, Moen.
Pacific Sales
Statewide Best Buy showroom.
Kohler, Toto, Hansgrohe, Grohe.
Pirch (closed 2019) / Snyder Diamond / Studio41
Premium boutique showrooms LA + Bay.
Duravit, Hansgrohe Axor, Dornbracht.
What it costs this year.
Toto Drake II 1.28 GPF (round)
+4% YTD
≈$385
Ceramic + glaze pricing stable.
Hansgrohe Logis lavatory faucet
+5% YTD
≈$220
German import + currency.
Duravit ME wall-hung bowl
+6% YTD
≈$685
Premium ceramic + long lead.
Geberit Sigma 8 carrier + actuator
+4% YTD
≈$520 + $185
In-wall plumbing standard.
What we tell owners — off the record.
Toto Drake II is the contractor consensus toilet in California. 1.28 GPF + Tornado Flush + 4" trapway = 99.5% flush success. The premium of ~$80 over Kohler Cimarron pays for itself in zero callbacks.
Wall-hung toilets save 9-12" of floor depth — meaningful in a 30 sf JADU bath. The setup requires a Geberit Sigma in-wall carrier ($520 carrier + $185 actuator + framing labor) which adds ~$1,800-2,400 to the toilet cost — but creates a floating bathroom look that's hard to achieve any other way.
Hansgrohe Ecostat thermostatic shower valves prevent scalding from upstream pressure changes (someone flushing the toilet upstairs). They're the best in the industry; the premium over a non-thermostatic Delta is ~$150 — worth it.
Compact stall showers (Sterling, Aker, Maax) are the right answer for budget JADU baths. 32"x32" or 36"x36" molded fiberglass = $500-900 fixture, 1-day install, no waterproofing risk. Skip the tile if budget is tight.
What the brand reps won't tell you.
- Most JADU baths fail inspection at one of two items: ventilation fan CFM (must be 50+ CFM ducted to exterior) and shower drain slope (1/4" per foot to drain). Both are routinely missed.
- Pressure-balanced shower valves (Delta Monitor, Moen Posi-Temp) are CRC-mandated. Don't confuse 'pressure-balanced' with 'thermostatic' — the former is code-minimum, the latter is the premium upgrade.
- Wall-hung toilet carriers must be installed in 2x6 walls minimum. Don't try to retrofit into 2x4 walls — the carrier doesn't fit.
Our default spec
Default: Toto Drake II 1.28 GPF, Hansgrohe Logis or Delta Trinsic lavatory faucet, Hansgrohe Ecostat thermostatic shower valve, Schluter Kerdi-built shower OR Sterling stall pan, Panasonic WhisperGreen 80 CFM fan ducted to exterior, code-compliant pressure balance + scald protection.
In short.
- How small can a JADU bathroom be?
- Practical minimum is 30 sqft with a 30 in x 30 in shower. Tub-shower combo requires 45 sqft minimum. Most JADU baths we build land at 36–40 sqft with a shower-only design.
- How much does a JADU bathroom cost?
- $8K–$24K complete depending on layout. Shower-only with wall-hung toilet: $8K–$18K. Tub-shower combo: $10K–$22K. Curbless shower with linear drain: $11K–$24K.
- Do I need a tub in a JADU?
- No — state law requires a full bathroom (toilet + sink + tub OR shower). Most JADU owners go shower-only for space efficiency.
- Can the JADU share the main house's bathroom plumbing?
- Yes — the JADU bath taps the existing main-house drain and supply lines. We verify the existing system has capacity for the added fixtures during feasibility.
- What's the best ventilation fan for a JADU bath?
- Panasonic WhisperGreen with humidity sensor (50–80 CFM, < 0.3 sones) is the best-in-class — quiet enough to leave on, automatic moisture control. Cost is $250–$400 installed.
- Do I need a separate water heater for the JADU bath?
- No — most JADUs share the main-house water heater. A point-of-use tankless heater is an alternative if the main heater is far from the bath or undersized.
- How long does a JADU bath take to install?
- 2–3 weeks once plumbing and electrical rough is complete. Tile setting and waterproofing is typically the longest phase.
- Can I install a curbless (zero-threshold) shower?
- Yes — requires a recessed subfloor (or floor build-up around the shower) and a linear drain. Adds $1,500–$4,000 vs a curbed shower. Worth it for aging-in-place or for the modern aesthetic.
Keep reading.
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