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Schluter Home Additions & ADU: The San Francisco Owner’s Guide
Schluter home additions and ADU construction in San Francisco typically run $53,100 – $153,400 installed, depending on square footage, site access, foundation work, and finish level. We stock Schluter waterproofing membranes, KERDI-BOARD, DITRA-HEAT, and Schluter trim profiles on the truck, and we match the right Schluter product line to your specific addition or ADU scope. Most owners discover a failed Schluter component during a remodel or addition, not as a sudden breakdown. The signs are usually visible for months: cracked grout lines at the KERDI seams, discolored baseboards where shower waterproofing failed, curling DITRA edges at a doorway transition, or worse, soft subfloor under tile in a wet zone. By the time you see it, the moisture has been moving through the substrate for a while.
This page covers the Schluter products that fail inside home additions and ADUs, what the repair or replacement actually costs in San Francisco, and how to know whether it’s a simple fix or a full tear-out. We’re an independent contractor, not affiliated with Schluter Systems. We install and repair their products because they work when they’re installed correctly, and we hold ourselves to a written standard on every job.
Which Schluter Models This Applies To
Schluter’s product line for additions and ADUs breaks into four families: KERDI waterproofing membranes (shower walls, steam rooms, tub surrounds), KERDI-BOARD (waterproof building panels for showers and backsplashes), DITRA and DITRA-HEAT (uncoupling membranes and heated floor systems under tile), and Schluter edge profiles (SCHIENE, RONDEC, QUADEC trim at tile edges and transitions).
The compatibility gotcha most San Francisco homeowners hit: DITRA and DITRA-HEAT are not interchangeable under the same tile assembly in a load-bearing addition. DITRA-HEAT requires a dedicated circuit, a floor sensor, and the heating cable spacing specified for your tile size. If you’re adding a second-story ADU over an existing garage, the deflection limits in the California Building Code (L/360 for tile, L/480 for stone) matter more than the membrane choice. We see this in the Sunset and Richmond districts constantly: older balloon-frame homes with 2×8 joists at 16 inches on center that barely pass for ceramic tile, let alone a stone bathroom floor in an ADU.
For shower waterproofing, KERDI membrane and KERDI-BOARD are both correct answers, but not both on the same wall. KERDI-BOARD replaces cement board entirely, so if a previous contractor installed KERDI over cement board and then added KERDI-BOARD at the niche, you get a double waterproofing layer that traps moisture between two vapor barriers. That’s a common failure we repair in gut-and-rebuild additions. Our crews carry both product lines, and we match the spec to what’s already in your walls, not what’s cheapest to buy at the supply house.
Schluter trim profiles have a spec range most owners don’t know: SCHIENE and QUADEC come in heights from 1/4 inch to 1/2 inch, in both aluminum and stainless steel. We stock the most common San Francisco sizes on the truck: 3/8 inch stainless for floor transitions, 1/2 inch aluminum for backsplash edges, and 5/16 inch QUADEC for curbless shower threshold details.
Styles & brands we work with
Signs Your Schluter Home Additions & ADU Is Failing
Here’s what a failing Schluter installation looks like in a real San Francisco addition or ADU. None of these are subtle if you know what you’re looking at.
- Grout cracking in a stair-step pattern along KERDI seams. The membrane is pulling away from the substrate at the seam, which means the waterproofing layer is no longer continuous. Water’s getting behind the tile and into the wall cavity.
- Efflorescence or white mineral staining on grout lines below a shower bench or niche. Water is wicking through the grout and evaporating, leaving mineral deposits. The KERDI seam beneath has failed or was never properly bonded with unmodified thin-set.
- Hollow-sounding tile when tapped, especially over DITRA. The uncoupling membrane has delaminated from the substrate, usually because modified thin-set was used where unmodified was specified, or the membrane was walked on before the mortar cured.
- Baseboard warping or discoloration at the shower-to-floor transition in an ADU bathroom. That’s not a plumbing leak under the slab; it’s water traveling along the DITRA edge where the KERDI band wasn’t installed at the floor-wall junction.
- Visible mold or mildew behind silicone caulk at a Schluter trim profile joint in an addition that’s been in use less than two years. A properly waterproofed Schluter assembly should not grow mildew in the wall cavity. If it does, the membrane was punctured during tile installation or a fastener was driven through the KERDI layer.
In San Francisco specifically, we see one pattern more than any other: fog-driven moisture pushed into exterior walls during the long June-to-August overcast season, then pulled inward as the house heats and cools. If the KERDI on an exterior shower wall in an Outer Sunset addition wasn’t sealed properly at the window or niche, that wall will fail within 3 to 5 years. Not a guess. It’s the same failure we’ve corrected across a dozen additions in that neighborhood. Curtis Lane has worked through enough of these fog-zone waterproofing failures to spot the telltale sealant gap within minutes of walking the site.
See the difference
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AfterReplacement Cost & What’s Included
For a full Schluter home addition or ADU build in San Francisco, the installed range runs $53,100 – $153,400. That’s the number for the whole project: permits, structural work, rough-in, Schluter waterproofing and uncoupling installation, tile or finish work, and close-out. A small ADU bathroom with a KERDI shower and DITRA-HEAT floor lands at the lower end. A two-story addition with a full bath and heated tile throughout an addition lands at the upper end.
What drives the range:
- Foundation and structural work. San Francisco hillside lots often require retaining walls, piers, or upgraded footings before a single Schluter product goes in.
- Square footage of the addition or ADU. The more tile and waterproofing surface, the more membrane, board, and trim.
- Plumbing and electrical rough-in. A DITRA-HEAT floor requires a dedicated electrical circuit and a thermostat. That’s not optional.
- Access. Tight San Francisco lots with no street parking near the crane or small alley access add time and labor.
Every Bradford Remodeling quote is a written price before work starts. That’s The Garrison Standard, and it’s non-negotiable. The number on the proposal is the number on the invoice, with no change orders sprung after demo. If the Schluter work fails within 365 days, the 365-Day Done Right Promise applies: we return and correct it at no charge. You get a signed, written guarantee at close-out, not a verbal promise.
DIY or Call Us?
If you’re adding an ADU or building a home addition, this isn’t a DIY project. Schluter products are unforgiving when installed incorrectly, and the failure you don’t see for two years becomes a five-figure tear-out. Waterproofing is a system, not a product. Get the seam coverage wrong, use the wrong thin-set, skip the corner pieces at a curbless shower, and the only question is how long before the tile and drywall fail.
Here’s where we’re direct with you: we don’t sell parts for homeowner installation. We install Schluter products as part of a permitted, documented addition or ADU project. We have replaced too many failed homeowner membrane installations to suggest this is a weekend job. If you’re already in a failing condition and need a repair, we’ll assess it, write a scope for the repair only, and put the price in writing. Call (831) 610-5598 for a free estimate. We’ll give you a straight number and a real scope.
FAQs
Schluter KERDI membrane, properly installed, should last the life of the tile assembly, typically 20 – 30 years or more in a San Francisco addition. The failure point isn’t the membrane; it’s the installation. In fog-zone exterior walls, a badly sealed seam fails within 3 – 5 years. Call (831) 610-5598 for a free assessment if you suspect a leak.
Small repairs are possible if the damage is localized to a single seam or corner and the substrate is still sound. If moisture has reached the wall cavity or the subfloor, you’re looking at a tear-out and rebuild. We’ll open a small inspection area before quoting anything. Call (831) 610-5598 and we’ll assess it on site.
A small ADU bathroom addition typically takes 6 – 10 weeks in San Francisco, including permit approval, rough-in, waterproofing, tile, and close-out. A full two-story addition runs 4 – 8 months, with the Schluter work itself taking 1 – 2 weeks of that. We’ll give you a written timeline with the written price. Call (831) 610-5598 for a free estimate.
We stock KERDI membrane, KERDI-BOARD, DITRA, DITRA-HEAT cable, and common Schluter trim profiles on our trucks for San Francisco jobs. Specialty profiles and specific trim finishes are ordered from our San Francisco supplier, typically 2 – 5 business days. Call (831) 610-5598 to confirm what’s available this week.
DITRA-HEAT works in both new additions and retrofit renovations, as long as the electrical panel has capacity for a dedicated circuit and the subfloor meets deflection requirements. We’ll check the joist span and the panel load before we quote. Call (831) 610-5598 for a free estimate.
Schluter membranes carry the manufacturer’s spec for vapor permeability and seam bonding that generic products don’t always document. The distinction matters in San Francisco’s fog and marine layer conditions, where a product that works in a dry interior wall can fail in an exterior shower wall within a few seasons. We use Schluter because the documentation is complete and the performance is consistent. Call (831) 610-5598 if you want a scope that names the exact product going into your addition or ADU.
Written by Curtis Lane, Owner, Bradford Remodeling Co – San Francisco, CA at Bradford Remodeling Co San Francisco, serving San Francisco and nearby areas.
