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Building Code Reference

Got a CRC R703.1 correction?

Exterior wall weather barrier

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

CRC R703.1 is the California Residential Code section that requires exterior walls to be constructed with a weather-resistant envelope, including a water-resistive barrier (WRB) installed behind the cladding and properly flashed openings at windows, doors, and wall penetrations. The barrier must resist wind-driven rain and direct moisture from reaching the wall framing or sheathing. Single-family homes, ADUs, and room additions all trigger R703.1 whenever new exterior wall cladding is part of the scope.

How to fix it

  1. Add an exterior wall assembly detail with WRB called out

    Draw or revise your typical wall section to show the full cladding assembly in order from inside to outside: framing, sheathing, water-resistive barrier, optional drainage mat or rainscreen gap, and cladding. Label the WRB by category (e.g., "Grade D building paper, min. 60-min. rating" or "housewrap per ASTM E2556 Type I"). If you are using a liquid-applied membrane, note the manufacturer and minimum dry-film thickness. This detail should appear on the A-series sheets, not buried in a spec note.

  2. Show WRB lapping direction and sequence

    R703.2 requires the water-resistive barrier to be lapped so it sheds water. That means upper layers overlap lower layers, not the other way around. On your wall section or a separate assembly detail, note that horizontal joints lap a minimum of 2 inches and vertical joints lap a minimum of 6 inches. If you are using housewrap, note that fasteners and seam tape are required per the manufacturer installation instructions and that seams must be taped before cladding installation.

  3. Add sill pan flashing detail at all windows and doors

    Every window and door opening needs a sill pan flashing detail showing: how the pan is sloped or sealed to direct water to the exterior, the back dam height, and how the pan integrates with the WRB on the sides and head. Show whether you are using a pre-formed pan (metal or flexible flashing membrane) or a site-built pan with dam tape. The sill pan must drain to the exterior, not into the wall cavity. This detail goes on the window schedule sheet or an enlarged detail sheet.

  4. Show head flashing above all openings

    Above each window, door, and any through-wall penetration, show a head flashing that directs water away from the opening and integrates with the WRB above it. The flashing must extend past the sides of the opening (minimum 4 inches each side is common practice, though local jurisdictions may differ). Show the flashing material: galvanized sheet metal, copper, or flexible self-adhered membrane. The WRB above laps over the top of the head flashing, not under it.

  5. Specify kickout flashing at roof-wall intersections

    Where a sloped roof meets a vertical wall, water runs along the rake and wicks into the wall assembly without a kickout. Show kickout flashings at every roof-wall intersection on the drawings: at the low end of step flashing runs, at dormer cheek walls, and at roof-to-addition transitions. Note the material (galvanized, copper, or aluminum min. 0.019-inch thick) and show how it integrates with both the step flashing and the WRB on the wall below.

  6. Address the WRB transition at ADU-to-existing-building interface

    For ADU projects, the junction between new exterior walls and an existing building wall is a common omission. Draw an enlarged detail at this condition showing: how the new WRB laps over or under the existing WRB or cladding, the kickout flashing at any roof connection, and any sealant joints. If you cannot expose the existing WRB at the tie-in, note the field condition and specify that the contractor will install a minimum 9-inch-wide self-adhered flashing tape at all seams as an alternative.

  7. Include a weather-barrier inspection note on the drawings

    Some jurisdictions require a framing inspection or exterior sheathing inspection before cladding goes on, so the inspector can verify WRB installation. Check your local jurisdiction's inspection card or ordinance. If required, add a note to the drawing set: "Water-resistive barrier installation shall be inspected prior to cladding installation per CRC R703.1." This avoids a stop-work call in the field later.

  8. Resubmit with a response-to-comments sheet

    When you resubmit, add a cover sheet that lists each R703.1 correction item and references the sheet and detail number where it was addressed. For example: "R703.1 WRB detail added, see A4.1 Detail 3." Plan-checkers review dozens of sets and a clear response matrix cuts the back-and-forth. If you have a CrossBeam pre-check report, attach the AI findings sheet to your response package.

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Why you got flagged

Here is why plan-checkers flag R703.1 corrections.

The most common reason is missing or underspecified water-resistive barrier notes on the exterior wall assembly detail. If your wall section shows siding or stucco directly over sheathing without calling out a WRB layer, the plan-checker marks it. California code requires that the barrier be identified by type, such as Grade D building paper, housewrap meeting ASTM E2556, or a liquid-applied membrane. Writing "WRB per code" without a product category or ASTM reference is not enough.

Flashing is the second major trigger. R703.1 works together with R703.4 through R703.8, which require sill flashing, head flashing, and kickout flashing at every exterior wall opening. Plans that include a window or door schedule but no flashing detail, or that show window installation without specifying sill pan dimensions and drainage method, almost always come back with a correction on this section.

A third scenario is room additions and remodels where the scope includes new siding. When you demo existing cladding and resheath, the replacement assembly must meet current R703.1 requirements, even if the underlying framing is original. Plans that say "match existing" at the exterior assembly get flagged because the original construction often predates current WRB standards.

ADU plans frequently omit the transition detail where the new exterior wall meets an existing building. That intersection needs a kickout flashing and WRB lapping sequence spelled out on the drawings. Without it, the plan-checker flags R703.1 and often adds a paired note citing the roof-wall intersection requirements in Chapter 9.

The official code

California Residential Code Section R703, Exterior Wall Covering, official adopted text via DGS Building Standards Commission

Read the source →

Common questions

Does CRC R703.1 apply to my ADU if I am only adding a bathroom and not changing the exterior siding?
If you are not touching the exterior cladding, plan-checkers generally do not require you to retrofit the full R703.1 assembly on existing walls. But if your bathroom addition creates a new exterior wall, that new wall must comply with R703.1. The trigger is new exterior wall construction, not just interior remodels. Check your plans: if the scope shows any new sheathing or new siding on an exterior surface, budget for WRB and flashing details.
What counts as an approved water-resistive barrier under R703.1?
The California Residential Code accepts several WRB types. Grade D building paper (60-minute rating minimum) is the traditional option and still widely used under stucco. Housewrap products that meet ASTM E2556 Type I or Type II are also approved. Self-adhered sheet membranes and liquid-applied membranes can qualify when they meet ASTM E2357 or ASTM E1677. What is not acceptable is bare OSB or bare gypsum sheathing without a barrier layer, or a single coat of stucco scratch coat as the sole moisture barrier. Your plan notes need to specify which category you are using.
Do I need a separate flashing detail for every window or can I use a general note?
A general note is not enough for most plan-checkers. You need at least one representative detail that shows the sill pan, head flashing, and WRB integration at a typical window. If you have multiple window types, such as fixed vs. operable or wood vs. vinyl, show a detail for each type since pan dimensions and integration methods differ. A note that says "flash all openings per manufacturer" will get flagged because it does not demonstrate the assembly meets R703.4 through R703.8.
My contractor always uses a liquid-applied WRB. Does the plan set still need a detail?
Yes. Even when the field practice is well established, the plan set needs to document it. Show the liquid-applied membrane in the wall section, note the product or at minimum the ASTM standard it meets, and include the required dry-film thickness or number of coats. The plan-checker cannot approve "liquid WRB per contractor" as a specification. If the product has a code report or ESR number from a testing body, include that reference on the drawings.
What is a kickout flashing and where exactly is it required?
A kickout flashing, also called a diverter, is a small bent piece of metal or flexible membrane installed at the bottom end of a step-flashing run where a sloped roof meets a vertical wall. Without it, water flowing down the roof stays against the wall and works into the siding over time. R703.1 and the related Chapter 9 roof requirements call for kickout flashings wherever a sloped roof terminates at a wall: at dormer side walls, at roof-to-addition junctions, and at any eave-to-wall condition. Show it on your plans. It is one of the most commonly missed items on residential resubmittals.
Will the inspector check my WRB installation before I install siding?
That depends on your jurisdiction. Many California cities require a framing inspection that includes a WRB check before cladding goes on. Some require a separate exterior sheathing or weather-barrier inspection. If you skip it and install siding before the inspector signs off, you may be asked to remove cladding to expose the WRB. Check with your building department before scheduling inspections. If the corrections letter cites R703.1, ask whether a pre-cladding inspection is required in that city.

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