Deck Builders SOP Example

Deck Ledger Attachment & Waterproofing

Proper ledger board installation to the house rim joist with through-bolt pattern, flashing, and drainage plane integration.

1. Locate rim joist & remove sidingSnap a chalk line at the ledger height, accounting for the decking thickness and any slope requirements. Use a stud finder to confirm the location of the rim joist (band joist) — the ledger must attach to solid framing, not to sheathing or siding alone. Remove all siding within 1" of the ledger perimeter using a pry bar, scoring the paint line first to prevent tearing. Set siding aside if reusable. Remove any housewrap in the attachment zone. Photograph the exposed sheathing and rim joist before proceeding.
2. Inspect rim joist & sheathingProbe the exposed rim joist with an awl or pocket knife — sound wood resists penetration; rot punches through easily. Probe at all four corners, at midspan, and around any existing penetrations. If rot depth exceeds 1/2" or spans more than 12" of the rim joist, stop and notify the homeowner — the rim joist must be sistered or replaced before ledger attachment. Do not attach the ledger to a compromised rim joist under any circumstances. Inspect the sheathing for delamination or moisture damage at the ledger zone.
3. Install self-adhering flashing membraneApply self-adhering waterproofing membrane (Grace Vycor or equivalent) to the sheathing in the ledger attachment zone. The membrane must extend a minimum of 4" above the top of the ledger location, lap 4" below the bottom, and extend 6" beyond each end of the ledger. Work from the bottom up, overlapping each course minimum 2". Seal all cuts and edges with flashing tape. The membrane protects the drainage plane from water that penetrates behind the ledger — this step prevents the most common cause of deck-related rot.
4. Set ledger & fasten per IRC bolt patternHold the PT 2x10 ledger against the flashed sheathing at the correct height. Pre-drill 1/2" holes through the ledger and sheathing into the rim joist — stagger holes in two rows per the IRC Table R507.9.1.3(1) bolt pattern for the specific joist span and ledger depth. Install 1/2" diameter galvanized or stainless lag screws or through-bolts with large-diameter washers. Torque all fasteners snug — do not over-torque lags into PT lumber (fiber crushing weakens the connection). Verify the ledger is level across its full length.
5. Install Z-flashing & integrate with drainage planeBend or install pre-formed aluminum Z-flashing so the top leg slides behind the remaining housewrap or siding above the ledger, and the bottom leg laps over the top face of the ledger. The Z-flashing prevents water from entering behind the ledger at the top edge. Do not caulk the bottom edge of the Z-flashing — this must remain open to drain any water that penetrates. Reinstall siding with a 1" gap at the siding-to-ledger line on each side to allow drainage and air circulation.
6. Documentation & load path verificationPhotograph the completed ledger from three angles: the bolt pattern with fasteners visible, the flashing above the ledger, and the siding reinstalled with the drainage gap. Verify the load path from the ledger through the rim joist to the floor framing — look for any rim joist blocking or connector hardware required by the project plans. Document the bolt size, spacing, and depth in the project file for the permit inspection. The ledger inspection is typically a required inspection point before deck framing proceeds.