The signs you need wood shake roofing are shakes cupped, split, or warped across the roof, a shake that cracks under the flex test, moss or lichen, rot on shaded slopes, or daylight through the deck, per InterNACHI, the Cedar Shake & Shingle Bureau, and This Old House.
Each of those signs traces back to the moisture that, not insects, drives most cedar wear, so reading them early separates a localized repair from a full re-roof.
When Has a Cedar Roof Reached End-of-Life?
A cedar roof reaches end-of-life when wood roofing passes the 25-year mark on the InterNACHI life-expectancy chart, or when cedar shake passes the 20-to-40-year range the Cedar Shake & Shingle Bureau sets. Maintenance decides where in that span a roof lands.
Wood shake and shingle carry two reference lifespans, because InterNACHI folds both products into a single 25-year "Wood" category while the Cedar Shake & Shingle Bureau separates cedar shake at 20 to 40 years and cedar shingle at 30 to 50 years. A roof at or past those figures favors replacement over another round of shake-by-shake repair, and a fungicide or algaecide treatment every few years pushes a maintained cedar roof toward the upper end of the range.
The flex test confirms end-of-life independent of how the surface looks: a shake that cracks under light bending has degraded internally, the InterNACHI field test for spent cedar. A shake that snaps rather than flexes has lost the structural integrity that sheds water, so a roof failing the flex test across many courses points toward replacement even when the shakes still appear whole from the ground.
What Surface and Moisture Signs Appear on Wood Shakes?
The surface and moisture signs are cupped, split, or warped shakes, moss or lichen colonizing the surface, and rot beneath shakes on north-facing or shaded slopes. Moisture, not insects, drives most premature cedar failure, per Cedar Shake & Shingle Bureau and NRCA guidance.
Cupped, split, and warped shakes mark the moisture-cycling degradation that ends a wood roof, as cedar expands and contracts with its moisture content and loses its flat seat against the course below. Moss and lichen colonizing the shake surface signal moisture retention and active decay rather than a cosmetic stain, since the growth holds water against the cedar and accelerates the breakdown the Cedar Shake & Shingle Bureau attributes to moisture.
Rot beneath cupped shakes on north-facing or shaded slopes appears first where the cedar dries slowly, because shaded slopes hold moisture longer and degrade faster than sun-exposed slopes, per Cedar Shake & Shingle Bureau guidance. A ventilated cedar assembly carries at least 1.5 inches of air space beneath the shakes so each course dries from the underside after rainfall, and rot on the shaded faces indicates that drying space has been overwhelmed or was never built into a cedar shake roof.
When Does Damaged Area or Deck Decay Favor Replacement?
Damaged area or deck decay favors replacement when shakes cup or split across more than 25 to 30% of the roof, or when daylight shows through the deck from inside the attic. That crosses the contractor-consensus threshold above which full replacement costs less than continued shake-by-shake repair.
Cupping or splitting across more than 25 to 30% of the roof crosses the replacement threshold, the point at which a full re-roof costs less than chasing individual failed shakes across the field. Below that share the failures stay localized and a shake-by-shake repair holds, so the percentage of affected area, not any single damaged shake, sets the repair-versus-replace decision.
Daylight through the roof deck seen from inside the attic indicates holes worn through the sheathing and shakes, a sign that points toward replacement rather than a patch, per This Old House. A permitted cedar re-roof requires complete tear-off of the existing wood, because N.J.A.C. 5:23-6.4 bars a recover-over when the existing covering is wood shake, slate, clay, or tile, so deck-level decay rebuilds the ventilated assembly from the sheathing up rather than layering new shakes over failing ones.
Wood shake roofing signals replacement when shakes cup, split, or warp across more than 25 to 30% of the roof, when a shake cracks under the InterNACHI flex test, when moss or rot marks trapped moisture on shaded slopes, or when daylight shows through the deck, while localized damage on a sound deck still answers to a targeted repair.