Roof Hip and Valley in Columbia, MD: Why Only One of Them Leaks

A hip sheds water away from itself. A valley concentrates it. From the driveway they look like one line bent opposite ways, which is exactly what they are.

That asymmetry explains the failure record. Hips mostly do not leak. Valleys do, constantly — and the ones that do the most damage have no fall in them at all.

Hip and valley: the same joint, opposite jobs

A hip is the convex line where two planes turn away from each other, so water landing near it runs off down both slopes. A valley is the concave line where they turn toward each other, so both slopes deliver their runoff into one channel — any foot of which carries a multiple of what a foot of open field sees. That makes a hip a covering problem, cap shingles and wind lifting the ends, and a valley a drainage problem. Drainage problems arrive as ceiling stains.

The wind trade-off is worth knowing. A hip roof has no gable ends, so all four planes brace each other and it takes high wind better than a gable of the same size — Florida's uniform mitigation verification form, OIR-B1-1802, pays a roof-shape credit for a full hip, defined as no other roof shape over ten percent of the perimeter. What it costs is complexity, a driver in roof replacement cost.

Roof valley types: three ways to close one joint

Every valley has a lining under it; what changes is what sits on top. Open, where metal stays exposed and water runs on it. Closed-cut and woven, where the shingles are the valley. Plus the California valley, which exists to skip the cutting.

Closed-cut is the residential default: one plane's shingles run through the valley and a foot up the far slope, the other plane's are cut in a straight line an inch or two off the centerline, and that edge is trimmed and bedded. Done well it works. Its problem is not performance but opacity — the lining sits under two layers of shingle and nobody sees it again.

Woven interlaces courses from both planes alternately, so nothing gets cut. On old 3-tab it was fine. On modern laminate it is the worst option on the roof: laminate is thick and stiff, will not lie flat into a trough, and gives you a bridge with a void under it. Then somebody walks the valley and cracks the shingle. IKO notes it can void a warranty.

Open roof valley: the water runs on metal, not on asphalt

An open valley is metal laid over the lining and left exposed, shingles cut back both sides. The most durable of the three, and the reasoning is not complicated: water and ice slide on sheet metal faster than on the sawn edges of asphalt, debris clears instead of catching, and nothing abrades granules at the point of highest flow.

What separates a good one from a bad one, all trade practice:

• A center crease or rib, stopping cross-wash: runoff from the steeper plane shooting across and up under the other plane's shingles. And a channel that widens toward the eave, so a jam of pine needles at the top does not dam the run.
• No fasteners in the channel — the metal is held at its edges or with clips. A nail through the middle of a valley is a hole at the wettest point on the roof.
• One metal, not two. Aluminum downstream of copper corrodes galvanically, fastest in a wet channel.

The honest objection is appearance. An open valley is a metal stripe up the roof and plenty of people do not want one — a fair reason to pick closed-cut. "It lasts the same" is not.

California roof valley: the fast one, and where it runs out

A California valley — also called a Long Island or New Jersey valley — is a shortcut on the open valley. Rather than cutting the field shingles back along a chalk line, a run of shingles is laid vertically up the valley, butt edge to the center, and the field courses land against it. Nothing gets cut, which is the whole reason it exists.

It is not automatically wrong. IKO calls it adequate on steeper slopes, roughly 6:12 and up, where water moves fast and downhill, and worse as the slope drops: slower water travels laterally and works under the edge of that vertical shingle instead of past it. Some jurisdictions prohibit it and some manufacturers restrict it — one of the few valley questions where the local answer genuinely differs from the general one.

Roof dead valley: the one that actually fails

A dead valley is a valley with little or no fall. It arrives three ways: the valley dies into a wall instead of running out to an eave; a dormer or later addition was framed on top of an existing plane, leaving a pocket behind it; or two already low-slope planes intersect and the line between them is nearly flat.

Everything a valley does right, it does because it has somewhere to go. Take the fall away and the geometry inverts: water stands, debris packs into the corner and stays wet, snow sits longest. And the material in that puddle is asphalt shingle, which is a water-shedding product — it works by handing water to the piece below it — not a waterproofing membrane. Shingles are not rated to sit in standing water, and a dead valley is standing water by definition.

So the fix is a different material, not better shingle work:

• A metal pan, soldered or seamed, carried well up both adjoining planes and any wall it dies into. McElroy Metal is explicit that it must run high enough to allow for water washing upward under wind-driven rain.
• Or a fully adhered membrane — self-adhering modified bitumen, or a single-ply — lapped under the shingles above and behind the counter-flashing.
• Often a cricket underneath, manufacturing the fall the framing never gave it. Splitting the water two ways is the only permanent answer to a pocket with no downhill.

One signal for how seriously the trade takes this: several metal panel manufacturers exclude dead valleys from their weathertightness warranties, or cover them only on stated conditions. A manufacturer carving out one detail by name is telling you where the claims come from. In the field, meanwhile, a dead valley gets sealed two or three times before anybody rebuilds it, because caulk is cheap and looks like a repair. What the delay adds is in the cost of fixing a roof leak.

What the code actually requires in a valley

Valley linings for asphalt shingles are IRC R905.2.8.2, "Valleys" — the same number in 2018, 2021 and 2024. Checked against a licensed 2021 printout and the 2018 Seattle Residential Code reprint, since codes.iccsafe.org serves an empty page.

The mandatory part is one sentence: linings shall go on per the manufacturer's instructions, before the shingles. What follows opens "valley linings of the following types shall be permitted" — a menu, not a specification:

• Open valley, metal. Not less than 24 inches wide, in one of the corrosion-resistant metals of Table R905.2.8.2 — aluminum at 0.024 inch, 26-gauge galvanized, 16-ounce copper.
• Open valley, roll roofing. Two plies of mineral-surfaced roll roofing, an 18-inch layer under a 36-inch.
• Closed valley. One ply of smooth roll roofing at least 36 inches wide, or either option above. Self-adhering polymer-modified bitumen — ice-and-water membrane — is permitted in lieu of the lining, not on top of it. The 2024 edition puts a 36-inch width on that sentence; 2018 and 2021 do not.

Same finding as a sister post reached on sidewall flashing: the code permits several, and trade copy asserts one. Nobody is required to put metal in your valley, and the ice barrier the IRC does require, R905.1.2, is an eaves rule, not a valley rule. What binds a detail is the manufacturer's-instructions clause plus your jurisdiction's amendments.

Dead valleys are not in the code at all — the term appears nowhere in Chapter 9, so anyone quoting you a dead-valley section is inventing it. What bites instead is R905.2.2: asphalt shingles only at 2:12 and above, double underlayment from 2:12 to 4:12. A dead valley is usually under 2:12, so the argument is not that the shingles went on wrong. It is that they were never permitted there.

Who Maryland lets take money for a valley

A valley re-line is small enough to fall under whatever threshold a state wrote with whole re-roofs in mind, and the rules differ in kind, including states that set no bar at all.

The credential is an MHIC license from the Home Improvement Commission, and the number to know is that there is no dollar threshold at all - any home improvement work needs one, whatever it costs. Your deposit is capped at one third, and no money may be taken before you sign. The guaranty fund pays up to thirty thousand dollars per claimant, but only against a licensed contractor, and an unlicensed one cannot enforce the contract against you.

Reading your own valleys from the ground

Binoculars from the lawn settle most of it:

• A metal stripe — open valley. Check the center crease for rust, pinholes or a dulled line where the coating abraded off.
• Unbroken shingles, one straight cut line — closed-cut; nothing to see, which is the point. Rippling across the trough means woven, worth noting on a laminate roof.
• A vertical seam, no metal — California valley. Fine on a steep slope, a question on a shallow one.
• A valley ending at a wall rather than a gutter — dead valley. Confirm a day after rain: still wet, or holding a debris line or dark stain while everything else dried.

Past that, ask for a written roof inspection that photographs the valley from above and from the attic side. Nobody settles an argument about a closed-cut valley from the driveway, and a verbal all-clear leaves you nothing to hold anybody to later. The metal at the head of a valley belongs to the wider family in flashing on a roof.

Bottom line

Hips are a covering detail and they mostly behave. Valleys take the concentrated runoff of two planes, and they are where the roof gets decided. Ask which valley type is being quoted and get it in writing — open, closed-cut, woven or California is a choice, not a default. And if a valley dies into a wall, treat it separately and in a different material. No shingle detail has ever fixed one.

Columbia MD Roof Pros does valley and dead-valley rebuilds, roof leak repair, roof inspections and roof replacement across Columbia and Howard County. Call (866) 814-0634 and we will photograph every valley before anybody quotes.