Decks

Almost every catastrophic deck failure is a ledger failure. The ledger is the board bolted to the house that carries one entire side of the deck, and when it lets go the deck does not sag — it drops, usually while loaded with people. Two things cause it, and both are avoidable.

The first is attachment. A ledger nailed on, or fastened with deck screws, or lag-bolted into siding rather than into the house’s rim joist, is relying on fasteners loaded in withdrawal. Correct attachment uses through-bolts or structural lag screws in a staggered pattern into solid framing, with the siding removed so the ledger bears on sheathing or rim rather than standing off on a compressible surface.

The second is water. A ledger bolted flat to the wall creates a horizontal shelf that traps water at the exact point where the deck framing meets the house framing, and the bolt holes give that water a path straight into both. Ledger flashing — a Z-flashing or membrane detail that runs up behind the water barrier and out over the top of the ledger — is what keeps that joint dry. Without it, the rim joist rots quietly behind the deck boards for a decade and then the connection fails without warning. Free-standing decks on their own posts avoid the problem entirely, and are worth considering on additions and on walls with a leak history.

Footings carry everything to the ground and have to reach undisturbed soil below the local frost depth. Frost depth is shallow across most of Texas and deeper in Oklahoma, Arkansas, and Tennessee, and it is set by local code, not by rule of thumb. Two soil problems matter more here than frost anyway: fill dirt around a newer house has not consolidated and will settle under a footing bearing on it, and expansive clay heaves and shrinks seasonally, which is what causes a deck to move relative to the house year over year. Footings sized to the load and taken to competent bearing solve both.

Joist spacing depends on what goes on top. Wood decking is typically framed at sixteen inches on center. Composite decking is not structural — it spans between joists rather than contributing stiffness — and most composite products want sixteen inches on center for perpendicular installation and twelve inches on center when boards run diagonally, with some products requiring twelve throughout. Framing a deck at twenty-four inches and then installing composite over it produces a floor that feels soft underfoot and boards that sag visibly between joists in summer heat. Check the decking requirement before the framing goes up, not after.

• Pressure-treated pine — the economical structural standard and a common decking surface. Treated for rot and insects, but it moves, checks, and cups as it dries, and it needs cleaning and sealing on a cycle to stay presentable.
• Cedar — naturally rot and insect resistant, dimensionally calmer than treated pine, cooler underfoot, and better looking with age. It is softer, so it dents, and left unfinished it weathers to gray.
• Composite — a wood-flour and polymer board that does not rot, splinter, or need sealing, and holds color for a long time. It costs more up front, it gets hot in direct Texas sun in darker colors, and it has stricter joist spacing requirements than wood.
• Aluminum decking — the longest-lasting surface. It does not rot, burn, warp, or attract insects, many systems are watertight enough to create dry storage below, and it stays cooler than dark composite. It is the highest initial cost and a specific look.

Hidden fasteners clip into a groove milled in the edge of the board or screw through the side into the joist, leaving a surface with no visible screw heads. Beyond appearance, they eliminate the face penetrations where water sits and where wood boards check around the screw, and most composite systems are designed around them. The tradeoff is installation time and a board that is slightly harder to remove individually later. Where face screws are used, they should be coated or stainless — modern pressure-treatment chemistry is corrosive to plain steel, and a deck fastened with the wrong screws loses its connections from the inside.

Railings are a life-safety item and are governed by code rather than preference. Residential guards are generally required at thirty-six inches minimum above the walking surface where the deck is more than thirty inches above grade, with balusters spaced so a four-inch sphere cannot pass between them, and the assembly has to resist a specified lateral load at the top rail. Stairs have their own handrail height range and their own graspability requirements. Local amendments vary, so the governing number is whatever your jurisdiction has adopted — but a wobbly guard that moves when you lean on it fails the load requirement regardless of how tall it is.

• Ledger attachment and flashing corrected where the original was nailed, unflashed, or bolted through siding.
• Rotted rim joist, joist ends, and posts at grade replaced.
• Footings underpinned or replaced where settlement or heave has moved the frame.
• Guard and handrail assemblies rebuilt to current height and load requirements.
• Decking surface replaced over sound framing, including conversion from wood to composite where spacing allows.
• Corroded fasteners and undersized hangers replaced with properly rated hardware.