Should You Repair or Replace Your Boise Deck?

Start with the structure, not the boards

Most repair-or-replace decisions get made by looking at the deck boards, because that's what you see and walk on. The boards are the cheapest part to fix. The decision really turns on four things underneath: how the deck connects to the house, the condition of the joists and beams, the footings, and the guards. If those are sound, almost anything above them is a repair. If any of them is failing, new boards on top are money spent on a deck that still has to come apart.

The 2018 IRC's deck section, R507, is a useful yardstick. An older deck doesn't have to match today's code to stay in use, but the code describes what a sound deck looks like, and the gaps between your deck and that description are the list of risks.

What should you inspect first?

1. Ledger and house connection

The ledger is the board bolted to the house that carries the house end of every joist. Look for:

• Fasteners. IRC R507.9.1.3 calls for 1/2-inch lag screws or bolts, hot-dipped galvanized or stainless, in a set pattern. R507.8 prohibits attaching a deck with toenails or nails subject to withdrawal. A ledger held by nails is a replace-the-ledger item at minimum.
• Flashing. R507.2.4 requires corrosion-resistant metal flashing at least 0.019 inch thick, or approved nonmetallic flashing, and DCA 6 calls for continuous flashing with a drip edge at the ledger. No flashing, or dark stains and soft wood behind it, means water has been getting into the house framing.
• What it's attached to. R507.9.1.1 says ledgers can't be supported on stone or masonry veneer. A ledger on veneer needs to come off.
• Lateral connection. R507.9.2 calls for hold-down devices tying the deck to the house floor framing. Most older decks don't have them; adding them is usually a repair.

2. Joists and beams

Rot in joists starts at the top edge under the boards, where water sits, and at the ends in hangers. Push an awl or screwdriver into the top of joists and around hangers. Firm wood resists; decayed wood lets the tip sink in. Also check hanger nails for rust, joist hangers that have pulled away, and beams made of plies that have separated. A few bad joists on an otherwise sound frame can be replaced or sistered; widespread softness means rebuild.

3. Posts and footings

Look at the base of every post. Posts buried in soil or set in concrete without a base often rot at the ground line. Then look at the footings. Boise's frost line is 24 inches, and a deck that heaves each winter, with gaps opening at the ledger or stairs lifting off their landing, is probably sitting on shallow footings or pier blocks. Footings can sometimes be replaced post by post under a sound frame, but that's careful work. Our footing depth guide covers what a correct footing looks like.

4. Guards and stairs

Guards and stairs are where an older deck is most likely to fall short of current rules, and where a fall does the most harm. Compare yours against the 2018 IRC:

Shake each guard post. Movement usually means the post was notched and bolted only to the outside of the rim, a detail that loosens over time. Replacing a railing system is a common repair on a sound deck; our deck railing options and railings and stairs service cover the choices.

5. Hardware and corrosion

Modern preservative-treated lumber is corrosive to plain steel. IRC Table R507.2.3 requires hot-dipped galvanized or stainless fasteners and connectors with specified coatings. Rusted hangers, bolt heads with flaking rust, and staining around nails are signs the hardware is losing section. Hardware can be replaced, but widespread corrosion usually travels with other age problems.

6. Decking surface

Soft spots, deep splits, cupping that holds water and popped fasteners on the boards are surface problems if the frame below is sound. Our maintenance guide explains which checking is normal in Boise's dry air and which isn't.

Where do Boise decks fail first?

Decks wear unevenly here, and knowing the pattern tells you where to look:

• South- and west-facing boards and rails take the most UV and heat, so they gray, check and lose finish first.
• Steps and the landing outside the door see the most snowmelt and refreeze, so treads, stringers and their footings deteriorate early.
• Posts and joists within reach of a sprinkler stay wet all summer and rot at the bottom and along the top edge.
• The ledger corner where a downspout or roof drip lands soaks the band joist behind it.
• Low decks with no airflow underneath stay damp and grow decay where you can't see it.

Boise's 108 freezing nights a year, with only 16 days that stay frozen, mean water in a check or a fastener hole freezes and thaws over and over. That's why small openings in wood become splits faster here than the dry climate suggests.

Repair, resurface or replace: a decision table

When does resurfacing work?

Resurfacing means new decking, and often new rails, on the existing frame. It works when the frame passes the checklist above and will outlast the new boards. Three checks decide it:

1. Joist spacing. The IRC limits joist spacing to what the decking allows: Table R507.7 allows 16 inches on center for 1-1/4-inch wood decking laid square, and plastic composite follows the manufacturer's rating. Trex's installation guide, for example, lists 16 inches on center for residential decks. Joists at 24 inches usually mean added joists before composite goes on.
2. Joist condition and remaining life. Putting decking rated for decades on 20-year-old joists with soft tops doesn't make sense. Many builders add joist tape on the top edges of sound joists during a resurface to slow decay.
3. The ledger and guards. A resurface is the cheapest time to fix the ledger flashing and railings, because the boards are off.

If those pass, deck resurfacing can give an older deck a new surface for a fraction of a rebuild. If they don't, a full replacement is the better spend. The deck replacement cost guide has sourced ranges.

Do deck repairs need a permit?

Boise requires a permit for decks more than 12 inches above grade, and replacing structural members, posts, beams, joists or the ledger, is structural work. Board-only resurfacing on sound framing isn't addressed directly in the city's brochure; call the permit counter with your scope. Other cities differ; see our permit pages for Boise and Caldwell, where the city states decks need separate permits and inspections.

How we inspect

A Valley Decks assessment starts underneath: ledger fasteners and flashing, joist tops and hangers, posts and footings, then guards and stairs, then the boards. We note each finding against the IRC section it relates to and tell you which items are safety issues, which are durability issues and which are cosmetic, so the repair-or-replace call is yours to make with the facts in hand. Our deck repair page covers the common fixes.

Shortcuts to avoid

• Screwing new composite boards onto 24-inch joist spacing.
• Covering a soft or unflashed ledger with new decking.
• Sistering rotted joists without fixing the water source that rotted them.
• Adding a hot tub or a roof to an older deck without an engineer.
• Pressure-washing or painting over soft wood instead of replacing it.
• Reusing rusted hangers and nails on new joists.
• Leaving loose guards in place because the rest of the deck looks fine.