Overview: The weak deck problem and solutions
Now for the good news. Most of the fixes are quick, inexpensive and easy. Home centers and lumberyards carry the tools and materials you'll need. Or visit strongtie.com to find local stores that stock anchors, post bases and connectors.
In this article, we'll show you the warning signs of a dangerous deck—and how to fix the problems. If you're still not sure whether your deck is safe, have it inspected by your local building inspector.
Problem 1: No lag screws in ledger board
Starting at one end of the ledger board, drill two 1/4-in. pilot holes. Offset the holes so the top isn't aligned with the bottom hole. Then drive the lag screws (with washers) using a drill and an impact socket (you'll need a socket adapter that fits in your drill). Don't countersink the screws—that only weakens the ledger board.
Problem 2: Missing nails in joist hangers
Problem 3: Rotted posts
Problem 3: Rotten Posts - Brace the deck
Mark the post location on the footing, then remove the post by cutting through the fasteners that tie it to the rim joist. Use a metal blade in a reciprocating saw (or knock out the post with a hammer). If there's already a bolt sticking out of the footing, use it to install a new post base. If not, you'll need to add a 3/8- by 4-in. wedge anchor. Do this by placing the post base at the marks where the old post sat, and then mark the center. Remove the post base and drill the center mark with a 3/8-in. masonry bit. Drill down 3 in., then blow the dust out of the hole.
Problem 3: Rotten Posts - Install an anchor and base
Problem 3: Rotten Posts - Install the new post
Problem 4: Wimpy post connections
Ideally, posts should sit directly under the beam or rim joist to support the deck. If the posts are fastened to the side of the beam or rim joist, like the one shown here, the weight is put on the fasteners that connect the post to the deck. This deck had only three nails in the post—a recipe for collapse. Nails alone aren't strong enough for this job, no matter how many you use. For a strong connection, you need 1/2-in.-diameter galvanized carriage bolts.
Add two of these bolts by drilling 1/2- in. holes through the rim joist and post. An 8-in.-long 1/2-in. drill bit costs around $10. The length of the bolts depends on the size of your post and the thickness of the rim joist (add them and buy bolts at least 1 in. longer than your measurement). We used 8-in. bolts, which went through two 1-1/2- in. rim joists and a 3-1/2-in. post. Tap the bolts through with a hammer, then add a washer and nut on the other side.
Problem 5: Wobbly deck syndrome
Run a treated 2x4 diagonally from corner to corner, under the deck. Drive two 16d galvanized nails through the brace into each joist. If a single board won't span the distance, use two, overlapping the braces by at least two joists. Cut the bracing flush with the outside edge of the deck.
Problem 6: Missing ledger flashing
To add flashing, first remove the deck board that runs alongside the house. If the boards run diagonally, snap a chalk line 5-1/2 in. from the house, then set the blade in a circular saw to the depth of the decking boards and cut off the board ends. (Replace the cutouts at the end of the job with a 5-1/2-in.-wide board installed parallel to the house.)
Problem 6: Missing ledger flashing - Loosen the siding
Problem 6: Missing ledger flashing - Insert the flashing
We used vinyl flashing, but you can also use galvanized metal or aluminum flashing. At each joist location, make a small cut in the flashing lip with a utility knife so it'll lie flat over the joists. The rest of the lip should fit over the top edge of the ledger board.
Problem 6: Missing ledger flashing - Seal the bottom
Problem 7: Rickety railing posts
Required Tools for this Project
- Tape measure
- Circular saw
- Socket/ratchet set
- Socket adapter
- Deep socket
- Caulk gun
- Adjustable wrench
- Drill/driver, cordless
- Impact driver
- Drill bit set
- Masonry drill bit
- Hammer drill
- Pry bar
- Reciprocating saw
- Safety glasses
- Utility knife
You'll also need a small hydraulic jack and gloves.
Required Materials for this Project
- Lag screws, 1/2-in. x 3-in.
- Joist hanger nails
- Treated deck post, 4x4 or larger
- Metal post base
- Wedge anchor, 3/8-in. x 4-in.
- Carriage bolts, 1/2-in.
- Acrylic caulk