Introduction: How to Attach Railing Posts to a Deck Frame
Hello again everyone, in this instructable, I will be showing how to properly attach railing posts to a deck frame. I decided to make this instructable because when I repair or rebuild a deck, the railing posts are by far the most common place where previous builders have done things improperly, oftentimes so poorly that the railing would present a serious safety hazard if people were to lean against it. Properly attaching railing posts not only gives you a safer deck, it also helps prevent lawsuits and moral guilt if someone falls off. Let's get started!
Step 1: Check Local Building Codes
Before you begin building your deck, it is important to check your local building codes to ensure that you are meeting or exceeding their requirements. It is a good idea to view building codes as a minimum standard, a passing grade; if you will. It is always better to exceed the requirements if you can afford to.
Building codes will likely specify minimum railing height (I usually use a 42" railing when I build), maximum post spacing (usually 4' or 6' on center), and minimum fastening requirements such as the diameter of bolts and the proper connectors to use. My instructable should meet or exceed building codes in most areas, but be sure to check just in case. For example, near large bodies of salt water, stainless steel fasteners may be required instead of hot-dipped galvanized ones to prevent premature corrosion.
Step 2: Post Height Calculations
To find the proper height of your posts for a given railing height, simply add the desired railing height and the actual (not nominal) height of your deck joists. For example, a 42" railing with a 2x10 joist requires a post that is 51 1/2".
Step 3: Clamp Post and Blocking
IMPORTANT: This procedure is for sides of the deck with the rim joist. For the sides where there is no rim joist, read the "Modification for no rim joist" section near the end of the instructable, then begin from step 1.
First, place a clamp spanning between 2 deck joists as shown in the second image. Set the post on top of the clamp, this will ensure that the post is at the correct height without measuring error. Place a piece of blocking to fit between the deck joists and clamp it against the post.
Step 4: Mark and Drill Holes
Mark one hole 2" down from the top of the blocking, and 1" over from where the joist meets the blocking (NOT on the center line of the post). Mark a second hole 2" up from the bottom of the blocking, and 1 3/4" over from where the joist meets the blocking (this WILL be on the center line of the post). Using a 5/8" diameter drill bit capable of drilling at least 7" deep, drill all the way through the blocking, post, and rim joist. Be sure to avoid drilling a crooked hole.
Step 5: Add Bolts
Insert a 1/2" by 8" hot-dipped galvanized hex bolt with a flat washer through each hole. Add a washer and nut to the bottom bolt and use a 3/4" socket to tighten it up.
Step 6: Level Post
Before you attach any more hardware, check to make sure that the post is vertical and make any adjustments necessary. Remember that closing one eye and sighting from directly in front of the bubble will make your readings more accurate.
Step 7: Add DTT2Z Tension Tie
Add a DTT2Z Deck Tension Tie to the top bolt of the post. Add a flat washer and nut, and tighten the nut. You may remove the clamps at this time. Using a 3/8" socket and the screws that came with the DTT2Z, attach the tension tie to the deck joist.
Step 8: Screw in Blocking
Using 3 1/2" deck screws, attach the blocking to both joists with 3 screws on each side as shown in the images.
Step 9: Modification for No Rim Joist
On the sides of the deck where there is no rim joist, you will need to install 2 pieces of blocking perpendicular between the last 2 joists as shown in the image. Use 3 1/2" deck screws, 3 on each end of each block. Be sure to space them far enough apart that you can still get your impact driver in between to attach the screws to the tension tie. I needed a 12" space, but my impact driver is rather stubby, so yours may need to be slightly bigger.
Step 10: Finished!
Congratulations, you now have a post-to-deck connection easily sturdy enough for a linebacker to tackle your railing without going over the edge. Repeat for remaining posts, and good luck building the rest of your deck!