How to Attach Railing Posts to a Deck Frame

Intro: 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!

Comments

[dmmayerart]

Thanks for instructable. I am needing to update the deck at our cabin with these brackets... definitely overkill but needed for code.

[netdoctor]

Very helpful rundown on how the DTT2Z is intended to be used. This will be used in my deck project that I am working on now. Thanks for posting!

[cpcfreak]

That's the first time I've ever seen the use of the DTT2Z, is that purely to tie stop the deck from collapsing than supporting the post? We normally use purlin brackets on alternate joists to stop the joists separating from the bearer. I've also seen some T-Shaped caps used for similar reasons. Putting it on the posts seems like a good idea, that would be a tie stop every second or third joist depending on how far apart the joist are.

[TheNecromancer13]

The DTT2Z transfers the forces from pushing against the railing into the deck joist, rather than the rim joist. Since the rim joist is often only attached with screws, this results in a connection hundreds of times stronger than just using bolts and washers through the rim joist. To make the railing fail without the DTT2Z, all that needs to happen is for the screws holding the rim joist to pull out; whereas if you use the tension tie, you either have to break the post, break the joist, or shear off the screws which hold the DTT2Z in place. As for the purlin brackets, I use H1Zs to connect every joist to the beam.

[skaegget]

Why is your wooden beams perforated with small rectangular holes?

[goldscott]

That's how treated wood comes.

[skaegget]

I have never seen that before, only without holes. I'm from Sweden.

[TheNecromancer13]

I'm in the USA, and here we have treated wood both with and without holes. The holes allow the chemical to penetrate deeper into the wood, resulting in longer-lasting wood, the tradeoff is that it looks uglier; so stores often sell both types, at least in common sizes.

[TheNecromancer13]

It is pressure treated ground contact lumber, which is required by code for pretty much all structural framing which is exposed to the elements. It prevents the wood from rotting as quickly. Note that you must treat all freshly cut ends of boards with wood preservative to prevent them from rotting, as the treatment does not penetrate all the way to the center of the board.

[skaegget]

I know about treated wood for ground contact but I have never seen one with those holes. Are the holes there to make the treating chemical to reach further into the wood?

[fzbw9br]

Yes

[alanlf5280]

Is using the DTT2Z required to meet code in this instance? I would have assumed just adding a washer and nut on the top bolt would have met code. Asking because I will be adding new hand rail posts soon to my deck.

[TheNecromancer13]

In most places some sort of tension tie on the top bolt is required in addition to the washer and nut. The reason is that if you only attach with washer and nut, all of the force from leaning or falling against the railing is amplified by the leverage generated by the post, and then transferred to the rim joist because that's what the bolts run through. The rim joist is usually only attached to the rest of the deck joists with screws, so the only thing required for the railing to fail is for those screws to rip out. If you use an additional tension tie on the top bolt, the forces are then directed into the joist that runs under the surface of the deck, to break the joist requires forces several orders of magnitude stronger than those required to rip out a few deck screws; thus your railing will not fail unless enough force is placed on it to break the post or joist, or shear off the large screws that attach the tension tie.

[chefspenser]

Very well done-thanks for sharing! Is that a socket adapter for you drill...if so, where is it available?

[TheNecromancer13]

It's actually an impact driver, but yes. You can get them at lowes/ace/home depot in the tools section near the drill bits.

[charlessenf-gm]

"...moral guilt..." "level a post" " Look at your man, now look at me, now back to your man, now back to me. Sadly, he isn't me . . ."
Frankly, it seems a bit of over kill - but, then, I've nary a single linebacker friend to test my deck - so maybe . . . Nah!

[TheNecromancer13]

If you're going to do it, you might as well do it right. The whole point is that it seems like overkill, that way when some fat drunk person at a party does a faceplant into it, they don't go over the edge and fall to their death. Too often I see railing posts held in by a couple of deck screws, that's a disaster waiting to happen.

[amdijefri]

Would you consider writing a companion Instructible for stair handrails?

[TheNecromancer13]

I eventually hope to have a whole series of decking instructables! So yes, next time I do a stair handrail I'll make one.

[amdijefri]

Thanks!