I have always been on the lookout for a better way to make a more secure rail post connection at the bottom of a set of deck stairs. Over the years, I have tried the old ways of mounting the post on the outside of the stringer and adding a couple of bolts—a technique that never worked, and especially won’t work today because of the way that building codes have changed: Deck posts must now withstand 200 lbs. of lateral force. This new code requires a lot more thought, and the installation requires a lot more hardware.
(Note: Click any image to enlarge)
Two years ago, I worked on a large deck project with a good-sized set of stairs. Because of the overall length and height of the stairs, and the span limitations for the composite railing, I had to move the bottom posts back a few inches to make sure I could span between the mid-post and the bottom post. That’s when I came up with the first technique in this article.
Since then, I’ve started using a second approach that is a bit more acceptable given recent changes in code requirements for continuous handrail. I’ll review my second approach as well.
Start with the Stringers
First, you’ll probably notice in some of these photos that there are a few more stringers than normal. That is due to the decking manufacturer’s span limitations for stair stringers—in this case, about 11 in. on center. With some PVC decking, it can be as close as 9 in. on center (just for the stairs; not the deck itself).
After the stringers are carefully cut, I clamp all the stringers together to check them for uniformity. I use my grinder with a sanding disc to remove any irregularities.
Once all the stringers are finished, I mark the layout, starting with the level line at the height of the first riser—measuring down on the rim joist from the top of the finished decking. Next I mark on-center spacing for each stringer.
I use 2x stock for hanger boards, and whenever possible I attach the hanger boards to the tails of the deck posts to add strength to the railing and help support the hanger board.
…and then I drill pilot holes with a hammer drill into the concrete for Tapcon screws, which secure the bottom board to the concrete.
It’s always a good idea to make sure that the bottom riser is at the proper elevation—that’s where most mistakes are made in stringer layout (see Solving Porch Problems).
I also check the O.D. width of the stairs for parallel before moving on.
Once I’m certain that the outer stringers are set correctly, I install a solid 2x sub-riser—ripped to the first riser height—and I attach it with more HeadLOK screws.
Note that if you install the sub-riser on the front of the stringer, as I have, you have to adjust the face of your outer stringers for the additional 1 1/2 in. of run. After this project, and for future stairs, I decided to put the solid riser in between the outer stringers to avoid having to adjust or cut the stringers. Whatever you do, be sure to pre-drill for all fasteners at the bottom of the stringers! These holes are close to the ends of the boards and they’ll split easily.
Once the bottom riser is installed, I transfer my on-center measurements to the top of the riser.
Each of the remaining stringers must be trimmed off the bottom…
…and the front to accommodate the bottom plate and the sub-riser board.
I always end up doing a little fine-tuning to make sure all the stringers are flat and level across the bottom riser.
I use any leftover cutoffs from the 2×12 stringers to make blocking that goes in between each of the stair stringers.
I try my best to make the two outer blocks as plumb as possible because that’s where I attach the railing posts.
Once all the blocking and backing is installed, I flash the tops of the risers and blocking with a waterproof membrane.
This will prevent water infiltration from rotting out the stringers at the flat riser cuts.
To protect the bottoms of the posts, I wrap them with flashing tape, too.
I leave the posts long and then cut them to finished height afterward—it’s much easier than doing the math horizontally!
I start by driving in a HeadLOK bolt through the back of the blocking and into each post.
I carefully plumb the posts before tightening the first bolts and installing more.
The final blocking is the most critical—that’s what really secures the bottom rail post. I install a 4×4 block on the inside of the post and cut that piece snug. I have to tap it into place with a hammer, and then bolt that block in with more HeadLOK screws.
In the past I used a 2x block in that location, but I wasn’t nearly as pleased because I didn’t have enough ‘meat’ to really secure the post. The 4×4 block really resists twisting much better—the post doesn’t even flex.
Most of my stairs get skirt boards. I trace the outer stringers onto the trim boards before installing the stringers, and then I cut them out later after the rough framing is done.
I always feel kind of bad covering up all the effort that goes into framing a solid set of stairs, but that’s life.
I’ve used this same blocking technique several times.
It works well, even with long runs…
Of course, inspectors are now requiring continuous handrail on many jobs, which makes it even tougher to secure the bottom post. Now I install the post against the back of the bottom riser, but I still use some of the same blocking techniques:
I start by cutting a notch in the bottom plate, so it’ll accept the base of the post.
Next I install that same 4×4 block on the inside of the post between the stringers.
Now I use an 8-10-in. TimberLOK screw to go from the outside of the stringer right through the post and into the 4×4 block.
Though I try to use the same methods on every job—repetitive approaches are the best way to improve efficiency and productivity—I still try new techniques, especially for securing that bottom rail post. That’s one of the trickiest jobs I know of!