With my deck holes dug and approved by the county inspector, it was time to fill them in. Following the same approach I used when setting fence posts last year, I began by placing a couple of inches of gravel in the bottom of each hole for drainage. Local deck builders all recommend this beneath the concrete we planned to pour to secure the posts. Since I dug at least 21″ deep, adding 2–3″ of gravel still left the required 18″ depth for our county.
As I poured rocks into the first hole, a few small creatures startled me by hopping out of the rubble—tiny frogs that had been hiding in the dirt. I rescued them quickly and carried on, being extra careful to check each hole for wildlife before adding more gravel. Even so, I missed a sizable toad at first; once he announced himself I scooped him up with gloved hands and let Clara watch the rescue from behind the sliding glass door. It turned into an impromptu little nature lesson for her.
Once all but one of the amphibians were relocated, and after placing about three inches of drainage rock in each hole, I moved on to the concrete footings. Several readers had suggested pre-cast dek-blocks, but those aren’t permitted in our county. We are allowed to use other pre-cast concrete blocks, but I chose to mix my own concrete. Pre-cast blocks would have required square 12×12″ holes and perfectly flat bottoms in every location, which would have meant more digging and leveling. Mixed concrete conforms to the hole shape and levels itself, and 84 Lumber had already included concrete with my lumber order.
To mix the concrete, I opened each 60 lb bag in my wheelbarrow and added water until I reached a creamy consistency, stirring with a garden hoe. The first batch was a bit soupy, so I used less water in later batches. Each pour naturally leveled itself and formed a nice flat surface to set the posts on.
Mixing and pouring the concrete was simple in technique but tough in practice because it happened during a heat advisory. The warnings about avoiding strenuous outdoor activity were real—the work made me sweaty and exhausted fast. I did my best to stay in the shade and stay hydrated. Once all 12 holes had about eight inches of concrete, I called it a day and took a photo later in the evening when temperatures cooled.
The next day, additional materials from 84 Lumber arrived after the county required more posts and girders when they reviewed my plan. The extra pieces were modest compared to my first order, but they included the 4×4 posts I needed. I’d ordered 12-foot posts, which gave me three posts per board thanks to the deck’s low height—nice economy.
I staggered post lengths to accommodate the slope away from the house. This setup was more complex than fence posts because these posts would support substantial 2×10 girder boards running the long way underneath the deck. Joists spanning the short direction will rest on those girders and must line up with the ledger boards already attached to the house (which I now consider rim boards; they’ll provide lateral stability rather than carrying the joists’ full load).
Before setting posts, I created guides to align everything with the rim boards. After temporarily hanging joists at each end, I ran a taut nylon string along the bottoms; this represented the top of the girder where joists would sit. With the string in place, I set a post in a hole, checked it with a post level, and marked where the string met the post to indicate the future top of the girder.
My county allows either metal post brackets or notches cut into the post to support girders. I cut notches into the posts so the 2×10 girder boards could sit directly in them—a method I’d seen done successfully and which felt secure. I used a reciprocating saw to cut the notches, then returned each post to the hole, checked alignment and plumb, and staked them temporarily.
To secure the posts more permanently than tamping soil, I used Quikrete no-mix concrete, an approved method locally and the same product I used for the fence. The process is simple: pour the dry powder around the post, add water, and let it cure. It’s much easier than mixing bags manually and provided a solid base.
The third workday focused on the girders. I wished I had my dad’s help to maneuver the 18-foot boards, but he was out of town, so I improvised. I clamped the first girder to a notched post and supported the other end with a sawhorse. Using the girder itself as a reference, I marked and cut the remaining posts to the correct height, double-checked level and spacing, and then set and secured each post in concrete. The weight of the girder helped hold posts steady while the Quikrete cured.
Each girder is supported by three posts. One side of the deck was straightforward, but the opposite side required two girder sections that butt together at a middle post because the span was 21 feet—too long for a single board. I temporarily set a joist across the center to reference height and ensure continuity between the two girder segments.
By the end of a very hot day, I had all six posts set in concrete and the girder boards temporarily in place. The girders still need to be doubled (two 2x10s nailed together) for full strength, which will require an extra pair of hands—my dad will help when he returns. After that I’ll add two more posts and a girder to create the angled edge at the deck’s end. Those holes are already dug but I decided to get the main girders in place first.
It’s been a productive series of days and the structure is finally starting to resemble a deck. Once the girders are permanently fastened, installing the joists will go quickly, followed by the decking boards. I’m excited for those visible milestones. Have you been working on any outdoor projects recently? Or are you taking a more relaxed approach to summer—maybe a beach day instead?