Finally got the Costco pool set up on the new PVC deck and it feels solid

I did the exact same thing with a 10-foot Intex round pool a few summers back. Our deck is built with 2x10 joists on 12-inch centers, so I figured it was overkill for anything we’d throw at it. It looked incredible next to our Traeger grill, and just like you, I didn't hear a single pop or groan during the initial fill. We spent the whole weekend lounging in it without a care in the world.

The trouble started about four days later when I noticed the sliding glass door to the kitchen was suddenly sticking at the top. Even though the footings were deep, the sheer weight—thousands of pounds of water—was causing the ledger board to slightly compress against the house siding. It wasn't a catastrophic collapse, but the structural shifting was enough to throw off the alignment of the whole house frame in that corner. Even if those PVC planks look perfect, I’d keep a close eye on your door frames and the gap where the deck meets the house. Water weight is no joke; a full pool can easily outweigh a heavy SUV concentrated in one small spot. We ended up draining ours and moving it to a leveled patch of sand in the yard just to save our door headers from more damage.

I went thru this exact phase with a Summer Waves pool a couple of seasons ago. everythign felt stable at first, but after about two weeks, I started noticing that my sliding glass door was sticking. It turns out that even without audible creaks, the sheer weight—over 3,000 pounds for just a few hundred gallons—was causing the ledger board to pull slightly away from the house siding. It is not just about the joists holding up; it is about how that concentrated load transfers down to the dirt. After a heavy rain, the ground softened, and one of my concrete piers settled about half an inch deeper than the others becasue of the constant pressure from the pool. I had to drain the whole thing and spend a weekend under the deck with a bottle jack and some 6x6 posts to level it back out. Now I keep the water features on the patio. I still use the deck for the grill and the seating, but I realized my "rock solid" feel was a bit deceptive once the soil conditions changed. It is amazing how much 8 pounds per gallon adds up when you are talking about those Costco-sized inflatables.

That resort vibe you're talking about is exactly what I'm trying to build on my own place! I'm new here and just getting into all this deck stuff. Having a pool right next to the grill sounds like the best summer ever! Quick question for the group though—do you find that the PVC planks get relly hot in the sun compared to wood? I'm looking at swapping my old boards for PVC soon and I'm worried about burning my feet while walking to the pool!

Wow, I really didn't know water weighed that much. I honestly thought if the boards didn't break immediately, it was probaly totally fine! Is the ledger board the part that actually bolts into the house wall? I'm still trying to learn all the names for the different parts of the structure.

If I don't have a sliding door nearby, are there other signs I shold look for to see if the deck is struggling? I’m mostly worried about the posts sinking into the dirt or something if I try this.

While your concrete footings might be sufficient for static residential loads, you relly must consider that a standard deck is typically engineered for a live load of only 40 pounds per square foot, whereas even a shallow pool filled to a depth of only eighteen inches exerts approximately 93.6 pounds per square foot, wich effectively more than doubles the design capacity of your joists. I whould be particularly concerned about the potential for perpendicular-to-grain crushing at the ledger or the beam interfaces, as the structural integrity of the wood fibers can be compromised under such extreme hydrostatic pressure long before you hear any audible structural failure.