So I am building a ground-level deck, following this video more or less. I got enough of those concrete support blocks with notches at the top to hold the joists in place, to put one at each corner, one between every two corners, and a few in the center to support the joists (2x6x8).
The various videos and diagrams seem to show at least one concrete support block for EVERY joist not connected to a corner, i.e. all the ones in the middle that will support the deck planks once they’re on top of the frame.
However, the prospect of going back to Lowe’s and buying more of these huge, heavy support blocks and burying them (with gravel underneath for drainage) under every single one of the eight joists that will be in the center, does not really appeal to me. That’s when I realized I already have a bunch of concrete blocks lying around, left over from another landscaping project - they’re not the notched pylon-type blocks, of course, but I wondered if I could get away with just burying these in the ground to support the joists, rather than having to use more of the deck blocks?
I should just add that I would be burying those blocks into the ground, on top of several inches of gravel - they would NOT be just sitting directly on the dirt.
Looking up deck building and frost line - now has me concerned about whether or not this setup is going to be sufficient. Most decks are built on posts, which are set into the ground several feet (to get below the frost line) with concrete poured around them. I really didn’t want to go to the trouble of doing all that for this project, hence the concrete blocks. So…what, are these blocks going to crack now once it gets cold?
No, you’re good. The point of the floating deck is that it all of the parts kind of float together through temp changes and frost heaving. Make sure all of the blocks have gravel under them.
Yes, they all have, or will have, about 2 inches of gravel underneath.
The good thing about wood is that it’s a naturally flexible material that is capable of flexing and bending a little and still maintaining its strength. I was more concerned that the frost might cause the cement blocks to crack.
I wouldn’t bother adding the bricks. If it sags you can always go back and throw some in but I don’t see it happening. If that were 1 story up you wouldn’t have posts under each joist. If the load bearing board is bending then it’s undersized.
I asked about the flooring because the non-wood boards need closer spacing underneath to keep from sagging. One thing I’d recommend is torx head screws. They’re the least likely to strip out.
