I am building a shed from a kit. The floor kit has a pretty standard 8×12 layout, but the instructions state that it should be leveled by setting it on 3 parallel treated 4x4s (runners), and that the 4x4s should be leveled by putting supports under the 4x4s about 4' apart.
The sample they show illustrates supporting the 4x4s setting on dirt, and they suggest stone blocks on the ground, 4 inch wood blocks above any blocks, then a bit of asphalt shingle, and finally the runners sit on the shingles.
I'm setting the deck on the concrete patio, shown here. The low point is the top left, high point bottom right. We do get water pooling on the patio in the rain but it does drain off within 24 hours.
When setting the treated runners on concrete should I still lift them off the concrete with blocks? Can I just put pieces of shingle under them at the high point and use wood blocks + shingle to lift the other points to be level?
Best Answer
I would want to keep the shed as low as possible so you don't have a tall step up into it. Instead of pressure treated 4x4s I would consider composite lumber, which you can reasonably expect to last as long as the shed. It's more expensive of course, but you only need three pieces.
I would pull drylines at level and measure every 16 inches between the line and the existing concrete. Transfer those dimensions to your footing lumber and cut the tapers into them. I think I'd shoot for about an inch at the high corner, just enough to allow water to flow underneath the deck without soaking it.
This approach gives you high durability, full contact support of the footings, plenty of support for the shed floor framing, and a low step-in height.