If you're planning to drop a new outbuilding in your backyard, getting your shed blocking sorted out is easily the most important part of the whole project. It's one of those things that isn't particularly glamorous—nobody's going to come over and admire your foundation—but if you get it wrong, you're going to be dealing with sticking doors and a warped frame for as long as that shed stands.
I've seen plenty of people try to skip this step or just toss a few bricks on the grass and call it a day. Trust me, you don't want to be that person. A little bit of effort upfront saves you a massive headache down the road. Let's talk about how to do this the right way without overcomplicating things.
Why You Should Care About Your Foundation
Let's be real: ground moves. Between the rain, the freezing and thawing cycles, and just the sheer weight of whatever you're storing, the earth under your shed is going to shift. If your shed is sitting directly on the dirt, it's going to rot. Moisture is the enemy of wood, and the ground is basically a giant sponge.
By using shed blocking, you're doing two big things. First, you're leveling the structure so that the weight is distributed evenly. Second, you're creating an air gap. That airflow is crucial because it keeps the underside of your floor joists dry. If you keep the wood dry, it'll last decades. If you don't, you'll be looking at a soft, bouncy floor in about five years.
Picking the Right Blocks for the Job
You can't just grab any old brick from the garden. You need something that can handle the load. Most folks go for solid concrete blocks, usually the 4x8x16 inch variety. These are great because they have a wide footprint, which helps prevent them from sinking into the soil.
Some people like using those "deck blocks" with the pre-cut slots for 4x4 posts. Those are fine, but for a standard garden shed, a flat solid block is often easier to work with. Whatever you do, avoid the hollow cinder blocks if you can, or at least make sure the holes are facing up and down. If you lay a hollow block on its side, it's surprisingly easy to crack it under a heavy load.
Prepping the Site (Don't Skip This!)
I know it's tempting to just start stacking blocks on the grass, but you've got to clear the area first. You want to remove the sod and at least a couple of inches of topsoil. Grass will rot away and leave a void, which leads to—you guessed it—settling and unleveling.
Once you've cleared the area, I highly recommend putting down a layer of crushed stone or gravel. This provides a stable, well-draining base for your shed blocking. If you just put blocks on bare mud, they're going to sink the first time it pours. A four-inch layer of compactable gravel makes a world of difference. It's a bit of extra digging, but your future self will thank you when the shed is still perfectly level three years from now.
Setting the Perimeter
This is where the actual work starts. You'll want to place your blocks at the corners first. A good rule of thumb is to have a block every 4 to 6 feet along the main skids (the heavy timbers that run the length of the shed).
If your shed is 8x10, you're probably looking at two or three rows of blocks. Don't just support the outer edges; if you don't have support in the middle, the floor is going to feel like a trampoline every time you walk on it.
Finding the High Point
The trick to shed blocking is finding the highest corner of your site. Start there. Set your first block so it's just an inch or two above the ground (or your gravel bed). This is your "master block." Every other block you set will be leveled relative to this one.
If you start at the low point, you might find that by the time you reach the high point, you have to dig a hole to get the block low enough. Start high, and you'll just be stacking blocks as the ground drops away.
Squaring and Leveling
You're going to need a long, straight board (a 2x4 works well) and a 4-foot level. If you have a laser level, even better, but the old-school way works just fine. Place one end of the board on your master block and the other on the next block in the line. Adjust the height of the second block until the bubble is dead center.
Pro tip: Don't just check the level from block to block. Check the diagonals too. If your blocks aren't square, the shed won't sit right on them, and you'll have a nightmare trying to get the walls up. Use the "3-4-5 rule" or just measure from corner to corner to make sure the distances are identical.
Dealing with Sloped Ground
Very few backyards are actually flat. If you're working on a slope, your shed blocking might end up looking like a small staircase. This is totally normal.
When you have to stack blocks to reach the right height, make sure they are stable. If you're going more than two blocks high, I'd suggest using wider blocks at the bottom for a "pyramid" effect. It prevents the stack from tipping. If the slope is really aggressive, you might want to consider digging the high side into the hill a bit rather than building the low side up like a skyscraper.
The Finishing Touches: Shims and Anchors
Sometimes, you'll get everything nearly perfect, but one block is just a hair too low. Instead of trying to add a tiny bit of gravel, you can use shims.
Avoid wooden shims if they're going to be in direct contact with the ground or concrete. They'll rot or crush. Use composite shims or thin pieces of pressure-treated lumber. Some people even use pieces of asphalt shingles—they're waterproof, they don't rot, and they're great for making those tiny 1/8-inch adjustments.
Anchoring the Shed
Depending on where you live and how heavy the shed is, you might need to think about wind. A light garden shed can actually move in a nasty storm. While shed blocking raises it up, it also makes it more susceptible to wind catching the underside. In high-wind areas, it's a smart move to use some earth anchors (basically giant corkscrews you drive into the ground) and strap the shed frame down to them.
Maintenance (Yes, Really)
The job isn't quite done once the shed is built. About six months to a year after you finish, take a peek under there. The weight of the shed and its contents will have settled the ground. It's very common to find that one corner has sunk a bit.
If you notice a door is starting to rub or the roofline looks a little wonky, just grab a car jack, carefully lift the low corner, and slide an extra shim onto the shed blocking. It's a ten-minute fix that prevents permanent damage to the frame.
Wrapping It Up
At the end of the day, shed blocking is about stability and longevity. It's the skeleton that holds everything else up. It might feel like a lot of measuring and lugging heavy concrete around, but it's the difference between a shed that lasts thirty years and one that becomes an eyesore in five.
Take your time, use a good level, and don't be afraid to redo a block if it isn't sitting quite right. Once that shed is finished and you're standing on a rock-solid floor, you'll be glad you took the time to do it right. Happy building!