Once you’ve determined the location of your shed, we need to prepare the area where your shed is going to sit. Whether you decide to build a shed foundation on a concrete pad, block piers, or skids, we want to do a few things that you would not be able to do once the shed is built.
Preparing The Site Before We Build A Shed Foundation
Clear the area where the shed will be placed of all weeds, grass, or any other ground cover. Even if you want to build the shed on piers or skids, it’s a good idea to clear out about 4″ of top soil and later replace it with gravel that we will tamp down to compact.
Make sure the area is nice and level. If you need to add dirt to make the area level because one end sits higher or lower than the other end, do what ever it takes to make the pad level.
Once you have level ground to build on, spray the pad area with insecticides. This will help to keep damaging insects from destroying your shed. You don’t want to see all this time, effort, and money go down the drain in a few years due to insect infestation.
The next thing we want to do is put down some kind of barrier to prevent weeds or grass from growing up into the building. Spray some round up all over the pad and then purchase some plastic (use black to keep any light from getting through) or a cloth weed barrier you can pick up at the local hardware store. There’s nothing worse than having to clean out weeds that are trying to grow through the floor of your shed.
How To Build A Shed Foundation – Concrete, Block Piers, Skids
If you went through and made a plan on the foundation, your all set to put it together. Depending on the type of foundation your going to have will determine how you start. In the following paragraphs, I will go over each type of shed foundation and explain how to complete it so when your done, you will be ready to start framing the shed walls.
Building Concrete Shed Foundations:
Building a concrete foundation for your shed will probably be the most difficult of the three types of foundations to build. There is more preparation time involved, but in the end I believe the concrete foundation gives you the most stable and secure platform to set your shed on.
The thickness of the shed foundation needs to be about 3-4 inches thick. The forms you use only need to be standard 2×4′s. Begin by nailing the 2×4′s together to form the desired layout that the structure will sit on. Remember that the inside of the forms will be the same as the shed itself, unless you want a pad that is larger than the structure itself. You can decide for yourself. The example I use is if the pad is the same size as the shed.
If your shed is 6′x 8′, the inside measurements of the forms when nailed together will be 6′x 8′. Place the forms in the location where the pad will sit. Make sure the pad is level before you start. Nail the forms together and set them in position where the shed will be. Take some wood stakes (2 per corner) and place them about 6 to 8 inches in from each corner. Pound the stakes into the ground and up against the 2×4′s.
To level the forms, use concrete nails to secure the forms to the stakes and adjust as needed to level. Make sure the form is square by measuring from one corner diagonally to the other corner. Then, measure the other diagonal and adjust the forms as needed until you have a form that’s square.
Next, add a couple of inches of stones inside the forms and tamp down firmly. Cover the stones with a layer of sand and water down so the bedding is compacted. Once this is done, your ready to pour your concrete and finish it. Let the concrete set up 24 hours before you remove the forms and begin framing on it.
Building A Pier Foundation:
When building a floor with piers as its support, there’s two different types of piers to choose from. The first type is pier that has a flat top where the floor joist sit. The second type (which is more secure) have crosses inset where the floor joist sit down in the piers giving the floor more stability.
There are 2 ways to set up concrete piers for your floor system. The first way is to lay down a couple of inches of stones where you originally took out ground when we first leveled the site. Tamp the stones down until they are compacted. Then, place the piers on top of the stones.
The second way is to determine where the piers are to be located and dig holes a couple feet deep and pour concrete into them and then set the piers on top of the concrete. This way gives less of a chance that there will be any movement of your shed. Add a layer of stones before you put down the floor joists and plywood flooring.
Depending on the size of the floor will determine the spacing of the piers. Place one pier on each corner, then place other support piers about 4′ apart around the perimeter of the floor. Place support piers under each floor joist no more than 4′ apart. The more support you give to the floor, the more solid it will be.
After you have the piers down and the floor joists in place and nailed together, you can sheet the floor and finish it off by using wood floor screws to hold down the sheathing. I recommend using screws and glue to finish the floor instead of using nails. It give the floor a good solid feel and holds everything together better. Nails alone tend to pop up after a while and loose their grip.
Note: All material that comes in contact with concrete, earth, or ground moisture should be pressure treated wood. This type of material is injected with chemicals that fight insect infestation and prolong the life of the wood by fighting against wood decay. DO NOT BURN THIS MATERIAL OR ALLOW PETS TO CHEW ON IT. POISONOUS!
Building A Skid Foundation:
The skid foundation is similar to the pier foundation. The difference is that instead of using piers to support the floor joists, we will be using 4×4′s, 4×6′s, or even 4×8′s as supports for the shed.
Lay down a layer of stones a couple of inches thick. Tamp down to compact. Lay down the skids in the direction that will be the length of the building. Place them no more than 2′ apart if your using 4×4′s as skids. You can increase the distance between the skids as you go up to larger skids.
See the picture to get a better idea of how this is put together.
Once the skids are down and the floor joist are nailed to the skids, you can then cover the joist with plywood and fasten it down. And your now ready to go to the next step in the process of building your shed which will be framing the structure.
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