I'm about to build a 12' x 12' shed. I've drawn the plans, elevations and sections in AutoCAD and have every detail hammered out. I'm going to dig 4 holes for the footings and am planning on pouring concrete in the holes to make a base for CMUs. The question I have is how do I make sure that once I've stacked and mortared the CMUs that the top of them are all at the same elevation height so the floor joists that rest on them are nice and level? Do I use some sort of stake and water level or laser level to make sure that each poured base is at the same elevation? Do I just fudge it in the thickness of the mortar between the CMUs so that the last one on top of the stack is level with the others? What's the process that the pros use?
Either a water level or a laser level will work. You only have to make sure the top of each is level - "close enough" is okay for the bottom.
Since you're planning on using concrete to fill the cells, I'd use Sonotube and forget about the block. Excavate, pour the spread footings, insert and plumb Sonotube, backfill, laser level to mark the outside of the Sonotube for the top of the pour, poke a nail through the side of the tube, pour concrete and install anchor bolts.
I'd also use more than four points of support to better distribute the load and minimize differential settlement. People often underestimate the amount of load they'll put in a shed, and yours is a substantial size.
I've seen those before and they look much easier. Originally I wanted to use CMUs because they're square. I see on the sonotube's website that they make square ones. I didn't want to use circular forms because I don't want the footing to extend out beyond the wall but a square form wouuld work great. I've never seen them in Lowe's or Home Depot. I will find a distributor and see if I can't snatch some.
I will definitely consider using more than just one in each corner since forms would be quicker and easier.
If I use these forms, do I still need to pour a base for them? Should I be putting gravel in these holes?
The "pro's" would probably use a transit, but a laser level would work fine if you have one. I personally use a simple water level made from an old wine bottle and a length of 3/8" clear tubing. It's accurate, and can work around corners or other obstructions a laser or transit would have difficulty with. A home built water level is also cheap. :)
I didn't realize square sonotubes were available, all I've ever seen is round. In any case, you could also build some simple square forms out of plywood and 2x4 reinforcements. Remember to add some rebar to your posts and footings.
Have you considered pouring a concrete slab? It would be faster, easier, and cheaper than pouring support columns and building a floor. You could build a simple perimeter form with 2x8's or 2x10's, and dig down on the edges for perimeter footings. If you're in an area with deep frost lines, you could dig holes for "posts" and pour the slab and footing posts at the same time.
*Getting off topic, but have you considered the property tax ramifications of building a shed with permanent footings. In my area of NJ that is considered an improvement and contributes to the tax base of the property. Everyone around here just lays out a gravel base and puts a shed with skids on top.
I have another way also. build your frame out of 12' x 12' joist. Temporarily stake it level. Prior to that dig your holes and place the frame over them. Level the frame, and stake it, fill the holes with concrete and use a post or whatever to the frame. Use post bracket attachment and imbed the post in the concrete and attach to the frame.......Let it set, and then take out the temporary stakes...... voila. just one way to do it. Most just pour the concrete, and set pier blocks in the concrete. then after the concrete is set, cut small posts to support the floor system so that it is level. the posts are cut level, the piers are pored without worrying about level.
In addition to that good advice, the OP should verify the zoning requirements. Some areas don't require a permit for a shed that's under some arbitrary size (10' square in my area). Over that, and you do, which opens up many cans of worms. Others have posted about digging a hole and just filling it with concrete. That's not "legal" according to some codes. In my area the permit and foundation trigger required and separate inspections for excavation, footing, framing, etc.
The caveat there is that the 2x12 frame would weigh somewhere between
700 and 800 pounds. Not exactly something that a DIYer would "place" easily, and it's not clear if the OP has help on hand.
Leveling the deck platform for smaller sheds and decks and then pouring the concrete works well, but after a certain point working around the holes and frame just takes more time and presents certain risks. I doubt the OP will be operating at contractor speed, so there's no great time lost by doing the foundation first.
The caveat there is that the 2x12 frame would weigh somewhere between
700 and 800 pounds. Not exactly something that a DIYer would "place" easily, and it's not clear if the OP has help on hand.
Leveling the deck platform for smaller sheds and decks and then pouring the concrete works well, but after a certain point working around the holes and frame just takes more time and presents certain risks. I doubt the OP will be operating at contractor speed, so there's no great time lost by doing the foundation first.
So you want to go footing and CMUs and beam instead of pier and beam...
Dig the holes, throw in a chair in each hole. Pour the footings and piers (sonobouy or 1X12 cedar form with rebar tied to the chair). Done.
How many footing/piers depends on the anticipated weight it has to support. But that was left out for a negative reply from you or another respondent anyway. I'll bow out here.
Sorry for my ignorance, but what's the 'chair' that you're talking about thowing into each hole?
I talked to the guy at the Project Desk at Lowe's last night and he suggested that I just dig the hole and make a box shaped form out of plywood and put that on top of the hole and pour the concrete into it all. That way I have the square form above ground that will make a nice corner and I don't have to worrry about making and removing a form underground.
What do you guys think about that solution?
I am definitely considering more supports after reading everyone's comments. Better safe than sorry anyways!
A chair is a small platform, for lack of a better word, that supports the rebar and keeps it encased in concrete to the depth required by code. Otherwise the rebar rusts and loses its strength.
There are many ways to do it, but you haven't addressed our questions about your zoning and code situation. It's pointless to give advice if it's prohibited construction.
BTW, big box stores are absolutely the last place you should be asking for construction advice. They're notoriously bad and ill-informed. You'd do far better to check out Fine Homebuilding's web site or The Journal of Light Construction. Better yet, hie thee to a library and peruse the home improvement aisle. It'll be time well spent.
I called the county and there's no need to pull a permit for this size shed. The other sheds in my community all have foundations as well. I've seen sheds around where I live that have foundations and some that don't. It's a rural county. I've seen some pretty crazy stuff being built :)
I figured I would ask the guys at Lowe's since I was there getting some stuff anyway. Couldn't hurt.
I did by a book about building sheds. There's plenty of good advice in the book, but they either poured a slab or just set the shed on timber "sleds". They didn't show anything about digging for a foundation like I want to do. I really don't want to build a slab because I am planning on storing stuff under the shed and hiding it with lattice all the way around. It will be a good place to put certain types of things.
Sorry for my ignorance, but what's the 'chair' that you're talking about thowing into each hole?
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Start from the beginning, I assume you understand what pier is, and a sonobouy as well.
A "chair" is what a pier sits on to prevent side to side walking or sinking.. Its made of rebar covered by concrete. The "chair" has emanations of rebar, integral to the rebar in the chair, above it as part of the pier itself.. The pier is then formed up and poured over this same rebar emantions from the "chair" below. A sonobouy can be substituted but must use the same rebar emanations from the "chair".
Contrary to Rico's thing on rust. Nothing could be further from the truth. No significant rebar rust can occur using the method I mentioned, but has nothing to do with the purpose of a "chair". A "chair" is more lilkely to be used if the soil can't support the pier as in fractured rock, soft soils or sand. Hillside foundation is also a factor in choosing a "chair".
"Chairs" are available for sale. They can easily be created on-site if you're into cutting rebar and tying same. Its easier to make a "chair" specifically for your needs rather than purchasing a generic "chair" and working your way around that chair with mods and so forth for tying into the pier or sonobuoy. Typically, in an on-site "chair" fabrication, the hole is dug and the chair is "thrown" into the hole. Concrete is poured on the rebar chair. The rebar emantions for the pier are adjusted for plumb and square with the anticipated foundation prior to the pour. A couple of days later, the pier is formed up and poured..
A simple footer below the frost line may be ample. I don't know your locale and soil and elevation slope specifics. Not knowing that, I tend to overkill based on the unknown. Read A_S_S_U_M_E.
The "chair" is simply a way to hold the rebar up so it ends up in the middle of the concrete instead of laying on the ground (where it would add no strength). You can buy specially made chairs at home centers or other sources, but resting the rebar on a piece of a brick or stone before pouring the concrete usually works just as well.
Have you thought about pouring a slab and building a taller shed with a "loft" floor inside? You could construct the floor at whatever height you want, and still be able to store things under the main floor. This would keep your lower items off the dirt, out of the weather, and away from bugs/thieves.
I did several sheds in our neighborhood and I just set them on blocks on top of the ground. No foundations. You really do not need a foundation for a small shed.
Thats what I did, everyone recomended it and my area goes to -15f, my shed is maybe 9x12, needed no permit, is not taxable. Just every 3 ft or so is a block, its alot easier and cheaper than a footing. I could only see a footing necessary if you wanted to bolt it down because of high winds. The shed is off the ground for air circulation and screening used to keep critters from making nests under it.
Thats what I did, everyone recomended it and my area goes to -15f, my shed is maybe 9x12, needed no permit, is not taxable. Just every 3 ft or so is a block, its alot easier and cheaper than a footing. I could only see a footing necessary if you wanted to bolt it down because of high winds. The shed is off the ground for air circulation and screening used to keep critters from making nests under it.
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I agree. Its all depends on the slope, if any, and soil conditions. "Blocks" are easiest to seat in both level, square, and so forth. Whether these "blocks" walk later depends on what I just stated before.
So, just because one solution works for one individual and their situation does not mean it will work for another person and their own situation. That is a dangerous implicaiton if that's what's being implied.
Whether a shed "blows away" due to high winds has little to do with its foundation. A building, including a shed, is most likely to be decapitated, then the walls go due to high winds. Am assuming the shed has adequate weight due to itn internal storage matter in this instance.
Dave, Your ramblings clearly show your ignorance of reinforced concrete construction. NO reinforcing steel should be closer than 3" to the subgrade or closer than 2" to an exposed surface. When rebar rusts it expands and causes the concrete to fail; the expansion of the steel caused by oxidation or expansive rust creates more force than the tensile strength of concrete can overcome. This is the reason highway agencies all across the country specify epoxy coated rebar for decks, parapets and any other concrete exposed to the weather and or chlorides. That means NO calcium chloride when it gets chilly.
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