I want to build a 12x14 shed.

I live in Canada where it gets very cold, so I want to build the shed on concrete piers set at least 3-4 feet deep.

Home Depot provided me with a rough plan for the floor. The floor joists run along the 14' length of the building, with one girder in the middle.

My question is how many piers do I need to support a building this size, where do I set the piers, and how do I assemble the girder and the rest of the floor on top of the piers.

 

Since there is a girder across the center, I'm pretty sure that there will another one at each end. That way the shed can sit level, rather than rocking on the center girder.

What size are the girders? I would guess that the are 4X4's, since that is all of the height that they need to get forklift forks under the shed.

9 piers total -- 3 across each end and 3 under the center girder.

The only way to get in to attach the girders to the piers is goint to be removing sections of flooring since the shed is prebuilt. A Skilsaw set just deep enough to cut through the plywood, and add blocking before you reinstall the cutout(s). You may be able to reach in to get the end piers connected, in which case you'll only need access to the center girder.

 

I'm building the shed myself. I have shed plans but not for the floor. I need to know how to make a floor.

I want to use 2x8's for the end plates adn all the joists.

I don't know what to use for a centre beam that will be strong, but not take up too much room under the shed.

 

Site built -- that changes everything!

Do the 9 footings. Set post bases in the top of each, with the side plates oriented so that the girder can pass through them. Use a 4X6 on edge for the girders. don't worry about the tops of the footings being level with each other. Once they are in, you'll find the highest and level everything off of that with shims or posts, as needed. (This is just like building a deck on a slope, only you don't need a post for the highest footing.)

Girders need to be 4X6's on edge, given that they will be spanning about 6' between the footings. Joists can be 2X6's rather than the 2X8's that you are thinking about. At 24" O.C., 2X6's can span 6-1/2' easily. That part is just a deck. Once you have the framing, install the flooring, then build the walls, the roof, side it, and you are on your way.

 

The ground is pretty level. I was thinking to make the footings at the four corners as level as I can, then assemble the end plates right on top of the piers. That way if there's ever any movement in the piers, we can level it out with some shims. And more importantly, I don't want to be measuring where to put post holders in the wet concrete. my father in law's gonna be the one helping me with this job, and he gets impatient when I want to double check everything. So I'd like to keep the surveying part of the job as simple as possible.

What I had in mind was to start by assembing the endplates and side plates on the ground, right where I want the shed to be. Then once I've got a 12x14 box and checked it's square and lines up nicely with the house, use that to mark where my piers are gonna go, instead of trying to figure everything out with string and math.

Then once my holes are dug, and it's time to set the piers, all I have to do is take a string level and line them all up the same height.

 

That makes sense -- set the 4 corners first and work off of those. The end footings and bases for the middle girder then are just a matter of locating them half way between the corners. The row down the center -- the center footing of each beam -- is just a matter of finding the center of the beam and setting them there. The only time consuming part will be getting the 4 corners set square.