No Measure DIY Shed Floor

Introduction: No Measure DIY Shed Floor

About: The Dogfather, Chris Giffrow || Youtuber, Maker of things... mostly from wood.

For the past few months I've spent a ton of time getting into complex joinery and fine woodworking. However, my workspace has found a way to be congested and not so aesthetically pleasing. ie. blue handled harbor freight pliers on the walls, plywood cleat systems covered in dust and cobwebs, etc.

So in an effort to start freeing up my walls and workspace, I bought a shed. It was a basic steel shed and I've got a patch of concrete next to my shop that is perfect to house it, but my house is on a bit of a slope, and water runoff directed flow into the shed. Getting a proper floor in there was the only thing that made any sense and I chose to just whip up something simple with pressure treated 2x4's and plywood.

Essentially I built a deck floor that was placed inside the shed. The principles are all the same: joists, ledgers, and braces capped with a floor. Your version can be any size and with a number of the tricks I used in this project, you can likely do the same and scale it accordingly as I took no tape measured measurements for the entirety of the build (aside from checking my work for the camera).


Pressure Treated 2x4s (6) [I actually ended up with almost a whole 2x4 extra so scale accordingly]

4x8 sheet of plywood 3/4 inch (1) [If you follow my "design" of joist brace spacing every sixteen inches then you could probably go with a much thinner sheet of ply.]

Construction Adhesive

Pocket Hole Jig and Screws (linked below)


Circular Saw

Chop Saw

Speed Square


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Outsunny 3' x 8' Backyard Garden Tool Storage Shed with Lockable Door, 2 Air Vents & Steel Construction:

Duratec Positioning Squares, Woodworking Tool, Clamping 90 Degree Angles for Picture Frames, Boxes, Cabinets or Drawers .Set of 4pcs (4 Inch):

Ryobi P508 One+ 18V Lithium Ion Cordless Brushless 7 1/4 3,800 RPM Circular Saw w/ Included Blade (Battery Not Included, Power Tool Only):

Ryobi P197 Battery ONE + (PLUS) Compatible Replaces P108 Rechargeable Lithium Ion 18 v Volt 4.0 Ah / 72 Wh UL Listed Faster Recharge Single Battery with Fuel Gage:

Kreg Pocket Hole Jig 320 (Pocket Hole Jig 320):

Minwax 140030000 Ultra Fast-Drying Floors Polyurethane, Gallon, Clear:

Kreg SML-C250B-250 Blue-Kote Weather Resistant Pocket Hole Screws - 2 1/2", 8 Coarse, Washer Head, 250 count:

The Complete Japanese Joinery (Book):

XFasten Double Sided Tape:

Step 1: Cutting Your Joists

Your joists are essentially your long boards and that'll bear a lot of the weight load. I use a trick for finding inside measurements by taking two pieces of scrap that are less than the overall length and sliding them out till they touch the sides. Clamp them and then move that piece to your workpiece to mark.

These pieces of plywood interestingly enough came from the box that the shed came in, so I didn't have to look far to find scraps. This relative measurement trick will save you a ton of frustration.

Furthermore, the joists will be capped on the ends of the shed by a ledger, so to calculate the ultimate length of the joist that I require, I took an off cut of my 2x4 and marked off two thicknesses (or thickni? or thiccnesses?) and then cut that to length. With that, I'm able to use that first piece as a story stick to measure off the other two joists.

And in the event you haven't seen this cross cutting rig, I just clamp a square to my 2x4 and use it as a fence to get a square cut. This particular saw's base plate edge is exactly 1 1/4 inch from the blade. You can take the time to measure that out, but I typically line the blade up to my marker line, slide the square up, and clamp accordingly. Easy peasy japanesey.

Step 2: Cutting and Aligning the Ledgers

As said before, the ledgers cap your joists on either end, so I used the same relative measurement trick to get the width of my shed and then take that to the workpiece to mark off.

I happen to know that my shed is 3' wide so joist placement is going to go exactly halfway. For most subfloors or decks, joists should be spaced 16" apart. I end up just a little bit over that, but with the joist bracing I have and the 3/4 ply this flooring will be plenty sturdy, likely overkilled.

To calculate the center of the board, I bump in from either end twelve inches and strike a line. You don't necessarily have to go in 12" from either end, but finding center on long boards this way gets a bit tricky as the intersection point is harder to delineate. Going 12" from either end in this instance makes the "X" that you're going to form a lot more clearer. Anyway, I digress...

Strike a line from the opposing corner to the other and form an "X" over your workpiece. The center point of that will be the middle of your board. It'll actually be the true center of your board, both at thickness and length, but really the length in this instance is all you're concerned with. Do the same on the center joist, but just do the "X" at the end, drill some pocket holes, and then align your center marks and screw together.

As Emeril says: "Bam."

Step 3: Joist Bracing

Now joist bracing is a lot of times unnecessary, especially if you've ran your joists exactly 16" apart and they're not uber long. However, since I was a little wider, I went with braces and I spaced this 16" apart as well. Super overkill. Do a bit of research on weight tolerances if you want to reduce material. Now when using reference pieces, it's important to understand blade kerf and how to remove material to make sure you're getting the perfect cut and fit. Since I'm using a fat marker here, 1/16 of a line on average, I strike the line off the edge of the piece I'm referencing onto my workpiece. Then when I make a cut, I want to remove that entire line to ensure I am at the same length as my reference piece. It's the Japanese carpentry concept of take the line, leave the line, or split the line. Taking the line brings me to reference. To nail the joist brace spacing, there's some 16" scraps that I'll use on either side as I pocket hole the boards in and any boards that are proud of the center joist are brought down to surface using a door planer.

Step 4: Affixing and Finishing the Top

Now this is where your order of operations might need to differ from mine. If I had a time machine, I’d go back and screw the plywood on first, trim, and then remove the plywood so that the substrate can be put in the shed and then attached with construction adhesive and screws after. The way I did it, made this a fair bit cumbersome on the install but we’ll cover that later.

I used a festool track saw track as a fence to trim the excess plywood off and thoroughly upset a bunch of grouchy folks on the internet. If you don’t have a track saw track, it’s no worries. I afterward used a piece of plywood and some double stick tape to do the exact same thing.

Welcome to the laziest finish application ever. Water based polyurethane for floors and just dumping it from the bottle. I’m using a semi smooth paint roller and I’m just gonna do one thicc coat and call it a day.

Step 5: Install

Now as I said before, I should have installed the top after it was in the shed already, but with some help from my neighbor and a little shimmying we somehow got it to settle just right.

The ideal way to do this would have been to pre-finish the top outside and then re-attach the top inside the shed. I probably could have actually moved the subfloor in by myself had I done that.

Great Stuff expanding foam fills the space around the floor to keep water and more importantly critters from coming up and in.

Step 6: You're Done! Rejoice.

That's it folks! I've got a lumber rack coming soon and then it'll be a full clean and paint job for my actual shop before trying to do a proper hand tool cabinet, so hopefully you won't have to suffer through too many of these super DIY projects before we're back to the good stuff. Hope you learned something! Don't forget to watch the video and thanks always for your support.

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    1 year ago

    You want treated ply if its going down there . If you must seal it you should seal the bottom first before you attach it . Treat the edges tripple . The foam down the sides will serve well to hold moisture against the steel and should get the rust going nicely and keep it going.