How To Build A Shed Floor

The second step in the How To Build A Shed series

This tutorial shows you the necessary steps for shed floor framing from laying out the rim joists to squaring the joist system.


How to layout rim joist for floor framing
The first step to building the shed floor is to install layout marks on the rim joist boards. Prepare the boards for the layout marks by cutting the rim joist boards to the length shown on the plans and then standing the two rim joist boards on edge next to each other. Make sure that the crown edge is on the top sides and the ends of the boards are flush with each other.

Now you are ready to mark layout marks on the two boards. We will be marking the floor joist locations at 16 inches on center. Hook your tape measure on the ends of the two boards, pull the tape measure down and put a mark at 16 and three quarters inches. Then put an X on the side of the mark closest to the tape measure hook end to help you remember what side of the mark the floor joist will go on. Continue making marks every 16 and three quarters inches along the edges of the boards.

The reason you go three quarters of an inch past is because the floor joist boards that you will be installing on the marks are 1 ½ inches wide. If the center of the board is to be at 16 inches on center, then the edge will need to be three quarters of an inch past the 16 inch point. It is easier to line up the edge of the board with a mark than it is to line up the center of the board. Thus the marks are at 16 and three quarters, 32 and three quarters, 48 and three quarters and so on.

Wall sheeting materials like plywood and drywall come in multiples of 4 feet, and the 16 inch layout allows the edges of the sheets to meet on the center of a floor joist or wall stud.

Once all the layout marks are made you will transfer marks to the other board and make a line across both boards using a speed square. Make sure that both boards have an x to show the side of the mark that the joist will go on.


Set the shed rim joists on the foundation
The second step in building the floor joist system is to set the rim joists and floor joists on the foundation rails.

Start by separating the rim joists and set them on the shed foundation rails. Make sure that the rim joist layout marks are still facing up and that the layout marks start on the same end of the shed.

How to build a shed floor installing floor joists
Crown each of the floor joists and then set them down on the foundation rails and align them with the layout marks you made earlier on the rim joists.


nailing floor joists to rim joists how to build a shed floor

The Third step is to nail the rim boards to each of the floor joists. For 2x6 and 2x8 floor joists you will use 3 nails at each connection. Make sure that each floor joist end is aligned with its respective layout mark before nailing.


Attaching the floor joists to the foundation

The fourth step is to attach the rim boards to the foundation rails. Line the rim board outer edges up with the outer edges of the foundation rails and then nail the rim boards to the rails by toe-nailing at 16 inches on center.

It is also recommended to use an angled framing connector every 3 to 4 feet to strengthen the connection of the floor joist system to the foundation rails.


How to build floor joist framing - squaring the joists
The fifth and final step is to make sure the floor framing is square so you can attach the floor sheeting.

This is done by measuring diagonally from corner to corner. Your goal is get both of the diagonal measurements to be the same length.

Measure the two diagonals and then move one of the rim joist boards, and the floor joists attached to it, parallel to the other side until the two diagonal measurements are the same.

Once the floor framing is square you are ready to install the floor sheeting. You can learn how to install the floor sheeting by Clicking on the How To Install Floor Sheeting Video link at the end of this tutorial.

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