Sometimes the design of a home's floor structure calls for attaching floor joists to a concrete block wall. The most common means of securing floor joists to a concrete wall is to install a ledger board that matches the joist size. The method used in typical 2 by 8 floor joist construction will insure proper support for the floor joists. The installation procedure can also be adapted to any floor joist size.
Things You'll Need
- Tape measure
- Chalk line
- Framing square
- Power drill
- 9/16-inch wood drill bit
- 5/8-inch masonry bit
- 2 by 8 pressure treated lumber
- 1/2-inch by 3-inch concrete anchors
- Epoxy cement (optional)
- 1/2-inch diameter by 4-inch steel bolts
- 1/2-inch flat washers
- 2 by 8 joist hangers
Determine the designated level of the top surface of the floor joists and mark that point on the vertical surface of the concrete block wall at both ends of the wall. Snap a chalk line between the marks to establish a guideline and check the line with a level. This guideline will define the top edge of the ledger board.
Measure the horizontal length of the concrete block wall and cut 2 by 8 pressure-treated lumber to the length measured. The cut boards will be used for the ledger board(s). If your construction plans call for a different joist dimension, cut the appropriate corresponding lumber size for the ledger board(s).
Lay out anchor bolt locations on the ledger board(s). Hook the end of a measuring tape on the end of the ledger board(s) and place marks over the full length spaced 30-inches apart. For ledgers with multiple pieces, repeat the marking procedure for each board. Extend each of the marks across the width of the board(s) using a framing square.
Place a mark 3 inches in from the edge at every other line marked on your ledger board. This will mark the center points of the anchor holes along one edge of the ledger board(s).
Repeat Step 4 for the alternate marks at the opposite board edge to create a zig-zagged pattern for the anchor bolt positions.
Add an additional anchor bolt location 3 inches from each end of each ledger board and centered in the board's width.
Drill a 9/16-inch hole at each anchor bolt center point marked on the boards.
Position the ledger board(s) against the concrete block wall with the top edge aligned with the chalked guideline and mark each of the drilled anchor bolt holes on the wall. Insert a pencil into each hole to mark the wall surface, or you can insert a nail set and tap it with a hammer to place a mark in the concrete. When the anchor hole locations have been marked on the concrete wall, set the ledger board(s) aside.
Bore a horizontal hole in the concrete block wall at each anchor bolt location using a power drill mounted with a 5/8-inch masonry bit. Drill the hole depth to match the specific anchor length being used, typically about 2 1/2-inches deep. Blow or brush the concrete dust out of each hole as it is completed.
Insert a concrete anchor into each hole drilled in the concrete block wall.
Reposition the ledger board against the wall and align the top edge with the chalked guideline. Slide a flat washer onto a 1/2-inch by 4-inch steel bolt and insert a bolt into each anchor location. Tighten each bolt using an adjustable or socket wrench to secure the ledger to the concrete block wall.
Repeat Step 11 for additional ledger boards, if applicable.
Mark the floor joist layout along the installed ledger boards and extend the layout lines vertically using a framing square.
Install one joist hanger at each floor joist location and install the joists following standard framing practices.
Tips & Warnings
- Holding the ledger boards in place for marking the anchor bolt locations and installing the ledger boards is easier with assistance.
- A layer of epoxy cement can be applied to the concrete anchors during installation to strengthen their attachment to the concrete block wall. Be careful not to allow the epoxy to get into the anchor threads and prevent proper bolt installation.
- For applications where the floor joists run parallel to the concrete block wall, the floor joist that runs adjacent to the wall can be installed in the same manner as the ledger beam using concrete anchors. When this is the case, the floor joist against the block wall should be pressure-treated wood.
- There are a wide range of concrete wall anchors available and many types that work well for attaching wood framing to block walls. It is recommended you consult your local building department for information on local code requirements regarding size and spacing before selecting the wall anchor to use for this project.
- It is recommended that all wood that is installed in direct contact with concrete or other masonry be pressure-treated to resist mold and rotting.
How to Frame a Basement Wall Without a Floor Joist
Framing additional dividing walls in a basement can increase your living space, and is cheaper than building an addition to your house....
How to Install Floor Joists
A nice, solid floor is a must in any home and installing floor joists is something you can do yourself.
How to Attach Floor Joists to a Concrete Block House
Floor joists are structural members used to support floors in the majority of homes built today. For homes built with concrete block,...
How to Attach a Ledger to a Cinder Block
Builders use ledger boards to attach one structure to another. Typically made of two-by lumber, ledger boards attach horizontally to an existing...
How to Install Floor Joists Over Concrete Slab
Building a framed wood floor over an existing concrete slab can provide the space needed for electric wiring, heat venting, plumbing drain...
How to Fasten a Sole and Top Plate to a Concrete Block Wall
Foundations, framing, windows, doors and roofs get all the attention, but anchor straps hold it all together. Anchor straps secure the sole...
How to Connect Wood Floor Joists to a Cinder Block Wall
A traditional cinder block foundation wall or stem wall supports wood floor joists with a simple wood frame. The frame consists of...
How to Attach a Joist Hanger to Brick
A joist hanger is a metal bracket, designed to attach the end of a rafter, or joist to a perpendicular beam, or...
How to Use Joist Hanger on LVL
A laminated veneer load-bearing (LVL) beam is an item used in home construction. Sometimes referred to as Micro-laminated or Microlam beams, engineered...
Screw Types for Plywood Underlayment
Securing the sub floor of a home to the floor joists properly prevents floor squeaking and ensures bearing strength. Besides staggering the...