A cleat is a flat bar that fastens to a wall to support something that hangs over it. A French cleat increases the holding power by hooking the two items together at an angle.
To make a French cleat, the wooden strip that mounts to the wall will have an angle along the top. This angle slopes down toward the wall surface.
You attach the other angled piece to the item you’re hanging; when you hook the hanging piece over the bar, these two angles create a very strong hook.
French Cleat weight limits
Properly mounted to the wall and affixed to the item you’re hanging, a French cleat can hold between 200 and 300 pounds. The manner of attachment, the surface you’re mounting to and the sturdiness of your hardware will have an impact on your success.
Prepping the Item you’re Hanging
French cleats need sturdy mounting both on the item you’re hanging and on the wall.
If the item you’re hanging is very heavy but not very thick, you may need to add a box frame around the entire back of the object for stability and strength, then mount your attaching cleat to the bottom of this box frame.
A single bar across the top may not be strong enough over time.
The Wall Attachment
Before you attempt to hang up something that heavy on a French cleat, you will need to be very sure of your wall mounting.
The first step with the mounting cleat on the wall is to make sure that you are screwed into the studs. Use a stud finder and, if your studs are metal, drill pilot holes as necessary. Use a level to make sure that the hanging cleat will support the item evenly.
Because a French cleat can bump the item away from the wall, you can avoid too much of a gap by countersinking the screws when you mount the cleat.
If your walls are plaster you may be facing a serious challenge. Depending on the age of your home, the studs behind the lathe and plaster may not be on 16-inch centers.
Locate a flush-mounted electrical box, turn off the breaker and pull the cover. You should be able to see inside the box to see if it’s attached to a stud and on which side.
This will give you your starting point so you can measure over 16 inches to determine the probable location of the next stud.
To drill through lathe and plaster, make sure you use a pilot hole to avoid cracking the plaster and creating a large hole.
Locate where you want to mount your French cleat and where you expect your stud to be. Drill a pilot hole below the spot where you’re going to hang your cleat and make sure you can see or feel the stud.
Mounting a French cleat only into lathe may hold for a while, but when it gives up, the item you mounted and the wall will pay a terrible price.
Material
You can make a French cleat out of any lumber that isn’t prone to cracking. Very hard woods, such as cured oak or rock maple, may not be the best choice. Pine and poplar can work well, as can plywood.
You’ll want plywood that is at least 3/4 inches thick and of an A or B grade. A grade plywood is cabinet grade. It will be smooth on both sides and free of knots. B grade plywood is generally of very good quality and very low in knots.
Plywood that is C grade or below is not a good choice because of the knots. Knots in wood are points of extreme hardness.
When you try to hammer or drill through a knot in a plain piece of lumber, the knot may split or completely pull out the wood, leaving a hole.
Knots in plywood are failure points; the plywood can split or tear at these places along your French cleat.
Making the Cut
You can create a French cleat with a strip of plywood that is 5 inches wide. If you have access to a table saw, you can rip down your own cleats by angling the blade and cutting this 5-inch piece into 2 each 2.5-inch cleats minus the kerf.
Mount one to the wall with the shorter edge against the wall surface and mount the other strip to the item you’re hanging so the two angles will meet flush.
If you don’t have a table saw you can still use French cleats; you may simply have to use shorter pieces of lumber. A miter saw can create a similar angle cut on shorter pieces.
Another option is to see if your hardware store can rip the angle for you when you buy the plywood; even if all they can do is rip one angle, you can cut the rest of the wood to the necessary dimensions with the tools you have at home.
Using French cleats gives you a lot of weight tolerance. Unlike hanging on a single point, there is less risk of failure across the length of a very heavy object.
Take your time when setting the first cleat on the wall and use a helper if at all possible so you get it level. It may be tempting to measure from the ceiling or the floor, but ceilings and floors can be crooked.