How to Float a Concrete Bench From a Wall

Find the stud at the midpoint where you want the bench to hang with an electronic stud finder. Mark the height an inch lower than where you want the bench to sit and draw a 48-inch horizontal line across the space. It is important that you drill the holes directly into the horizontal center of the supporting studs, so this means you will have to remove a small, approximately 2-inch-wide and 1/2-inch-high, portion of siding in front of the middle stud. Use a wood or rotary saw to cut through the siding.

Set a drilling jig onto your drill to hold it steady. Place the bit into the chuck and drill a 3-inch hole into the center of the middle stud along the horizontal line. Measure 16 inches from the center of the middle stud to each side for the location of the outer supporting studs. Drill through the siding and 3 inches deep into each stud.

Coat the end of each stainless steel rod with adhesive and slide them into the holes so that the rods project from the walls approximately 11 inches. Let the adhesive dry while you work on the studs.

Mark the center of each stud along the 2-inch side. Drill two of the studs completely through from side to side along the center mark. The hole must be perfectly straight so use the jig to keep the drill level when cutting into the wood. Measure 16 inches to each side of the center hole and drill matching holes through the wood. Before starting to drill, ensure that the holes on each side will match up with the rods projecting from the side of the wall.

Fill in the hole that you cut into the siding with wood putty. Allow it to dry.

Drill matching holes 1 inch along the edge of the stainless steel flashing. Slide the flashing over the rods with the higher margin on the top. Coat the inside of the holes in the studs with the adhesive. Slide the first two studs over the rods and push them against the flashing. There should be about 1 inch of flashing exposed above the studs.

Measure the length of the exposed rods still left to be covered by the last piece of stud. They should be 2 to 3 inches long. If they are longer than 3-1/2 inches, then cut enough off to reach the correct size.

Drill into the last stud the same as the first two but instead of drilling all the way through the wood, just go deep enough to set it on the rods. Place it on the rods and force all three studs firmly against the flashing. Staple the studs together along each seam so that they do not separate from each other. If the studs do not quite match at the ends, then use the saw to shave them down to a better match. They do not have to be exact, just fairly close. The same applies if one stud is a little higher than another.

Mix a 40 lb. bag of concrete, according to the instructions but keeping it a little on the thick side. You want it stiff like cake batter. When it has reached the desired consistency, scoop some of it up with a trowel and begin applying it to the top of the bench just as you would batter a cake. Start in the corners and work your way toward the middle with about an inch of concrete as the surface. Do not go higher than the steel flashing in the back near the wall. A rustic look will allow for flaws in the concrete; but if you take your time, you can completely smooth out the top. There should be a slight slant from the wall to the front to allow rain water to drain off.

Apply concrete along the sides and front, again the same as icing a cake. If the concrete falls off as you apply it, then nail some scrap plywood along the bottom of the bench on the sides to give a temporary lip around the bench bottom to hold the concrete. Remove the plywood after the concrete dries.