How to Make Hidden Walls

Make photocopies of your house floor plans on transparent paper or acrylic. Most copy stores can do this for you. This will allow you to see one floor directly over the floor below. Tape down the first-floor plan over white paper so that you have good contrast. Tape the second or additional floor plans on one side so that the tape acts like a hinge, allowing you to flip through the plans for each floor.

Look at the floor plans for possible hidden wall placement. Look for larger rooms with a wall that has no windows and doors. A room larger than 18 feet can absorb the 30 inches of space you need to walk between the walls as a passage. A hidden passage needs to go somewhere; this can be to an adjacent, closed-off room or through a ladder up or down to a second passage or room above or below the passage. Use the floor plan to see where good candidate walls line up over each other or to locate your hidden room and a path it.

Measure away from the existing wall 24 inches along the entire length of the wall. Remove carpet and pad in the new passageway area until you reach the hardwood or subfloor. Measure the width of the wall, and cut two 2-by-4-inch boards to this length. These boards are the top and bottom plates. A plate is the horizontal cross member that supports and attaches to the wall studs at the top and bottom of a wall. Lay the boards parallel with the 4-inch side flat on the floor and with the ends aligned. Position the tape measure over the joint between the two boards. Hook the tape on the end of the wood board and measure 16 inches. You will notice that the tape measure highlights "16" in a different color; this is because code requires house studs be set at 16 inches on center.

Mark the boards at 15 1/4 inches. This is one side of the stud. Mark the board at 16 3/4 inches. This is the second side of the same stud. Make a large X between your marks to indicate your stud location. Open the tape another 16 inches to 32 inches. Subtract 3/4 inch from the 32-inch location and mark the board. Add 3/4 inch to the 32-inch location and mark the board. Make your X. Continue measuring out 16 inches, making one mark 3/4-inch short of and one mark 3/4-inch past the 16-inch location, across the entire length of your plates.

Add an "X" 1 1/2 inches wide at the ends of each plate, because you will have a stud that rests against the walls. Keeping your plates flat and aligned, place your framing square across both of your plates. A framing square is L shaped. The thinner side of the framing square is 1 1/2 inches thick, the same thickness as your studs. Line up the thin side square perpendicular to the boards and even with your stud marks, and draw lines across both plates at all your stud locations. The thicker side of the square will be parallel with the boards.

Stack two pieces of 2-by-4 inch boards with the 4-inch sides down on top of each other, and measure from the ceiling to the top of the boards. The two stacked boards represent the thickness of your plates in the finished wall. This is your standard stud height.

Decide on the location of a secret entryway. This can be an opening blocked by furniture, a mirror, bookcase, tapestry or any item larger than the opening. Frame a doorway at the location.

Use one of your stud location marks as one side of your hidden opening. Call this a king stud. Your doorway will have two king studs when you are finished. Cut your studs with a table saw. It is easiest to build a wall on its side. Separate and position your plates on their 2-inch side parallel with each other and standard stud length apart. Place a stud at each end of the two plates. Nail through the top plate with two framing nails into the end of the stud. Nail through the bottom plate the same way. Repeat for both end studs. Locate your king stud and nail it to the plates. Measure 1 1/2 inches from the king stud toward your hidden doorway. This is the location of the sister stud that will support the header over your hidden opening.

Measure and mark the width of the doorway opening you want to create. Add a measurement of 1 1/2 inches for your second sister stud position. Add a measurement of 1 1/2 inches for your second king stud position. It is likely the second king stud will not line up with your existing standard studs, which is why you measure for your desired opening. Use a tape measure to line the second king stud up with the top plate. Nail your second king stud. Cut two short studs the height of your hidden opening. Place one sister stud against the king stud on the hidden opening side. Nail the sister stud to the king, using two nails every 12 inches. Repeat for the second sister stud.

Measure the distance between your king studs above the sister studs. Cut a 2-by-4-inch board to this size; this will be the header for the doorway. Position the header over the opening, and nail it through the king studs into the ends of the header. Place all of your remaining studs on the X marks on the plates, and nail them into position. Add cripple studs above your header by measuring from the bottom of the top plate to the top of the header. A cripple stud is a shortened stud that supports the wall from the top of the header to the top plate. Cut one piece of 2-by-4 inch board for every 16 inches of opening width. Evenly space your cripple studs and nail them to the plate and header.

Stand up your wall with the help of a friend. Position the wall 24 inches away from the existing wall. Nail the wall to the ceiling joists, wall studs and floor. Trim away the bottom plate between the sister studs of the hidden opening.

If you plan to run electricity through the wall, drill half-inch holes through the wall studs. Mount electrical boxes facing the room. String electrical wire from the boxes through the stud openings, and leave the wires hanging out of the electrical boxes.

Measure and mark a piece of drywall so that it will touch an adjacent wall at one end and reach half across a stud at the other. Measure and mark each additional piece of drywall so that it reaches from the midpoint of one stud to the midpoint of another, until you have measured enough to cover the bottom half of the wall. This will be the bottom row. For the upper row of drywall, drywall should also reach from the middle of one stud to the middle of another, but the joints should be staggered from the bottom row so that no vertical joint goes straight from floor to ceiling. Measure and mark drywall for the upper row. Place the drywall horizontal and 1 inch off the floor. Mark the locations of wall outlets, and cut the drywall with a drywall saw around the outlet locations. At the sites marked for cutting, place a drywall straight edge on the side edge of the drywall, and using the straight edge to guide your utility knife, rag the knife down the straight edge to cut the paper. Remove the straight edge, and press the board away from the cut side. The drywall will snap along the cut. Use the utility knife to cut the paper on the other side of the drywall.

Screw the drywall to the studs using drywall screws. Butt the ends of the drywall halfway across a stud so that fasteners can be used on both sheets of drywall. Finish by placing paper corner tape at the ceiling and walls. Place flexible mesh tape over the drywall joints. Apply joint compound to the tape, and spread the compound out toward the edges until it is smooth. Fill the screw holes with compound. Scrape off the excess with a wide drywall knife.