How to Add a Porch Yourself

Mark out the basic porch area, rake it free of grass and debris and level it. Lay out the specific size with stakes and builder's twine and cover it with a membrane to block moisture and weeds. Lay a couple of inches of gravel over the membrane to secure it and aid in drainage from water that gets under the porch.

Dig holes with a posthole digger at the outside corners to install precast piers with metal joist holders in the top for 2-by-6-inch lumber. Dig the holes at least 2 feet deep or below the level at which ground freezes. Square the corners by measuring diagonally with a tape measure until both angles are identical.

Set the piers in the ground, making sure the holders are aligned perpendicular to the house wall, and with a slope from the house wall of at least 1/4 inch per foot, or 2 inches for an 8-foot-wide porch. Start the slope from below the bottom of the frame of the door that opens onto the porch or the top of a house rim joist. Plumb the piers with a level and secure them with dirt or concrete.

Strip any siding from the house to expose the rim joist, which should run right below the door frame. Install a 2-by-6-inch ledger board. Nail it temporarily in place with 16d framing nails and a hammer, using a level to get it level; make it the width of the planned porch. Mark attachment spots on the ledger and drill pilot holes into the rim joist with a power drill and 3/8-inch bit. Fasten the ledger with 1/2-inch lag bolts driven into the rim joist with a ratchet wrench.

Put metal joist hangers on the ledger aligned with the joist holders in the piers. Fasten hangers to the ledger with 3-inch galvanized screws and a screw gun. Set 2-by-6-inch band joists in the ledger hangers and the pier tops and secure them with galvanized screws. Cut another 2-by-6 with a circular saw to go across the ends of the band joists outside the piers. Fasten this board with screws into the band joists.

Nail metal flashing to the house wall, up the wall and over the top of the ledger. Remove any bottom door trim temporarily or slide the flashing up under it. Fasten the flashing with galvanized shingle nails.

Install joist hangers for 2-by-4-inch joists between the side bands. Space these 24 inches apart, starting from the house wall; put the first one against the ledger. Cut boards to fit between the sides and fasten them to the hangers with galvanized screws. Use a level to keep the tops of these joists level across the porch.

Cover the porch with plank siding, tongue and groove for a solid floor, butted planks to allow drainage between boards. Rip the groove off one plank to start with an even face. Nail flooring planks to the 2-by-4 joists with galvanized nails; use finishing heads and nail through the tongues on that style flooring, use 8d nails for thicker planks, such as 2-inch redwood boards. Rip the tongue off the last board on that style to make a smooth edge.