How to Add a Side Porch

Clear the area down the side of the house where the porch will be built so there is no furniture or other items in the area. Dig away the topsoil down to 6 inches below ground level by the house, using a spade. Dig down to a depth of 8 inches at the opposite edge of the porch.

Taper the ground between the two edges so the ground slopes from 6 to 8 inches deep. Compact the ground with a plate compactor so it is flat but retains the slope. Fill the area with gravel up to ground level. Rake the gravel flat. Compact the gravel using the plate compactor.

Cut two strips of 3/4-inch thick plywood as long as the width of the porch area and 8 inches wide, using a circular saw. Cut a strip of 3/4-inch thick plywood as long as the length of the porch area and 8 inches wide. Stand the sheets around the perimeter of the porch area with the 8-inch long sides vertical. Screw the sheets together using two L-brackets on each corner.

Prepare a batch of concrete from one part cement, two parts sand, three parts aggregate and one part water. Fill the porch area with concrete up to 3 inches in depth. Lay the steel mesh sheets across the top of the cement. Fill the porch area with concrete up to the top of the plywood sheets. Allow 72 hours for the concrete to set before continuing.

Remove the plywood sheets from around the edge of the porch area. Cut a piece of 2-by-4 lumber to the length of the porch. Hold the 2-by-4 horizontally against the wall at the height you wish the porch roof to be fitted, with the 4-inch faces vertical. Drill holes through the wood into the wall 3 inches from both ends of the wood and every 6 inches between the ends, using a hammer drill.

Cut two pieces of 2-by-4 to the width of the porch minus 4 inches. Cut a piece of 2-by-4 to the length of the porch. Screw the width and length pieces, including the piece with holes drilled in it, together using two 4-inch long screws per joint to form a rectangle that's the length and width of the porch.

Place a wall plug in each hole in the wall. Line up the holes in the rectangular frame with the holes in the wall. Screw the wood to the wall using 6-inch long screws. Cut two pieces of 2-by-4 16 inches long. Cut both ends of each piece at an angle of 45 degrees using a miter saw, with the angles both facing in toward one another.

Hold the angled pieces under the width-long ends of the rectangular frame, with one end against the wall and the other against the underside of the frame. Drill two holes through both pieces of wood and into the wall using the hammer drill. Fill the holes with wall plugs.

Screw the wood to the wall using 6-inch screws. Screw the other end of the wood to the underside of the frame using two 6-inch screws per joint. Cut a piece of 2-by-4 to the length of the porch. Screw the wood to the wall 18 inches above the rectangular frame using one 6-inch screw every 6 inches along the length of the wood to form the wall plate.

Divide the length of the porch by six to find the number of rafters needed to assemble the roof. Cut this number of pieces of 2-by-4 to the width of the porch plus 16 inches. Balance one rafter on the wall plate and the outer edge of the rectangle. Hold a plumbline to the upper corner of the rafter on the end nearest the building.

Draw a vertical line down the rafter with a pencil, using the plumbline as a guide. Cut along the marked line with the miter saw. Use the rafter as a guide to cut the end of all the other rafters in the same manner. Stand the rafters on the wall plate and rectangle, with the cut end pressed against the wall.

Draw a vertical line with the plumbline as a guide at the points where the rafters touch the wall plate and the rectangle. Bisect these lines with a horizontal line using a ruler, to mark out a notch on the rafters. Cut out the notches using a jigsaw. Stand the rafters on the wall plate so the notches allow the rafters to sit flush on the wall plate and the rectangular frame.

Screw the rafters to the wall plate and the rectangular frame using one 6-inch screw per joint. Divide the length of the rafters by four to find the number of beams required to cover the roof. Cut this number of 1-by-2 boards to the length of the patio. Screw one beam across the top of the roof using 2-inch long screws, with the 2-inch wide face flat agaist the rafters.

Leave a 2-inch gap below the beam. Screw a second beam across the roof in the same manner. Continue screwing beams to the roof with 2-inch gaps between them until you reach the bottom of the roof. Screw the final beam across the bottom of the roof, regardless of the size of the final gap.

Cut strips of roofing underfelt to the length of the roof. Nail the first strip to the beams across the bottom of the roof using a hammer and clout nails. Nail the second strip above the first with a 1-inch wide overlap. Continue to nails sheets across the roof with 1-inch overlaps on the sheet below until the roof is covered.

Nail a row of slate roofing tiles along the bottom of the roof using 1-inch long galvanized roofing nails. Lay a second row of tiles above the first with a 1-inch overlap over the first row. Alternate nailing and laying rows of tiles with 1-inch overlaps until you reach the final row. Nail the final row to the roof even if the row before it was also nailed down.