If you would like to improve your front porch, adding a gable roof over it is a good idea. The roof will allow you to enjoy the porch in inclement weather. It will also provide shade on those hot summer days when you would like to enjoy a cold drink outside. The steps below will guide you in building one of these functional roofs yourself.
Use the planned dimensions of your roof to mark the locations on the porch floor where each of the support posts will be mounted. The roof's support posts will be placed at each corner of the roof and every 10 feet in between.
If your porch is made of concrete, go directly to Step 3. For wood porches, you will need to cut away a large-enough section at each post location in order to get enough working room to make the post foundations and stand a 4x4-inch post. Dig a hole 18 inches deep and 10 inches in diameter at each post location and compact the soil at the bottom of the hole. Set cylindrical concrete forms in each hole and fill with concrete. Let the concrete cure for at least five days.
Use an electric drill with a masonry bit to drill a 3/8-inch hole in the concrete at the centre spot of each post location. Align 4x4 post anchors over the holes and attach by using a 3/8-inch expanding concrete bolt in the holes.
Set the 6x6 posts in the post anchors, plumb them and attach to the anchors with the included hardware. Brace the posts with 2x4 lumber.
Measure and cut 2x10 lumber to size for two sets of double roof beams. These beams will be the same length as the distance between the outside edges of the support posts on the sides (rather than the front or back end) of the porch.
Raise the beams on either side of the support posts on one side and temporarily fasten them with a few nails. They should be flush with both the tops of the posts and the outside edges. Drill 3/8-inch holes through both beams and the centre of the support posts. Permanently attach the beams to the posts with 3/8-inch bolts, washers and nuts.
Raise the end roof truss and position it to span the porch and rest on both sets of beams, flush with the outside edge of the beams and posts. Toe nail securely to the beams on both sides. Raise the rest of the roof trusses one at a time and nail to the beams every 24 inches on centre.
Deck the roof by nailing 5/8-inch plywood sheathing to the roof trusses. Apply two layers of 6.8kg roofing felt over the plywood sheathing and attach it with roofing tacks.
Add drip edge to both sides of the porch. Shingle the roof with asphalt shingles and roofing nails. Add finishing board to the front and back of the porch. Paint or stain your lumber in a colour of your choice.
Once the beams are raised and secured, mark the tops every 24 inches on centre for quick and easy placement of the roof trusses.