A pergola is a graceful addition to a house; it creates an outdoor living space to enhance enjoyment of your property. Pergolas are often free standing structures supported by posts that are joined by beams then topped with rafters to provide shade. Building a Pergola Attached To The House is not overly difficult; this approach eliminates a set of posts but otherwise the construction techniques are the same as for free standing pergolas.
Start by obtaining a good set of plans and checking with the building codes administrator in your town or city. The first step in construction is accurate placement of the posts; pergolas longer than 8 feet may require additional support. A short cut to accurate placement involves using a frame built of 2×10 boards; verify the squareness of the frame by measuring the diagonals from one corner to another; if the measurements are the same, the frame is squared and true. Place the frame against the foundation to locate the post holes, make appropriate marks where the holes will be dug, remove the frame and dig the post holes. Code requirements vary but generally the holes should be a bit deeper than the frost line.
Use a motorized auger or a post hole digger to make your hole. Line the bottom of the hole with about 4″ of gravel. Dip the end of the posts in roofing tar as a preservative measure. Replace the frame. Set the posts vertically, check carefully that they are plumb; use the inside of the frame as a boundary marker to guarantee proper location. Brace the posts with 2″x4″ material, mix concrete according to directions and pour it into the hole; cone shape the concrete above ground level to enhance water runoff.
Attach an appropriately sized, usually 2×10, ledger board to the side of the house. It should be lag bolted to vertical members of the house framing; this may require removal of siding and should be planned for in advance.
The bottom of the ledger board should accord with the height of the beams that will be attached to the posts. Be sure to flash and seal the ledger board properly.
The beams that join the posts together run parallel to the side of the house. Two beams, typically 2×16, are attached to the top portion of the posts, one on each side; this forms a kind of sandwich, the beams being the bread. They should be attached with properly sized, weatherproof carriage bolts or lag screws. The rafters will attach to the ledger board on one end and rest atop the beams on the other end.
The rafters are attached to the ledger board using joist hangers; they are usually spaced 16″ apart. The other end is stabilized atop the beams using a part commonly called a hurricane tie bracket which is screwed to the beams and has flanges between which the rafter sits; the rafters are screwed to the brackets. Additional rafters may added atop the first level to provide more shade.
6″x6″ posts provide the best support but do not detract from the graceful appearance. Cedar is a popular choice for material, although pressure treated lumber is often used for posts. Decorative notches are most easily cut into the beam and rafters on the ground. You may want to use posts that are a bit longer than required then trim them to the proper height after the concrete has cured to make sure they are equal. Building a Pergola Attached To the House requires good planning and follow through but will add enjoyment, comfort and value. It will typically require several days of carefully done work.