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Build an Attached Carport

Construction How-To, Garages July 17, 2007 Sonia


The posts can be set on and anchored to concrete piers poured in holes in the ground. Or you may be able to utilize pre-cast piers. Another method is to set the posts in the concrete. In this case, pressure-treated posts must be used. Again, check with local building authorities as to methods suitable for your area. Regardless of the method of erecting the posts, make sure they are positioned correctly to create a square construction, again checking with a string and the triangular method. Also make sure the posts are plumb, bracing them in place two ways with temporary stakes and 2-by-4 braces.

With a helper, hold an end board (rafter) up against the existing house wall and against the end of the support header. Determine the location of the end rafter on the end post, as per pitch or outer roof height needed. Mark the rafter bottom edge location on the end post. Also mark the angle of the end of the rafter against the existing building; it must be cut so it will fit snugly against the building wall. Measure for rafter length, allowing for overhang, and cut the angle. Cut the same angle on the outer end of the rafter as well. Repeat for the opposite end of the building. Then use one of the cut rafters as a pattern to cut the remaining rafters.

Left: Cut the rafters to length and cut the angle on the building end to match the angle of the building support header. Cut the opposite end at the same angle and the fasten the ends into the joist hangers. Right: Attach the outer ends of the rafters down on the top plate with metal hurricane braces.

Fasten the front support beam in place to the posts, locating it below the rafter bottom edge line marked on the posts. This beam is actually made up of three 12-foot lengths on the building shown. Make sure the beams are level. Locate the positions of the rafters on the header and fasten joist hangers in place. Fasten the rafters in place in the joist hangers with their outer ends resting on the outer support beams.

An inside header provides additional support.

Fasten the opposite end of the rafters to the support beams with metal hurricane bracing plates. Cut the post tops level with the rafters. Fasten a second inner support beam up against the bottom edges of the rafters and to the inside of the posts. Cut the end support beams. Note the outer end may have to be cut at an angle to fit up under the rafter, depending on roof height and pitch. The existing building end must be fastened to a block anchored to the existing wall. The outer end is fastened to the post and/or rafters. Cut blocking pieces to fit between the end rafters and the end support beams. Fasten in place on 24-inch centers by toenailing one end, or use angle braces.

The outer fascia is added to the ends of the rafters.

Blocking between the rafters provides nailing support for the metal roof.

Next, cut and install the braces. The front braces have a 45-degree angle on both ends. The end braces are best cut by first cutting the bottom 45-degree angle, positioning a brace in place and marking the top angle to fit the end beam. With the end braces in place, cut and install siding over the ends. You may also wish to add trim around the ends to match the existing building. A fascia board is fastened to the front of the rafter ends to finish off the outer end.

Fasten the angle braces to the posts an dunderside of the outer header. Then fasten the metal roofing in place.

The building shown was covered with metal roofing. The roofing is brown to match the shingles on the existing building. Other choices include a variety of polycarbonate materials, such as SunTuf. A gravel, or better yet, concrete floor, can add to the usefulness of the carport.


Tools & Supplies

  • Support posts, 4×4” x 10’, 5 req’d.
  • Headers, 2×8” x 12’, 2 req’d
  • Joists, 2×6” x 16’, 17 req’d
  • Front beams, 2×6” x 12’, 4 req’d
  • End beams, 2×8” x 16’, 2 req’d
  • Front braces, 2×6” x 3’, 8 req’d
  • Side braces, 2x4x12”, cut to fit, 4 req’d
  • Blocking, 2×4” x 16”, cut to fit between rafters, 80 req’d
  • Roofing of choice, 16×24’
  • Fascia, 2×8”x12’, 2 req’d.