How to Build a Patio Cover
Patios are a great way to extend a home’s living space into the open air of the outdoors. They can take many forms, from framed wooden platforms (decks), to integrated hardscape, including a wide variety of designs and materials. But outdoor living can be a blessing and a curse. As much as we crave the outdoors, being exposed to the elements—the sun and rain—can render a patio space unusable.
PATIO COVERS Typically as soon a deck or patio is built, most folks start thinking of ways to cover or protect the space from both sun and rain. The best protection option is a light-weight wooden frame covered with translucent panels that let the sunlight through but keep the rain out. For a patio adjacent to a home, the most common framed patio cover usually attaches to the building itself and then extends out to shelter all or most of the patio area in lean-to fashion.
The critical connection for a patio cover is where and how it attaches to the house. In the past those connections were notorious for collecting debris, promoting wood rot, while inhibiting air circulation. SkyLift Roof Risers
www.skylifthardware.com, are an innovative way to attach the patio cover to the house, while providing the necessary support and mitigating all of those problems commonly associated to patio covers.
The following sections will take you through the sequence of successfully designing, building and installing a framed lean-to patio cover, including proper installation of the SkyLift hardware. Although each situation is slightly different, this process of designing and constructing the patio cover should be adaptable to just about any scenario.
Planning (Designing?) Your Patio Cover
When designing a patio cover, it can help to make a drawing of cover including the house and the patio itself. SketchUp or other designing software can be helpful in your planning, but in lieu of those aids, scale drawings on graph paper will work just fine. For our purposes we will design a cover that is 12 ft. wide by 16 ft. long.
Start by measuring from grade or ground next to the foundation up to the underside of the eaves. Next measure out to the fascia or vertical finish of the eaves. Determining the roof pitch completes this part of the drawing. The simplest way to hold one end of a 2-ft. level against the roof, and then measuring straight down to the roofing material. Divide that number by two and that gives you the pitch, or the amount of vertical rise in the roof per foot of run. Transfer those calculations to your drawing.
Next measure out from the house to the edge of the patio. Most often the grade slope away from the house slightly for drainage. (Because the height of the outboard support can be adjusted, this slope should not affect the patio cover installation).
SUPPORT AT THE HOUSE
The Skylift Roof Risers install through the roof plane, centered on wall framing of the house. To find the center of the framing, measure in from the edge of the siding 1 inch for the siding (shingles or clapboards), plus 1/2 inch for the sheathing, plus half of the stock thickness of the framing (1 3/4 inches for 2x4 framing and 2 3/4 inches for 2x6 framing). Add that number to the overall width of the eaves overhang and that will tell you the Roof Risers will sit. The Roof Risers support a continuous beam that the patio cover will rest on. The saddle on the Roof Riser is 3 1/2 inches wide to accommodate the nominal size of a 4x beam, typically either 4x6 or 4x8.
The outboard support of a patio cover usually consist of columns supporting a beam that the cover rests on. There are a couple of different approaches to anchoring the columns to the ground. The first option is digging holes to whatever depth is required by your code jurisdiction—3 ft. to 4 ft. is common. The column in this scenario must be rot-resistant material. If you opt for treated wood columns, they must be rated for Ground Contact with a treatment specification of .40 or better. Most Lumberyards stock treated wood with a .15 or .25 rating, so you must be specific that you want Ground Contact material with a minimum of .40 treatment. When the column is installed, suitable gravel or fill should be packed around the column in the hole to hold the column plumb. Having the post buried in this fashion offers enough lateral resistance for a patio cover in most applications. The biggest drawback to this strategy beyond the installation itself is having wood treated with toxic chemicals in a living space, albeit outdoors.
Another common approach to anchoring the outboard support columns starts with poured concrete footings. Wooden columns then sit in on hardware called Moment Post Bases or MPBs (Simpson Strong-Tie MPB44, 66, or 88), that hold the posts off the ground eliminating the need for using treated wood. The MPBs also offer resistance to lateral forces. Yet another support strategy is using pre-cast concrete columns or Wet-Set Bases called Perma-Columns that are buried in the ground or set in concrete, and that also resist lateral forces.
Regardless of the support strategy you choose, it’s a good idea to have an engineer to review your plans for approval or to suggest alternatives for supporting and constructing your patio cover.
Once you’ve decided how to support your patio cover, the next step is properly sizing the lumber for the cover. Remember that the larger the patio cover, the bigger the stock size for the lumber you’ll need to build it. You also need to choose what translucent material you will use as the “roofing” for the patio cover. There are many choices out there that vary in appearance, light transmission and the actual material that the panels are made of. And those choices can vary from region to region. Because of the weight and the fastening requirements, your choice of translucent material will have some bearing on the frame design.
To design the frame for your patio cover, it helps to think of it in layers with each layer perpendicular to the ones above and below. The bottom layer of the frame consists of the beams or girders that sit on the vertical supports. This layer runs parallel to eaves of the house. In most cases 4x6 or 4x8 lumber will be sufficient to carry the weight of the patio cover. And with an engineer’s approval you may be able to use engineered lumber or a built up sandwich of dimensional lumber for this layer. These built-up beams typically consist of two plies of 2x lumber with a middle layer of 1/2-inch plywood, with a very strict fastener schedule. Built-up beams can be a cost effective option in certain regions depending on the stock beam sizes available.
The patio-cover rafters form the next framing layer. These framing members sit on top of the support beams and run perpendicular to the eaves of the house. Again the spacing and sizing of the rafters can vary depending on the type of roofing panels you choose. Because those panels are typically light-weight, 2x6s would be adequate to span the 12 ft. for our patio-cover example.
The attachment strips or purlins comprise the final framing layer. These strips serve to stabilize the rafters below while providing attachment for the translucent panels above. Optional purlins can also be added to create a desired grid or shading patterns. The easiest strategy is installing the purlins in long lengths on top of the rafters, but purlins can also be cut to fit between the rafters or let into notches in rafters, both of which are much more labor intensive. Again, consult with the installation instructions of the roofing material you choose to determine spacing of the purlins. The wind and snow load ratings for your particular area may affect that spacing as well.
Not all lumber was created equal. Different regions of the country get their lumber from different sources, and the lumber species can vary greatly. Framing lumber must carry a grade stamp that lists the species, and the IRC has span tables for various lumber species that can offer general guidelines in that regard. Again the overall weight of the patio cover, as well as the snow and wind loads will affect how specific species might preform in a patio cover frame.
CONNECTING THE LAYERS
Once you’ve determined the lumber size and spacing for each layer, the next step is determining how the layers will be connected, and once again there are many options.
Girder to column: The easiest way to make this connection is with heavy-duty structural screws driven at an angle from the column into the beam. You can drill pocketed holes to conceal the heads of these screws. Another option is using metal brackets that attach to the beam and to the column. These brackets can be basic or decorative, and can be incorporated into the aesthetic design of patio cover.
Rafter to girder: For the strongest rafter to girder connection, the rafters should have level seat cuts where they sit on the girders at both the roof and the outboard supports. Again construction screws can provide the actual attachment. Depending on your jurisdiction requirements, you may need to install rafter ties between the rafters and the girder to prevent wind uplift.
Purlin to rafter: Construction screws again are the best option for this connection. You will probably need to countersink the heads flush with the tops of the purlins so that they don’t interfere with the panel installation.
Panel to purlin: Make this connection strictly according to manufacturer’s recommendation. They will specify and often provide the proper fastener along with recommendations as to where those fasteners should be driven to maximize holding power of the fasteners and to minimize the chance of leaking.
PROPER PATIO COVER PITCH
After determining the size and design of the patio cover, go back to your drawing and add the cover. Starting at the outboard support, there should be at least 6 ft. 8 in. of clearance between the ground and the bottom of the lower girder. That will set the lowest point of the patio cover.
Now set your ruler from that point up to the roof. The height of the patio cover above the roof will determine what length Roof Riser you will need. The point here is that you need to provide enough pitch or slant so that the patio cover readily sheds precipitation. The proper pitch will be determined by manufacturer recommendations as well as the rated snow loads for your area. The pitch of the patio cover can also affect the sizing of the rafters. If need be, the pitch can be raised easily by installing taller roof risers.
DO I NEED A PERMIT?
Many states and local jurisdictions allow patio covers under a certain size to be built without obtaining a permit. In Oregon, for example, the code reads that patio covers: “not [be] over 200 sq. ft. and supported by an exterior wall.” SkyLift Roof Risers are supported by an exterior wall, so our 12 ft. by 16 ft. cover would not require a permit. However, even this maximum dimension can vary in local areas. So it is always a good idea to consult your local building official to see if a permit is required. Be aware also that local zoning regulations regarding overall height and proximity to property lines may apply.
Building officials can also be a huge help in reviewing your plans to make sure you’ve made the right choices in materials and fasteners. These folks are in public-service positions and can often offer guidance regarding the construction of your patio cover.
Patio Cover Materials List
Once you have a plan for your patio cover that has been approved and that you are happy with, the next step is making a comprehensive list of all the materials you’ll need. Many of the design software options will do a list automatically, but assuming that you did the drawing by hand, let’s make the list longhand. As with the design phase, it makes sense to work in a logical pattern to make the list. For consistency let’s start with the supports and work up.
Installation of Skylift Roof Risers
Location Layout: Building the patio cover begins with installing the SkyLift Roof Risers and stabilizers when needed. First mark the center of your patio cover on the fascia of the overhang. Note that for aesthetics, it may be desirable to center the patio cover over a door or some other architectural feature. The patio cover is to be 16 ft. long, but assuming a 2 ft. cantilever of the beam at each end, the distance between supports would then be 12 ft. To find the positions of the SkyLift Hardware, measure 6 ft. in both directions from the center point.
Another critical factor is adjusting the Roof Riser layout so that they fall between the rafters or trusses. Rafter layout can often be determined by locating the fasteners that attach the fascia to the rafter tails.
On your drawing you have already determined the level distance from the edge of the eaves to the center of the plate atop the wall framing. At each of the marked positions, measure in that distance squaring up from the edge of the asphalt shingles. Drive a nail to temporarily mark each location for the roof risers.
Strip shingles: Starting two full courses above the locator nails, carefully slide a flat bar under the courses to separate the adhesive points. (Note that this step may be easier first thing in the morning when the roof is cooler). Find the nearest edge of a shingle and drive the flat bar claw around the nail from below the shingle. Gently pry upwards to lift the nail along with the shingle. Then insert the claw of the flat bar around the nail from above the shingle and remove the nail completely. Repeat this process until all of the nails holding the shingle are removed. The shingle should be free to slip down. Depending on the position of the locator nail in regards to the seam between shingles, you may have to remove more than one shingle from a course. You will need to reuse these shingles so stack them carefully in a safe place once they are removed..
Removing the first shingles exposes the nails for the shingles immediately below, which simplifies their removal. Depending on the original installation pattern, you may have to lift adjacent shingles to access all the nails necessary for removing the shingles. Continue working your way down the roof toward the eaves until you have exposed an area large enough to insert the base of the SkyLift Roof Riser.
Remove sheathing: Remove the shingle underlayment (tar paper) from around the locator nails and find the edges of the nearest rafters. Between the edges of the rafters, lay out a rectangle approximately 12 inches square starting a few inches below the locator nail. When Lateral Stabilizer Straps will be installed, the rectangle should extend the entire width between the rafters or trusses. Below the rectangle mark the side-to-side position of the locator nail for future reference.
Using a circular saw, plunge in along the layout lines to cut out the rectangle. The blade of the circular saw will not finish the cuts in the corners of the square, so either over cut the corners or use a jig saw to finish the cuts. Remove the sheathing and save it to be reinstalled later.
Install the Roof Riser: With the sheathing removed, the top plate of the wall framing should be readily visible. Set the Roof Riser on the wall plate aligning the center of the column with the reference mark on the sheathing, and centering the Roof Riser base plate on the wall plate. Mark the fastener holes and pre-drill holes at each of the locations. Secure the Roof Riser base to the wall plate with 1/4-inch by 3-inch structural screws. Be sure to drive a screw at every hole in the base plate.
Install the Lateral Stabilizer Strap: The stabilizer strap needs to fasten to solid framing, so cut a length of 2x6 to the distance between the rafters above Roof Riser. This 2x block can be either nailed or screwed to the rafters on either side. If you opt for screws, drill three or four pocket holes at each end of the 2x6. Set the 2x6 in place flush with the tops of the rafters, and drive truss head screws through the pocketed holes to secure the 2x6 to the rafters.
On the piece of sheathing removed earlier, cut a hole larger in diameter than the support post of the Roof Riser and centered on the locator nail. Slip the sheathing section over the post, and attach the sheathing to the 2x6. (You may opt for additional blocking to secure the bottom edge of the sheathing piece as well).
Slip the Stabilizer Strap around the post, bending the radius section of the strap to match the roof pitch. Using tongue and groove pliers squeeze the strap around the post until the fastener holes on the top and bottom plates line up. Framing screws, truss-head screws, Teco nails or 8d nails are fine for securing the strap, but they should be at least 2-inches long to penetrate the plywood/block assembly. Drive fasteners into every hole on the Stabilizer Strap to secure them to the sheathing and the 2x blocking below.
Close up the roof: With the Roof Riser installation finished, cut a piece of roof underlayment big enough to cover the open area. Cut a hole so that the underlayment slips over the Roof Riser. The underlayment needs to slide under the existing underlayment above the Roof Riser and lap over the shingles below the Riser.
Slip the appropriate diameter roof boot or pipe flashing over the post of the Roof Riser. Trace the perimeter of the flashing onto the underlayment, then raise the flashing slightly and install a generous bead of roofing cement inside the perimeter line of the flashing. Press the flashing down into the bead of cement.
Starting at the bottom, carefully re-install the shingles saved earlier, cutting the shingles to fit around the rubber boot around the Riser Post. The bottom edge of the roof flashing should extend over the shingles below, but then the flashing should go under the succeeding courses above. When the shingles are all reattached, secure the exposed bottom corners of the flashing with roofing nails, and smear roofing cement generously around the nail heads to prevent water incursion.