How to Build a Patio Cover with a Corrugated Metal Roof
Houses are money pits. Between the taxes, the maintenance, and the repairs, it’s a wonder anyone can even afford to own one. One way to save a bit of money is to take on some home repair and renovation projects yourself. For instance, the bay windows at the back of my house leak during thunderstorms and the backdoor freezes shut during winter. While it would be difficult and expensive to fix both the windows and the door, I decided that since both overlooked my patio, a patio cover would effectively keep foul weather away from the bay window and back door, making it a cheaper and easier fix. If you’re interested in making your own patio cover read on for instructions for how to do so.
Selecting Materials to Build a Patio Cover
While looks are important, you want to make sure that the materials fit the structure. Since my patio cover was going to have a slight slope, shingles were out. A tar roof would work, but it would be heavy smell like a BP oil spill. I decided on corrugated metal roofing because it’s resistant to high winds, is light weight, and is structurally sound.
Using corrugated metal also allows me to reduce the degree of slope, or roof pitch, needed to a mere 10 percent, or a 1 to 10 pitch. This meant the patio cover could start at the edge of the house’s roof at a height of eight feet and slope down to seven feet, leaving a clearance of more than six and a half feet between the lowest part of the frame's headers and the ground at its outer edge.
Tips for Purchasing Materials:
- Be flexible. I had originally planned on using 4”x4” beams and joists, but local codes wouldn’t allow for them, so I used 10”x2" headers and 6”x2" joists, which worked out just fine. Also, be prepared to modify your plan at the store when you’re getting your materials, as doing so can save you money. For instance, I chose drywall screws instead of nails because, for some reason, they were less expensive, and they won’t try to work themselves back out after a few years. Another substitution I made was choosing three- and four-inch deck screws instead of framing nails. Although more costly, they hold much better than framing nails outdoors.
- Shop around. Shopping around for the best prices for materials was absolutely necessary. In the same town, in an area of less than 10 miles, the difference in prices was enormous. Total material costs ranged from $2,200 down to $800.
- Beware the store associates. Some are aggressive and want to push customers into an insane buying frenzy, bringing up a storm of confusing nonsense that somehow equates spending more to saving more. The lumber store I bought from had an associate who simply made sure I bought the correct materials for the job by looking over my plan and suggesting shorter screws for the joist hangars and a lower grade of lumber for the areas of the patio cover that would not be exposed to the weather. The associate also arranged for delivery, which cost $25.
Materials Used (Lumber)
2”x6” x 10’ boards (joists)
2”x8” x 10’ boards (beams)
1”x6” x 10’ boards (metal roof nailers)
4”x4” x 8’ treated (patio cover posts)
Getting a Building Permit for a Patio Cover
Some people said a building permit was unnecessary, while others said it was impossible to get without a contractor's license, or that it would raise my property tax, etc. So I called the permit and licensing office and got the correct answers.
- Yes, a permit was required.
- No, it wouldn't raise my taxes,
- As long as the property owner didn't care if I wasn't a licensed contractor, they didn't either.
Getting the building permit was actually much easier than I thought. I took the plans to the town’s permit and licensing office, filled out some paperwork, and the next morning I got a call and went back to the permit office to pick up and pay for the permit, which came to $85. They made a couple of alterations to the plan that not only were easy to accommodate but also made the project easier and cheaper! To prepare for the final inspection, I took pictures of each critical step to show the building inspector, which made the final inspection a snap.
Beginning Construction on the Patio Cover
Early the next morning the materials arrived at my house. Once the materials were unloaded, I began carrying the ten foot long boards and corrugated metal sheets to the back yard, laying them out in a pattern to roughly match how they would be assembled. I also separated the corrugated metal sheets, wiped each one down with a light coat of vegetable oil, and then re-stacked them. This was something I had seen a neighbor do a long time ago, when I was a child. I don’t know if it served any purpose other than making me feel better. It’s a step I probably could have skipped, but who was I to doubt the wisdom of the ancients?
Step 1: Installing the Ledger Board
First I removed the 1/4” plywood dressing right below the drip edge and saw a very solid framing 2”x4” underneath, perfect for attaching the ledger board, which attaches the cover to the roof frame. The local building code required a 2”x6” ledger board, which meant I had to saw off two inches of wood from the top of the bay window’s box.
Next I pre-drilled 1/8” holes, 6 inches apart, in the ledger board, because it was treated lumber and the deck screws would need a little help getting started. After attaching the ledger board with 4” decking screws, I used a large staple gun to staple the phone, internet and cable lines to it, on the inside toward the house, to better protect them from the weather.
Step 2: Dig Post Holes
It was a little bit difficult to figure out where to dig the post holes. I wanted them to be exactly 9.5' from roof edge, but the house’s foundation was recessed 2' from the roof’s drip edge and stuck out 26” from under the bay windows. How was I going to get an accurate measurement? All sorts of neat tools I saw people use on TV shows and formulas from various math classes flashed through my mind. Here's what I did:
- I stood up up a couple of posts at the roof’s edge, using a bubble level to make sure they were perfectly upright.
- Then I measured and marked nine and a half feet on a couple of joist boards and laid them on the ground, with one end by the upright posts and the markings on the other end showing where the hole should be dug. I did this at both edges of the ledger board, and laid two more ten foot joist boards between them.
- I then used my square, or angle iron, to make the corners square.
- I marked the spots for the three post-holes, with the middle post-hole going where the two 10 foot joist boards met.
- I then measured corner to corner, one way and then the other, and made slight adjustments until both measurements came out the same. With the exact centers for the post holes marked, I marked 18” circles around them because I planned to dig the holes 18” deep and wanted them to be as wide as they were deep, in accordance with local building codes. (See pictures above)
- I started digging the holes with a simple shovel, all the while thinking about those post-hole diggers, the ones with motors and big augers, that take two people to operate, like I saw used on various home improvement TV shows. Before I could formulate a plan for renting a hole digger, though, I had already finished digging all three holes with just a plain old shovel. Then I used my garden hoe to tamp down and compact the dirt at the bottom of the holes.
Step 3: Make the Posts Even
Next I scratched my head as I thought about how I’d make sure that the tops of the three posts would be even once they were placed into the post holes. Moreover, without anyone to help hold things in place, I needed to figure out how to attach the rest of the frame to posts that would already be standing upright.
What I came up with worked, although I never saw it done on TV. I laid a board on the patio slab, and set a bubble level on the end of that board. Then I took that end of the board to the hole and stood the 4”x4” post up straight, holding it by hand, and lifted the board with the bubble level up until it was level and then made a mark on the 4”x4” post. I then laid down the post and measured seven feet from its top and marked it. The difference between the two marks was how much taller I wanted the post to be, so I attached a length of treated 2”x4” to the end, adding enough length to the post so that its height would be perfect. I did this for all three posts.
Step 4: Assemble the Frame
The rest of the frame I assembled on solid ground, not wanting to hold everything in place with one hand while installing decking screws with the other.
- Cut four braces with precise 45 degree angles. I cut them from a single 10-foot long 2”x10” board. I measured the width of the board with a ruler, then marked that length from the end of the board and cut from there to the corner to make a triangle of wood that was exactly the right shape. I measured the short sides of that wooden triangle-shaped block and they were exactly the same so I knew it was cut at a 45 degree angle. I used that to mark the lines I would cut to make the braces. I made the two outside braces three feet long at their outsides, and the two inside braces two feet long at their outsides.
- Square the pieces for assembly. With the braces cut, I laid out the frame on the ground in the position they would eventually be in. I pre-drilled the screw holes with a 1/8” bit to prevent cracking and on the braces I pre-drilled halfway into the wood with a 1/4” bit so that the screws could sink deeper. After attaching each piece, I checked each joint to make sure it was square and that nothing had been knocked out of place. Luckily, the pieces stayed where I wanted them to and I didn’t have to make any further adjustments. After assembling the frame I marked 24” all along the center and on the ledger board and attached 11 joist hangars to each. Then it was time to get the frame, which weighed about 300 pounds at this point, ready to be raised.
- Prepare the joists. (11 ten-foot long 2”x6”s). I had to cut an angle and a 1/2” notch at the top ends so the roof of the patio cover would come in below the house’s drip edge. I then cut off seven inches from the other end at an angle so it would mach up to the frames’ header at the far end. For this I made a template from a piece of cereal box cardboard, cut out the pattern and drew it on the ends of each board. Then I cut with a circular saw and used a bow saw to take out the last little bit of the notches. If I had one, I would have used a jig saw. For the far ends, I made another template, one without a notch, to ensure all the angles and lengths were the same. A real pro might have made measurements for each cut instead of making a template, but I didn’t want to risk the possibility of human error.
Step 5: Raising the Frame
To stand up the frame without help, it was necessary to attach prop sticks; that is, I used a single framing nail to attach a 10-foot long 2”x6” board (I used my joists) to the outside of the frame, one board length away from the bottom of the frame, on each side. These two boards would rotate on their nail, their end holding up the frame as I lifted, while their other end would be on the ground, preventing the frame from going back down.
Then, in the middle, I attached a 10-foot board to the center post and lifted it from the very end, the leverage cutting the strength needed to lift the frame in half. As I lifted the frame I walked in toward it, and had the frame standing in its post holes without having to strain myself. Next I attached the joists to the left and right sides, and with the corners secure I was able to remove the prop sticks and center lifting board and install the rest of the joists.
Step 6: Pour the Concrete
At this point I had the frame attached to the joists, and the joists attached to the ledger board on the house. To make the frame perfectly level across the top, I lifted the posts just a little and tossed in just a bit of dry concrete ready-mix to raise its height just enough to make my bubble read perfect. Then to make the posts exactly straight up and down, I lifted and moved the bottom ends in the post holes, measuring with the level after each adjustment. After letting things settle for about a half hour, I re-checked everything with the leveler again. It was still plumb and square, so that meant it was time to pour some concrete.
I chose six 80 lb. bags of post-set concrete. I mixed one bag at a time, using my garden hoe to stir in water until the concrete became a near-liquid, something resembling sloppy mud. Then I used my shovel to put equal amounts into each post hole, repeating this process until I got to the last bag. For the last batch of concrete I added less water and mixed it to the consistency of raw cookie dough and, wearing work gloves, I grabbed gobs by hand and formed it into a dome at the base of each post to prevent water from pooling. Then I used a block of scrap wood as a trowel to tap and smooth the surface of the concrete. Then I let the concrete set.
Step 7: Finish the Job
After that it was simple but repetitive work. I attached 1” x 6” boards to the top of the joists, and then screwed the corrugated metal roof to them. The most difficult part was getting the upper end of the metal sheets to go under the drip edge and roof decking of the house and to butt up against a bead of clear-drying roof cement I had put in there with a caulking gun. Also, putting a bead of sealer along the edge of the metal sheets before overlapping them was a bit demanding, though absolutely necessary.
The job was done at that point. As for the corrugated metal roofing, I chose rubber washer metal-into-wood screws with ¼” bolt heads and used a ¼” magnetized drill adapted socket to put them in. That type of screw goes into into every valley at the top and bottom ends of the panels and every other valley throughout the rest of the roof, into the 1” x 6” boards placed 24” on center.