DIY Flat Pergola Roof (How to Put a Roof on a Flat Pergola) - Home Gardening (2023)

I love the pergola in my backyard. I like the light that the open ceiling provides. But I don't like getting caught in the rain when I'm in it. So I found a solution that allows me to have a canopy against the rain and still see the sky above: clear polycarbonate canopy panels. So all I had to do was figure out how to put a roof on a flat pergola, and I was done!

I posted some a while agowaterproof roof ideas for pergolasbecause I was looking for inspiration to cover the pergola over the barbecue in my backyard.

It's not an area I use much when it rains, so you may be wondering why I need a waterproof cover.

After each rain, the bench and grill are covered in leaves and flower bits that need to be washed before the grill can be used again. Which makes me not want to use the grill so much 🙂

Also, it would be nice not to get drenched if a downpour hits right when I'm cooking (which seems to happen every year at my 4th of July barbecue).

All of which is to say that I finally made up my mind about which cover to put on and installed it. And I am very happy with the result.

I ended up opting for clear corrugated polycarbonate roofing panels that can be installed right on top of the existing pergola... which is exactly what I wanted.

Read on to find out how to put a roof on a pergola.

supplies

Materials

• transparent cover panels*– I used 26″ x 8′ SunTuf panels. They also come in 12' lengths if you have a larger roof to cover.
• Horizontal plastic closure strips* – Attaches to the top of the pergola to hold the roof panels. Since they are supposed to be installed every 2 feet, you will need about 5 for every 8 feet of panel length.
• Vertical plastic closure strips* – They run inside the raised part of the corrugated panels. You will need them if you want to close off the gap at the edges of your pergola. Or to attach the panels to your pergola if you have ends that go beyond the main structure (like mine)
• 1″ wood screws with washers*
• 2″ wood screws with rubber washers*

Tools

• Variable Speed ​​Cordless Screwdriver – You will need to use low speeds to install the panels, so the variable speed option is important
• broca 1/4"
• 1/4″ screwdriver*

1 | Decide which direction to install the panels

If your pergola roof slopes or is attached to the house, the direction of the panels is determined by you. The slots should point down and away from the house.

However, if you have a free-standing pergola with a flat roof (like mine), you'll need to decide which way the slots will go. Which also determines which way the water will flow.

I decided to do the slots front to back primarily because I could use 8' roofing panels to go the entire distance without the need for longitudinal seams.

Another consideration may be the direction your pergola boards run. Horizontal closure strips must be installed on parallel boards within 3 feet of each other. So if the boards at the top of your pergola run the wrong way, you'll need to add some additional boards at the top.

2 | Add slope to flat pergola

These ceiling panels are to be installed on a sloped ceiling rather than a flat one.

Since my pergola doesn't have a slope, I wanted to add something that would at least prevent water from pooling in the middle of the roof.

The manufacturer's guidelines say that the step should be 1 1/2" per foot of panel.

My pergola roof is about 7 feet wide. So to raise the roof at one end would require a 10 1/2″ drop! Which I thought would look very weird.

So I decided to raise the roof in the middle of the pergola instead of at one end.

By cutting the panels in half and installing a ridge cap on top, I was able to shorten the length of the panels to 3 1/2' on each side. Which, with the manufacturer's instructions, means about 5″ of slope.

Since I live in an area that doesn't get a lot of snow, I decided to go with an even lower slope: 1 1/2″.

To do this, I installed a 2" x 2" board on top of my pergola, right in the middle.

And I saved some money. Because the panels are flexible, they were folded over the midboard without the need for grooves.

In theory, I should have sealed the roof panels along the overlaps to prevent water from seeping through. But since I'm not that concerned about making it fully waterproof, I didn't.

If you live in an area with more snow, you may want to create a steeper slope than what I did. But I think you could use a similar idea by cutting the panels in half. Then install a taller midboard, additional backer boards at lower heights to support the panel, and add ridge caps to seal the top.

3 | How to install clear plastic ceiling panels

If you want to see the default installation method, this video is a good place to start:

Attach horizontal closure strips

The first step is to fix the horizontal closing strips at the top of the pergola.

For this you will need wood screws. They work best if they have grommets to keep them from slipping through the plastic fastening strips.

Align the end of one of the horizontal closure strips with the edge of your gazebo. Make sure you run straight along the beam.

Screw it to the joist at the bottoms of the closing strip.

When you reach the end of the first strip, attach the next strip and continue screwing it into the joist until you reach the end of the pergola frame.

When the first row is complete, cut the extra closure strips with tin snips.

Then it goes to the next line. Ideally it should be 2 feet from the first strip, but it could be 3 feet away.

The important thing is to make sure that the hills and valleys are lined up facing each other. Otherwise, you will have trouble getting the corrugated roof to lay flat as it should.

Keep adding horizontal closure strips until you reach the top of your pergola.

Attach the vertical closure strips

Once all the horizontal closing strips are installed, add the vertical closing strips.

If the roof panels end at the edge of the pergola frame, line up the vertical closing strips along the edge between the last raised part of the horizontal strips.

Cut vertical closure strips to size with tin snips.

Since my pergola roof extends beyond the frame, I used the vertical fastening strips to secure the edges of the panel to the overhanging rafters.

If you are doing this, be sure to only install the vertical tie strips on the joists that line up with the raised part of the horizontal tie strips.

Screw in ceiling panels

You are then ready to start joining your panels together.

Position the first panel so that it is straight on the horizontal supports and the last raised groove runs on top of the vertical strip (if you have one).

Make sure you have it right side up. There should be a label on the panel indicating which side it is on. Remove the label before placing the panel.

Since my panel was slightly larger than my pergola roof, I left it overhanging on both sides. That way, if my roof isn't perfectly square (which I'm pretty sure it isn't), I can trim the panels later to end up at the edge of the pergola roofline.

Then use a quarter inch drill bit to drill holes in the panel where the screws will go. These screws will be installed at the top of the horizontal supports and along the vertical supports.

You do not need a screw in each raised section of the horizontal closure strip.

For the strips that run along the outer edges of the pergola roof, drive a screw through each raised section.

For enclosure strips that run down the middle of the pergola roof, drive one screw into every three raised sections.

Then tighten the screws with rubber washers using the pipe bit.

The washer should rest firmly on the plastic cover panel, but not tight enough to cause the panel to curl.

When you get to the edge where the next panel will be attached, don't drive the screws yet.

Position the next panel so that the first raised section of the new panel overlaps the last raised section of the old panel.

Drill holes in the new panel as you did the first. Then attach the first and second panels where they overlap the pergola frame.

Continue installing the panels until you reach the roof of the pergola.

trim the edges

When you are done, trim all the edges of the ceiling panels with strong scissors or tin snips.

If you are sure that your pergola roof is square and you know how to measure well, you can do this step before placing the panels. Which would make cutting easier.

But doing it afterwards ensures that the roof will fit perfectly.

And then that's it.

This whole project of putting it up took me less than a day. So it was a very quick and easy way to put a roof on my pergola.

I love that you can see through the panels.

I trimmed the corners a bit so that there would not be such a large piece of unsupported ceiling panel. I think this could cause problems if a strong wind comes.

And it's not that obvious from the front either.

I think it was definitely worth the effort!

Other outdoor projects you may like

• Waterproof cover ideas for pergola do it yourself.
• pergola lighting ideas
• backyard privacy ideas

Do you have comments or questions about how to put a transparent roof on a pergola? Tell us in the section below.