How would I build a rain proof roof for my aluminum pergola?

I would add a beam in the center to raise it. You could add rafter like supports on each side. You may not eve need the supports on each side as log as the canvas is tight enough with out sags.

Replace the fabric with corragated metal or fiberglass roofing panels, Home Depot or Lowes. Just make sure you have a slight slope so the water drains off

Hello I bought one of those pergolas and after the first rainstorm it filled with water and bent the rods that held the fabric. We got thoroughly soaked emptying water from the heavy grooves of fabric and needless to say, we took it back to the store trying to be very polite !🤐

They assured me I wasn't the first customer with the same complaint. I looked into buying some plastic roofing to make a roof, but the cost was as much as the pergola! I thought maybe aluminum? Same too expensive. I wish I had an inexpensive alternative for you, but

I don't . I do have one suggestion, tilt it so one end is higher to allow the rain to roll down instead of pooling. Are you able to shim up the one side? That should help channel out the water. If the store didn't take it back that was my option. Hope this is somewhat helpful. I do love the look of the pergola 😊

I bought roofing from lowes, it was called ondura roofing I think. I have had mine for eight years, I love it.

You can weatherproof your canopy with weatherproofing for fabric and canvas. You can buy it online at West Marine (For boats). I have the same pergola, works great! The product costs about $54 but it is well worth it. apply the weatherproofing yearly

We tore the old roof off my covered 20'x25' patio and used Tuftex polycarb panels from Lowes. https://tuftexpanel.com . This not plastic: you can take a baseball bat to it. Comes in Clear, Opaque, and translucent. We got translucent Smoke, but it lets too much light thru'. Otherwise it's terrific and will last a lifetime.

Home Depot has something similar/different name. No one actually uses fiberglass anymore.

These pergolas are for shade only in the summer months. If you want a "rain proof" pergola, you need a better structure. In order for this to function properly during rain, one end needs to be slightly higher than the other for the rain to run off rather than puddle.

You would need to consider the weight of anything attached to the top it could cause the structure to collapse if rain collected on the roof. Better off buying a pergola with a solid metal roof.

Rain does not usually come down vertically!

Without sides, how do you expect it to keep you dry? From which direction is the wind blowing it?

Raising one end (side) will cause any water to run off one side but without actual sides it ain't gonna keep you dry!

Big Lots has canopy covered pergolas at fairly inexpensive prices. They come with a tent type roof that beads and directs off rain water. They also have waterproof curtains that can be used open or closed. However if you really want to modify what you already have first it shouldn't be to bad. It looks like you already have support running across but the canopy hangs from those supports. See if it is possible to weave the tarp over and under the supports already there. Or add a cross support to bring just the center up. Either way should cause a gentle slope diverting the water. Add some PVC pipe between all the supports and hang shower curtains (8 in total). Polycarb is also an option for the top. I installed the Smoke at an angle. Problem is you need to make sure it can be screwed in at every 12-24 inches and then you need to caulk all the seams and screws. Otherwise you get leaks. it lets the light in but not the heat or rain. The easiest fix all together would be ditch the tarp add patio pavers and a table chairs and umbrella then run for cover when it rains.

You will never get much rain protection from your pergola no matter what you do with the roof because it is a tall structure with open sides - the rain just blows in underneath. It is meant for shade only. If you are home when it's raining , close the top. If water pooling in the roof is a problem, adjust the frame so that it is not perfectly level.

Suntuf

26 in. x 6 ft. Solar Control Silver Polycarbonate Roof Panel

running about $15 a sheet. (cost was same at both Home Depot and Lowes) You would not need many, but you would neet to make sure you have a little tilt to it for water to run off.

Roll-Flex.com makes a Motorized Retractable Pergola Canopy that mounts on top. Check it out.