PVC is light and can be assembled fairly quickly using adhesives and connectors. However, PVC structures are easily blown over in the wind unless they are anchored to the ground. PVC gazebos should have one or more screw-in tie-down anchors for each post or the posts need to be set in concrete. The instructions below call for cementing the posts.
Purchase a cloth-covered octagonal gazebo top of your desired diameter. Choose the location of your gazebo. If you have a large yard with multiple vistas, center your gazebo so that you will be able to enjoy all of them.
Assemble your gazebo top according to the manufacturer's instructions. Lay the top on the ground where you intend to build your gazebo. Mark the eight corners with stakes. Remove the top and and run survey tape from one stake to the next. Measure the distance between each stake to determine how long the eight PVC poles that will create the top frame should be. Dig 2-foot deep post holes just inside the survey tape at each of the eight corners.
Assemble the top frame of your gazebo. Apply PVC cement to one end of one of the PVC poles you've cut for the top frame. Allow the cement to dry until tacky. Insert the pipe into a three-way connector. Continue until you have all eight pipes connected in an octagon, with the third connection at each point facing the sky.
Apply PVC cement to 1 inch of one end of each 10-foot long PVC pipe. Insert the coated end into the third connection of each corner of the gazebo frame. When the adhesive has had time to dry, get one or more assistants to help you lift and flip the frame. Move it until each pipe is set into one of the holes you dug in Step 2.
Backfill each hole with flat sided gravel. Mix quick-drying cement in a wheelbarrow according to package directions. Fill each hole with concrete.
Hang a plumb bob from a spirit level set on top of each corner of the gazebo one at a time. Adjust the posts until they are vertical and even with the plumb line. Brace the posts until the cement dries to keep them straight.
Attach the fabric-covered top to your gazebo according to the manufacturer's directions.