I learned from your web that pergola posts should follow a tradional way of footings to ensure a sturdy structure. My question is if many posts are nailed to the deck surface without accesing deck board under (including joists or digging another holes), can I also get a strong pergola? For example, one pergola with tradional footings has four posts at for corners. Now in my design, each corner there are 3 posts and so in total I have 12 posts. At every corner the 3 posts form a righ angle triangle shape with perhaps 2 feet apart from each other. Trellis will be added in between to reinforce each other and a planter box with soil filled inside is secured to both deck surface and the 3 posts. I wish to get an advice to see whether such an design will generate a strong pergola structure?

I have also seen some designs use raing posts as the support of the pergola. These posts are merely naided to the deck side. I notice perhaps the structure is still good because so many railing posts are supporting the pergola. Each post will not take too much load. The 12-post pergola idea comes from such a design.

Thanks for help.

The blocks are only intended for used on decks up to 5' in height. The pergola is basically an extremely light frame construction deck. Thus you cannot use the blocks in the corners.

Deckman