Our patio is similar sized, 26x24. The pergola is 8x12 so roughtly a quarter of the space. We do have other shade however.

That’s really nice! It seems like a great size for the space.

1/2 is all you really need, my first concern is how it will affect the lighting inside the house.

are you okay with some shade over either the window(s) or the door?

What direction does this side of your house face? The primary function of a pergola is to provide light shade. If the direction is southwest or west, the sun will be at a lower angle, and not every space under the pergola will be shaded.

That’s been our debate. I love the sun and heat. We put in this patio and my husband never uses it because the lack of shade. Thanks for pointing that out. I’m willing to give up a little sun to the kitchen, but hate to lose it by the sliding glass doors.

This area is West facing. Thanks for the photo. Great point.