Below are comparative drawings of the 4 different rafter and slat spacing options for pergola roofs:
Open Roof Slats 18”, Rafters 18”: The standard Open Roof is the most popular. It uses 1 3/4" x 1 3/4" roof slats spaced 18" apart on center (or slightly less depending on roof size so as to be equidistant from one another). The rafters below the slats are also spaced 18" on center or slightly less and run perpendicular to the slats. This spacing results in a balance between visibility and shade. You get excellent visibility and more shade from it than you normally would think due to the height of the timbers and because the sun is rarely directly overhead.
Open Roof Slats 12”, Rafters 18”: If you prefer more shade you can increase the amount of roof slats to 12" apart on center or closer. Pricing is higher to cover the added timber involved. The least expensive route to add shading is to add roof slats and leave the rafters at 18 inch spacing. If you want more shading than the 12 inches on center, just contact us or make a note in the comments box when you order.
- Open Roof Slats 6”, Rafters 18”: For greater shade than the 12” slat option.
PLEASE NOTE: The best way to increase shading while retaining maximum visibility and not spending anymore money on extra roof timbers is to orient the rafters north and south. If the rafters are running north and south, the sun has to rise and set over them. This gives you a lot of shade in the mornings and afternoons.
The most popular roof style has always been with the slats and rafters both set at 18 inches on center. Please keep in mind it is easy to underestimate the amount of shade the 18 on center spacing creates. If after installation you realize you prefer extra shade, you can add slats then. We keep your construction details filed, so you can add roof slats anytime to create the on-center spacing that will work best for you. Our design pros can help you calculate how many more slats you'd need based on the spacing you'd like to move to.