Decks, Patios, Porches and Docks - Pergola

I want to build a pergola and can't decide whether to use 2x10's or 2x12's and on what centers to best provide adequate shade. The 2x's will run east-west and it will be adjacent to the east side of the house so it is mainly morning and mid day sun that I am trying to block.

Assuming Chicago latitude does anyone have any experience or recomendation?

What you use for the rafters (or joists) and how far apart you space them is determined by how far they are spanning and what snow and wind load they have to meet, what they are supporting -- their dead load -- and what species of wood you are using.

Sorry, but it is not a matter of loads, span or wood species. The pergola will be 2x10 or 2x12 on edge like floor joists, but that's it...no floor, no ceiling, no load except the weight of the joists that will span only 10 feet. The purpose is to provide shade on the patio, and can serve as an arbor for flowering vines if one desires. I could show a picture of what I have in mind here if I knew how to do it. (I have read other posts that included photos)

My question has to do with the proper proportions to provide shade. If the joists are too short or too far apart they will not be affective. If they are taller and closer together than necessary it is a waste of lumber. I am trying to find the ideal proportion if someone has some experience with this type of overhead sun screen.

Your best bet would be to build a small example of some saw horses (using the saw horses as your girders) and then position 3 or 4 of your choice of joist matter to determine what manner of shade best suits your personal tastes. Each joist only has to be about 3 feet long to give you enough of an example to work with.

I recently saw a pergola made with the top slats at an angle, which would provide more shade than just the upright boards. I don't know the problems involved (if any), but just thought I'd share that. :)

Your best bet would be to build a small example of some saw horses (using the saw horses as your girders) and then position 3 or 4 of your choice of joist matter to determine what manner of shade best suits your personal tastes. Each joist only has to be about 3 feet long to give you enough of an example to work with.

Thanks. I did a test and I don't get as much shade as I expected. :(

I recently saw a pergola made with the top slats at an angle, which would provide more shade than just the upright boards. I don't know the problems involved (if any), but just thought I'd share that.

Thanks. I thought about putting the slats at an angle, but wondered if that would look goofy. I also thought about making them adjustable like a venitien blind, but that seems too involved. :wall: How did the angled slats look to you?

Well we usually will build our pergola frame (girders and joists) similar to how a deck is built with the exception of adding decorative tails to the girder ends and joist ends (or ceiling rafters in this case). We then use 1x4 as a shade decking over the top of the joists (spacing about 2 to 3 inches inbetween each 1x4). The 1x4's actually are whats producing the most shade but unfortunately their far from being up to the job of carrying any sort of snow load (something we rarely worry about down here). You may want to look into building your pergola to deck code with snow loads in mind but then actually spacing your shade/decking (probably 5/4 boards ripped in half) to suit your shade preference. In essence, your building a second level deck without the handrails and it needs to meet any and all snow load concerns.