Greengate Ranch Remodel
Remodeling a Daylight Ranch in Oregon

Wednesday, May 20, 2009

Backyard #4 - Patio Cover

Now that the fire pit is done, and the patio has had a chance to cure, I have moved on to the patio cover. I was able to get the main structure in place this weekend - here is a rendered image of what I plan to build...

It's a pretty simple design:
  • Ledger attached to the house
  • Main beam to support the rafters
  • Four posts (two on each end) with stone bases
  • Large 4x6 rafters, on a 4/12 pitch (same as the rest of the house)
  • Solid wood roof deck, stained on the under side for the vaulted ceiling
  • Total area is about 160 square feet

    Here is the progress so far...

    The main beam is built up of three 2x8's glued and nailed together. Here is how I calculated the needed beam size:
  • The span between the two inner posts is just under 12 feet, and the rafter span from the beam to the house is 6.5 feet.
  • The general load requirements for Portland, Oregon are 10lb dead load / 25 lb live load (for snow). Even though there are no formal requirements for patio covers under 200 sf in my area, I of course want my project and my house to last (not sag).
  • I looked at various span tables for patio covers (I will link to these below) and determined that I needed either a 4x10 or a 6x8 beam. I wanted a thicker looking beam anyway, so I chose the 6x8. I built it from 2x8's since I am going to wrap it in hardiplank later on. Doing 3 pieces also allowed me to easily leave mortice holes for the posts.
  • The rafter requirements are very light - 2x4's on 24" centers. I think going that route would save a few dollars, but the cover would look light-weight and cheap. After looking at 2x6 and 4x4 rafters on other houses, I decided to go with 4x6's. They are substantial enough to give the cover a "craftsman" feel, and not really much more expensive. These are painted the brown color that we are going to paint the house trim. They should contrast nicely with the stained roof deck. I put these on 32" centers - the spec sheets say I can go up to 48", but I like the look of them closer together. At $11 a peice for 10' long ones, it only cost me $22 extra.

    The ledger on the house took longer to get in place than I thought it would. I took my time to make sure it was square, level and centered with the beam I put up. I attached it with 1/2" lag bolts on 32" centers. If this isn't installed very level and even, then getting everything else lined up later on will be painful.

    I decided to go with a 2x8 ledger, so I could attach a 1x2 lip at the bottom for the rafters to sit on. I did this for two reasons: It makes holding the rafters much easier when you are attaching them, and it covers the bottom gap where the rafters meet the ledger. I noticed this on a number of patio covers I looked at.

    The rafters are attached to the beam with L-brackets and then lag bolted through the tops in to the beam.

    Helpful documentation that I used to design the patio cover:
  • This patio cover building permit form gives a lot of design information. Note that is for a 10lb live / 10lb dead load (no snow)
  • This document is for patio covers in Fort Collins, CO - 30lb live / 10lb dead loads (lots of snow).
  • Finally, here is a good middle of the road one at 20lb live / 10lb dead load.

    From these three sources, you should be able to spec an appropriate cover for your area and design choices.
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