Wednesday, March 12, 2014


I am thinking of putting a roof/cover over my existing patio. I will be using corrugated metal and building the frame from lumber. It will attach to my house and extend out only 8'. My question is would using 2x4's for the frame be sufficient for the 8' span or do I need to step up to 2x6's? I was planning on putting the joists on 24 centers unless you think I need to go to 16 oc. Secondly, would a 1-2 drop be enough of a fall for water drainage on the metal roof. The area where I will be attaching this is already low so I would like to go with as little of a drop as possible to keep from losing to much of the height underneath on the end away from the house. I live in Texas so weight from snow in the winter is not a major concern (although we did have 10 fall this year which was a first to me in the 37 years I have been alive and lived here). Thanks in advance for any suggestions and advice you have.

Welcome to the forums! How low is low. Your starting height is critical. You don't want the outer edge of the roofline to be lower than your head, and you need to have a good drop for rain run off. Don't forget the overhang, which will add another foot to the roof, making it 9', which will require 2x6's. Also 24 is minimal. I prefer 16. You will be installing strapping across the joisting to attach your metal, so be sure to extend it out past the last joist.

chandler already covered your questions but I’ll add a couple thoughts.
While you may be planning to do this project w/o pulling a building permit, I would build the roof over patio to be code compliant . . . it will help save you from future headaches when selling the property or filing an insurance claim if damaged (insurer will likely demand cost documentation possibly ask for a building permit). If a building permit is required and you elect not to get one, this doesn’t mean you’re completely free of all possible headaches but they should be lessened if you have detailed photos showing how the structure was built and can demonstrate it was code compliant when built. Remember, when selling the property, there is usually a standard clause in the purchase contract whereby you’re making a representation that the building is compliant with building codes. If you sign the contract without modifying that representation when having knowledge that no building permit was pulled (fairly easy to evidence approximate time it was built if your state does a periodic fly-over taking aerial photos or looking at Google earth), then you’re picking up future cost liability should the new buyers run into a code compliance issue or someone is injured by what was unlawfully constructed .
With respect to 24 vs. 16 oc, I would definitely go 16 oc if your home was originally framed this way as it should be easier to tie together and less noticeable to a home building inspector if hired by the buyer when home is sold . . . if your existing frame construction is 24 oc and 24 oc is still code compliant for a new roof structure, then the call is less clear and you’ll need to weigh tradeoffs with respect to a shallow sloping roof being sufficiently strong to handle a 1 in 100 yr. snow event as you just experienced. Don’t bet “Global Warming” means less cold or snow in future as that is now covered by the new “Climate Change” terminology should we enter into another ice age era.

low would be 89 from the concrete patio to where the top of the framing would be. I should also clarify that I will be using 8' metal so the 2x frame won't be 8'.
thanks for the replies

89 is minimal, but probably necessary in your case. In figuring your metal length, don't forget your soffit overhang and the overhang past the framing. You can have metal cut any length you want from a metal fabrication company.

yes, 89 is all I have. I was given the metal which is 8' so that it what I will be working off of. Thanks again for your responses.

Tags: metal, roof, patio, building permit, code compliant, metal length, selling property, that building, when selling, when selling property, which will, will using