Roof Pitch

[Byron Trantham]

How is the pitch referred to when it rises 12" for every 24" of lateral travel? Is this pitch reasonable for an area that gets about 20" of snow at any one time (it is a rare event)?

Thanks

[Wes Bischel]

How is the pitch referred to when it rises 12" for every 24" of lateral travel? Is this pitch reasonable for an area that gets about 20" of snow at any one time (it is a rare event)?

Thanks

Byron,
If I did my math right, 6/12 pitch. It's not a bad pitch for snow - the bigger issue is to make sure your structure has the snow load calculated in with the roof load plus a safety factor. If you are getting pre-made trusses the engineer and the local code will dictate the size of the framing lumber to carry the loads + safety factor.

Just for reference, my cape cod has a 10/12 pitch which is pretty steep. (especially when attempting to walk it - emphasis on attempt)

What are you building - a new shop? :D

Wes

[Chris Padilla]

Byron,

Think of it this way: rise/run and then adjust the denominator of this fraction (the 'run') to 12 since that is how roof pitch is normally dictated.

The angle created by a rise of 12 over a run of 24 is 26.6 degrees.

To figure that out, you'll need to use trigonometry:

Tan x = rise/run; x = Arctan rise/run

Here, we have tan x = 12/24 or tan x = 6/12; x = arctan 6/12 = 26.565 degrees.

Arctan is the same thing as tan^(-1) also called the inverse tangent.

To check yourself, a rise of 12" for every 12" would result in a perfect 45-degree angle. x = arctan 1 = 45 degree.

Hope this helps.

[Dean Baumgartner]

Byron,
As others have said that's a 6-12 pitch. Pretty common here in Wisconsin were we often get lots of snow. As long as the roof is designed for the snow load that pitch should be fine.

Dean

[Michael Perata]

Byron,
As others have said that's a 6-12 pitch. Pretty common here in Wisconsin were we often get lots of snow. As long as the roof is designed for the snow load that pitch should be fine.

Dean
A little story.

Back in 1976 I was an executive for a major homebuilder located in California. At the time, most of our roofs were 5 - 7/12 with no added structure for snow loads.

We bought a project in Boulder, Colo and proceeded to put up 68 homes in the summer, and replaced 68 roofs the following spring after they all failed. We took a house designed for the moderate climate of coastal California and simply (ignorantly) plopped them down in snowy Boulder. (This wasn't the only REALLY stupid mistake we made, but I'd be typing for hours to tell you all about them.)

6/12 roof pitch is fine, as long as it was built for the load.

[Julie Wright]

So what if you dont need to have a snow load roof? I was thinking about putting up a cover over our back porch. The main problems here is the intense sun!!!

What kind of pitch would we need?

[Frank Pellow]

I have built 3 buildings at my camp inear Hearst in Northern Ontario (about 1000 kilometres north of Toronto) and they all have 6 in 12 pitch with 1/2' plywood on 2x6 spruce rafters set 16" apart. We get at least 40" of snow depth on each winter and there has never been any problem.

[Rob Russell]

So what if you dont need to have a snow load roof? I was thinking about putting up a cover over our back porch. The main problems here is the intense sun!!!

What kind of pitch would we need?

Julie,

When I was designing our addition, roof pitch became a little of an issue for us because of the width of the addition. I wanted to maximize the width we could build, but there's a window on the second floor that was going to get sorta close to the roof. The existing house was a 5/12 pitch, addition ended up 4.5/12; since the ridge of the addition roof is perpendicular to the main roof (addition sticks out the back of the house), you can't see the pitch change. My architect Dad told me that the minimum pitch in our area is 3/12 - flatter than that and you need to treat it like a flat roof (big can of worms I didn't want to open).

Getting back to your question, for your needs, it's more a matter of shedding rain than snow load. You could do a fairly flat roof, like a 2/12 pitch and that'd be fine. I'd think a nice 2' - 3' overhang to give you shade on the porch even in mid-mornig or mid-afternoon sun would be nice. I put a 2' overhang on our addition and it means we can open the top awning windows even when it's thunderstorming. Nice to have the extra shade and I think we can all agree that snow load for you is probably not a long term problem.

I'd guess the biggest issue you have is framing to meet local hurricane codes. Around here, the roof shingle nailing schedule was changed a couple of years ago to require 5 nails per 3-tab shingle instead of the old 3 nails. Hurricane clips might be a local code requirement. These become especially important if you do a wide overhang on the porch roof because that wide overhang provides a nice big area for hurricane force winds to develop lift and try to take the roof off of your porch. The wide overhang isn't a problem - I'd do it in a heartbeat. Just plan accordingly.

Rob

[Byron Trantham]

As usually for this site, thanks for all the help. I making shed for lawn stuff. I went out and priced a 10x12 and it went for about $2400. Materials are about $1200. Think I'll build it IF the Home Oweners Association will let me. The original request was rejected. They want a picture! Well, let's see now, a picture, hum, I don't think I can get there from here. :o

The original request included everything except the pitch and door. I don't have a clue what they want to know about the door. Let's see, it will be about 6' high, have three hinges on each panel and a lock. Man I hate the HOA! Another month gone by. :mad:

I think I will submit the 24 pages of Autosketch and Cut List Plus that describes the project. Think they will be able to make heads or tails of it?

[Glenn Clabo]

Byron...
HOA??? Oh how Fredericksburg must have changed. I can remember when there were only farms and fields.

[Byron Trantham]

Byron...
HOA??? Oh how Fredericksburg must have changed. I can remember when there were only farms and fields.

Tell me about it. We moved here about 10 years ago and we did pass cows, fields, etc. Now we pass 7-11s, strip malls, you name it. Our HOA seem to be a bunch of "we don't know s..., but we're going to tell you how to do it!" :D

[Mark Rios]

So what if you dont need to have a snow load roof? I was thinking about putting up a cover over our back porch. The main problems here is the intense sun!!!

What kind of pitch would we need?


Julie, I agree with Rob Russel on the point of roof pitch. Your concern would be with shedding the water. On shallower pitches, < 3/12, the water tends to hang around and find little place to start growing things. There is a lot of moss/mold that grows on shallow roof overhangs. Just my added two cents.

[Jim Becker]

Tell me about it. We moved here about 10 years ago and we did pass cows, fields, etc. Now we pass 7-11s, strip malls, you name it. Our HOA seem to be a bunch of "we don't know s..., but we're going to tell you how to do it!"

I'm really surprised you have this issue being out in the woods like you are! At any rate, perhaps you can download the 8hr trial of SketchUp and give them a 3D picture to die for...:p