Carpenter/Roofer...Help! Need 35 degree roof...I need a clue....bewildered here

julesfl · December 30, 2014, 05:13:58 PM

Hello, Merry Christmas! I have researched, watched Utube videos, and self- taught myself on building this Solar kiln. Now, I have hit a "wall" ha, ha, ha. I am now trying to figure out, how to build the roof at a 35 degree angle. I have read about pitch, span, unit of run, hypotho's theory. I am not building a house. I just need a short, simple explanation. I am using 2 x 4's. Any and all ideas, experiences, knowledge, will be greatly, immensely, so appreciated!

beenthere · December 30, 2014, 05:50:22 PM

Do you have a protractor?

Or use an internet site like this one.
http://www.blocklayer.com/riserun.aspx

Plug in the angle of 35° and the "run", and it will give you the "rise", or the height of the wall.

julesfl · December 30, 2014, 07:14:41 PM

Thank you Beenthere. Let's pretend I am an alien who is asking this question (which I have been told by my co-workers that I am). And one is teaching in " room 101", in building a 35 degree angled roof. The alien replys, ohh, yes...pitch, angle and slope calculation, and whipping out their protractor, Oh, Karumba, I still don't get it. They walk away whittling on their 2 x 4, saying , I must be able to make a notch...a notch...just maybe, skipping off into the sunset, whittling away......

thecfarm · December 30, 2014, 07:16:52 PM

Speed square.

Don_Papenburg · December 30, 2014, 07:48:53 PM

Yep , more precise Swanson's Speed Square

If you have any length to the roof I would keep the 2x4s for the next wall.

To make fast calculations try a construction master 5 calculator.
35*=70.02075 %grade , 0.583183 slope , 8 3/8 pitch

thechknhwk · December 30, 2014, 07:57:57 PM

Figure your pitch with a right angle triangle calculator.

http://www.cleavebooks.co.uk/scol/calrtri.htm

On this particular one "a" is your rise and "b" is your run, so like a 4/12 pitch is 4" of rise for every 12" of run and yields an angle of 18.4 deg. Looks like you need between an 8/12 and 9/12 pitch. Cutting the top of the rafter (highest side) on this shed type roof at the 8 or 9/12 will give you ends that are parallel to your outside wall or "plumb". Now you need to figure the birds mouth cut on the low side of the roof and how much higher the wall on the high side of the building needs to be to obtain the desired roof angle.

https://www.youtube.com/watch?v=lr4NwLx_ctk

r.man · December 30, 2014, 08:05:39 PM

Peak roof or shed roof?

pineywoods · December 30, 2014, 09:02:33 PM

On a solar kiln I'd just make everything 45 degrees and don't worry about it. Garontee you can't tell the difference. Every dimension on a solar kiln is a compromise in one way or another.

julesfl · December 30, 2014, 09:51:21 PM

Piney, thanks for the advice. But I really am at a latitude of 27 degrees, and adding 10 for winter, and just evening it out..to 35 degrees. If you really think it doesn''t matter, then that would be a lot easier. I wanted it to be correct, so that's why I went 35 degrees.

I want to thank everyone for their input and expertise on how to get this roof done correctly. I didn't realize what skills are involved with roofing! What I have read is that it is the most difficult part of framing, when it comes to building a house. All I want for Christmas is a roofer. Oh, wait that would be a year from now.
Thanks again, everyone for your help!
Jules

Gary_C · December 30, 2014, 10:17:58 PM

The angle of the sun changes every day from summer to winter so for any location any fixed angle is only going to be "correct" for two days each year. So being close to the midpoint is good enough.

Or you can put those panels on a movable mount and adjust the angle daily or better yet get a tracking mechanism and follow the sun every day. I understand you do not gain much from from the precision tracking.

So bottom line is, close is good enough.

Remle · December 31, 2014, 08:05:17 PM

julesfl
A 35.31 degree angle is formed with a run of 8.5" and a rise of 12". Build the kiln floor to your width of choice, then measure it's width in inches, divide that measurement by the 8.5" run, then multiply the answer by the rise 12". The resulting number is the additional height that you need to add to the short to make the tall wall. Build both tall and short walls, set them braced up plumb on the floor. Take your rafter and hold it on top of the walls, mark a plumb line on the inside of the tall wall and the outside of the short wall face of the rafter. With the rafter in the same location take a piece of 2X4 placed on top of both walls and mark the top surface of the piece. This will form the bird's mouths for the rafter to set on the walls. Cut out the bird's mouths and use this as a pattern to mark the required number of rafters for your project.. one additional note: if you are using 2X4 for rafters the bird's mouth should not cut more than 1/3 the width of the 2X4 or it's strength may be compromised and you need to use a taller rafter. Good luck with your build. Yes guy's, I know the 45 degree roof would work, but why not give him the roof slope he asked for ??

John Mc · January 05, 2015, 11:42:54 AM

If you aren't hung up on the exact 35˚ slope, consider making your roof an 8:12 pitch (8" rise for every 12" of run). That's a standard roof pitch, and comes out to roughly 34˚ (I install PV modules for one of my jobs - the difference in solar performance will not be measurable).

The suggestion of getting a speed square is a good one. You can get one at just about any hardware store. They often come with directions for use, but it's pretty simple - they already have markings on them for doing various roof pitches, which makes cutting the angles on rafters or birds-mouth cuts much quicker. You just line of the square on the 8-pitch mark and draw the line.

BTW... if you don't know what a birdsmouth is, google "birdsmouth rafter" for some pictures and youtube videos. Basically, it lets the rafter sit "nicely" on top of the wall that supports it

Do you plan to dry year-round, or mostly in one season of the year?