Help required to judge the pitch of a roof as an angle?

[Ed Bray]

I am going to build my wife a summerhouse which will be 11ft x 8ft x 6.5ft at the eaves. The building will be made from LogLap.

I fancy using western red cedar shingles for the roof, but these require a minimum pitch of 14 degrees. The roof will be pitched from both long dimensions.

How do I calculate the anticipated pitch of the roof, and what pitch would I need to have to get a 14 degree slope for the shingles?

Hoping someone can help, thanks in anticipation.

 

[Bigbud78]

That's approx 1:4 slope, which face is the slope on ?

 

[blackrodd]

Is this link to an angle calculating table any use? Has other useful stuff too!
Regards Rodders

http://www.blocklayer.com/PitchAngle.aspx

 

[Ed Bray]

Thanks for the prompt reply, the slopes will be on the long faces.

Is that 1 along and 4 up?

 

[Jacob]

14º might work but would look a bit shallow. I'd think of 30º at least.
If you can't work it out go for 45º - the rise will equal the run

 

[Ed Bray]

Is this link to an angle calculating table any use? Has other useful stuff too!
Regards Rodders

http://www.blocklayer.com/PitchAngle.aspx

Thanks Rodders.

 

[Ed Bray]

Thanks for the reply Jacob,

I've just downloaded the data sheet and it states 3-12 which is the same as BigBud78 said, but isn't that 3 along and 12 up which seems a very steep slope to me?

www.roofingsuperstore.co.uk/user/u/file ... ingles.pdf

 

[Bigbud78]

You want a minimum of 19 degrees really as you will get better coverage on the shingles, if you look at the specs for the different grades they tell you what coverage you get. Shingles are lovely to look at but a pain to fit lol

https://dl.dropboxusercontent.com/u/98674611/house.jpg

 

[Bigbud78]

Also you say 6.5 for eaves level but will there be an entrance or window in this face ? Standard door opening is 2100mm (6'11") which is also standard window head height

 

[Ed Bray]

You want a minimum of 19 degrees really as you will get better coverage on the shingles, if you look at the specs for the different grades they tell you what coverage you get. Shingles are lovely to look at put a pain to fit lol

https://dl.dropboxusercontent.com/u/98674611/house.jpg

Wow, that's a great drawing, many thanks, still looks a bit shallow to me though, could I go for either 30 degrees or even up to 45 degrees as Jacob suggested, to make the building look more in keeping with her ideas?

 

[Bigbud78]

This is 45 with grade 2 shingles

https://dl.dropboxusercontent.com/u/986 ... G_6239.jpg

 

[Ed Bray]

Thanks again, that looks great, so if I take 1/2 of the side 4ft and make a right angle with the same dimension 4ft, square them both 16ft x2 add them together 32 and take the square root of that give me a hypotenuse of 5.65ft. If I multiply that by the length of the building 11ft I get 62.15 square feet per slope. Does that seem correct?

 

[NickWelford]

Isn't 14 degrees closer to 1 in 6.5?

 

[NickWelford]

Thanks again, that looks great, so if I take 1/2 of the side 4ft and make a right angle with the same dimension 4ft, square them both 16ft x2 add them together 32 and take the square root of that give me a hypotenuse of 5.65ft. If I multiply that by the length of the building 11ft I get 62.15 square feet per slope. Does that seem correct?

Essentially correct. I make it 62.25 but you will need extra anyway to cater for splits and cut ones. Be careful placing shingles so that you get the correct overhang at the bottom and meeting at the top. (Badly explained, but someone will know the right words!).

 

[Bigbud78]

Isn't 14 degrees closer to 1 in 6.5?

1/4=0.25
0.2Tan-1=14.036

or

14Tan=0.249
1/0.249=4.01

1:6.5 is 8.746 Degrees

 

[Bigbud78]

Thanks again, that looks great, so if I take 1/2 of the side 4ft and make a right angle with the same dimension 4ft, square them both 16ft x2 add them together 32 and take the square root of that give me a hypotenuse of 5.65ft. If I multiply that by the length of the building 11ft I get 62.15 square feet per slope. Does that seem correct?

Essentially correct. I make it 62.25 but you will need extra anyway to cater for splits and cut ones. Be careful placing shingles so that you get the correct overhang at the bottom and meeting at the top. (Badly explained, but someone will know the right words!).

That doesn't allow for any over hang at eaves or gable either does it ? As Nick says you need to make sure the spacing is such that the joints don't line up over 3 course's ala

http://inspectapedia.com/BestPractices/Figure2-50.jpg

 

[Sheffield Tony]

The maths is pretty easy here : tan(14) = opposite/adjacent = 0.249328 which is near enough 1 in 4; one unit up for each 4 horizontally.

Now, I have heard that 45 degrees as a roof pitch is avoided in architecture, and sometimes called "the ugly angle"; steeper or shallower looking better than not quite decided. But that picture from Bigbud78 does not look at all ugly to me.

Edited to add: someone got there before me !

 

[Ed Bray]

Also you say 6.5 for eaves level but will there be an entrance or window in this face ? Standard door opening is 2100mm (6'11") which is also standard window head height

Sorry, missed this one in all the posts, yes there will be a set of double door and a window each side of them. there will also be a window in each of the sides, but the back will be just loglap!

I was going to make the doors myself so was planning on them only being about 6ft or so with 6" above them for the header (casing).

Thanks to all for your thoughts and advice and it is truly welcomed.