Ridge beam and Rafter size

[Quebeker]

I suppose it has been discussed before but...

I'm building a 16'x20' shed. I will put my ridge beam and rafters next w-e. I've been screaning the web to find the exact calculations for my beam and rafter size but I'm not 100% sure. I've attached a picture to show you how the structure looks like.
I'm using hemlock rough sawn wood.
Beam lenght is 21'8" suported halfway.
Wall lenght is 16'
I'm using 2 2"x10" nailed together for the beam (so 4"x10") and 2"x8" for the rafters every 16".
My ratio is 6/12 or 45deg.

Can someone help me make sure my roof will hold!

Tks

Mat

 

[Woody610nb]

Well first off, a 6/12 pitch roof is not 45*, a 12/12 is 45*. A 6/12 would be 22 1/2.

 

[Quebeker]

My mistake...

12/12... 45deg.

About the beam and rafters? Any idea on the size it should have?

 

[kbs2244]

If you are putting a support post midway you only have a 10 foot span.
A 4 x 10 will be plenty strong, even in pine.
Just be careful with your splice locations.

 

[Woody610nb]

Well I'm not an engineer, but your whole shed is over build, which is not a problem, I think it is very safe to say that your roof design is more than adequate for any roof load you will encounter.

 

[pattenp]

Most definitely.

Well I'm not an engineer, but your whole shed is over build, which is not a problem, I think it is very safe to say that your roof design is more than adequate for any roof load you will encounter.

 

[Falcon67]

If you have rafters with tails that sit on the top plates, the ridge carries no roof weight. If you are using 2x6 rafters, a single 2x8 ridge should provide plenty of nailing surface. Now, if you don't have rater ties (joists) at the top of the walls, then you could use a big beam supported on both ends. But you won't need 2x8 rafters. Span for Pine shows 2x6 is plenty for that span.

http://www.wclib.org/pdfs/simpspantbls.pdf

 

[borgdog]

I think we are missing a key piece to the puzzle, and that is roof load or snow load. With out that any discussion doesn't mean much.

 

[Quebeker]

My cotage is in Saint-Michel-des-Sains 100 miles North of Montreal. From what I've find on internet snow load (Ss) is 77.3 psf or 3.7KPa and rain (Sr) is 8.35 psf or 0.4KPa.

The top of the rafters will hold with steel connectors: http://www.uspconnectors.com/discontinued_products/136.pdf

The bottom also with huricane connectors RT7

Birdsmouth cut 3-1/2" x 3-1/2"

Tks again!

 

[borgdog]

Very nice looking shed! Wish I could help with the structural, but I'm not an engineer and the table Falcon67 posted does not go that high on loads, I just know that it is needed, hopefully somebody more knowledgeable chimes in, but my seat-o-pants meter says what you propose should work.

 

[Quebeker]

Well Dan... We're using the same meter! I would just sleep beter with a confirmation that it will hold for the next 100 years or so...

I checked on Falcon's chart and it's not close to the load we have here because of the snow!

Tks
Mat

 

[Zeke]

I think we are missing a key piece to the puzzle, and that is roof load or snow load. With out that any discussion doesn't mean much.

How much snow can stay on a 12/12?

 

[readhead]

Old steel or shingles, a lot.

 

[Quebeker]

Well I guess I will do as planed!

I will also put 2 bottom chord where I don't have a beam... A friend sugested that the walls could open up with the weight of the snow and everything could colaspse.

I'm thinking threaded rods or something... Any sugestions?

 

[DekeT]

Doesn't anybody read books anymore?

 

[Quebeker]

Doesn't anybody read books anymore?

I suppose you are refering to the ignorance of your answer?

 

[Falcon67]

I think we are missing a key piece to the puzzle, and that is roof load or snow load. With out that any discussion doesn't mean much.

Good point. If he'd posted 78 lbs/sq ft snow load in the OP I would not have even bothered to post a span table. Want nothing to do with snow, personally.

 

[Jim Riseborough]

78 psf is alot of snow load. can you spend 200-300$ to have it engineered, instead of asking online?

 

[DekeT]

I suppose you are refering to the ignorance of your answer?

If you don't like my response you may ignore it. But to call my response ignorant? Obvious you don't understand that your answers lie in a good textbook on the subject. So you ask for free advice on the web and won't know if the answers are good or bad. And to top it off you are rude to the person who is giving you best long term solutions to your problems. Who really posted the ignorance here? I know the solutions to your problem because I read books.

 

[blazentrout]

Well Dan... We're using the same meter! I would just sleep beter with a confirmation that it will hold for the next 100 years or so...

I checked on Falcon's chart and it's not close to the load we have here because of the snow!

Tks
Mat

I think it will as my 100 plus year old farm house does not have a ridge pole in it and the rafters just **** up to each other.

 

[C96]

Are you kidding me, I just looked at the picture and your proposed ridge beam / rafters. Hell, you could hang beef in there along with the snow.