Roof Pitch; 4/12 or 3/12?

[EddieWalker]

A lot of those don't really have triangles. What I did is based on those designs, dividing the spans into manageable sections and combined them with what I see in my own garage that has been standing for close to 20 years. That is sort of an inverted Fan with a vertical down from the ridge to the center of the bottom chord and just one web angled down and outwards from near the ridge to the center of remaining width of the bottom chord.

If you do not see a triangle shape in a truss, it is not a truss. The triangle shape is the secret to the strength of a truss and it's ability to span distances. Your design lacks this and it does not qualify as a truss. It is not something that I would use.

Google or look up a "Howe Truss" and copy that. It is very simple to build and probably the strongest design out there.

 

[/pine]

FWIW...
Almost all engineered wooden trusses are built with an engineered camber in the bottom based on the weight and design of the truss and roof load...without this camber there will be some sag depending on the span...

 

[PILOON]

OK, this is crazy.
40 or so years ago I built a nice log cabin and di not want snow problems.
I made the roof 6/12 eg 45 deg's. (6/12)
Also insulated to prevent heat loss.
Well it never shed snow! I actually measured as much as 5 ft accumulation when I shovelled it.
I believe it was due to fact that it was well sheltered by the surrounding trees.
Good news is I no longer own it. (owner was well warned)

 

[buckeyefarmer]

Isnt 6/12 like 22.5°? 12/12 is 45°, and it wont hold snow.

 

[EddieWalker]

12:12 is 45 degrees

 

[ultrarunner]

OK, this is crazy.
40 or so years ago I built a nice log cabin and di not want snow problems.
I made the roof 6/12 eg 45 deg's. (6/12)
Also insulated to prevent heat loss.
Well it never shed snow! I actually measured as much as 5 ft accumulation when I shovelled it.
I believe it was due to fact that it was well sheltered by the surrounding trees.
Good news is I no longer own it. (owner was well warned)

The Swiss Chalet design uses low pitch roofs to hold winter snow... they find it a benefit plus people are killed every year when sheets of snow slide off steeper pitch roofs so those roofs have added hardware to hold the snow...

 

[Diggin It]

Got a few more boards up today. Starting to take shape so I can see what I have to work with. I don't do well with images or sketches on paper, I have to see it in the raw. I'll start working on the webs tomorrow. Will probably be either a Howe or modified Fink of some sort. I need those center verticals but I can add some W's also.


It's a little deceiving due to the wall in the foreground. That's a little over 4 feet, so the bottom of the bottom chords is about 9 feet above what will be the floor. The new will be built in stages as I have funds and sweat available, but it make take a few months. The plan is to build it over the old in part so I have something to stand on while working. Eventually, the old will be torn down from inside the new.

 

[BukitCase]

You got a good start; when I did mine I knew myself well enough to go with the modified queen - the center vertical and extra angled chords add strength, and I wanted the ability to have 120 volt, 240 volt, air and dust collection ANYWHERE in the shop, WITHOUT tripping over cords and hoses - so I have drops for all those @ strategic locations, and NONE will give me a headache (I'm 6'0", NONE of the drops are less than 6'6" from floor level.) Truss bottom chords are @ 11', door header is 10' (my 580B's ROPS just clears the door header)

If I someday need power/air/suck somewhere ELSE in the shop, those're ALL light enough that I can just run a piece of 2" square tube across between the 12' centered trusses and tie the wire or hose to that. So far, not necessary... Steve

 

[EddieWalker]

Nice. You might want to add a diagonal brace from the top of the gable peak to the ceiling joist, along the ridge line. 12ft 2x4 should be more then plenty.

 

[Diggin It]

Haven't got a picture of the trusses right now. Went with sort of an inverted Fink, I guess. Looks like a W with a center vertical, spaced at roughly thirds top and bottom. Part of the metal roof is on, but it needs lots more screws once I get the gumption to try to get on top of it.

Been working on moving some of the old barnwood boards off the old shed to cover the new wall. Added a cheap 24 x 24 slider window.

Why can't I find a 6' wide roll up door? I know they make them since I see them on portable buildings/sheds and storage buildings.