The biggest cost factor for the op is the fact that the garage was built with the pitched roof as part of the design and to modify that as well the attachment of the joists to support a deck over the flat roof would almost certainly be deal killer.
Convert pitched roof to deck.
To do this simply convert the rise and run as a fraction to a decimal form eg.
Putting aside the obvious question of that s a terrible idea why would you want to do that there are really only two ways to go about that.
Since most roof decks are floating structures that sit on top of flat roofs it s crucial to weatherproof the roof below the deck to prevent water from seeping into the home.
To safely install a roof deck the roof needs to be able to support about 55 pounds of weight per square foot in general.
You can use purchased rafters for a pitched roof to be covered with shingles you can place roof joists from your side walls for a flat roof or you can use framing lumber to build supports for a lightweight fiberglass or similar roofing material.
You either have to raise the height of the eaves or lower the height of the ridge.
First convert the pitch to a slope.
However this calculation can vary depending upon what you plan on.
I repair replace and build decks i do not notch my 4x post but when it is there already i like to use metal bracket on the two sides and if possible go underneath the deck and beef up the framework and add more support were i can the main idea in my opinion on rail system and support depends on how high the deck is.
Instead a pair of beams rest on supports called sill plates to create a frame for the deck.
I am working on a roof deck.
Rise run rise run slope.
The roof must be able to support 55 pounds per square foot at a minimum.
To find the angle of a roof in degrees convert the pitch to a slope then convert to degrees by finding the arc tangent of the slope.
Install your rafters or roof framing.
Roof deck framing unlike for decks at ground level doesn t entail a ledger attached to the rim joist of a house.
The typical way is to remove the existing roof and add new framing to the home that create a pitched roof over the old flat roof area.
For a pitch expressed in.
If you are building a flat roof allow some slant to drain water.
Likewise the structure can be.
Before installing a roof deck you must be certain the roof is stable and weatherproofed.
On houses new pitched roofs typically are supported by the exterior walls as with standard sloped roof construction.
There are several ways to convert a flat roof to pitched.
The op acknowledges there are other spots on the property to build a deck in a more traditional.