Calculating Dormer!

softgun

Pitch: 5 in 12
Span of hip roof: 8'
Span of dormer (based on the length of the ridge board): 4'
Thickness of each lumber: 2" by 4"
Openning of window: unknown

Is it possible to calculate the heigh of the dormer stud?
Is this dormer too small?

--Thanks

PainterPaul

“Span” refers to the distance 2 common rafters joined together would cover… usually the width of a structure. Your 4’ reference is the length of the ridge, not the span.

>>> Pitch: 5 in 12

If your dormer IS 4’ wide, you’d divide the span in half (2’). Your 5/12 pitch means for every 12” of span, your rafter rises 5”. So for 2’ (24”) you’d have a total rise of 10”.

Don’t know what you mean by “dormer stud”.

Scott Young

from your post, it sounds like you are a beginner or a homeowner. if it is the former then find someone to study under, basically you do the same as you would a rake wall. but instead of placing it under the roof you are placing it on top.

if you are a homeowner, then the math computations and figuring will only give you a head ache and then it will become a migrane when you try to apply it to the actually structure. best advice i can give to a ho is as follows:

lay out the bottom plate and the measure each stick while up on the roof. start on the longes stud first, and then place your top plate. then trial and error the rafters. it is small enough to do in a day even building it in place. trust me it will save you time in frustration.

Scott Young

i just reread you post again. if total distance of the ridge is 4', i would think that would be entirely too small for a house. now for a small workshop trying to mimic the main house maybe, but i would make everything proportional to the eye. this means it may not be an exact ratio mathmatically.