adding dormer

[chrisbrowning]

I have the outside of the 12x 18 cabin done (shingles and siding). Now a crazy thought entered my mind. What if I added a shed dormer to the loft area. The floor is already there. I would just have to cut shingles off, sheathing off, and frame in the added height. Since the ridge is aprox 5 ft tall the ceiling height would be quite short. Probably enough to make my grandsons happy for a couple of years. How difficult would the framing be? please share thoughts

[glenn kangiser]

Hi chris-- as I remember this framing manual has good pictures of shed dormer framing and is printable -about 55 pages.

http://countryplans.com/cgi-bin/yabb/YaBB.cgi?board=0003;action=display;num=1107753097

[chrisbrowning]

Glen,

Is it more difficult adding this shed dormer now that I am done with the house? Because I will be replacing some of the rafters to form the dormer. Do the collar ties or in this case the floor joists add enough support to the house while you are removing rafters and redesigning the form.
Also does this added weight on one side of the house change the stability of the house?
thanks chris

[glenn kangiser]

It's always a bit more work to change things after they're done-- I consider it as 3 times usually--1 time to do it the first way or in a case of a mistake, the wrong way.  1 time to tear it apart and 1 more time to put it back - of course this only applies to the affected area.

I don't see a problem if the joists hold things together and the weight change is not that much.

Possibly if someone else sees a problem they will add to this.

[John Raabe]

I agree with Glenn. Double the rafters and tie it in well with the floor system. Check below to see if you are adding a heavy point load to the center of a wide window header (might not be able to open that slider next year  ). Other than that the loads will likely work their way down to the foundation without too much complaint.

[chrisbrowning]

John,
Thank you for your reply. Just want to clarify- when you say double the rafters. I take it you mean the rafters over the dormer itself?
That would mean the spacing would be 12 inches over this area of the roof. Right?

[John Raabe]

No, you just need to double the rafters where the dormer side walls will land. The rafters at the roof of the dormer itself will still be 24" o/c.