Adding a shed dormer to a log house with exposed log ridge beam

WillyJohan · February 21, 2021, 07:24:58 PM

Hi All,

My wife and I recently bought a log house that needs a new roof (and likely a bunch of new roof structure as well). The current roof pitch is 14 over 12 and we figure that while we're up there we might as well throw in some dormers (proposed pitch 6:12). We'd like to have simple shed dormers that start at the exiting peak but we're struggling with the detail of how the rafters will come together and also rest on the exposed log ridge beam.

Hoping there is a solution to this other than starting the dormer down from the existing peak. any thoughts or advice would be appreciated.

Here is the current condition (more or less):

Here is the problem:

And here is what we are shooting for:

Obviously a case at being better at computers than real life...

firefighter ontheside · February 21, 2021, 08:41:44 PM

Looks a lot like my house. I have 2 dormers on my second floor. Main roof is 9/12 and dormers are 3/12. Both dormers are in the master bedroom. They come from the roof ridge log. One goes all the way to the outer edge of the house and creates the master bath and the other goes about 2/3 of the way to make the rest of the master bedroom. They could have been done from the second purlin down, but that would have made the roofing more complicated. I wish I had made another one in the loft area. It has too low of a ceiling. If I remember correctly, we made the dormer roof thicker to make up for the issue you show of the two not lining up.

firefighter ontheside · February 21, 2021, 08:43:38 PM

Sorry about my head being in the pics. I took them with my laptop that does not have a front camera. In the second pic, there is a fake purlin on the outside around where the blanket hangs on the wall. That way from the outside there is still a main roof and a dormer roof above it.

WillyJohan · February 21, 2021, 09:20:16 PM

Hi there, thanks for the response. It does indeed sound like we're attempting to do what you did with your place, glad to hear there is a relatively simple solution, though because of the existing 14/12 pitch and the existing 2 x 14 rafters this solution would require ~24" deep roofs on the dormers, I guess i wouldn't have any issues with finding places to put insulation. That said, with the price of wood these days it might be cheaper to go the cripple rafter route and just invest the money we save on wood into properly detailing out the additional valley.

Nice looking place you got (head notwithstanding), did you build it your self?

Thanks again for the insight.

firefighter ontheside · February 21, 2021, 09:35:05 PM

Thanks. The logs were peeled and assembled in MN and then taken back down and sent to MO. The log home builder came down with one of his guys and then we spent 2 days stacking the logs with the help of a crane. I spent the next year finishing the house.

barbender · February 22, 2021, 10:24:57 AM

What company did your place, firefighter?

firefighter ontheside · February 22, 2021, 04:52:11 PM

Quote from: barbender on February 22, 2021, 10:24:57 AM
What company did your place, firefighter?

Senty Log Homes out of Grand Marais. I just looked them up and it appears they may be closed. Not sure. I know they had started doing regular contracting and Mike was probably upper 40's 20 years ago when we built the house. Maybe he retired.

Don P · February 22, 2021, 06:16:27 PM

I think you could add about 10 years to that age.

Looking at the first pics I was thinking just drop the dormer rafters onto the ridge beam, and I amm assuming it is a beam capable of supporting half the roof load. Then finish out the dormer to the upper deck. Then make a return from the higher pitch down to the dormer on the topside.

firefighter ontheside · February 22, 2021, 07:09:47 PM

I was never sure of his age. When I went to visit him the year before we started building, he had very young children, so I figured he was younger than he looked.

WillyJohan · February 23, 2021, 12:55:47 AM

Hi Don P, Thanks for the suggestion. I am also assuming/hoping that the beam can hold half the roof (It has been for 40 years, is there any reason to think it wouldn't?). I'm not sure I understand your suggestion correctly, are you suggesting that we run a second set of smaller rafters between the dormer end and the ridge line? something like the attached picture? How would the snow load get transferred to the beam?

If that works I could save a few dollars reducing the lower rafters as well.

thanks again.

Don P · February 23, 2021, 08:37:03 AM

That's it but return back down to the 6/12 at the 14/12, I think it should intersect pretty quick.

WillyJohan · February 23, 2021, 02:20:34 PM

Ah, so like this?

i do like this solution more than the cripple rafters, it still has the pitch change that we were trying to avoid but now that where not doing a metal roof anymore i guess it doesn't really matter that much.

Thanks again.

Don P · February 23, 2021, 07:35:47 PM

Yup, that's it

.
Don't forget to somehow get a good connection between the shed and old rafters at the peak.

Looking at your elevation drawing in the op it looks like you are eliminating a purlin that was at midspan up the roof. You are changing ridge loading. I'd get a local engineer to come visit and check this all out.

WillyJohan · February 23, 2021, 07:44:33 PM

Quote from: Don P on February 23, 2021, 07:35:47 PMDon't forget to somehow get a good connection between the shed and old rafters at the peak.

Will Do. We're super curious (read: terrified) as to what were going to find under there. Apparently the original builder milled the 2x14s rafters out of cottonwood. So there that, and a 40 year old cedar shake roof, so we may be looking to get a good connection between the shed and new rafters at the peak...

No current leaks and only one obvious stain around the chimney, so perhaps we'll get lucky.