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-   -   Roofing a German Style Dormer (http://www.diychatroom.com/f9/roofing-german-style-dormer-131774/)

Thomas O 01-29-2012 06:59 AM

Roofing a German Style Dormer
 
Hello,

I am wanting to build a german style dormer on my house. (dachgaube in German) They are constructed similar to a typical shed style dormer, except that the side walls are angled and thus shingled. My question is, can this be shingled with your typical 30-year asphalt shingles? Of course, in Germany all the construction is clay or other hard shingles as shown in this photo. My only real concern is where the top connects to the side walls. At first, I was thinking that it would just be shingled over top and down the sides, then have ridge-cap along that edge. But would that trap water on the top ? How can this be done? I am really interested in this aesthetically, and would love to be able to pull it off roofing wise with the same 30-year asphalt shingles that the rest of my house has.

Thanks and Danke

http://www.schaefer-holzbau.eu/attac...e/gaube_12.JPG

http://uber-werks.com/temp/dachgaube1.jpg

seeyou 01-29-2012 07:45 AM

Yes, you can shingle the sides. They are roofs rather than walls in this case, but the roofing material (usually slate or cedar shingles) was often used for dormer wall siding. You'll need a transition flashing at the side/top junction that goes under the top roof shingles and over the side roof shingles.

Thomas O 01-29-2012 07:53 AM

But would the transition flashing at the top/side junction be unsightly? Or can that be hidden with ridgecap? And if I add ridgecap, it makes me wonder if water would get caught on the topside of the ridgecap.

seeyou 01-29-2012 08:10 AM

Quote:

Originally Posted by Thomas O (Post 837774)
But would the transition flashing at the top/side junction be unsightly? Or can that be hidden with ridgecap? And if I add ridgecap, it makes me wonder if water would get caught on the topside of the ridgecap.


To my eye, a properly formed flashing would look cleaner. But that's why Baskin Robbins has 32 flavors. Ridge caps could be certainly be used. The way they are installed is just like shingles - the 2nd one is lapped over the 1st one and so on. In your pictures, there is some sort of flashing or cornice between the sides and top. I can't quite make it out.

edit: the top picture uses tile ridge and the lower picture uses a metal ridge. Both lap over both roofs like your ridge cap idea would. My concern about using ridge cap on this detail would be water moving toward the side on the upper roof. With my detail, the water would be shed over the side. Using ridge caps of any type, there's the potential for entry from the side. Some extra steps should be taken to make sure any water that gets under the ridge caps is shed over the side roof material.

Ridge caps are normally installed where both either side is sloped away from them. In this case, one side is sloped away, but the water would be running parallel to the cap on the top roof. Add a little wind and there's a potential leak.

Thomas O 01-29-2012 08:56 AM

I can tell you understand me. Water getting in sideways in the ridgecap was what I was worrying about. By properly formed flashing, what do you mean? I think it means that you shingle the sides first, then add the flashing, then add the top shingles. So then you would had remaining only the overlaped flashing along the side. But how would that look? Could it be done tastefully?

shazapple 01-29-2012 09:16 AM

I imagine the tile uses a transition with some sort of lip to keep water out of the top roof, so using a transition strip as seeyou mentioned wouldn't be so different (the ridge on the tiles are mostly for aesthetics in this case). The dormer you show reminds me of a gambrel roof, so the transition between the top and sides would be similar. You could go for a simple strip like so http://www.nachi.org/images10/Change-of-pitch3.jpg
Or built a slight overhang with a 2x4 and install a drip edge like you would on a normal sloped shingle roof, then use metal flashing to join in with the shingles below.

seeyou 01-29-2012 09:50 AM

Quote:

Originally Posted by Thomas O (Post 837840)
I can tell you understand me. Water getting in sideways in the ridgecap was what I was worrying about. By properly formed flashing, what do you mean? I think it means that you shingle the sides first, then add the flashing, then add the top shingles. So then you would had remaining only the overlaped flashing along the side. But how would that look? Could it be done tastefully?

I would use about 5" overhanging the sides with a hemmed edge and a 1/2" kick back toward the roof for strength. All fasteners would be under the top roof shingles. Nice, clean look. Similar to your bottom photo, but without the bulky part extending back up on the top roof. Much cleaner than either of your photos, not that they look bad.

edit: See shazapple's photo above. Very similar to that detail.

Thomas O 01-29-2012 09:54 AM

Something like this?
http://www.shanghaibuildingmaterial....dgewithhem.jpg

chende9 01-29-2012 11:26 AM

as long as you peel n stick the whole area before you roof it you should have no leaks

seeyou 01-29-2012 11:28 AM

Quote:

Originally Posted by Thomas O (Post 837901)


Yup, except I'd bend the kick back toward the roof, rather than away from it, so it hugs tighter.

seeyou 01-29-2012 11:30 AM

Quote:

Originally Posted by chende9 (Post 838006)
as long as you peel n stick the whole area before you roof it you should have no leaks


Peel and stick - making poor roofers into mediocre ones since 1968......:whistling2:

Frank53 01-29-2012 03:07 PM

I would use a bead of sealant and seal all of the shingles on the upper side to the flashing so water doesn't roll back under, cheap insurance.


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