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jogr 10-09-2009 11:27 AM

"Dormer" roofing/fascia detail
Anyone have or know where I can get any good diagrams/pictures/details on flashing/shingling and installing fascia, gutter apron (drip edge) and gutters in the area where a Dormer roof dives into the main roof?

The dormer subfascia dives into the main roof where the bottom of the valley is for the dormer/main roof junction.I'm planning on wrapping the 2x subfascia with steel fascia.

Can anyone give me a sanity check on my detail plans in the following areas:
1) how/where to end the bottom of the metal valley; flush with the subfascia or some overhang? How do I ensure the water kicks out away from the Dormer subfascia/fascia - it can't be good to dump all the valley water right at the area where the subfascia dives into the main roof.

2) Running the main roof shingles where the bottom of the valley discharges - I need to run the shingles up to the dormer subfascia so do I overlap the bottom of the metal valley over the main roof shingles? Otherwise the valley water will drive under the shingles.

3) flashing where the main roof shingles run into the dormer subfascia -use step flashing with the vertical against the subfascia like you would for a roof/wall junction?

4) Cut the metal fascia to cover the vertical parts of the step fascia

5) Cut the end of the Dormer gutter apron to match the slope of the roof where it dives into the main roof and so it stops a little short ( 1/2 inch) of touching the main roof shingles?

6) End the Dormer gutter short of the valley so that there still is clearance (an inch?) between the main roof shingles and the bottom of the gutter to avoid blocking water flow.

I'm still a little worried about that point right where the valley ends and the gutter apron, fascia and main roof all come together seems like a prime candidate for water issues.

AaronB 10-09-2009 02:21 PM

1. We step flash the dormer fascia in order to keep the water out and away from the inevitible openings under the dormer soffit. We also shingle up to the valley, install a wrapped valley flashing, cutting INTO to the flow of water and then counter wrap the valley flashing onto that. If it is just a tin and then a closed cut valley, I will shingle up to the valley, and then ice guard the fascia'/valley transition "just in case, and then wrap all the flashings properly. Metal valleys can be constructed and tied together with the wrapped step flashing from the fascia IF you make a custom flashing for the detail. This does not work out well with just using a regular piece of step flashing.

2. Yes, the valley goes over the lower courses. If you do it right, you can cut and fold/lock the seams at the fascia flashing/valley metal and never worry about it.

3. Yes. If the fascia is clad, I will use the cladding to counterflash the step flashing as well as making sure to install the ice barrier in case there is a buildup of ice in winter, like we see so often in this area.

4. Yes. I take the fascia cladding and run it to the angle of the roof, and use it as stated above.

5. No. I like to see the gutter cut back to vertical and end capped. This will prevent water from flowing out of the gutter and against the water flow at this critical juncture. Just install the gutter apron square cut and into the boxed off gutter end.

6. Yes, as stated.

If you do these things as I do, you will never have an issue.

cellophane 10-09-2009 02:27 PM

the ching books are incredible for any basic architectural graphics and quite a few complex ones. if you dig around ebay you can probably find some older versions for cheap.

jogr 10-09-2009 05:40 PM

Thanks Aaron, I think I understand what you described except that I'm not quite sure about the shape and installation of the "wrapped valley flashing" in this part:

"install a wrapped valley flashing, cutting INTO to the flow of water and then counter wrap the valley flashing onto that."

Is this coming across the main roof shingles and up the fascia where the valley dumps (and maybe extending some up the valley and over the sheathing above the fascia) and then the main valley flashing overlaps this "wrapped valley flashing"?

I'm planning on using the open w valley flashing

AaronB 10-09-2009 06:52 PM

Yes, precisely.

dannydan 08-27-2013 08:47 AM

Some threads never age! Great concise questions Jogr awesome Tech/sound advice Aaron..! My bottom of valley and dormer does not have fascia! Can anyone elaborate as to my wrapping of I&w and metal? Are there any drawings "online" that I can be referred to? My time to git to a library and our bookstore to try to find "Ching" book is slim to nil... THANK YOU IN ADVANCE! I've learned very much in here for my first roof! I have plenty exp. With DRYVIT and conventional plaster/stucco flashing, but not asphalt shingle...

PatChap 08-27-2013 03:52 PM

Maybe take a picture.Do you mean that there's no fascia metal or no fascia there at all? If the former its simple, Get the step flashings behind the wood, or install a fascia wrap.If the latter I would need a picture to see how it's built.

dannydan 08-27-2013 08:39 PM

Thanks Pat... I'll try to do that this week if I can get home before dark! Up at 0430 gone by 0530 and not back till bout dusk. Kids and wife here but she is not gittin up there and kids instructed not to our else! Ty again sir :)

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