| Author | Message | ||
     Joe (Joe) Moderator Username: Joe Post Number: 797 Registered: 07-2006  |
You can use 30 lb. felt as a separator between the metals. If water isn't going to contact the metals inside the sleeve, there probably won't be a reaction anyway. | ||
| Old_school (Old_school) Senior Member Username: Old_school Post Number: 995 Registered: 01-2009 |
Joe, that could be done, but you would want to separate the metals from each other. I suppose that could be the I and W, but that is going to want to melt when the heat is applied to solder it. | ||
| Joe (Joe) Moderator Username: Joe Post Number: 795 Registered: 07-2006 |
You could possibly make a copper cover for the ductwork and solder the counter flashing to it. | ||
| Old_school (Old_school) Senior Member Username: Old_school Post Number: 994 Registered: 01-2009 |
That works! | ||
| Timtrain35 (Timtrain35) Junior Member Username: Timtrain35 Post Number: 17 Registered: 03-2011 |
Old School, we're thinking along the same lines. I figured fabricating all metal work using 24 gauge G90 stock. However, instead of sealant, we will probably go with pressure sensitive EPDM flashing membrane. We'll also use the IWS for a belt and suspenders approach. Joe, the duct work is coming straight out of the attic, straight through the slate roof. It is connecting the unit in the attic space with the unit on the flat roof the slate roofs drain on to. The slate roof sections are not that long from eave to ridge, maybe 30' tops. At this point, it's just a bid. If we get the work, i'll try and post some pics. | ||
| Joe (Joe) Moderator Username: Joe Post Number: 794 Registered: 07-2006 |
How high will the duct work stand off the roof? | ||
| Old_school (Old_school) Senior Member Username: Old_school Post Number: 993 Registered: 01-2009 |
Just use galvanized step flashings and a termination type of counter/flashing. Fasten down the slates on the roof and then screw the termination type counter/flashing to the duct work. Caulk the kick out with a good grade of caulk and it will last for a long time. Some of the guys might disagree with this, but I would consider installing some Grace Ice and Water shield to the roof and to the duct-work before the step flashings are installed. This will act like a gasket when you screw the counter/flashing to the sides of the duct work. It will also stiffen it up a bit. Good luck with that one. | ||
| Timtrain35 (Timtrain35) Junior Member Username: Timtrain35 Post Number: 16 Registered: 03-2011 |
It's horizontal. The top and bottom are the (relatively) easy part. It's the sides that concern me. It's not like masonry where you can step and counter flash, it's metal, and that's the rub. | ||
| Old_school (Old_school) Senior Member Username: Old_school Post Number: 992 Registered: 01-2009 |
Is it going through vertically or horizontally? If it is vertical, you can treat it just like a chimney. If it is horizontal, you will have to make some type of diverter at the top to kick the water to the left or right of both. | ||
| Timtrain35 (Timtrain35) Junior Member Username: Timtrain35 Post Number: 15 Registered: 03-2011 |
Greetings all. We are being asked to flash some somewhat large duct penetrations into an existing slate roof. Listed below are some particulars about the project; - Existing slate roof is roughly a 6:12 that drains onto a PVC flat roof. - Duct work is designed to fit in between the existing rafters and is roughly 16" wide by 3' long. - Duct work is lined (insulated from inside) and will be fabricated from light gauge galvanized. Lost of things to consider on this one including, but not limited to; - Potential for dis-similar metals in contact with each other. - How to effectively and economically counter flash. We've kicked around a lot of ideas in the shop, but I am curious how you all would approach this. Thanks in advance. |
