| Author | Message | ||
     brad t. siegmund New member Username: Bsiegmund Post Number: 3 Registered: 07-2007 |
Thanx again, Joe. It makes some sense to me now. | ||
| Joe Jenkins Senior Member Username: Joe Post Number: 147 Registered: 07-2006 |
The purpose of the underlayment is to keep any rain water out of the roof until the slate is installed. It should be as simple and unobtrusive as possible to avoid interfering with the long term maintenance of the roof. If the roof ever needs repaired, someone will need to slide a slate ripper underneath the slates. If there is asphalt material underneath the slate, it will interfere with the ripper. Also, the underlayment should be flat and smooth so the slate will lie flat. | ||
| brad t. siegmund New member Username: Bsiegmund Post Number: 2 Registered: 07-2007 |
thanks Joe. I guess I don't understand the purpose of the underlayment. Seems like shingles would be better than felt but my brother(now sadly deceased)was a slate /tile roofer in St.Louis and I seem to recall him saying you should remove them ,too. | ||
| Joe Jenkins Senior Member Username: Joe Post Number: 144 Registered: 07-2006 |
Brad - take the shingles off. It's only half a square. | ||
| brad t. siegmund New member Username: Bsiegmund Post Number: 1 Registered: 07-2007 |
I want to install recycled buckingham slate on my side porch roof( 0.5 squares). can I leave the single layer of asphalt shingles(7 yrs. old) as underlayment and slate over them? | ||
| Joe Jenkins Senior Member Username: Joe Post Number: 134 Registered: 07-2006 |
I'd suggest using a larger slate (square footage - not thickness) and giving it a double headlap as they do on low slope roofs in Italy. For example, a 12"X24" slate with a 7" exposure would have a 3" headlap on the third course below it. This would probably be leakproof regardless of the underlayment at 3:12. The only problem would be people walking on the roof and breaking the slate. [The larger slate means less weight.] | ||
| David Spradlin New member Username: David_spradlin Post Number: 2 Registered: 06-2007 |
P.S.- The extra slate would be needed for the added headlap you'd want for such a low pitch. The more headlap, the less roof coverage per slate. Thus, needing more slate to cover the roof. If you do decide to go with the slate over the rubber, you might want to run counter-battens or sleepers, vertically up the slope of the roof. Then install skip-sheeting or lath strips over the counter-battens. Then fasten your slate to the lath. This will leave your slate roof floating above your secondary roof, without blowing a million holes through it. Which will allow the rubber to function much better as a backstop for any water that makes it through the slate above. This will also allow any water that gets through to travel freely to the gutter or drip edge, much easier than being trapped between slate nailed directly to the deck. Its still a pretty low pitch for slate. You won't get the longevity you'd get if you could squeeze a little more pitch out of the building department. But we all know how that goes. | ||
| Thomas Massie Intermediate Member Username: Thomas Post Number: 35 Registered: 07-2006 |
As for the rigid insulation serving as a vapor barrier, I have heard that it can, but I would say it depends on how tightly the rigid insulation was installed and whether the gaps were religiously "great-stuffed with expanding foam." Also, was there a plastic vapor barrier put down before the rigid insulation? Even that is likely to be perforated with nail holes. A little breathability above all of it would be nice insurance, but that's probably a regional issue, best answered by a local roofer. I would give David a call. A meeting with a conscientious slate roofer is worth a million random internet posts. -Thomas | ||
| David Spradlin New member Username: David_spradlin Post Number: 1 Registered: 06-2007 |
It doesn't sound like your set up right for a good slate application, Mike. Is your roof already framed up? Just a little more pitch would go a long way. We're in Northern California also, and I'd be happy to come by and take a look at what your working with there and figure out some options with you. Give me a call at Ryder Roofing (800)510-3761. Good Luck  | ||
| Mike Korchinsky New member Username: Mkorch Post Number: 1 Registered: 06-2007 |
I am an owner builder in Northern California, at the coast, and am building a rammed earth house, and have always wanted a slate roof. Due to local height restrictions my roof pitch is 3:12, ridge and hips, no valleys. I have open ceiling timber framing, but due to Title 24, rigid insulation filling the 2x6 sleeper bay on top of the 2x6 ceiling decking. Architect/engineers then spec'ed roofing ply on top of the insulation. I have read much about NOT using slate on less than 4:12 slopes, and NOT using plywood decking and NOT using a rubber membrane under the slate, but in my case CAN I use slate and if so, SHOULD I use a rubber membrane over the plywood due to lack of slope ? A local slate installer here is willing to do the job, but wants to put way more slate than on a typical slate roof, and install over rubber membrane for good measure. I read somewhere else that in this application the slate is essentially just protecting the membrane, and therefore LESS slate than on a typical roof can be used. Which is correct ? Apologies to all of you slate experts for introducing what may be an obvious question, but my local slate installers are not interested in discussing pros and cons with me at all. Finally, my architect said that due to rigid insulation keeping warm air relatively contained i the living space, and lack of air gap in rigid roof, that I will not have a moisture problem from below, but I wonder if that is true ? |
