Does "code" require that reroofing over a catheral ceiling be ventilated by 1" minimum standoff from the original substrate or sheathing? I recently discovered BOCA now requires the old shakes to come off, and I am attempting to minimize my labor and expense. Secondly, a commercial installer recently used a "tyvek" type house wrap instead of 30# felt to drain condensation from underside. It is a tough product that is vapor permeable in my experience and appears to be compatible to use. Are you familiar with this application?
Todd Miller
Classic Products, Inc.
4/30/2003
Al Reid on this board is much more of an expert in this area than I am so I will preface everything by saying that you might want to email him direct at [email protected] The International Bldg Code, which is the model code adhered to by BOCA now, requires a minimum 1" vented airspace between the bottom of the roof deck and any insulation or inside ceiling. The purpose of this ventilated area is to prevent an unhealthy build-up and accumulation of moisture. This would be moisture which originates inside the house from cooking, showers, plants, etc. With an existing house, I do not think you "must" adhere to this new part of the code. However, A-frames do frequently have ventilation concerns and it would not be a bad idea. The vented airspace would also help you with cooling costs and overall energy efficiency. I do not understand where you say that BOCA requires the old shakes to be removed. BOCA requires there to be no more than two layers of roofing but I am unaware of it specifically saying that existing shakes must be removed. Perhaps you have another layer of roofing on top of the shakes so it all must come off? Of course, I need to preface all of this by saying that the codes are always subject to interpretation by local building inspectors. If the inspectors are insistent on something that you really question, hire a structural engineer to review the situation on your behalf and perhaps issue a report. The type of underlayment you use must be compatible with the roofing you install. It is helpful to have a breathable underlayment in your case. However, ultimately, the underlayment must be something that is prescribed by the roofing manufacturer. I do not think that Tyvek is approved by anyone for roofing underlayment.
Guest User
4/30/2003
Todd, Thak you for your reply. I found the tear off requirement on the BOCA website as an update in 1999. It stated that all old shingles must be removed on reroofing. I got told this more than once after we had reroofed our older house to put it on the market. There does seem to be some confusion in the field about this - and I may be, too. The house only has the one layer of cedar shakes, and I also wonder if they would be considered suffiecient to handle condensate runoff, even if not too good a roof now. Mark Monteleone
Todd Miller
Classic Products, Inc.
4/30/2003
Hi Mark, Well, like I said, I have not seen that in any currently enforced code. It might have been in some interim version but then was revised. I probably mentioned this earlier but Al Reid might have some good input on this -- [email protected] I would definitely place an underlayment on top of the shakes if you go over them. I'd prefer to not see them subjected to condensation. If you're in an area where a building inspector exists, I'd suggest contacting them about the tear-off question. And, if you do try to add a vented airspace, contacting a structural engineer to review the situation maybe wouldn't be bad. One other idea is to consider one of the batten-mounted steel roofing systems. They could be mounted on a lattice of vertical purlins against the shakes followed by horizontal purlins. This could allow for very good airflow. Contact me again if I can be of help!
Guest User
5/2/2003
Todd, Al has corresponded comprehensivley. The batten and purlin system with addtional insulation seems to be gaining favor as the way to go, and will even be a little easier to install rather than just randomly attaching a new roof with questionable vertical support. The last thing I need is to watch my 26 foot sheets slowly slipping off the roof! Mark Monteleone
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