Chris, I'm pretty sure that what David means by "blocking" is if the roof has rafters (peak to eave) rather than purlins (horizontal) then, IF you can access the underside of the roof, you properly install 'blocking' (2x4, 2x6, 2x8) against the underside of the roof sheathing, perpendicular to the rafters. Then you can drill your bolt anywhere along the blocking which then eliminates the restriction of having to attach to a rafter every 16-24". Keep in mind that there are proper methods of doing this to make sure the blocking is properly attached to the rafters, otherwise any uplift pressure from the array is only supported by the roof material and not the structure (rafters/purlins)
Then again, access to the underside of the roof is not always available or is restrictive, so this is an important factor to figure out before you land on site with your roof attachments and racking, ready to go. Cheers, benn DayStar Renewable Energy Inc. www.daystarsolar.ca 780-906-7807 Construction Electrician Solar Photovoltaic Systems Certified Certificate # 0007S HAVE A SUNNY DAY On 04/07/12 5:23 PM, "Chris Mason" <cometenergysyst...@gmail.com> wrote: I use corrugated mounting bridges - that's the problem. If the center of the beam falls in the trough, the corrugated bridge is useless. I am not sure how blocking would help. Corrugated is a pain. On Wed, Jul 4, 2012 at 12:11 PM, David Brearley <david.brear...@solarprofessional.com> wrote: > In some cases, you can install blocking to get up on the ridge consistently. > One alternative to hangar bolts is to use corrugated mounting bridges from DPW > Solar or something similar from another company. > > Sorry I can't link to the PDF. Google: "corrugated mounting bridges" > > Since exposed-fastener metal roofs already have a bunch of holes in them, > you're not voiding the roof warranty by punching more holes in the ridge. (I > don't think these roofs even meet the NRCA definition of a "roof assembly" > because of the exposed penetrations.) Penetrations in the valleys on a roof > are problematic for obvious reasons. > > > On Jul 4, 2012, at 6:01 AM, Chris Mason wrote: > >> > All of this refers to shingle roofs, which we don't see much of. We mostly >> deal with concrete and corrugated steel/galvalume, the latter being a >> nightmare. Does anyone have good ideas for dealing with corrugated? There's >> no way to flash it, the blocks are fine when you hit a beam on the ridge but >> half the time your penetration has to be on the trough of the corrugated >> steel. >> > Other than lots of goop, I don't know how else to seal it.
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