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Mark Mouton
Posted: Jul 11, 2012 04:58 PM
Partial foam roof job
I am going to insulate a small grocery store (10,500 sq ft).We will pull out rows of dropped ceiling tiles running with the purlins( forgot to mention its a conventional metal bldg with 3' wide R- panel) and spray 3-4" of oc. at roofline. We are going to bring the back wall that separates a small ware house area from conditioned space to the roofline and spray it to make a conditioned attic in store. There is an add- on to the bldg where the roofline is low and dropped ceiling is against purlins with aluminum bubble wrap and Fiberglas batts so we have no room above ceiling to work. At this part (2400 sq ft), I was thinking of applying roofing foam and coating for insulation purposes. Will it hurt to do part of a metal roof this way?
Bryan Kwater
Posted: Jul 11, 2012 06:25 PM
Don't forget that the foam on the interior side of the building needs to be covered by a 15 minute thermal barrier. Drop ceiling doesn't count. Roofing foam is not my thing, so I will let someone that knows more to chime in on that.
Mark Mouton
Posted: Jul 12, 2012 09:58 AM
I failed to explain that the add-on part is a continuation off to the side where the pitch is sloping down and the roof panels are tied in at same elevation. What my concern is that the exposed R-panel area will expand and contract different than the area with the roofing foam. Will this cause a problem? This is South East Texas and it gets hot.
Dennis Davidson
Posted: Jul 14, 2012 05:21 PM
Why not spray the whole roof and be done? If your concerned about metal expansion differences between the two sections, then spray the wall too from the higher roof to the lower one.

What part of South Texas? I used to live in Harlingen and Brownsville.
Mark Mouton
Posted: Jul 15, 2012 08:35 AM
MACS,My explanation wasn't very good. The roof is one solid surface. There isn't any drop down areas(with wall) where the add-on is.
About spraying the whole roof, I haven't done a foam roof as yet, but doing a small job like this 2400 sq ft area, I have confidence I can handle.
I'm thinking of spraying up to about 6-12" from the joint(overlap) where the roofs tie in and the coating heavy over the joint.
I will consider talking to them about foaming the whole thing. Would you consider doing the job?
I'm from Vidor, Texas(next door to Beaumont).
Dennis Davidson
Posted: Jul 15, 2012 11:01 AM
I would not recommend just foaming over the roof joint. There is just to much movement across the rest of the roof and it will tear it open. If you have enough confidence in yourself to do the 2,400sf roof then think of the rest as simply three more of those same roof sections.
I would consider working with you on this project but it would have to be later in the year. We're working in Illinois right now but may have a project in Louisiana in a couple months. We would only be a little over 100 miles for you if we get it.

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