old adobe house - attic floor w/ rigid insulation ??


Old 12-16-12, 11:32 AM
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old adobe house - attic floor w/ rigid insulation ??

I'm working on an old adobe house. The ceiling is the traditional beams (vigas) with decking on top. There was a layer of "mud" (adobe) on top of the decking, but it's been removed, and the house also has a pitched roof of rafters covered with corrugated steel sheets. ¡Muy Tradicional!

Because the mud's gone, I need to put something up there, and a little insulation would be nice, too. At this point, in-house air just goes up between the decking boards into the attic space and blows away. It's not going to be a lived-in space, just storage (pitched roof not high enough).

Since I'm going to re-wire as well I thought this might work:

- lay down roofing paper (old school, I know)
- do the wiring, use flexible conduit. Wiring will be mostly along the edges, then out to the middle of the decking to go down to the living space.
- lay down rigid insulation, maybe 1 inch think, cut into pieces as needed to fit around the conduit.
- lay down another layer of rigid insulation, 1 inch, on top, to create a more seamless surface
- lay down 1/2 or 5/8 plywood.

The decking is rough short boards, not a flat smooth surface. I'm assuming the rigid insulation material will be ok with that.

Moisture problems?
Fire code problems?
Specific recommendations for the insulation type?

Thanks in advance for any time you might have for a reply.
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Old 12-16-12, 11:51 AM
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Welcome to the forums! I am not "up" on adobe construction, but if you have a waterproof "roof" over the ceiling vigas, could you not just install rigid insulation directly over the vigas, then install your decking, performing your wiring over the decking, so it will be accessible for later repairs, additions, etc. You could run the wiring in raceways from and to your locations to protect it.
Old 12-16-12, 01:00 PM
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Hi Chandler,

Thanks for the reply.

I need to leave the current decking in place and work above it.

Forgetting the electrical, will my notion of:
- old decking
- roofing paper
- rigid insulation
- new decking
work? or are there fire code / moisture / other problems that make problematic.

If it's workable, I do realize the advantage of doing the electrical on the top of the above sandwich. But I was hoping to avoid it. Seem like in the sort of attic space one is always tripping over conduit. Nothing slides when you need it to. If I went with conduit from the side of the space, through my sandwich (decking/insulation/decking) to the interior of the home (so there would be no junction boxes hidden), would that work? Ie, the conduit would be go across through the insulation, down through the bottom decking, leaving the top surface smooth.

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