# Question about insulating a 3 season porch



## Jim McC (May 22, 2013)

How would you insulate the following 3 season porch floor? The floor will be about 18" above grade. That's too low to get under there and use spray foam, correct?


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## Windows on Wash (Aug 30, 2011)

Unless you are really small.

I would glue and screw rigid foam across the underside of the joists first (more is better) and insulate the cavity after it is framed but before it is floored.


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## Gary in WA (Mar 11, 2009)

I'd get a permit as many H.O.'s skip this step and add windows/doors/drywall/insulation all on a weak perimeter foundation. Is this a conversion?

Gary


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## Jim McC (May 22, 2013)

Windows on Wash said:


> Unless you are really small.
> 
> I would glue and screw rigid foam across the underside of the joists first (more is better) and insulate the cavity after it is framed but before it is floored.


If I can't get under there to spray it, how can I screw foam insulation in place?

If I can't get under the 18" tall deck, what do you guys recommend as far as insulating the floor?


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## Jim McC (May 22, 2013)

Gary in WA said:


> I'd get a permit as many H.O.'s skip this step and add windows/doors/drywall/insulation all on a weak perimeter foundation. Is this a conversion?
> 
> Gary


No. We would remove our current deck and start fresh. I know about the permits.


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## Windows on Wash (Aug 30, 2011)

Jim McC said:


> If I can't get under there to spray it, how can I screw foam insulation in place?
> 
> If I can't get under the 18" tall deck, what do you guys recommend as far as insulating the floor?


Are all the joists going to be in from the start? If not, you can have enough of the joists in to provide attachment surfaces but that will allow you to maneuver inside of the space without having the confines of the 18" from earth to structure.

You could always tack up some poly and spray foam from the top down as well.


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## Jim McC (May 22, 2013)

Thanks. The joist framing can be done either way I guess


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## Gary in WA (Mar 11, 2009)

You would still need the required crawlspace access door for future access; http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_4_par112.htm
in addition to the required ground clearance, ventilation or air supply/exhaust from conditioned areas (if unvented).

"*R317.1 Location required.* Protection of wood and wood based products from decay shall be provided in the following locations by the use of naturally durable wood or wood that is preservative-treated in accordance with AWPA U1 for the species, product, preservative and end use. Preservatives shall be listed in Section 4 of AWPA U1. 

1. Wood joists or the bottom of a wood structural floor when closer than 18 inches (457 mm) or wood girders when closer than 12 inches (305 mm) to the exposed ground in crawl spaces or unexcavated area located within the periphery of the building foundation. 2. All wood framing members that rest on concrete or masonry exterior foundation walls and are less than 8 inches (203 mm) from the exposed ground. 3. Sills and sleepers on a concrete or masonry slab that is in direct contact with the ground unless separated from such slab by an impervious moisture barrier. 4. The ends of wood girders entering exterior masonry or concrete walls having clearances of less than 1/2 inch (12.7 mm) on tops, sides and ends." found here; http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_3_sec017.htmIf you can not get under the deck, you may need to hire that part out...


Gary


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## Jim McC (May 22, 2013)

Gary, thanks for the bad news. :furious: I had no idea this was needed. Does this only apply if the porch is skirted and closed off? What if it's left open around the perimeter of the porch to the ground?


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## Gary in WA (Mar 11, 2009)

The foundation perimeter/interior beams has to transmit any live/dead loads to the earth; wall/roof/floor loads, people, seismic, snow, wind, elements, etc. The spread footing is sized for the addition height/use, the ground strength, concrete strength, etc. all works together. Your building department will have local requirements to help you build safely, and satisfy your H.O. Insurance carrier concerns if ever a claim or when you go to sell.

Gary


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## Jim McC (May 22, 2013)

Gary in WA said:


> The foundation perimeter/interior beams has to transmit any live/dead loads to the earth; wall/roof/floor loads, people, seismic, snow, wind, elements, etc. The spread footing is sized for the addition height/use, the ground strength, concrete strength, etc. all works together. Your building department will have local requirements to help you build safely, and satisfy your H.O. Insurance carrier concerns if ever a claim or when you go to sell.
> 
> Gary


Thanks, but what does this have to do with my questions in post #9?


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## Jim McC (May 22, 2013)

I talked to an architect who said I shouldn't use a frost wall and slab because the floor would always be cold. Even with 2" insulation for the slab and frost walls. He said I should use concrete pier footings and the largest joists I can fit(floor is only about 16" above grade). Does that sound right?


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