# Safe room under concrete porch?



## JimS27 (Jan 22, 2019)

I am planning a house with a walkout basement.  Previously I put a room under the porch and topped it with hollow core concrete and poured the final concrete over that.  Wanting to do similar but getting pushback from various people.  Plans person says they have tried it before and AHJ would want the whole room to be insulated - the reason they gave was the top was exposed to the outdoor temperature.  We will use it for storage and tornado shelter (and perhaps a wine cellar).  When I called it a "safe room" AHJ stated it would have to be in compliance with ICC/NSSA-500.  And the use of premanufactured concrete panels would require an ICC report or signed and sealed plans that show the construction was in accordance to ACI318.  Not sure if that documentation is easily available but the use of 6" hollow core for a porch with 6' span is clearly overkill and much stronger than 4" poured in place that is acceptable to them.  I stated it was impractical to meet all those requirements for a residential space and that perhaps I should have called it a "cellar".  I then got this:
If the space is labeled as ‘Unfinished’ or as ‘Cellar’ then you would have to show that it meets the requirements of the 2009 IRC.  The space would not inherently need insulation, but would need to meet minimum room size, electrical and ventilation.

Proposed room would be 6 x 28 (actually that's the outside of the foundation so room will be close to 5' x 26').  The alternative is to build the same room inside the basement - seems like duplication to build a slightly shallower room under the porch and fill it with gravel just to have another one inside the basement. This room will have a door into the rest of the walkout basement so the egress issue I think is met.

That may not be too hard to meet - does that just mean running a duct run in?  What electrical is required?  Just a light?  

Minimum room size might be the main issue.  It is about 130 sq ft so over the 120 minimum.  But one dimension is less than 7' required for a "habitable room".  But if it is cellar or unfinished I don't see why it would be considered habitable.

Anyone know specifically what sections of code might allow such a space or if a case could be made that this meets IRC2009 code (the version we are on)?  If I have specific code to reference I may get some traction with the plans review.


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## steveray (Jan 22, 2019)

Put closet on plans...or cold storage...


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## mtlogcabin (Jan 22, 2019)

Label the room "Gun Safe" they will be so worried about why you need a room of that size to store all of your guns and what you might do if they deny your plans you will have approval in 24 hours


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## classicT (Jan 22, 2019)

Insulate the wall between the basement and the "safe room", label as non-conditioned space, and the energy code is met.

As for the porch, some design is probably required. As a more conventional method, use nominal lumber with a plywood deck that is topped with a 4-inch slab. Do the design for 100psf live and 75psf dead; that will well exceed the maximum loading that the patio will see. 

(100psf covers the fridge, etc. coming in to home; 75psf is good for 6" thick patio)


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## Pcinspector1 (Jan 22, 2019)

steveray said:


> cold storage...



Mother-in laws room should do the trick!


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## JimS27 (Jan 22, 2019)

Excellent replys!    But does anyone have any specific references to the code for the size issue?


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## TheCommish (Jan 22, 2019)

Use the 4" acceptable method, make it part of the basement with a very heavy door and call it a closet


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## JimS27 (Jan 23, 2019)

4" method would take care of the top although I like the hollow core and membrane under the slab to prevent leaks.  Looking at the cost now.

AHJ now tells me if it is not labeled as habitable space it doesn't need to meet width requirements and doesn't need to be conditioned, only vented.  Then suggests a series of 4" holes at the top and bottom of the wall and that I need 4% of floor area.  

Floor area is about 130 sq ft.  4% is 5.2 sq ft.
A 4" hole is 12.6 sq in

I would need 60 holes to be at 4%.  Doesn't seem very practical, especially for a room that is supposed to keep out flying debris.  

I suspect I will have the same issue with ventilation for the option of a safe room inside the basement.  

I have a similar size unfinished room in my current basement with no ventilation and no HVAC registers although it was done 15 years ago under more lax plans review and inspections.  Different AHJ area too.


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## Pcinspector1 (Jan 23, 2019)

JimS27 said:


> AHJ now tells me if it is not labeled as habitable space it doesn't need to meet width requirements and doesn't need to be conditioned, only vented.



Did the AHJ give you a code section that sez it has to be vented, I'm curious now

My thought was a closet gets around the code a bit like the others have noted. 

Interior foundation wall to have insulation?


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## JimS27 (Jan 23, 2019)

Yes, the interior walls of the basement are to be insulated, even in the unfinished space.  The safe room is not insulated and outside the insulated space.

I didn't call it a closet when communicating with the AHJ.  If I call it a closet they may expect it to be within the insulation envelope.  This is very frustrating...


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## Pcinspector1 (Jan 23, 2019)

JimS27 said:


> This is very frustrating...



I agree, the codes are getting a little complicated.

I just approved a stoop box with space below and didn't think anything of it. It will need to be insulated with a light, switch and wiring in conduit, like it's always been done.


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## tmurray (Jan 23, 2019)

I have one of these under construction now. They installed two 4" vents on opposite sides for cross ventilation and to balance the pressure.


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## Paul Sweet (Jan 23, 2019)

4% ventilated area is only necessary for habitable rooms (IRC R303.1).  One square foot per 150 is adequate ventilation for crawl spaces (R408.1). I recommend a couple crawl space vents which can be closed.


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