# floor framing over slab



## bluebird5 (Dec 13, 2010)

Hey guys and gals. 

I have got a question for you all. 

I have a garage that was converted into a den back in the day. However, they just left the concrete for the floor so there are two steps down.

What I want to do is frame a floor over the concrete that is level with the house floor. When I do this, I will only have about 7 or 8 inches between the concrete. I believe the irc says 18" min between bottom of joists and floor in crawlspace. 

Is this situation treated like a regular crawlspace? Am I allowed to do this. I really see nothing wrong with it other than it is unaccessable underneith, but so is the bottom of a joist on the second story of a house.


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## greg24k (May 19, 2007)

bluebird5 said:


> Hey guys and gals.
> 
> I have got a question for you all.
> 
> ...


 Access shall be provided to all under-floor spaces. Access openings *through the floor* shall be a minimum of _18 inches by 24 inches_. Openings through a perimeter wall *shall be not less *than _16 inches by 24 inches_. When any portion of the through-wall access is below grade, an areaway not less than 16 inches by 24 inches shall be provided. 

With that said, your architect will provide you with all code compliant details..


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## bluebird5 (Dec 13, 2010)

greg24k said:


> Access shall be provided to all under-floor spaces. Access openings *through the floor* shall be a minimum of _18 inches by 24 inches_. Openings through a perimeter wall *shall be not less *than _16 inches by 24 inches_. When any portion of the through-wall access is below grade, an areaway not less than 16 inches by 24 inches shall be provided.
> 
> With that said, your architect will provide you with all code compliant details..


I'm the archi on this one Greg.


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## griz (Nov 26, 2009)

Does your state/city/county require permits?


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## bluebird5 (Dec 13, 2010)

griz said:


> Does your state/city/county require permits?


Sometimes. Just depends on what your doing. I am not adding square footage, so I might be in the clear. I will have to check with them.


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## greg24k (May 19, 2007)

bluebird5 said:


> I'm the archi on this one Greg.


If you the archi on this, I shouldn't be telling you about the code compliance... you should be aware or local requirements.


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## bluebird5 (Dec 13, 2010)

greg24k said:


> If you the archi on this, I shouldn't be telling you about the code compliance... you should be aware or local requirements.


haha well. I am still in the planning stages. I am just wondering if you are allowed to have a crawlspace that is "uncrawlable" You addressed the opening sizes to enter the space and I am looking on 317.1 #1 that says that you need to use P.T. if you are closer than 18" to exposed ground, so apparently you are allowed to be less than 18 inches, but is there a minimum? 

My local codes go by the IRC. I am just wondering if you guys know of anything in the IRC that says that I can't do what I am proposing.


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## greg24k (May 19, 2007)

bluebird5 said:


> haha well. I am still in the planning stages. I am just wondering if you are allowed to have a crawlspace that is "uncrawlable" You addressed the opening sizes to enter the space and I am looking on 317.1 #1 that says that you need to use P.T. if you are closer than 18" to exposed ground, so apparently you are allowed to be less than 18 inches, but is there a minimum?
> 
> My local codes go by the IRC. I am just wondering if you guys know of anything in the IRC that says that I can't do what I am proposing.


That doesn't apply to you, because you're not over exposed ground. The concern in your case is Section R408.


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## Rio (Oct 13, 2009)

If it's ventilated and will stay dry it should be okay although we have had inspectors want it to be 18" even though it is not to bare earth. 

If it's totally sealed off and will not be ventilated it's another situation. We've done enclosed areas with that scenario and have had to hot mop the assembly.


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## Mrmac204 (Dec 27, 2006)

fill it in with dirt/sand, and pour a new slab.


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## greg24k (May 19, 2007)

Rio said:


> If it's ventilated and will stay dry it should be okay although we have had inspectors want it to be 18" even though it is not to bare earth.
> 
> If it's totally sealed off and will not be ventilated it's another situation. We've done enclosed areas with that scenario and have had to hot mop the assembly.


Everything is about code interpretation... If the code states 18" required clearance from the exposed ground, and you don't have exposed ground, he can want anything he wants, he can't make you do anything if its not in the code or if this not adopted in state legislation.


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## Rio (Oct 13, 2009)

greg24k said:


> Everything is about code interpretation... If the code states 18" required clearance from the exposed ground, and you don't have exposed ground, he can want anything he wants, he can't make you do anything if its not in the code or if this not adopted in state legislation.


Sometimes the code isn't as clear as it could be. Below is the code section from the 2010 CRC (California Residential Code which is basically the International Residential Code). On the above issue usually there's been no problem but we have had plan checkers interpret the code to read it as a minimum of 18" required, an interpretation we didn't agree with......the part in question I highlighted and that is what is exposed ground. I take it to mean earth but they took it to mean any grade. This particular city is noted for extremely picky plan checkers and inspectors.


PROTECTION OF WOOD AND WOOD
BASED PRODUCTS AGAINST DECAY
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 Ul for the species,
product, preservative and end use. Preservatives shall be
listed in Section 4 of AWPA Ul.
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.
5. Wood siding, sheathing and wall framing on the exterior
of a building having a clearance ofless than 6 inches (152
mm) from the ground or less than 2 inches (51 mm) measured
vertically from concrete steps, porch slabs, patio
slabs, and similar horizontal surfaces exposed to the
weather.
2010 CALIFORNIA RESIDENTIAL CODE
BUILDING PLANNING
6. Wood structural members supporting moisture-permeable
floors or roofs that are exposed to the weather, such
as concrete or masonry slabs, unless separated from such
floors or roofs by an impervious moisture barrier.
7. Wood furring strips or other wood framing members
attached directly to the interior of exterior masonry walls
or concrete walls below grade except where an approved
vapor retarder is applied between the wall and the furring
strips or framing members.
R317.1.1 Field treatm


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