# Cold room under stairs (dirt floor) questions with pics



## Shawner (Feb 19, 2012)

I have a small room under the stairs that we use for storage.  It's also the entrance to the crawl space.  The wall straight in is concrete and the PO glued white foam on for insulation.  The floor is a vapor barrier, about 4-6" sand, then a wood deck on top.  The room smells very musty and if we were to store fabric/sleeping bags, etc, they pick up the smell.







This second picture shows where I cut out some drywall.  There is no concrete below that wall, they framed down, drywalled and backfilled sand against the drywall, causing some mold.







So, was hoping to use our tax return to try to fix this room but not totally sure what to do... here's what I'm thinking (with questions in different color)..

- remove sand and pour a concrete floor.  Form a new base for the wall that is currently missing it.
How much sand to remove, right down to vapor barrier?  Do I leave the vapor barrier there?  How thick do I need to pour the floor?

- remove foam insulation, replace with 2" polystrene

- remove old drywall, replace any moldy insulation.  Replace, tape and paint.


Can anyone add anything I might be missing or don't really need to do?

Thanks for any replies, much appreciated!


----------



## nealtw (Feb 20, 2012)

You didnt say how deep that wall is. How far it extends down into the sand. Your concrete want to be 3 1/2 to 4" thick. You do want vapour bearier under the concrete. We put it on top of the sand but in some places they put it under the sand. I would pore the floor wide enough to build the wall on top of the floor.


----------



## Shawner (Feb 20, 2012)

I'm not entirely sure how deep the footing goes.  In the first picture, outside grade level is probably about level with the first joint between the white foam and the sheetrock on the opposite wall.

Thanks for the reply


----------



## nealtw (Feb 20, 2012)

Do floor joist land on that wall? If it is a bearing wall with a footing it should be replaced with concrete or block at least to the height of the future concrete floor. I would like to see a photo of the floor joists and that wall  from the crawl space.


----------



## Shawner (Feb 20, 2012)

The floor joists run parallel to the moldy wall (or parallel to the deck boards on the dirt floor).

This pic is taken back towards where I was standing when I took the first picture in the thread.  That's the concrete footing under the plastic bump there.  






This picture is taken on the backside of the moldy wall


----------



## nealtw (Feb 20, 2012)

So it is non bearing and you will be able to just remove that wall and pore the new floor to include the wall and bolt down a treated 2x4 to attach drywall to.


----------



## Shawner (Feb 20, 2012)

Thanks for the help


----------



## inspectorD (Feb 21, 2012)

Looks like a fun hunched over project...I feel your pain

Everything sounds good, only I would stay away from any sheetrock below the existing floor joist area. Seeing as how you already had a mold issue, it will just come back again on ANY type of sheetrock. I would suggest using a cement board and just skim coat it with a thinset product. It will look like finished plaster, and mold will not grow since the is no paper or cellulose product.
Just a thought to save you work down the road.
Have fun!!:2cents:


----------



## Shawner (Feb 21, 2012)

inspectorD said:


> Looks like a fun hunched over project...I feel your pain
> 
> Everything sounds good, only I would stay away from any sheetrock below the existing floor joist area. Seeing as how you already had a mold issue, it will just come back again on ANY type of sheetrock. I would suggest using a cement board and just skim coat it with a thinset product. It will look like finished plaster, and mold will not grow since the is no paper or cellulose product.
> Just a thought to save you work down the road.
> Have fun!!:2cents:



Thanks for the :2cents:

Will I need to attach something over top of the polystyrene as a fire break?  There is a light in the room, but no other source of ignition.  If so, how?  Would I glue the foam to the conc. wall then build a wall outside of it?


----------



## nealtw (Feb 21, 2012)

For basements we build a 2x4 wall 1" away from the concrete and insulate that.


----------



## Shawner (May 21, 2012)

Finally got a chance to start pulling stuff apart this weekend.  Found vapor barrier  under the drywall (with the opposite side of the wall being the living area/family room).  If vapor barrier is needed, isn't it supposed to be on the warm side?  

Was also thinking that lack of air movement is probably contributing to the smell.  If I make the storage room into a part of the living area (vapor barrier on any walls separating the storage room from the crawl space), pipe a heat register in and cut a vent into the bottom of the door.... would that work?


----------



## nealtw (May 21, 2012)

Good luck on the project and yes that should work with air movement and yes the barrier should have been on the warm side.


----------



## Shawner (Jun 3, 2012)

Poured the floor yesterday and pulled down the old drywall and foam on the concrete.  

The picture below is the wall that used to have the white foam on it.  It's an outside wall.




The sill plate overhangs the concrete by about 1.5".  Could I:
- glue 1.5" rigid foam to the concrete, tape joints, acoustic sealant all around
- extend vapor barrier from 2x6 wall above down and taped to rigid foam 
- insulated 2x4 wall directly in front of it (with no vapor barrier) 
- drywall



The other side of this pictured wall below is the garage (un-heated) 
	

	
	
		
		

		
		
	


	



Edge of sill plate is flush with the concrete wall.  Wall is 2x4.  Could I:
- glue 1.5" rigid to the concrete, tape joints, acoustic sealant all around
- strap the 2x4 walls with 2x2's
- replace the 2x4 insulation with 2x6 insulation  
- vapor barrier on warm side of wood wall, down and taped to rigid foam
- insulated 2x4 wall directly in front of it (with no vapor barrier) 
- drywall

Sound right?


----------



## nealtw (Jun 3, 2012)

What we normally would do is build a 2x4 wall in front of the wall which would leave an inch away from the concrete and insulate that a vapour barrier behind the drywall. I think your plan will work fine.


----------

